Applied Surface Science (v.392, #C)

Electrochemical performance of electroactive poly(amic acid)-Cu2+ composites by Ying Yan; Fangfei Li; Ashley M. Hanlon; Erik B. Berda; Xincai Liu; Ce Wang; Danming Chao (1-7).
Electroactive poly(amic acid)-Cu2+ (EPAA-Cu) composites on the substrates have been prepared, whose electrochemical properties, including electroactivity, electrochromism and anticorrosion, reveal drastic enhancement after incorporation of Cu2+ ions.Display OmittedElectroactive poly(amic acid)-Cu2+ (EPAA-Cu) composites on substrates were successfully prepared via nucleophilic polycondensation followed by the use of an immersing method. Analysis of the structure properties of EPAA-Cu composites was performed using scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and Fourier-transform infrared spectra (FTIR). A significant current enhancement phenomenon of EPAA-Cu/ITO electrodes was found as evident from cyclic voltammetry (CV) measurements. In addition, Cu2+ ions were incorporated into the composites and had a positive effect on their electrochromic behaviors decreasing their switching times. The anticorrosive performance of EPAA-Cu composites coatings on the carbon steel in 3.5 wt% NaCl solution were also investigated in detail using tafel plots analysis and electrochemical impedance spectroscopy. The anticorrosive ability of these coatings significantly enhanced through the incorporation of Cu2+ ions.
Keywords: Polyaniline; Oligoaniline; Electrochromic; Anticorrosive;

Employing high-contact-ratio (HCR) gear is an effective method of decreasing the load on a single tooth, as well as reducing vibration and noise. While the spindlier tooth leads to greater relative sliding, having more teeth participate in contact at the same time makes the HCR gear more sensitive to the surface quality. Available literature regarding HCR gear primarily investigates the geometrical optimization, load distribution, or efficiency calculation. Limited work has been conducted on the effect of rough surfaces on the dynamic performance of HCR gear. For this reason, a multi-degree-of-freedom (MDOF) model is presented mathematically to characterize the static transmission error based on fractal theory, investigate the relative sliding friction using an EHL-based friction coefficient formula, and detail the time-varying friction coefficient suitable for HCR gear. Based on numerical results, the surface roughness has little influence on system response in terms of the dynamic transmission error but has a large effect on the motion in off-line-of-action (OLOA) direction and friction force. The impact of shaft-bearing stiffness and damping ratio is also explored with results revealing that a greater shaft-bearing stiffness is beneficial in obtaining a more stable motion in OLOA direction, and a larger damping ratio results in a smaller effective friction force. The theory presented in this report outlines a new method of analyzing the dynamics of HCR gear in respect of introducing surface roughness into MDOF model directly, as well as establishing an indirect relationship between dynamic responses and surface roughness. This method is expected to guide surface roughness design and manufacturing in the future.
Keywords: Surface roughness; High-contact-ratio gear; Friction; EHL; Fractal theory;

Novel tribological stability of the superlubricity poly (vinylphosphonic acid) (PVPA) coatings on Ti6Al4V: Velocity and load independence by Caixia Zhang; Zhifeng Liu; Yuhong Liu; Jing Ren; Qiang Cheng; Congbin Yang; Ligang Cai (19-26).
High stability and movement compatibility under friction is vital to guarantee long-term use of implants in the human body. In this study, the negligible wear of the poly (vinylphosphonic acid) (PVPA)-modified Ti6Al4V/polytetrafluoroethylene (PTFE) interface in phosphate-buffered saline (PBS, PH = 7.2) were confirmed. The depth of scratches on the PVPA-modified Ti6Al4V was no more than 20 nm, while there was slight wear on the PTFE ball, as indicated by the radius of curvature being almost the same as the initial value after sliding for 2 h. In addition, it should be noted that the novel velocity and load-independent tribological behaviors are exciting. The superlubricity of the PVPA-modified Ti6Al4V can be maintained over a wide velocity range, from 0.3 mm/s to 48 mm/s, even under a high pressure of 63.49 MPa, confirming its potential application in implants. The sufficient thickness of the firm PVPA coatings with specific lubricating state and the compatibility of the two tribo-pairs in this tribological system primarily account for the novel tribological stability. This study provides insights into the tribological mechanisms of the high-stability polymer coatings.
Keywords: Poly (vinylphosphonic acid) coatings; Ti6Al4V; Superlubricity; Velocity; Normal load; Stability;

Display OmittedCarboxyl functionalized carbon fibers with preserved tensile strength and electrochemical properties were acquired through a simple chemical oxidation method, and the proposed underlying mechanism was verified. The surface of carboxyl functionalizing carbon fibers is necessary in acquiring functional groups on the surface of carbon fibers to further improve the thermal, electrical or mechanical properties of the fibers. Functionalization should preserve the tensile strength and electrochemical properties of carbon fibers, because the anodes of structural batteries need to have high strength and electrochemical properties. Functionalized with mixed H2SO4/HNO3 considerably reduced the tensile strength of carbon fibers. By contrast, the appearance of H3PO4 preserved the tensile strength of functionalized carbon fibers, reduced the dispersion level of tensile strength values, and effectively increased the concentration of functional acid groups on the surface of carbon fibers. The presence of phosphoric acid hindered the over-oxidation of turbostratic carbon, and consequently preserved the tensile strength of carbon fibers. The increased proportion of turbostratic carbon on the surface of carbon fibers concurrently enhanced the electrochemical properties of carbon fibers.
Keywords: H3PO4; Carbon fiber; Functionalization; Multifunction structural lithium-ion batteries; Surface;

Display OmittedA facile strategy has been developed for the synthesis of H-TS-Au microspheres (MCs) with double-shelled hollow architecture and sub–5 nm Au nanoparticles (Au NPs). The synthetic procedure involves the successive sol-gel template-assisted method for the preparation of uniform hierarchical hollow-in-hollow H-TS MCs with TiO2/mSiO2 as yolks/shells, and the unique deposition-precipitation method mediated with Au(en)2Cl3 precursors for the in-situ construction of extremely stable Au NPs under a low-temperature hydrogen reduction. The synthesized H-TS-Au MCs were characterized by TEM, SEM, FTIR, XRD, BET and UV–vis absorption spectra. Catalytic activity of H-TS-Au was evaluated using the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4. Results established that H-TS-Au MCs possessed a large-size double-shelled architecture with high structural integrity and robustness,which can effectively confine numerous tiny Au NPs and restrict them from sintering aggregation even up to further calcination at 800 °C. Owing to the advantageous structural configuration and the synergistic effect of TiO2/mSiO2 double shells, the H-TS-Au MCs were demonstrated to exhibit a remarkable catalytic activity and stability, and preserve the intact morphology after 6 repeating reduction of 4-NP.
Keywords: Double-shelled hollow architecture; Gold precursor; Sinter resistance; Catalytic activity; 4-Nitrophenol;

Hydrogenated and halogenated blue phosphorene as Dirac materials: A first principles study by Minglei Sun; Sake Wang; Jin Yu; Wencheng Tang (46-50).
Display OmittedUsing first-principles calculations, we systematically investigate the structures and electronic properties of fully hydrogenated and halogenated blue phosphorene (P2X2). All these systems possess Dirac cone at high-symmetry K point, which are mainly contributed by P s px py orbitals. The Dirac cone in P2F2 and P2I2 systems lies exactly at the Fermi level. Formation energy analysis denotes that all the systems are energetically stable except P2I2. The mass density for P2H2 and P2F2 systems is rather small. Our calculations proposed that these systems, especially P2F2 system, have great potential applications in future nanoelectronics.
Keywords: Blue phosphorene; Dirac material; Hydrogenation; Halogenation; Functionalization; First-principles computations;

Display OmittedA reduced graphene oxide (rGO) wrapped Bi2WO6 (Bi2WO6@rGO) hybrid as photoelectrode for enhanced photoelectrocatalytic (PEC) degradation of organic pollutants is reported, which exhibited excellent charge separation and photoconversion efficiency. The core@shell structured Bi2WO6@rGO photoelectrode yielded a pronounced 1.56-fold and 23.8-fold photocurrent density at 1.0 V vs. saturated calomel electrode (SCE), than that of loading structured Bi2WO6-rGO and pure Bi2WO6. The Bi2WO6@rGO hybrid exhibited enhanced photoelectrocatalytic efficiency for degradation of Rhodamine B (RhB), which was 43.0% and 65.6% higher than that of photocatalytic (PC) and electrocatalytic (EC) processes, respectively. The enhancement in PEC degradation of RhB benefited from: (1) a strong interaction and a wide range of conjugation were formed in the core@shell system; (2) a 0.26 V of flat band potential was negatively shifted in case of Bi2WO6@rGO composite; (3) the photogenerated electrons and holes could be spatially separated by external electric potentials.
Keywords: Photoelectrocatalysis; Reduced graphene oxide; Bi2WO6; Hybridization; Organic pollutant;

Utilization of visible to NIR light energy by Yb+3, Er+3 and Tm+3 doped BiVO4 for the photocatalytic degradation of methylene blue by Chhabilal Regmi; Yuwaraj K. Kshetri; Schindra Kumar Ray; Ramesh Prasad Pandey; Soo Wohn Lee (61-70).
Lanthanide-doped BiVO4 semiconductors with efficient photocatalytic activities over a broad range of the solar light spectrum have been synthesized by the microwave hydrothermal method using ethylenediaminetetraacetic acid (EDTA). The structural, morphological, and optical properties of the as-synthesized samples were evaluated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The chemical compositions were analyzed by X-ray photoelectron spectroscopy (XPS). The toxicity of the samples was measured using Mus musculus skin melanoma cells (B16-F10 (ATCC® CRL-6475™)) and were found to be nontoxic for human cells. The photocatalytic efficiency of the prepared samples was evaluated by methylene blue (MB) degradation. The best photocatalytic activity was shown by BiVO4 with 6:3:3 mol percentage of Yb+3:Er+3:Tm+3 in all solar light spectrum. The synthesized samples possess low band gap energy and a hollow structure suitable for the better photocatalytic activity. The observed NIR photoactivity supports that the upconversion mechanism is involved in the overall photocatalytic process. Therefore, this approach provides a better alternative upconversion material for integral solar light absorption.
Keywords: Photocatalyst; Methylene blue; NIR light; Upconversion; BiVO4;

In situ one-pot preparation of reduced graphene oxide/polyaniline composite for high-performance electrochemical capacitors by Nali Chen; Yapeng Ren; Peipei Kong; Lin Tan; Huixia Feng; Yongchun Luo (71-79).
Display OmittedReduced graphene oxide/polyaniline (rGO/PANI) composites are prepared through an effective in situ one-pot synthesis route that includes the reduction of graphene oxide (GO) by aniline under weak alkali condition via hydrothermal method and then followed by in situ polymerization of aniline. X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope are employed to reveal that GO is successfully reduced by aniline under weak alkali condition and PANI can be deposited on the surfaces of reduced graphene oxide (rGO) sheets. The effect of rGO is optimized by tuning the mass ratios of aniline to GO to improve the electrochemical performance of rGO/PANI composites. The maximum specific capacitance of rGO/PANI composites achieves 524.4 F/g with a mass ratio of aniline to GO 10:1 at a current density of 0.5 A/g, in comparison to the specific capacitance of 397 F/g at the same current density of pure PANI. Particularly, the specific capacity retention rate is 81.1% after 2000 cycles at 100 mv/s scan rate, which is an improvement over that of pure PANI (55.5%).
Keywords: Reduced graphene oxide; Polyaniline; Hydrothermal method; Electrochemical capacitors;

Display OmittedNanostructured N doped TiO2/20%SiO2 thin films were developed on steel surface via sol gel method using a painting airbrush. Thin films then were calcined at various temperatures in a range of 400–600 °C. The effect of SiO2 addition on phase composition and microstructural evolution of N doped TiO2 films were studied using XRD and FESEM. Optical properties, visible light photocatalytic activity, hydrophilic behavior, and mechanical behavior of the films were also investigated by DRS, methylene blue degradation, water contact angle measurements, and nanoscratch testing. Results indicated that the band gap energy of N doped TiO2/SiO2 was increased from 2.93 to 3.09 eV. Crack formation during calcination was also significantly promoted in the composite films. All composite films demonstrated weaker visible light photocatalytic activities and lower mechanical stability in comparison with N doped TiO2 films. Moreover, the N doped TiO2/SiO2 film calcined at 600 °C showed undesirable hydrophilic behavior with a water contact angle of 57° after 31 h of visible light irradiation. Outcomes of the present study reveal some different results to previous reports on TiO2/SiO2 films. In general, we believe the differences in substrate material as well as application in visible light are the main reasons for the above mentioned contradiction.
Keywords: Composite thin film; Visible light activated TiO2; Photocatalysis; Hydrophilicity; Mechanical properties;

Lithium ion adsorption and diffusion on black phosphorene nanotube: A first-principles study by Jin Cao; Jing Shi; Yinquan Hu; Musheng Wu; Chuying Ouyang; Bo Xu (88-94).
Display OmittedLi ion storage performance of the single-walled black phosphorene nanotube (PNT), which is considered as potential anode materials for high-performance Li-ion batteries (LIBs), is studied from first-principles calculations. The Li ion adsorption, diffusion and structural evolution of the one-dimensional armchair type PNT (aPNT) upon Li intercalation on the inside (in-PNT) and outside (out-PNT) surfaces were explored, comparing with that of the two-dimensional phosphorene (Psheet). A maximum Li storage capacity (at the intercalated state of Li22P44) is evaluated to be 432 mAh/g. It is also shown that the in-PNT system has higher adsorption energy and lower Li diffusion energy barrier compared with that of the Psheet and the out-PNT systems. The reason on why the better Li storage performance of the in-PNT is also studied from charge distribution and transfer analysis. These results suggest that PNT can be served as potential anode material for LIBs.
Keywords: Phosphorene nanotube; Lithium ion storage; Lithium ion diffusion;

Investigation of the electrical and ethanol-vapour sensing properties of the junctions based on ZnO nanostructured thin film doped with copper by Dimitre Tz. Dimitrov; Nikolay K. Nikolaev; Karolina I. Papazova; Lyudmila K. Krasteva; Igor A. Pronin; Igor A. Averin; Assya S. Bojinova; Angelina Ts. Georgieva; Nadejda D. Yakushova; Tatyana V. Peshkova; Andrey A. Karmanov; Nina V. Kaneva; Vyacheslav A. Moshnikov (95-108).
Display OmittedWe present the investigation of ethanol sensing properties of the junctions composed by two plane-parallel nanostructured thin film electrodes. One of them consists of pure ZnO and the other one is composed of ZnO doped with Cu. The thickness of the lower layer was kept constant for all of the investigated structures. The thickness of the upper layer was varied. The samples were produced with different thickness of the top layer by changing the numbers of dip-coatings cycles. On produced junction structures we investigate the dependence of the potential difference on the temperature in the air flow and the changes that occur under exposure to flow of air with certain concentration of ethanol vapour. For ZnO/ZnO:Cu junction with top layer produced by two dip-coatings cycles, the potential difference under the air flow were getting more positive values up to 290 °C and then the values were decreasing, while for ZnO/ZnO:Cu junction with top layer produced by three dip-coatings cycles, the potential difference were getting more negative values with increasing the temperature. However in both cases the potential difference increases in value, when the structures are exposed to the vapour of ethanol. On this installation by the exchange the content of gas atmosphere at fixed temperature the ethanol concentration dependence of the potential difference of produced junction structures were evaluated. Both samples have shown nonlinear dependence of signal towards the concentration of ethanol vapour. The observed results for ZnO/ZnO:Cu were compared with those of the junctions composed by layers of ZnO doped with Ga and pure ZnO nanowires. The performed fractal analysis based on the SEM images showed a correlation between the fractal dimension of the surface of the upper layer of the samples and gas-sensitive properties of the sensing structures.
Keywords: Nanostructured ZnO thin films; Ga and Cu doped ZnO thin films; Ethanol gas sensor; Fractal analysis;

Formation of the double-layer electric field and capacitance of the water-metal interface is of significant interest in physicochemical processes. In this study, we perform first- principles molecular dynamics simulations on the water/Pt(111) interface to investigate the temperature dependence of the compact layer electric field and capacitance based on the calculated charge densities. On the Pt (111) surface, water molecules form ice-like structures that exhibit more disorder along the height direction with increasing temperature. The O―H bonds of more water molecules point toward the Pt surface to form Pt―H covalent bonds with increasing temperature, which weaken the corresponding O―H bonds. In addition, our calculated capacitance at 300 K is 15.2 mF/cm2, which is in good agreement with the experimental results. As the temperature increases from 10 to 450 K, the field strength and capacitance of the compact layer on Pt (111) first increase and then decrease slightly, which is significant for understanding the water/Pt interface from atomic level.
Keywords: Water/platinum interface; Compact layer; Temperature effect; First-principles molecular dynamics simulations;

Display OmittedMeasurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-d-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension ( γ S V ) as well as the Lifshitz-van der Waals component of the water surface tension ( γ W L W ). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γ S V and γ W L W . It occured that by using the values of γ S V , γ W L W and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.
Keywords: Surfactants; Polytetrafluoroethylene; Contact angle; Adhesion work; Surface excess concentration;

Antifouling activities of β-cyclodextrin stabilized peg based silver nanocomposites by N. Punitha; P. Saravanan; R. Mohan; P.S. Ramesh (126-134).
Display OmittedSelf-polishing polymer composites which release metal biocide in a controlled rate have been widely used in the design of antimicrobial agents and antifouling coatings. The present work focuses on the environmental friendly green synthesis of PEG based SNCs and their application to biocidal activity including marine biofouling. Biocompatible polymer β-CD and adhesive resistance polymer PEG were used to functionalize the SNPs and the as synthesized SNCs exhibit excellent micro fouling activities. The structural and optical properties were confirmed by XRD and UV–visible techniques respectively. The particle surface and cross sectional characteristics were examined by SEM-EDS, HR-TEM, AFM and FTIR. The surface potential was evaluated using ZP analysis and assessment of antibiofouling property was investigated using static immersion method.
Keywords: Silver nanocomposite; Stabilizer; Antibacterial activity; Antifouling activity;

First-principles study on the multiferroic BiFeO3 (0001) polar surfaces by Jian-Qing Dai; Jie-Wang Xu; Jian-Hui Zhu (135-143).
Display OmittedWe present first-principles DFT+U calculations to investigate the stoichiometric (0001) polar surfaces of multiferroic R3c BiFeO3. We predict that the complete Fe-O3-Bi trilayer, which is characterized by almost vanishing compensating charge, forms the most stable negative and positive surfaces. A large inward relaxation is found for the outermost Fe atomic layer at the negative surface, while the O3 atomic layer in the positive surface exhibits a remarkable in-plane rotational reconstruction. Our results show that the insulating nature of BiFeO3 persists at both surfaces but the negative termination is distinguished from the positive surface by the gap state. It is also found that the ferroelectric polarization and weak ferromagnetism of both surfaces have somewhat enhanced character because of relaxation and rehybridization of the surface atoms. Not only the different atomic/electronic structures but also the opposite polarization orientations indicate the distinct chemical properties between the negative and the positive (0001) surfaces and consequently many intriguing applications.
Keywords: BiFeO3; Multiferroic; Polar surface; Atomic relaxation; Electronic states; First-principles;

Nanostructured nickel oxide-hematite (NiO/α-Fe2O3) p-n junction photoanodes synthesized from in situ doping of nickel (Ni) during cathodic electrodeposition of hematite were successfully demonstrated. A postulation model was proposed to explain the fundamental mechanism of Ni2+ ions involved, and the eventual formation of NiO on the subsurface region of hematite that enhanced the potential photoelectrochemical water oxidation process. Through this study, it was found that the measured photocurrent densities of the Ni-doped hematite photoanodes were highly dependent on the concentrations of Ni dopant used. The optimum Ni dopant at 25 M% demonstrated an excellent photoelectrochemical performance of 7-folds enhancement as compared to bare hematite photoanode. This was attributed to the increased electron donor density through the p-n junction and thus lowering the energetic barrier for water oxidation activity at the optimum Ni dopant concentration. Concurrently, the in situ Ni-doping of hematite has also lowered the photogenerated charge carrier transfer resistance as measured using the electrochemical impedance spectroscopy. It is expected that the fundamental understanding gained through this study is helpful for the rational design and construction of highly efficient photoanodes for application in photoelectrochemical process.
Keywords: Electrodeposition; Hematite; Photoelectrochemical; p-n Junction; Solar energy conversion; Water splitting;

Display OmittedPreparation and immobilization of layered double hydroxides (LDHs) film onto multiple substrates is important and challenging in functional materials fields by date. In this work, a simple and universal polydopamine (PD)-based layer-by-layer assembly strategy was developed for the immobilization of LDHs film onto surfaces such as polypropylene chip, glass slides and metal coins. The surface of substrates was firstly modified by polydopamine functionalization, and then LDHs film was synthesized via urea method and directly immobilized on the PD layer by in situ growing strategy in one step. The PD layer as well as the final LDHs film was characterized by energy dispersive X-ray spectroscopy, scanning electron microscope, infrared spectroscopy, X-ray diffraction pattern and X-ray photoelectron spectra. It has been demonstrated the formation of the dense and homogeneous nanoscaled LDHs film with 400 nm thickness. Adsorption behavior of the fabricated NiAl-LDHs film toward anionic dyes and pharmaceuticals was further assessed. To demonstrate their extensive application, fast and high efficient adsorption of anionic dyes and pharmaceuticals was achieved by NiAl-LDHs-modified polypropylene centrifugal tube.
Keywords: Layered double hydroxides; Polydopamine; Nano-film; Immobilization; Adsorption;

The different poisoning behaviors of various alkali metal containing compounds on SCR catalyst by Xuesen Du; Guangpeng Yang; Yanrong Chen; Jingyu Ran; Li Zhang (162-168).
Display OmittedAlkali metals are poisonous to the metal oxide catalyst for NO removal. The chemical configuration of alkali containing substance and interacting temperature can affect the poisoning profile. A computational method based on Frontier Molecular Orbital analysis was proposed to determine the reacting behavior of various alkali-containing substances with SCR catalyst. The results reveal that the poisoning reactivities of various substances can be ranked as: E (MOH) > E (M2SO4) > E(MCl) > E(MNO3) > E(MHSO4). The experimental activity tests of the catalysts calcined at stepped temperatures show that NaOH can react with the catalyst below 200 °C. NaCl and NaNO3 start to react with the catalyst at a temperature between 300 and 400 °C. Unlike MOH, MCl and MNO3, which can produce volatile or decomposable species for the anions after reacting with the catalyst, M2SO4 and MHSO4 will leave both cations and anions on the catalyst surface. The sulfate ions left on the catalyst can generate active acid sites for NH3 adsorption. The experimental results also show that Na2SO4 and NaHSO4 will not lower the NO conversion. The after-reaction influences of various alkali metals were studied using theoretical and experimental methods. The theoretical results show that the acidity decreases with doping of alkali metal. Experiments show a consistent result that the NO conversion decreases as undoped >LiCl > NaCl > KCl.
Keywords: Selective catalytic reduction; Poisoning; Alkali metal; Density functional theory; Vanadia;

Display OmittedPd-doped Bi2MoO6 was prepared and investigated for the first time. The prepared samples were characterized by their crystal structures, chemical states, atomic compositions, optical properties and morphologies. The photocatalytic activities of prepared samples under visible light irradiation were determined by degradation of phenol, which is widely found in wastewater from many industrial processes and is difficult to destroy. The sample exhibiting the highest removal efficiency with respect to the degradation of phenol contained 2% Pd. The enhancement effect can be interpreted as the integrated effects of a reduction in the rate of electron-hole recombination, surface plasmon resonance, and production of Cl0. This work sheds light on the potential applications of noble metal nanoparticles in visible light-driven photocatalysis.
Keywords: Photocatalysis; Bi2MoO6; Phenol degradation; Surface plasmon resonance; Pd/PdCl2;

Contact angle goniometry on single micron-scale fibers for composites by Daniel Hansen; Niels Bomholt; Jonas Camillus Jeppesen; Adam Cohen Simonsen (181-188).
Display OmittedProbing the wetting properties of microfibers by polymer resins is of significant interest for the rational design of composite materials. Here, we demonstrate the measurement of contact angles on wetted micron scale fibers by imaging the fluid meniscus with telecentric optics at a spatial resolution of 4 μm followed by automated image analysis. The meniscus is described as a catenary in the zero gravity approximation and by fitting this to the measured profile, the contact angle is obtained at the intersection between the fluid and the fiber surface. The method is validated by measuring agreement between contact angles for the PMMA/H2O system for fibers with diameters 20–800 μm and for sessile drops. The ability of the method to discriminate contact angles for a series of commercial glass fibers against epoxy resin is successfully demonstrated. AFM imaging shows that the surface topography of the fibers does not have a simple relationship with the variation in contact angles. Contact angle goniometry by imaging of micron scale fibers appears as a viable alternative to Wilhelmy type measurements and the measurement principle could readily be extended to dynamic wetting experiments.
Keywords: Wetting; Fibers; Contact angle; Composites; Telecentric imaging;

Folate-targeted single-wall metal-organic nanotubes used as multifunctional drug carriers by Linyan Yang; Min Liu; Kebin Huang; Xia Ai; Cun Li; Jifei Ma; Tianming Jin; Xin Liu (189-195).
Display OmittedDoxorubicin (DOX) is a member of the anthracycline class of chemotherapeutic agents that are used for the treatment of many common human cancers. A self-assembled functionalized metal-organic nanotubes, SWMONTs could be loaded with the anticancer drug DOX. Via the modification of SWMONTs, DOX/SWMONTs-SiO2, DOX/SWMONTs-SiO2-NH2, DOX/SWMONTs-SiO2-NH2-FA samples could be obtained. The SEM characterization of the samples indicated that the particle size of DOX/SWMONTs-SiO2NH2 samples were smaller than 200 nm. Drug-release experiments implied that DOX from the DOX/SWMONTs-SiO2-NH2-FA samples could be released faster at acidic tumor tissue than at normal body fluid (pH7.4). DOX has strong cytotoxicity, and at 20 μg/mL dosage of DOX large amount of apoptotic cells could be seen. Cellular uptaking experiments were used to study the apoptotic mechanism, while for DOX/SWMONTs-SiO2-NH2-FA samples, the strong drug fluorescence was found in the cytoplasm rather than in the nucleus.
Keywords: SWMONTs; Drug delivery; Modification; Characterization;

ZnO microspheres-reduced graphene oxide nanocomposite for photocatalytic degradation of methylene blue dye by Jiaqian Qin; Xinyu Zhang; Chengwu Yang; Meng Cao; Mingzhen Ma; Riping Liu (196-203).
Display OmittedIn this work, ZnO microspheres-reduced graphene oxide (rGO) nanocomposites were synthesized via a simple solution method and used for the photodegradation of methylene blue (MB) dye from water under UV light. The SEM and TEM observations demonstrate that the microsphere morphologies of the ZnO microspheres-rGO nanocomposite is composed of ZnO microspheres anchored on rGO sheets, confirming the formation of ZnO microspheres-rGO composites. Raman spectra and X-ray photoelectron spectroscopy reveal that both of the reduction of GO tight contact between ZnO and rGO are achieved during the high temperature calcination process. During the photocatalytic test, in comparison with ZnO microspheres and P25 TiO2, the ZnO microspheres-rGO nanocomposite shows improved photodegradation of MB dye, because the rGO sheets could reduce the charge recombination in electron-transfer processes. According to the scavenger experiments, the possible MB degradation mechanism is contributed mainly to the generation of active species induced by the photogenerated holes (h+) and superoxide radicals (•O2 ).
Keywords: ZnO microspheres; Reduced graphene oxide; Nanocomposites; Photocatalyst;

The effect of different side chain groups of bisphosphonates (BPs) on the adsorption on the hydroxyapatite (HAP) is still a controversial issue. In this work, we studied the deposition and adsorption of a set of 26 BPs on the HAP (001) surface by using density functional theory (DFT) in which has been shown that the charge, the length or the presence of different functional groups at R2 side chain can modulate the adsorption energy of the BP. It was observed that negative charged groups at R2 enhanced the favourable electrostatic interactions between the BP and the HAP surface, but also that the length of R2 was important to enable the formation of the favorable electrostatic interactions between the functional group at R2 and the surface. A crossover study between the HAP/BP model (3D-QSAR/DFT) and the inhibition of the human farnesyl pyrophosphate synthase (FPPS) (3D-QSAR) pointed out that the electrostatic character of the R2 side chain provokes contrary effects in the inhibition of pathological crystallization and in the bone antiresorptive action of BPs.
Keywords: Hydroxyapatite; Inhibitors; Bisphosphonates; DFT; Deposition; Adsorption;

Nanoindentation of ultra-hard cBN films: A molecular dynamics study by Cheng Huang; Xianghe Peng; Tao Fu; Yinbo Zhao; Chao Feng; Zijun Lin; Qibin Li (215-224).
Display OmittedCubic Boron nitride (cBN) exhibits excellent mechanical properties including high strength, hardness and thermal resistance, etc. We optimized the parameters in the Tersoff interatomic potential for cBN based on its cohesive energy, lattice parameter, elastic constants, surface energy and stacking fault energy. We performed with molecular dynamics (MD) simulations the nanoindentation on the (001) and (111) surface of monocrystalline cBN thin films to study the deformation mechanisms and the effects of temperature and substrate orientation. It was found that during the indentation plastic deformation is mainly stress-induced slips of dislocations along {111}<110> orientations. It was also found that the hardness of cBN depends strongly on temperature, and the capability of plastic deformation is enhanced with the increase of temperature.
Keywords: cBN film; Tersoff potential; MD simulation; Nanoindentation; Temperature;

Density functional studies on the adsorption behavior of nitrous oxide (N2O) onto intrinsic carbon nanotube (CNT) and Pd-doped (5,5) single-walled carbon nanotube (Pd-CNT) have been reported. Introduction of Pd dopant facilitates in adsorption of N2O on the otherwise inert nanotube as observed from the adsorption energies and global reactivity descriptor values. Among three adsorption features of N2O onto CNT, the horizontal adsorption with Eads  = −0.16 eV exhibits higher adsorption energy. On the other hand the Pd-CNT exhibit strong affinity toward gas molecule and would cause a huge increase in N2O adsorption energies. Chemical and electronic properties of CNT and Pd-CNT in the absence and presence of N2O were investigated. Adsorption of N2O gas molecule would affect the electronic conductance of Pd-CNT that can serve as a signal of gas sensors and the increased energy gaps demonstrate the formation of more stable systems. The atoms in molecules (AIM) theory and the natural bond orbital (NBO) calculations were performed to get more details about the nature and charge transfers in intermolecular interactions within adsorption process. As a final point, the density of states (DOSs) calculations was achieved to confirm previous results. According to our results, intrinsic CNT cannot act as a suitable adsorbent while Pd-CNT can be introduced as novel detectable complex for designing high sensitive, fast response and high efficient carbon nanotube based gas sensor to detect N2O gas as an air pollutant. Our results could provide helpful information for the design and fabrication of the N2O sensors.
Keywords: Greenhouse gas; SWCNT; Adsorption; AIM and NBO; Chemical properties;

Interfacial engineering of two-dimensional nano-structured materials by atomic layer deposition by Serge Zhuiykov; Toshikazu Kawaguchi; Zhenyin Hai; Mohammad Karbalaei Akbari; Philippe M. Heynderickx (231-243).
Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise nanometer-thin two-dimensional (2D) nanostructures. It is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. ALD is especially advantageous when the film quality or thickness is critical, offering ultra-high aspect ratios. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even over a very large and complex areas. Digital control extends to sandwiches, hetero-structures, nano-laminates, metal oxides, graded index layers and doping, and it is perfect for conformal coating and challenging 2D electrodes for various functional devices. The technique’s capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO3) over the large area of standard 4” Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.
Keywords: Atomic layer deposition (ALD); Two-dimensional nano-materials; Nano-architecture;

Graphene-based materials via benzidine-assisted exfoliation and reduction of graphite oxide and their electrochemical properties by E.C. Vermisoglou; T. Giannakopoulou; G. Romanos; N. Boukos; V. Psycharis; C. Lei; C. Lekakou; D. Petridis; C. Trapalis (244-255).
Display OmittedBenzidine, a compound bearing aromatic rings and terminal amino groups, was employed for the intercalation and simultaneous reduction of graphite oxide (GO). The aromatic diamine can be intercalated into GO as follows: (1) by grafting with the epoxy groups of GO, (2) by hydrogen bonding with the oxygen containing groups of GO. Stacking between benzidine aromatic rings and unoxidized domains of GO may occur through π-π interaction. The role of benzidine is influenced by pH conditions and the weight ratio GO/benzidine. Two weight ratios were tested i.e. 1:2 and 1:3. Under strong alkaline conditions through K2CO3 addition (pH ∼10.4–10.6) both intercalation and reduction of GO via amino groups occur, while under strong acidic conditions through HCl addition (pH ∼1.4–2.2) π-π stacking is preferred. When no base or acid is added (pH ∼5.2) and the weight ratio is 1:2, there are indications that reduction and π-π stacking occur, while at a GO/benzidine weight ratio 1:3 intercalation via amino groups and reduction seem to dominate. The aforementioned remarks render benzidine a multifunctional tool towards production of reduced graphene oxide. The effect of pH conditions and the GO/benzidine weight ratio on the quality and the electrochemical properties of the produced graphene-based materials were investigated. Cyclic voltammetry measurements using three-electrode cell and KCl aqueous solution as an electrolyte gave specific capacitance values up to ∼178 F/g. When electric double-layer capacitors (EDLC) were fabricated from these materials, the maximum capacitance in organic electrolyte i.e., tetraethyl ammonium tetrafluoroborate (TEABF4) in polycarbonate (PC) was ∼29 F/g.
Keywords: Benzidine; Reduced graphene oxide; Pillaring; Intercalation; Graphene; Electrochemical properties;

The relation between photoluminescence properties and gas pressure with [0001] InGaN single quantum well systems by Toshiaki Tsutsumi; Giovanni Alfieri; Yoichi Kawakami; Ruggero Micheletto (256-259).
We show for the first time that photoluminescence of InGaN single quantum wells (SQW) devices is related to the gas pressure in which the sample is immersed, also we give a model of the phenomena to suggest a possible cause. Our model shows a direct relation between experimental behavior and molecular coverage dynamics. This strongly suggests that the driving force of photoluminescence decrease is oxygen covering the surface of the device with a time dynamics that depends on the gas pressure. This aims to contribute to the understanding of the physical mechanism of the so-called optical memory effect and blinking phenomenon observed in these devices.
Keywords: Science; Publication; Complicated;

Thermally stable hydrophobicity in electrospun silica/polydimethylsiloxane hybrid fibers by Zhonglin Wei; Jianjun Li; Chao Wang; Jungang Cao; Yongtao Yao; Haibao Lu; Yibin Li; Xiaodong He (260-267).
Display OmittedSilica/polydimethylsiloxane hybrid fibers exhibit thermally stable Hydrophobicity.In order to improve practical performances of silica-based inorganic/organic hybrid fibers, silica/polydimethylsiloxane hydrophobic fibers were successfully prepared by electrospinning. Silica sol and polydimethylsiloxane can be mixed homogeneously and become stable precursor solution in dichloromethane, which allows the transformation of silica/polydimethylsiloxane precursor solution into ultrafine fibers. Flame can ignite organic groups in polydimethylsiloxane directly and destroy the hydrophobicity of hybrid fibers, but hydrophobic feature may survive if electrospun hybrid membrane is combined with thin stainless-steel-304 gauze of 150 meshes due to its thermally stable hydrophobicity (>600 °C).
Keywords: Silica; Hybrid fiber; Thermally stable; Hydrophobicity;

Facile synthesis and enhanced magnetic, photocatalytic properties of one-dimensional Ag@Fe3O4-TiO2 by Xiaohua Jia; Rongrong Dai; Dandan Lian; Song Han; Xiangyang Wu; Haojie Song (268-276).
Fe3O4-TiO2 heterostructures were synthesized through co-precipitation method based on TiO2 nanobelts. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometry (VSM) were used to characterize the heterostructure nanocomposites. The results of XRD proved that the TiO2 nanobelt was anatase which was the most suitable crystal form for photocatalysis. SEM and TEM analysis indicated that Fe3O4 nanoparticles were adhere to TiO2 nanobelts which have one-dimensional structure with 100–200 nm in width. The VSM measurements showed that the photocatalyst can be easily recovered by an extemal magnetic field. X-ray photoelectron spectroscopy (XPS) of Ag@Fe3O4-TiO2 nanocomposites studies confirm that Ag is in Ag0 state. Finally, the photodegradation of rhodamine B (RhB) by the obtained magnetic photocatalyst was investigated via UV–vis absorption spectra. The photocatalytic activity of the composites was observed to be lower compared to bare TiO2 due to the higher degree of recombination reactions after combined with Fe3O4 nanoparticles. After coated the composite of 15% Fe3O4-TiO2 with Ag, the new nanocomposite of Ag@Fe3O4-TiO2 can be easily recovered after photocatalysis by an extemal magnetic field and showed enhanced photocatalytic activity. The mechanisms for the exhibited enhanced photocatalytic effect of Ag nanoparticle decorated Fe3O4-TiO2 nanocomposites with surface heterostructures are discussed.
Keywords: Ag@Fe3O4-TiO2 nanocomposites; Co-precipitation method; Magnetic properties; Photocatalysis;

Magnetic properties of the 2D Fen core Xm (X = C, N, O, Cl, S and F) shell clusters embedded in graphene by Ming-Yu Zhao; Ru-Meng Zhao; Wei Li; Ya-Qiang Ma; Tian-Xing Wang; Xian-Qi Dai (277-285).
Schematic representations of the electronic structure of (a)Fe/C4, (b)Fe2/C4, (c)Fe3/C6, (d)Fe/F4, (e)Fe2/F4 and (f)Fe3/F6 core/shell clusters systems are shown.Display OmittedUtilizing first-principle calculations, the structural, electronic and magnetic properties of monolayer graphene embedded with Fen/Xm (X = C, N, O, Cl, S and F) core/shell clusters are investigated, where n = 1, 2, 3 and m = 4, 6, respectively. We find that the graphene embedding with the Fen/Xm core/shell clusters are magnetic except the Fe/S4, Fe2/C4 and Fe3/Cl6 core/shell clusters. The graphene embedding with the Fe3/F6 core/shell cluster has the largest magnetic moment in these systems. Magnetism for Fen/Xm core/shell clusters embedded in monolayer graphene can be ascribed to the ferromagnetic coupling between the Fe atoms. Our calculations demonstrate that Fe atoms are successfully isolated at various C, N, O, Cl, S and F shells in graphene to preserve the high-spin state. On the other hand, the high-spin state is also effectively controlled by the amount of Fe atoms. The electron spin can be stored in magnetic thin film, lithographically prepared quantum dots, and electromagnetic traps. The Fen/Xm core/shell clusters embedded in graphene can be considered to have potential applications in nanoelectronics, spintronics and magnetic storage devices.
Keywords: Magnetic property; Graphene; Core/shell;

Durability of different superhydrophobic surfaces.Display OmittedVarious surface modification technologies have been used to develop superhydrophobic surface, however their durability has been recognized as the major obstacle for the real applications. Here a quantitative investigation was conducted to evaluate the effects of different surface modification methods on the surfaces’ mechanical durability. The superhydrophobic surfaces were prepared by the combination of two surface roughing methods (etching and sandblasting) with chemical modifications with four low surface energy materials: silica sol (SS), octadecanoic acid (OA), heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane (HDFS) and hexadecyltriethoxysilane (HTS). XPS was used to analyze the elements composition and AFM was used to measure the roughness of the surfaces. The durability of these surfaces was tested by a sandpaper abrasion experiment. The collective results showed that the low surface energy materials had significant effects on the surface roughness, which would then play an important role in the durability of these rough surfaces. The SS modified rough surfaces possessed higher roughness and better durability than the surfaces modified by other three low surface energy materials. SS modified rough surfaces could bear 60 cycles of abrasion with 10 g weights on 1500 CW sandpaper.
Keywords: Superhydrophobic; Surface roughness; Low surface energy material; Durability; Abrasion; Sandblast;

Low-crystallinity molybdenum sulfide nanosheets assembled on carbon nanotubes for long-life lithium storage: Unusual electrochemical behaviors and ascending capacities by Xiaodan Li; Gaoxiang Wu; Jiewei Chen; Meicheng Li; Wei Li; Tianyue Wang; Bing Jiang; Yue He; Liqiang Mai (297-304).
Low-crystallinity molybdenum sulfide (LCMS, Mo:S = 1:2.75) nanosheets synthesized by a facile and low temperature solvothermal method is now reported. The as-prepared LCMS anode material is composited of MoS2 layers mixed with amorphous MoS3, which leads to an unusual electrochemical process for lithium storage compared to typical MoS2 anode. The existence of MoS3 and Mo (VI) provide strong adsorption and binding sites for polar polysulphides, which compels abundant sulfur to turn into new-formed MoS3 rather than diffuse into electrolyte. To fully utilize this novel electrochemical process, LCMS is decorated on carbon nanotubes, obtaining well-dispersed CNTs@LCMS. As electrode material for lithium storage, CNTs@LCMS exhibits a noticable ascending trend in capacity from 820 mA h g−1 to 1350 mA h g−1 at 100 mA g−1 during 130 cycles. The persistent ascending capacity is ascribed to the increasing lithium storage caused by new-formed MoS3, combined with the reduced volume change benifiting from well-dispersed CNTs@LCMS. Furthermore, the ascending performance is proved to be able to effectively extend the circulation life (up to 200%) for lithium-ion batteries by mathematical modeling and calculation. Accordingly, the CNTs@LCMS composite is a promising anode material for long-life lithium-ion batteries.
Keywords: Low-crystallinity molybdenum sulfide; Nanosheets; Long-life; Lithium-ion batteries;

The aerospace bearings steel CSS-42L was ion implanted by carbon with implantation fluxes of 5 × 1016 ions cm−2. The composition, microstructure and hardness of the carbon implanted samples were characterized using X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction, and nanoindentation tests. The corrosion and tribological properties were also evaluated in the present work. The results shown that carbon implantation produced an amorphous layer and graphitic bounds formed at the near surface of CSS-42L steel. In the electrochemical test, the carbon implanted samples suggested lower current densities and corrosion rates. Carbon ion implanted samples shown a relative Cr-enrichment at the surface as compared with nonimplanted samples. The improved corrosion resistance is believed to be related to the formed amorphous layer, the enhancement of Cr diffusion in the carbon implantation layer which contributed the formation of passive film on the surface, the decrease of free electrons which caused by the increase of carbon fraction. The external hard layer had positive effect on the wear resistance, reducing strongly the friction coefficient about 30% and the abrasive-adhesive mechanism present in the unimplanted samples was not modified by the implantation process.
Keywords: CSS-42L bearing steel; Ion implantation; Electrochemical test; Friction;

Facile one-pot fabrication of nano-Fe3O4/carboxyl-functionalized baker’s yeast composites and their application in methylene blue dye adsorption by Zongjun Du; Yue Zhang; Zhengjie Li; Hui Chen; Ying Wang; Guangtu Wang; Ping Zou; Huaping Chen; Yunsong Zhang (312-320).
Nano-Fe3O4/carboxyl-functionalized baker’s yeast composites (NF/CF-BYs) were prepared for the first time based on the ultrasonic cavitation assisted oxygen implosion method using single Fe2+ as iron source. The series of characterization analysis results showed that the obtained NF/CF-BYs had not only the superparamagnetic properties of nano-Fe3O4, but their surface also had plenty of functional groups (especially carboxyl groups) introduced by strong oxidization. The adsorption properties of NF/CF-BYs for methylene blue (MB) were also evaluated. The results displayed that the uptakes of NF/CF-BYs for MB were higher than that of pristine baker’s yeast (P-BYs), and the adsorption process was followed by the pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of NF/CF-BYs for MB was estimated to be 141.75 mg g−1 at pH 6. The regeneration efficiency of the obtained NF/CF-BYs was attained to be more than 90%.
Keywords: Ultrasonic cavitation; Nano-Fe3O4; Baker’s yeast; Adsorption; Methylene blue;

Electrically responsive microreservoires for controllable delivery of dexamethasone in bone tissue engineering by Irina Alexandra Paun; Marian Zamfirescu; Catalin Romeo Luculescu; Adriana Maria Acasandrei; Cosmin Catalin Mustaciosu; Mona Mihailescu; Maria Dinescu (321-331).
Display OmittedA major concern in orthopedic implants is to decrease the chronic inflammation using specific drug therapies. The newest strategies rely on the controlled delivery of antiinflammatory drugs from carrier biointerfaces designed in the shape of 3D architectures. We report on electrically responsive microreservoires (ERRs) acting as microcontainers for antiinflammatory drugs, as potential biointerfaces in orthopedic implants. The ERRs consist in arrays of vertical microtubes produced by laser direct writing using two photon polymerization effects (2PP_LDW) of a commercially available photoresist, IP-L780. A polypyrrole (conductive)/dexamethasone (drug model) (PPy/Dex) mixture was loaded into the ERRs via a simple immersion process. Then, the ERRs were sealed with a poly(lactic-co-glycolic acid)(PLGA) layer by Matrix Assisted Pulsed Laser Evaporation. ERRs stimulation using voltage cycles between −1 V and +1 V, applied at specific time intervals, at a scan rate of 0.1 V s−1, enabled to control the Dex release. The release time scales were between 150 and 275 h, while the concentrations of Dex released were between 450–460 nM after three applied voltage cycles, for different microreservoires dimensions. The proposed approach was validated in osteoblast-like MG-63 cell cultures. Cell viability and adhesion assays showed that the Dex-loaded ERRs sustained the cells growth and preserved their characteristic polygonal shape. Importantly, for the electrically-stimulated Dex release, the level of the alkaline phosphatase activity increased twice, the osteogenic differentiation surpassed by 1.6 times and the relative level of osteocalcin gene expression was 2.2 times higher as compared with the unstimulated drug release. Overall, the ERRs were able to accelerate the cells osteogenic differentiation via electrically controlled release of Dex.
Keywords: Polymer; Two photon polymerization; MAPLE; Osteoblasts; Drug delivery;

The graphic abstract describes the research that we used modified activated carbons impregnated with iron nitrate, copper nitrate and aluminium nitrate to adsorb ceftazidime from aqueous solution. The surface functional groups of the modified activated carbons were different, and thus resulted in the big difference in the adsorption performance of the modified activated carbons. The theory and the experiments both showed the preferable adsorption of ceftazidime could be achieved on modified activated carbons.Display OmittedIn this paper, three impregnated activated carbon IAC (AC-Cu, AC-Fe, and AC-Al) promoted by Iron, Copper and Aluminum were used for adsorption of ceftazidime. Iron(III), Copper(II) and Aluminum(III) nitrate were used as an impregnant. The IACs were characterized by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) surface area analyzer, Fourier transform infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS).The influence of factors, such as ion strength, pH, temperature, initial concentration, and concentration of natural organic matter organic matter on the adsorption process were studied. The adsorption kinetics and isotherms of ceftazidime were studied for the three IACs. The results showed that the adsorption was accurately represented by pseudo-second order model. Under different temperature, the maximum adsorption quantity of ceftazidime on AC-Cu calculated by pseudo-second order kinetic model were 200.0 mg g−1 (298 K), 196.1 mg g−1 (303 K) and 185.2 mg g−1 (308 K). It was much higher than that of AC-Fe and AC-Al. And the process was controlled by both film diffusion and intra particle mass transport. The results also showed that, the Freundlich and Temkin isotherm fit the adsorption well.
Keywords: Adsorption; Activated Carbon; Impregnation; Ceftazidime; Kinetics;

Utilization of carboxylic functional groups generated during purification of carbon nanotube fiber for its strength improvement by Yong-O Im; Sung-Hyun Lee; Teawon Kim; Junbeom Park; Jaegeun Lee; Kun-Hong Lee (342-349).
One of the most promising method to produce carbon nanotube (CNT) fiber is directly spinning CNT fiber from CNT aerogel. Despite the advantage of this method in terms of productivity, the CNTs thus produced include impurities such as amorphous carbon and residual catalysts. To remove these unwanted materials, the CNT fiber is usually subjected to acid treatment. At the same time, however, the acid treatment damages the CNT wall, creating functional groups on it. In this work, specific tensile strength of CNT fibers was increased by introducing cross-links between the individual CNTs using carboxylic functional groups which were inevitably generated during the acid treatment of CNT fibers. The esterification of the carboxylic acid with 1,5-pentanediol as a linker resulted in cross-links in between the CNTs, thereby increasing the specific strength of the CNT fiber from 0.43 to 1.12 N/tex and Young’s modulus from 30.70 to 47.57 N/tex. Supporting weak shear interactions of untreated CNT fiber by adding covalent bonding through the cross-linking reaction led to the improvement of mechanical properties of the CNT fiber. Elimination of impurities and narrowed interspacing between CNT bundles caused by acid treatment was also confirmed, which additionally contributed to enhancing the mechanical properties of CNT fiber.

Display OmittedThe separation and aggregation of Si atoms around TaN grains during deposition of Ta–Si–N nanocomposite films were studied, and the adsorption energies, charge transfer and atomic partial density of state of Si–2N2Ta islands on the TaN (001) surface and diffusion energy of the islands during their evolution were evaluated using the first-principles method based on density functional theory (DFT). In the lowest total energy stable configuration, N and Ta atoms tended to combine to form 2N2Ta islands, whereas Si atoms tended to stay at a position diagonal to the Ta atom outside of the island. Si atoms entered the position of the missing N atom of the TaN island and formed a substitute solid solution during Ta–Si–N growth. The Si atoms of the solid solution in the island could be easily extruded by Ta- or N-rich island during the deposition process. The process of Si atom extrusion by a N atom which was the configuration of N–by–2Ta1N1Si island evolved into Si–by–2N2Ta island in rich N-atom. The process of Si atom was extruded by the Ta atom which was the configuration of Ta–by–2N1Ta1Si island evolved into Si–of–2Ta2N island, that reduced the total energy of island. The diffusion energies of these evolutions were 0.974 and 1.712 eV, respectively. The Si atoms and TaN grain phase tended to separate during the deposition process. Si atoms could give way to Ta and N atoms during the Ta–Si–N nanocomposite film deposition process.
Keywords: Si–2N2Ta Island; Charge transfer; Adsorption and diffusion; Density functional calculation;

X-ray diffraction analysis, X-ray photoelectron spectroscopy, and Electron Auger-spectroscopy investigation of phase transformation on the surface of the VT8 titanium alloy after a low temperature hydrogen-free nitriding in a glow discharge.Operational characteristics of titanium alloys defined physical-mechanical characteristics of the surface and their phase composition, which depend on the process parameters of nitriding. Surface modification of titanium alloys were carried out by low-temperature nitriding in a glow discharge in hydrogen-free environment. The main advantage of this method lies in the absence of hydrogen embrittlement and complete environmental safety process. Application of the glow discharge can not only speed up the process by the order of the diffusion surface saturation with nitrogen, but also significantly alters the kinetics of the process and quality of the nitrided layer, in particular its physio-mechanical properties and phase composition. For research purposes, the standards from an α + β alloy Ti-Al6-Cr2-Mo2,5 (VT8) were used.Research into the phase composition was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Stratified analysis by AES was conducted by etching the surface of the samples’ argon ion beam with diameters of 1.5 mm with an energy of 3000 eV and a current density of 400 mA/cm2 . The above material shows the promise of the technology of low-temperature hydrogen-nitriding by glow discharge. This greatly expands the range of practical applications of titanium alloys. In addition, changing the technological mode allows you to manage a wide range of modified phase composition of the surface layer and as a result – to form the surface of titanium parts, taking into account the conditions of the subsequent operation.
Keywords: Titanic alloy; Nitriding in glow discharge; Layer formation; XPS; AES;

Hydrogen adsorption and storage on Palladium – functionalized graphene with NH-dopant: A first principles calculation by Omar Faye; Jerzy A Szpunar; Barbara Szpunar; Aboubaker Chedikh Beye (362-374).
Display OmittedWe conducted a detailed theoretical investigation of the structural and electronic properties of single and double sided Pd-functionalized graphene and NH-doped Pd-functionalized graphene, which are shown to be efficient materials for hydrogen storage. Nitrene radical dopant was an effective addition required for enhancing the Pd binding on the graphene sheet as well as the storage of hydrogen. We found that up to eight H2 molecules could be adsorbed by double-sided Pd-functionalized graphene at 0 K with an average binding energy in the range 1.315–0.567 eVA gravimetric hydrogen density of 3.622 wt% was reached in the Pd-functionalized graphene on both sides. The binding mechanism of H2 molecules came not only the polarization mechanism between Pd and H atoms but also from the binding of the Pd atoms on the graphene sheet and the orbital hybridization. The most crucial part of our work is measuring the effect of nitrene radical on the H2 adsorption on Pd-functionalized graphene. Our calculations predicted that the addition of NH radicals on Pd-functionalized graphene enhance the binding of H2 molecules, which helps also to avoid the desorption of Pd(H2)n (n = 1–5) complexes from graphene sheet. Our results also predict Pd-functionalized NH-doped graphene is a potential hydrogen storage medium for on-board applications.
Keywords: DFT; H2; Pd-functionalized grapheme; Hydrogen storage capacity; Single and double side; NH radical;

Ultrasonic effect on etching tunnel morphology and distribution of aluminum foil by Bin Hu; Yanzi Sun; Bing Guan; Jing Zhao; Huaihao Zhang; Deqiu Zhu; Kunsong Ma; Changjing Cheng (375-383).
Etching aluminum foil was prepared by electrochemical DC etching under ultrasonic superimposition. Specifically, the relationship of electrochemical behavior, interface behavior and mass transfer enhancement from ultrasound was investigated intensively by chronopotentiometry, potentiodynamic polarization, cyclic voltammetry and electrochemical impedance spectra. Meanwhile, the etching specimens were characterized by SEM, N2 adsorption and XRD patterns measurements. The results showed that ultrasonic agitation inhibited the growth of aluminum oxide film and facilitated pit initiation effectively via increasing the Cl adsorption on electrolyte/aluminum oxide film interface, and strengthened the inward/outward migration of Cl and AlCl3 within tunnels by thinning the thickness of diffusion layer and decreasing the electrolyte resistance. Moreover, the double layer capacitance C dl, pit density, average pit size/tunnel length and its homogeneity are all enhanced under ultrasonic superimposition.
Keywords: Aluminum foil; Etching; Ultrasound; Mass transfer; Capacitance;

The nano size pores (∼10 nm) created in the microporous mordenite zeolite facilitated enhanced catalytic activity to produce as high as 97 wt.% yield of di-phenyl methane in the benzylation of benzene with benzyl alcohol at solvent-free liquid phase reaction conditions.Display OmittedZeolite mordenite has been treated with nitric acid at different severities so as to facilitate the framework dealumination and optimization of the textural properties such as acidity and porosity. The samples obtained have been characterized by X-ray diffraction, FTIR, SEM, TEM, surface area, porosity by N2 adsorption and ammonia TPD. The resultant samples have been evaluated towards the bulky alkylation reaction of benzylation of benzene with benzyl alcohol. The studies indicated the improvement in the textural properties such as surface area, pore volume and acidity of the samples after the acid treatment. While, the phenomenon of enhancement in properties was exhibited by all the acid treated mordenite samples, the highest improvement in properties was observed at a particular condition of acid treatment (SM-2 sample). This particular sample also exhibited highest acidity and the presence of ∼10 nm size pores that resulted in the effective catalytic activity towards the bulky alkylation reaction of benzene with benzyl alcohol to produce high yields of di-phenyl methane.
Keywords: Mordenite; Mesopores; Acidity; Benzylation; Di-phenyl methane;

Synthesis and application of iron and zinc doped biochar for removal of p-nitrophenol in wastewater and assessment of the influence of co-existed Pb(II) by Pei Wang; Lin Tang; Xue Wei; Guangming Zeng; Yaoyu Zhou; Yaocheng Deng; Jingjing Wang; Zhihong Xie; Wei Fang (391-401).
Display OmittedThe modification of biochar as a low-cost adsorbent is essential to improve its surface properties and shows great potential in water decontamination. The iron and zinc doped sawdust biochar (Fe/Zn-biochar) with large apparent surface area (518.54 m2/g) proposed in this work showed good performance for p-nitrophenol (PNP) removal compared with the pristine biochar (P-biochar), iron doped biochar (Fe-biochar) and zinc doped biochar (Zn-biochar) respectively. The batch experiments turned out that Fe/Zn-biochar exhibited larger PNP adsorption capacity under acidic pH solution, and the ionic strength had slightly negative impact on PNP adsorption. The adsorption kinetics and isotherms were discussed, and the experimental data fitted well the Pseudo-second-order equation and Langmuir model. The thermodynamic study indicated that the PNP adsorption was a spontaneous endothermic process. Furthermore, the simultaneous removal for PNP and Pb(II) by Fe/Zn-biochar was investigated. It implied that the adsorption of PNP and Pb(II) at their low concentration might be enhanced by the complexing-bridging mechanism of PNP and Pb(II) ascribing to the affinity between PNP and hydrophobic sites, in addition to the affinity between Pb(II) and oxygen-containing hydrophilic sites on Fe/Zn-biochar surface. However, the predominated competition between PNP and Pb(II) at their high concentrations with Fe/Zn-biochar suppressed their adsorption.
Keywords: Iron and zinc doped biochar; p-Nitrophenol; Pb(II); Adsorption; Complexing-bridging;

Macroscale cobalt-MOFs derived metallic Co nanoparticles embedded in N-doped porous carbon layers as efficient oxygen electrocatalysts by Hai-Sheng Lu; Haimin Zhang; Rongrong Liu; Xian Zhang; Huijun Zhao; Guozhong Wang (402-409).
Display OmittedMetal-organic frameworks (MOFs) materials have aroused great research interest in different areas owing to their unique properties, such as high surface area, various composition, well-organized framework and controllable porous structure. Controllable fabrication of MOFs materials at macro-scale may be more promising for their large-scale practical applications. Here we report the synthesis of macro-scale Co-MOFs crystals using 1,3,5-benzenetricarboxylic acid (H3BTC) linker in the presence of Co2+, triethylamine (TEA) and nonanoic acid by a facile solvothermal reaction. Further, the as-fabricated Co-MOFs as precursor was pyrolytically treated at different temperatures in N2 atmosphere to obtain metallic Co nanoparticles embedded in N-doped porous carbon layers (denoted as Co@NPC). The results demonstrate that the Co-MOFs derived sample obtained at 900 °C (Co@NPC-900) shows a porous structure (including micropore and mesopore) with a surface area of 110.8 m2  g−1 and an N doping level of 1.62 at.% resulted from TEA in the pyrolysis process. As electrocatalyst, the Co@NPC-900 exhibits bifunctional electrocatalytic activities toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media which are key reactions in some renewable energy technologies such as fuel cells and rechargeable metal-air batteries. The results indicate that the Co@NPC-900 can afford an onset potential of 1.50 V (vs. RHE) and a potential value of 1.61 V (vs. RHE) at a current density of 10 mA cm−2 for ORR and OER with high applicable stability, respectively. The efficient catalytic activity of Co@NPC-900 as bifunctional oxygen electrocatalyst can be ascribed to N doping and embedded metallic Co nanoparticles in carbon structure providing catalytic active sites and porous structure favourable for electrocatalysis-related mass transport.
Keywords: Co-MOFs; Co@N-doped porous carbon; Bifunctional oxygen electrocatalyst; Oxygen reduction reaction; Oxygen evolution reaction;

Analysis of the dynamics of reactions of SiCl2 at Si(100) surfaces by Keisuke Anzai; Nílson Kunioshi; Akio Fuwa (410-417).
The dynamics of reactions of SiCl2 at Si(100) surfaces was investigated through the molecular orbital method at the B3LYP/6-31G(d,p) level of theory, with the surface being modeled using clusters of silicon atoms. The intradimer adsorption of a SiCl2 molecule proceeded with no energy barrier, and in the structure of the product of the adsorption reaction the Si atom of the SiCl2 adsorbate formed a triangular structure with the two Si atoms of the surface dimer, in agreement with theoretical predictions published recently in the literature for a small cluster. However, the dynamics reported in this work indicates that SiCl2 undergoes molecular adsorption at the silicon surface, in contrast with the dissociative adsorption suggested by some available kinetic models. Intradimer adsorption of a second SiCl2 molecule, and interdimer adsorptions of a first, a second, and a third SiCl2 molecule were also seen to proceed without significant energy barriers, suggesting that the formation of the first additional layer of silicon atoms on the surface would be fast if the adsorption of SiCl2 were the only type of reaction proceeding in the system. The diffusion of the SiCl2 adsorbate over the surface and its desorption from the surface were found to have comparable activation energies, so that these reactions are expected to compete at high temperatures.
Keywords: Silicon surface growth; Cluster model; Reaction dynamics; Molecular orbital method;

Photochemical and photocatalytic evaluation of 1D titanate/TiO2 based nanomaterials by D.S. Conceição; D.P. Ferreira; C.A.L. Graça; M.F. Júlio; L.M. Ilharco; A.C. Velosa; P.F. Santos; L.F. Vieira Ferreira (418-429).
Display OmittedOne-dimensional (1D) titanate based nanomaterials were synthesized following an alkaline hydrothermal approach of commercial TiO2 nanopowder. The morphological features of all materials were monitored by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also Brunauer-Emmett-Teller (BET) technique. In addition the photochemical behaviour of these nanostructured materials were evaluated with the use of laser induced luminescence (LIL), ground-state diffuse reflectance (GSDR), and laser-flash photolysis in diffuse reflectance mode (DRLFP). The mixed titanate/TiO2 nanowires presented the least intense fluorescence spectra, suggesting the presence of surficial defects that can extend the lifetime of the excited charge carriers. A fluorescent ‘rhodamine-like’ dye was adsorbed onto different materials and examined via photoexcitation in the visible range to study the self-photosensitization mechanism. The presence of the radical cation of the dye and the degradation kinetics, when compared with a neutral substrate—cellulose, provided significant evidences regarding the photoactivity of the different materials. Regarding all the materials under study, the nanowires exhibited a strong photocatalytic efficiency, for the adsorbed fluorescent probe. The photocatalytic mechanism was also considered by studying the photodegradation capability of the titanate based materials in the presence of an herbicide, Amicarbazone, after ultraviolet (UVA) photoexcitation.
Keywords: Titanate/titania composite; Hydrothermal treatment; Alkaline medium; 1D nanostructures; Fluorescent dye; Amicarbazone; Photocatalysis;

Metastability of a-SiOx:H thin films for c-Si surface passivation by L. Serenelli; L. Martini; L. Imbimbo; R. Asquini; F. Menchini; M. Izzi; M. Tucci (430-440).
Display OmittedThe adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Si―H and Si―O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300 °C for 30 min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution of hydrogen in the film revealed by FTIR spectra, and we developed a model for the effect of both treatments on the Si―H bonding and the metastability shown in the lifetime of a-SiOx:H/c-Si/a-SiOx:H structure. We found that, after UV exposure, thermal annealing steps can be used as a tool for the c-Si passivation recovery and enhancement.
Keywords: a-SiOx; PECVD; Passivation; Metastability; Thermal annealing; FTIR;

Nicotinic acid as a new co-adsorbent in dye-sensitized solar cells by Phuong Tuyet Nguyen; Vinh Son Nguyen; Thu Anh Pham Phan; Tan Nhut Van Le; Duyen My Le; Duy Dang Le; Vy Anh Tran; Tuan Van Huynh; Torben Lund (441-447).
Display OmittedWith the aim of introduction a new inexpensive co-adsorbent to improve solar cell performance, the influence of nicotinic acid (NTA) used as a co-adsorbent in dye-sensitized solar cells (DSCs) was investigated. The findings showed that low concentrations of NTA (<10 mM) increased the N719 ruthenium dye loading on the TiO2 electrode surface by 10–12%, whereas higher concentrations of NTA lowered the dye loading. The adsorption of NTA onto the TiO2 electrode surface was studied by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and the blocking effect of NTA toward electron transfer between the electrode and 1,4-dicyanonaphthalene (redox couple electrolyte probe) was investigated by cyclic voltammetry. Subsequently, the performance of NTA in functional DSCs was evaluated by current–voltage (J–V) DSC characterization and compared with that of DSCs fabricated with two well-established co-adsorbents i.e., chenodeoxycholic acid (CDA) and octadecylphosphonic acid (OPA). The findings showed that under optimized co-adsorbent concentration (1 mM NTA, 0.03 mM CDA, 0.015 mM OPA), the efficiency of the corresponding solar cells increased to the same extent. Specifically, the use of NTA at optimum concentration improved the efficiency of the resulting DSC from 3.14 to 5.02%.
Keywords: Dye-sensitized solar cell; Co-adsorbent; Nicotinic acid; N719;

Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel by Hae Ri Lee; Hyo Ree Seo; Boeun Lee; Byung Won Cho; Kwan-Young Lee; Si Hyoung Oh (448-455).
Strategically-designed spinel-structured nano-scale surface layer, LiMxMnIV 1 − xO4, featuring a high Li+ ion conductivity and a good chemical stability was applied on Al-doped LiMn2O4 spinel for the drastic improvement of the electrochemical performance at the elevated temperature as a promising cathode material for lithium rechargeable batteries.Display OmittedLi-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO4 and LiMg0.5Mn1.5O4 layers on the surface of LiAl0.1Mn1.9O4. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.
Keywords: LiMn2O4; Spinel; Surface coating; X-Ray absorption spectroscopy; Oxidation state;

Display OmittedThe adsorption of nitrobenzene and 4-nitrostyrene on the Pt(111) and the Au(111) surfaces under the general reaction condition of nitroarene catalytic hydrogenation is investigated utilizing periodic density functional theory calculations with the Grimme’s empirical three-body dispersion correction to understand the influence of adsorption configurations on chemoselectivity of nitroarene compound hydrogenation. It is found that at the low coverage both nitrobenzene and 4-nitrostyrene tend to adsorb paralleling to the Pt(111) and the Au(111) surfaces. Based on the crystal orbital Hamilton population analysis, it is found that the chemical bonding between nitro group and Pt(111) surface is weak. The adsorption configurations of nitrobenzene and 4-nitrostyrene are determined by the chemisorption strength of phenyl group and vinyl group. Under the reaction condition, the 1/9 ML nitrobenzene and 4/9 ML hydrogen atom can be coadsorbed while the 1/6 ML 4-nitrostyrene and 1/3 ML hydrogen atom can be coadsorbed on Pt(111). With the increase of the coverage, nitrobenzene still remains its paralleled adsorption configuration while the adsorption configuration of 4-nitrostyrene is switched to the tilted adsorption configuration through vinyl group without the chemisorption of phenyl and nitro group on Pt(111). In addition, the competitive adsorption with hydrogen will not change the adsorption configuration of nitrobenzene and 4-nitrostyrene under the reaction condition. On Au(111), the physical adsorption strength determines the adsorption configuration. The paralleled adsorption with the shortest average distance between the adsorbate and Au(111) surface is preferred. At the paralleled adsorption configuration, the chemoselectivities of the hydrogenation on these functional groups are similar if only in terms of geometric configuration. However, the hydrogenation on nitro group encounters the problem of steric hindrance at the tilted adsorption configuration through vinyl group, which makes it unfavorable. Therefore, the catalysts which could form strong chemical bonding with nitro group, leading to the preferential vertical adsorption configuration via nitro group, are expected for the high selectivity towards nitro group hydrogenation.
Keywords: Adsorption; Pt; Au; Density functional theory; Hydrogenation of nitro compounds; Selectivity;

Preparation of Pt/TiO2 hollow nanofibers with highly visible light photocatalytic activity by Ziling Yang; Jing Lu; Weichun Ye; Chushu Yu; Yanlong Chang (472-480).
Display OmittedThe Pt-modified mixed phase TiO2 hollow nanofibers photocatalysts that exhibit enhanced visible light photocatalytic activity for Orange II degradation.The Pt/TiO2 hollow nanofibers (HNFs) as a photocatalyst have been successfully prepared by a uniaxial electrospinning method combined with photo-deposition. The as-synthesized photocatalysts were characterized by TEM, XRD, SAED, EDX, XPS, N2 adsorption-desorption, and UV–vis DRS. The TiO2 HNFs were composed of an anatase-rutile mixed phase, with the ratio of ∼70:30. The band gap of TiO2 HNFs decreased from 3.09 down to 2.77 eV with 2 wt.% Pt loading, this led to an enhanced photocatalytic performance under visible light. By evaluating the degradation of azo dye Orange II, the pseudo-first-rate constant (k) of Pt/350-TiO2 HNFs system was 0.0069 min−1, which was 11.5 and 3.63 times higher than for TiO2 HNFs and Pt/P25, respectively. The main factors affecting the photocatalytic activity were further investigated, these included the loading amount of Pt, the calcination temperature of TiO2 HNFs, the pH of initial solution and the light source. The results of repeated use of the Pt/TiO2 HNFs demonstrated that the photocatalysts exhibited an excellent stability even after ten cycles. The possible degradation mechanism was also studied. It was shown that •O2 radicals were the main reactive oxygen species for the degradation of Orange II.
Keywords: Electrospinning; TiO2 hollow nanofiber; Mixed phase; Orange II; Photocatalyst;

Fabrication and characterization of poly (bisphenol A borate) with high thermal stability by Shujuan Wang; Xiao Wang; Beibei Jia; Xinli Jing (481-491).
Display OmittedIn this work, poly (bisphenol A borate) (PBAB), which has excellent thermal resistance and a high char yield, was synthesized via a convenient A2  + B3 strategy by using bisphenol A (BPA) and boric acid (BA). The chemical reaction between BPA and BA and the chemical structure of PBAB were investigated. The results demonstrate that PBAB consists of aromatic, Ph–O–B and B–O–B structures, as well as a small number of boron hydroxyl groups and phenolic hydroxyl groups. The thermal properties of PBAB were studied by DMA and TGA. The results indicate that the glass transition temperature and char yield are gradually enhanced by increasing the boron content, where the char yield of PBAB at 800 °C in nitrogen (N2) reaches up to 71.3%. It is of particular importance that PBAB show excellent thermal resistance in N2 and air atmospheres. By analysing the pyrolysis of PBAB, the high char yield of PBAB can be attributed to the formation of boron oxide and boron carbide at high temperatures, which reduced the release of volatile carbon dioxide and improved the thermal stability of the carbonization products. This study provides a new perspective on the design of novel boron-containing polymers and possesses significant potential for the improvement of the comprehensive performance of thermosetting resins to broaden their applicability in the field of advanced composites.
Keywords: Poly (bisphenol A borate); Thermal stability; High char yield; Borates; Boron oxide;

Microcautery based on zinc metallic nanoparticles photodeposited on the core of an optical fiber by P. Zaca-Morán; C.F. Pastelín; C. Morán; G.F. Pérez-Sánchez; F. Chávez (492-497).
The experimental arrangement of a microcautery implemented by an optical fiber with zinc nanoparticles (ZnNPs) photodeposited on its core for the cauterization and coagulation in blood vessels hemostasis processes is presented. The interaction between a laser radiation source and the ZnNPS on the fiber core produces a controllable punctual heat source through the radiation intensity, which is capable of reaching a temperature up to 200 °C covering an area of approximately ten micrometers. By using three-to-four-month-old rats of CIIZ-V strain, we made several microcauterization experimental tests to stop blood flow. The findings show that the microcautery obliterates the smooth muscle of the blood vessels concatenating mutually to tissue in an average time of three seconds, at the same time, the blood elements responsible for the coagulation are thermally activated and thus the bleeding is stopped.
Keywords: Microcautery; Optical fiber; Laser; Metallic nanoparticles; Hemostasis; Blood vessels;

Inherent formation of porous p-type Si nanowires using palladium-assisted chemical etching by Jun-Ming Chen; Chia-Yuan Chen; C.P. Wong; Chia-Yun Chen (498-502).
Porous silicon (Si) nanowire arrays were directly fabricated from lightly p-doped Si substrates using a palladium (Pd)-assisted chemical etching at room temperature. The mechanistic studies indicated that anodic dissolution of Si was established by the accumulated positive charges at Pd/Si schottky interfaces in the presence of H2O2 oxidants. In addition to the primary etching direction vertically to the substrate planes, the additional sidewall etching was stimulated by the separated Pd nanoparticles during reaction that constitutes the porous features covering on the nanowires surfaces thoroughly. These combined effects lead to the distinct etching characteristics and remarkable photoluminescent properties of resulted nanostructures.
Keywords: Palladium nanoparticles; Etching; Band diagram; Porous silicon;

Controlled hydrodynamic conditions on the formation of iron oxide nanostructures synthesized by electrochemical anodization: Effect of the electrode rotation speed by Bianca Lucas-Granados; Rita Sánchez-Tovar; Ramón M. Fernández-Domene; Jose García-Antón (503-513).
Display OmittedIron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (α-Fe2O3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attractive operational conditions. The synthesized nanostructures were characterized by means of Raman spectroscopy, Field Emission Scanning Electron Microscopy, photoelectrochemical water splitting, stability against photocorrosion tests, Mott-Schottky analysis, Electrochemical Impedance Spectroscopy (EIS) and band gap measurements. The results showed that the highest photocurrent densities for photoelectrochemical water splitting were achieved for the nanostructure synthesized at 1000 rpm which corresponds to a nanotubular structure reaching ∼0.130 mA cm−2 at 0.54 V (vs. Ag/AgCl). This is in agreement with the EIS measurements and Mott-Schottky analysis which showed the lowest resistances and the corresponding donor density values, respectively, for the nanostructure anodized at 1000 rpm.
Keywords: Iron oxide; Nanostructure; Hydrodynamic conditions; Photocatalyst; Water splitting;

Surfactant-free synthesis of hierarchical niobic acid microflowers assembled from ultrathin nanosheets with efficient photoactivities by Wenhao Dong; Feng Pan; Yanyan Wang; Shuning Xiao; Kai Wu; Guo Qin Xu; Wei Chen (514-522).
Display OmittedThree-dimensional niobic acid microflowers assembled form two-dimensional ultrathin nanosheets were synthesized by a surfactant-free hydrothermal approach.Hierarchical niobic acid (Nb2O5·nH2O) microflowers are synthesized by a surfactant-free hydrothermal approach. The three-dimensional microflowers are assembled from two-dimensional ultrathin nanosheets with thickness of ∼5 nm. Using rhodamine B as a probe, the Nb2O5·nH2O microflowers exhibit high photocatalytic activity under UV light irradiation. Furthermore, the Nb2O5·nH2O microflowers are easily converted to niobium pentoxide without significant structural alteration.
Keywords: Hierarchical microflower; Nanosheet-assemble; Niobic acid; Niobium pentoxide;

Nanoscale mechanochemical wear of phosphate laser glass against a CeO2 particle in humid air by Jiaxin Yu; Hongtu He; Yafeng Zhang; Hailong Hu (523-530).
Using an atomic force microscope, the friction and wear of phosphate laser glass against a CeO2 particle were quantitatively studied both in humid air and in vacuum, to reveal the water molecules induced mechanochemical wear mechanism of phosphate laser glass. The friction coefficient of the glass/CeO2 pair in air was found to be 5–7 times higher than that in vacuum due to the formation of a capillary water bridge at the friction interface, with a contribution of the capillary-related friction to the total friction coefficient as high as 65–79%. The capillary water bridge further induced a serious material removal of glass and CeO2 particle surfaces, while supplying both a local liquid water environment to corrode the glass surface and a high shearing force to assist the stretching of the Ce―O―P bond, accelerating the reaction between water and the glass/CeO2 pair. In vacuum, however, no discernable wear phenomena were observed, but the phase images captured by AFM tapping mode suggested the occurrence of potential strain hardening in the friction area of the glass surface.

Effect of rutile TiO2 on the photocatalytic performance of g-C3N4/brookite-TiO2-xNy photocatalyst for NO decomposition by Huihui Li; Xiaoyong Wu; Shu Yin; Kenichi Katsumata; Yuhua Wang (531-539).
g-C3N4/rutile-brookite TiO2-xNy forms a Z-scheme photocatalytic system, which shows improvement on the photocatalytic activity than that of g-C3N4/single brookite TiO2-xNy.Display OmittedNovel g-C3N4/rutile-brookite TiO2-xNy composite photocatalysts were fabricated through a facile solvothermal approach. The effect of rutile phase TiO2 with brookite TiO2 and g-C3N4 on the photocatalytic activity of g-C3N4/nitrogen-doped TiO2 composite was studied. The photocatalytic performance of the photocatalyst was evaluated by measuring the degradation of NO gas under visible and UV light irradiation. It is suggested that g-C3N4/rutile-brookite TiO2-xNy forms a Z-scheme photocatalytic system, which shows improvement on the photocatalytic activity than that of g-C3N4/single brookite TiO2-xNy. By importing rutile phase TiO2-xNy, the photogenerated electrons can efficiently transfer from rutile TiO2 to g-C3N4, which results in the separation of electron and hole pairs, enhancing the photocatalytic ability. However, single brookite TiO2-xNy can not remove the photogenerated electrons efficiently and the photocatalytic performances of composites decrease with g-C3N4 amount increase.
Keywords: Rutile/brookite TiO2-xNy; g-C3N4; Z-scheme photocatalyst; DeNOx ability;

Remarkable photo-catalytic degradation of malachite green by nickel doped bismuth selenide under visible light irradiation by Chiranjit Kulsi; Amrita Ghosh; Anup Mondal; Kajari Kargupta; Saibal Ganguly; Dipali Banerjee (540-548).
Display OmittedBismuth selenide (Bi2Se3) and nickel (Ni) doped Bi2Se3 were prepared by a solvothermal approach to explore the photo-catalytic performance of the materials in degradation of malachite green (MG). The presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement in doped Bi2Se3. The results showed that the nickel doping played an important role in microstructure and photo-catalytic activity of the samples. Nickel doped Bi2Se3 sample exhibited higher photo-catalytic activity than that of the pure Bi2Se3 sample under visible-light irradiation. The photo-catalytic degradation followed first-order reaction kinetics. Fast degradation kinetics and complete (100% in 5 min of visible light irradiation) removal of MG was achieved by nickel doped Bi2Se3 in presence of hydrogen peroxide (H2O2) due to modification of band gap energies leading to suppression of photo-generated electron-hole recombination.
Keywords: Photo-catalysis; Bismuth selenide; Solvothermal; Nickel doping;

Comparison study of transparent RF-sputtered ITO/AZO and ITO/ZnO bilayers for near UV-OLED applications by Mahdiyar Nouri Rezaie; Negin Manavizadeh; Ehsan Mohammadi Nasr Abadi; Ebrahim Nadimi; Farhad Akbari Boroumand (549-556).
Schematic structure and band diagram of fabricated UV-OLEDs based on ITO/AZO and ITO/ZnO.Display OmittedHybrid inorganic/organic light-emitting diodes have attracted much attention in the field of luminescent electronics due to the desired incorporation of high optoelectronic features of inorganic materials with the processability and variety of organic polymers. To generate and emit a near ultraviolet (N-UV) ray, wide band gap semiconductors can be applied in the organic light-emitting diodes (OLEDs). In this paper, zinc oxide (ZnO) and aluminum-doped ZnO (AZO) thin films are deposited by radio frequency (RF) sputtering above the ITO electrode and poly [2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) conjugated polymer is utilized as a complementary p-type semiconductor in OLED structure. The impact of ZnO and AZO thickness on the structural, electrical, optical and morphological properties of ITO/AZO and ITO/ZnO bilayers are scrutinized and compared. Results show that with the enlargement of both ZnO and AZO film thickness, the physical properties are gradually improved resulting in the better quality of transparent conducting thin film. The average electrical resistivity of 8.4 × 10−4 and 1.1 × 10−3  Ω-cm, average sheet resistance of 32.9 and 42.3 Ω/sq, average transmittance of 88.3 and 87.3% and average FOM of 1.0 × 104 and 7.4 × 103 (Ω-cm)−1 are obtained for ITO/AZO and ITO/ZnO bilayers, respectively. Moreover, comparing the results indicates that the strain and the stress within the ITO/AZO bilayer are decreased nearly 19% with respect to ITO/ZnO bilayer which yield higher quality of crystal. Consequently, the physical properties of ITO/AZO bilayer is found to be superior regarding ITO/ZnO bilayer. For fabricated UV-OLEDs, the turn-on voltages, the characteristic energy ( E t ) and the total concentration of traps ( N t ) for the devices with the structures of ITO/ZnO/MEH-PPV/Al and ITO/AZO/MEH-PPV/Al are obtained 12 and 14 V, 0.108 and 0.191 eV, 9.33 × 1016 and 5.22 × 1016  cm−3, respectively. Furthermore, according to the electroluminescence (EL) spectra, the near band emission (NBE) peak for device with the structure of ITO/ZnO/MEH-PPV/Al is attained nearly in the wavelengths of 408 nm which is in N-UV region. For ITO/AZO/MEH-PPV/Al, a slightly blue shift in NBE peak is observed due to the Burstein–Moss (BM) effect. Ultimately, different charge carrier transport mechanisms of fabricated UV-OLEDs have been carefully investigated.
Keywords: ZnO; AZO; Bilayer electrodes; Hybrid LED; Near UV-OLED; J-V characteristic;

Rational design of multifunctional devices based on molybdenum disulfide and graphene hybrid nanostructures by Yi Rang Lim; Young Bum Lee; Seong Ku Kim; Seong Jun Kim; Yooseok Kim; Cheolho Jeon; Wooseok Song; Sung Myung; Sun Sook Lee; Ki-Seok An; Jongsun Lim (557-561).
We rationally designed a new type of hybrid materials, molybdenum disulfide (MoS2) synthesized by Mo pre-deposition followed by subsequent sulfurization process directly on thermal chemical vapor deposition (TCVD)-grown graphene, for applications in a multifunctional device. The synthesis of stoichiometric and uniform multilayer MoS2 and high-crystalline monolayer graphene was evaluated by X-ray photoelectron spectroscopy and Raman spectroscopy. To examine the electrical transport and photoelectrical properties of MoS2-graphene hybrid films, field effect transistors (FETs) and visible-light photodetectors based on MoS2-graphene were both fabricated. As a result, the extracted mobility for MoS2-graphene hybrid FETs was two times higher than that of MoS2 FETs. In addition, the MoS2-graphene photodetectors revealed a significant photocurrent with abrupt switching behavior under periodic illumination.
Keywords: MoS2-graphene hybrid films; Field effect transistors; Photodetectors;

Display OmittedNitrogen-doped carbon nanotube supporting NiO nanoparticles were synthesized by a chemical precipitation process coupled with subsequent calcination. The morphology and structure of the composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performance was evaluated using cyclic voltammetry and chronoamperometric technique. The effects of nitrogen doping, calcination temperature and content of NiO nanoparticles on the electrocatalytic activity toward methanol oxidation were systematically studied. The results show that the uniformly dispersed ultrafine NiO nanoparticles supported on nitrogen-doped carbon nanotube are obtained after calcination at 400 °C. The optimized composite catalysts present high electrocatalytic activity, fast charge-transfer process, excellent accessibility and stability for methanol oxidation reaction, which are promising for application in the alkaline direct methanol fuel cells.
Keywords: Nickel oxide; Nitrogen-doped carbon nanotube; Catalyst; Methanol oxidation;

Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma by M. Oujja; I. Lopez-Quintas; A. Benítez-Cañete; R. de Nalda; M. Castillejo (572-580).
Display OmittedHarmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium.
Keywords: Laser ablation; Harmonic generation; Nanoparticles; Zinc sulphide;

TiNi shape memory alloys (SMAs), used as long-term implant materials, have a disadvantage. Ni-ion release from the alloys may trigger allergies in the human body. Micro-arc oxidation has been utilized to modify the surface of the TiNi SMA for improving its corrosion resistance and biocompatibility. However, there are very few reports investigating the essential adhesive strength between the micro-arc oxidized film and TiNi SMA. Two primary goals were attained by this study. First, Ti50Ni48.5Mo1.5 SMA having a phase transformation temperature (Af) less than body temperature and good shape recovery were prepared. Next, the Ti50Ni50 and Ti50Ni48.5Mo1.5 SMA surfaces were modified by micro-arc oxidation in phosphoric acid by applying relatively low voltages to maintain the adhesive strength. The results indicated that the pore size, film thickness, and P content increased with applied voltage. The micro-arc oxidized film, comprising Ti oxides, Ni oxide, and phosphate compounds, exhibited a glassy amorphous structure. The outmost surface of the micro-arc oxidized film contained a large amount of P (>12 at%) but only a trace of Ni (<5 at%). The adhesive strengths of all the micro-arc oxidized films exceeded the requirements of ISO 13779. Furthermore, Mo addition into TiNi SMAs was found to be favorable for improving the adhesive strength of the micro-arc oxidized film.
Keywords: Shape memory alloy; Micro-arc oxidation; Adhesive strength;

Display OmittedTitanium dioxide − bismuth tungstate composite materials were prepared by pulsed DC reactive magnetron sputtering of bismuth and tungsten metallic targets in argon/oxygen atmosphere onto anatase and rutile titania nanoparticles. The use of an oscillating bowl placed beneath the two magnetrons arranged in a co-planar closed field configuration enabled the deposition of bismuth tungstate onto loose powders, rather than a solid substrate. The atomic ratio of the bismuth/tungsten coatings was controlled by varying the power applied to each target. The effect of the bismuth tungstate coatings on the phase, optical and photocatalytic properties of titania was investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and an acetone degradation test. The latter involved measurements of the rate of CO2 evolution under visible light irradiation of the photocatalysts, which indicated that the deposition of bismuth tungstate resulted in a significant enhancement of visible light activity, for both anatase and rutile titania particles. The best results were achieved for coatings with a bismuth to tungsten atomic ratio of 2:1. In addition, the mechanism by which the photocatalytic activity of the TiO2 nanoparticles was enhanced by compounding it with bismuth tungstate was studied by microwave cavity perturbation. The results of these tests confirmed that such enhancement of the photocatalytic properties is due to more efficient photogenerated charge carrier separation, as well as to the contribution of the intrinsic photocatalytic properties of Bi2WO6.
Keywords: Photocatalyst; Titanium dioxide; Bismuth tungstate; Visible light responsive; Magnetron sputtering;

In the present paper, we report the synthesis of Cetyltrimethylammonium Bromide (CTAB) and Sodium dodecyl sulfate (SDS) assisted Zirconia (ZrO2) nanoparticles by co-precipitation method. The effect of surfactant concentration on the structural and dielectric properties has been extensively studied. X-ray diffraction studies reveal the formation of tetragonal phase in the ZrO2 nanoparticles prepared by lower CTAB concentration. However, for higher concentration of CTAB some traces of monoclinic phase appeared along with tetragonal phase. SDS assisted nanoparticles shows crystalline tetragonal phase with lower concentration of SDS and amorphous nature with higher concentrations of SDS. FTIR results show the presence of Zr–O symmetrical stretching vibrations at tetrahedral site. The dielectric properties of all samples have been studied from 10 Hz to 1 MHz, revealing the low value of dielectric constant with CTAB and very high value with SDS as compared to bare ZrO2 nanoparticles. The dielectric behaviour of the bare and surfactant assisted nanoparticles has been correlated with the phase transition, size of nanoparticles and the nature of surfactants.
Keywords: Zirconia; Surface modification; Phase transitions; Dielectric properties;

Cobalt-doped graphitic carbon nitride photocatalysts with high activity for hydrogen evolution by Pei-Wen Chen; Kui Li; Yu-Xiang Yu; Wei-De Zhang (608-615).
Cobalt-doped graphitic carbon nitride (Co―CN) was synthesized by one-step thermal polycondensation using cobalt phthalocyanine and melamine as precursors. The obtained photocatalysts display high and stable activity for photocatalytic generation of hydrogen through water splitting.Display OmittedCobalt-doped graphitic carbon nitride (Co―CN) was synthesized by one-step thermal polycondensation using cobalt phthalocyanine (CoPc) and melamine as precursors. The π-π interaction between melamine and CoPc promotes cobalt doping into the framework of g-C3N4. The prepared samples were carefully characterized and the results demonstrated that Co-doped graphitic carbon nitride inhibited the crystal growth of graphitic carbon nitride (CN), leading to larger specific surface area (33.1 m2  g−1) and abundant Co-Nx active sites, narrower band gap energy and more efficient separation of photogenerated electrons and holes. 0.46% Co―CN exhibited higher hydrogen evolution rate (28.0 μmol h−1) under visible light irradiation, which is about 3.0 times of that over the pure CN and about 2.2 times of that over cobalt-doped CN using CoCl2  ∙ 6H2O as a cobalt source. This study provides a valuable strategy to modify CN with enhanced photocatalytic performance.
Keywords: Graphitic carbon nitride; Doping; Cobalt phthalocyanine; Photocatalysis; Hydrogen evolution;

Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light by Tianyu Liu; Wei Chen; Yuxiang Hua; Xiaoheng Liu (616-623).
Display OmittedIn this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.
Keywords: Nano Au; ZnO semiconductor; Inversed nanostructure; SPR effect; Visible-light photocatalysis;

Display OmittedTransparent conducting oxide films of undoped, Mo doped, Mo + F co-doped ZnO were deposited using a facile homemade nebulizer spray pyrolysis technique. The effects of Mo and F doping on the structural, optical, electrical and surface morphological properties were investigated using XRD, UV-vis-NIR spectroscopy, I–V and Hall probe techniques, FESEM and AFM, and XPS, respectively. The XRD analysis confirms that all the films are well crystallized with hexagonal wurtzite structure. All the synthesized samples exhibit high transmittance (above 85%) in the visible region. The current-voltage (I–V) characteristics show the ohmic conduction nature of the films. The Hall probe measurements show that the synergistic effects of Mo and F doping cause desirable improvements in the quality factor of the ZnO films. A minimum resistivity of 5.12 × 10−3  Ω cm with remarkably higher values of mobility and carrier concentration is achieved for Mo (2 at.%) + F (15 at.%) co-doped ZnO films. A considerable variation in the intensity of deep level emission caused by Mo and F doping is observed in the photoluminescence (PL) studies. The presence of the constituent elements in the samples is confirmed by XPS analysis.
Keywords: TCO; Mo+F co-doped ZnO film; Nebulizer spray technique; Electrical conductivity; Quality factor; XPS;

Composite organic-inorganic functional materials are of significant importance in various applications of science and technology. In this work, physicochemical characterization of such composite materials obtained after the exposure of polyamide PA 6 to K2SeS2O6 precursor solution was performed. Chalcogenized polymer surface was characterized using X-ray diffraction, infrared, and UV–vis spectroscopies while their bulk chemical analysis was performed using atomic absorption spectroscopy. Crystallite size was not found to change with the exposure to K2SeS2O6 precursor but PA 6 chain–chain separation decreased. Importantly, infrared and X-ray analyses showed chemical bonding taking place between the PA 6 and SeS2O6 2− ions via −NH− functional group. A distinct change in bandgap, Eg, value was observed in UV–vis spectra due to the presence of SeS2O6 2−, SeSO3 2− and Se2S2O6 2− ions formed via decomposition of the precursor material in acidic medium. After extended 4 h chalcogenation a distinct absorption due to the elemental selenium was also observed as obtained from Tauc plots.
Keywords: Polyamide; Potassium selenotrithionate; Inorganic-organic composite; Optical properties;

Facile synthesis of AgCl/polydopamine/Ag nanoparticles with in-situ laser improving Raman scattering effect by Yan Zhang; Wenqi Zhang; Lin Wang; Feng Wang; Haifeng Yang (642-648).
Display OmittedAgCl/PDA/AgNPs were prepared by the simply mixing of AgNO3 and dopamine solution under room temperature. AgCl/PDA/AgNPs show enhanced SERS effect upon continuous pulsed laser irradiation, showing a “in-situ laser elevating” SERS effect. The enhancement factor could reach 107 by using 4-Mpy as the Raman probe. The proposed SERS substrate showed long term stability and may be a promising substrate for SERS application in practical field.We reported a simple and fast method to prepare a composite material of polydopamine (PDA) adlayer covered cubic AgCl core, which was inlaid with Ag nanoparticles (NPs), shortly named as AgCl/PDA/AgNPs. The resultant AgCl/PDA/AgNPs could be employed as surface-enhanced Raman scattering (SERS) substrate for in-situ detection and the SERS activity could be further greatly improved due to the production of more AgNPs upon laser irradiation. With 4-mercaptopyridine (4-Mpy) as the probe molecule, the enhancement factor could reach 107. Additionally, such SERS substrate shows good reproducibility with relative standard deviation of 7.32% and long term stability (after storage for 100 days under ambient condition, SERS intensity decay is less than 25%). In-situ elevating SERS activity of AgCl/PDA/AgNPs induced by laser may be beneficial to sensitive analysis in practical fields.
Keywords: Composite nanoparticles; Laser; In-situ; SERS;

Photocatalytic performance of SrMoO4 was greatly improved by Bi3+ doping effects, including crystalline size reduction, band gap narrowing, and lattice contraction.Display OmittedIon doping is one of the most effective ways to develop photocatalysts by creating impurity levels in the energy band structure. In this paper, novel Bi3+ doped SrMoO4 (SrMoO4:Bi3+) nanocrystals were prepared by a simple hydrothermal method. By systematic characterizations using x-ray diffraction, infrared spectra, UV–vis spectra, X-ray photoelectron spectroscopy and transmission electron microscopy, it is demonstrated that all the samples crystallized in a single phase of scheelite structure, and particle sizes of SrMoO4:Bi3+ gradually decreased. The Bi3+ doped nanoparticles showed lattice contraction, and band-gap narrowing. The photocatalytic activity of the samples was measured by monitoring the degradation of methylene blue dye in an aqueous solution under UV-radiation exposure. It is found that SrMoO4:Bi3+ showed excellent activity toward photodegradation of methylene blue solution under UV light irradiation compared to the pure SrMoO4. These observations are interpreted in terms of the Bi3+ doping effects and the increased the surface active sites, which results in the improved the ratio of surface charge carrier transfer rate and reduced the electron–hole recombination rate. These results illustrate the potential of particle size and surface defect regulation for the construction of novel semiconductor oxide photocatalysts by ion doping.
Keywords: SrMoO4; Bi3+ doping; Photocatalysis; Surface defect;

Display OmittedRecently, the excessive consumption of fossil fuels has caused high emissions of the greenhouse gases, CO2 into atmosphere and global energy crisis. Mimicking the natural photosynthesis by using semiconductor materials to achieve photocatalytic CO2 reduction into valuable solar fuels such as CH4, HCO2H, CH2O, and CH3OH is known as one of the best solutions for addressing the aforementioned issue. Among various proposed photocatalysts, TiO2 has been extensively studied over the past several decades for photocatalytic CO2 reduction because of its cheapness and environmental friendliness. Particularly, surface modification of TiO2 has attracted numerous interests due to its capability of enhancing the light absorption ability, facilitating the electron-hole separation, tuning the CO2 reduction selectivity and increasing the CO2 adsorption and activation ability of TiO2 for photocatalytic CO2 reduction. In this review, recent approaches of the surface modification of TiO2 for photocatalytic CO2 reduction, including impurity doping, metal deposition, alkali modification, heterojunction construction and carbon-based material loading, are presented. The photocatalytic CO2 reduction mechanism and pathways of TiO2 are discussed. The future research direction and perspective of photocatalytic CO2 reduction over surface-modified TiO2 are also presented.
Keywords: TiO2; Surface modification; Photocatalytic CO2 reduction; Heterojunction construction; Alkali modification; CO2 reduction selectivity;

The influence of zeolites fly ash bead/TiO2 composite material surface morphologies on their adsorption and photocatalytic performance by Lu Yang; Fazhou Wang; Amer Hakki; Donald E. Macphee; Peng Liu; Shuguang Hu (687-696).
Display OmittedA low cost zeolite fly ash bead/TiO2 (ZFABT) composite materials with various surface structure features were prepared for describing those structures importance on TiO2 coating, adsorbability and photocatalytic performances. The results indicated that fly ash bead (FAB) surface was significantly altered by the precipitation/growth of secondary zeolite phases after alkali activation, which generates abundant open pores and stacked petal-liked spherical beads (∼2 μm, Sodalite zeolites). More importantly, this porosity increases as activation time was increased from 2 h to 12 h, through the precipitation of sodalite and then Na-P1 (lamellar crystals) and Na-X (octahedral crystals) zeolite structures. Compared to those of unsupported TiO2 or inactivated support/TiO2 samples, all of ZFABT samples exhibited a higher adsorption capacity and photocatalytic efficiency for RhB removal. However, adsorption is not only one factor to influence TiO2 surface reaction, the intraparticle diffusion rate of rhodamine B (RhB) molecules, and light penetration are also important parameters. Alkali activated 4 h ZFABT sample exhibited the highest photocatalytic activity, indicating its pore structure provided a better balance for those parameters to achieve a synergistic adsorption/photocatalytic process. The kinetics model suggested its high intraparticle diffusion rate allowed for more RhB molecules to easily reach the reaction surface, which is more important for high efficiency photocatalysis.
Keywords: TiO2; Zeolite fly-ash bead; Alkali activation; Enhanced adsorption; Intraparticle diffusion; Photocatalysis;

The electronic properties (electron inelastic cross section, energy loss function) of a nano-metalized polystyrene obtained by reflection electron energy loss spectroscopy (REELS) in a previous study [J. Deris, S. Hajati, S. Tougaard, V. Zaporojtchenko, Appl. Surf. Sci. 377 (2016) 44–47], which relies on the Yubero-Tougaard method, were used in the complementary application of Kramers-Kronig transformation to determine its optical properties such as the real part (ε1) and imaginary part (ε2) of the dielectric function (ε), refractive index (n), coefficients of extinction (k), reflection (R) and absorption (μ). The degree of intermixing of polystyrene thin film and gold nanoparticles of sizes 5.5 nm was controlled by annealing the sample to achieve a morphology in which the nanoparticles were homogeneously distributed within polystyrene.It is worth noting that no data are available on the optical properties of metalized polymers such as gold nanoparticles intermixed with polystyrene. Therefore, this work is of high importance in terms of both the sample studied here and the method applied. The advantage of the method applied here is that no information on the lateral distribution of the nanocomposite sample is required. This means that the REELS technique has been presented here to suitably, efficiently and easily obtain the optical properties of such nano-metalized polymer in which the metal nanoparticles have been vertically well distributed (homogeneous in depth). Therefore, for vertically homogeneous and laterally inhomogeneous samples, it is possible to make REELS imaging by scanning the sample and thus to make an image of their optical properties.
Keywords: Reflection electron energy-loss spectroscopy; Optical properties; Au nanoparticles; Polystyrene;

The CuFe2O4 and CuFe2O4/AgBr composites with different CuFe2O4 contents were prepared by a facile sol-gel and hydrothermal method, respectively. The as-synthesized photocatalysts were characterized by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectrum (UV–vis DRS). Their magnetic properties, photocatalytic degradation activities on methyl orange (MO) and tetracycline hydrochloride (TC) solution and photocatalytic mechanism were investigated in detail. The results revealed that the CuFe2O4/AgBr composites exhibited significantly higher photocatalytic activities than the pure CuFe2O4. The enhanced photocatalytic activity could be attributed to the matched band structure of two components and more effective charge transportation and separations. In addition, the quenching investigation of different scavengers demonstrated that h+, •OH, •O2 reactive species played different roles in the decolorization of MO and degradation of TC.
Keywords: CuFe2O4/AgBr composites; Photocatalytic mechanism; Visible-light; Photocatalysis; Magnetic separation;

Carbon fiber cloth supported interwoven WS2 nanosplates with highly enhanced performances for supercapacitors by Xiao Shang; Jing-Qi Chi; Shan-Shan Lu; Jian-Xia Gou; Bin Dong; Xiao Li; Yan-Ru Liu; Kai-Li Yan; Yong-Ming Chai; Chen-Guang Liu (708-714).
Display OmittedThe interwoven WS2 nanoplates supported on carbon fiber cloth (WS2/CFC) have been successfully synthesized by a facile solvothermal process. XRD and XPS confirm the formation of WS2/CFC. SEM images show the good dispersion of WS2 nanoplates with interwoven structures on the surface of CFC. Thanks to the 3D framework of CFC, WS2 nanoplates realize overall excellent-dispersion interwoven on the surface of CFC compared with pristine bulk WS2 with severe aggregation. Moreover, CFC not only serves as excellent conductive substrate to accelerate electron transport rate, but also contributes to the close combination between WS2 and CFC for long-term stability. The electrochemical measurements show that WS2/CFC exhibit a high specific capacitance of 399 F g−1 at 1.0 A g−1, demonstrating the obviously enhanced capability compared with pristine bulk WS2. Furthermore, WS2/CFC realizes ultra-stable cycling stability with 99% of retention of capacitance after 500 charge-discharge cycles. It may provide novel access of designing carbon-based transition metal disulfides composites for excellent super capacitive properties.
Keywords: WS2 nanoplates; Interwoven structure; Carbon fiber cloth; Supercapacitors;

Intercalation synthesis of graphene-capped iron silicide atop Ni(111): Evolution of electronic structure and ferromagnetic ordering by G.S. Grebenyuk; O.Yu. Vilkov; A.G. Rybkin; M.V. Gomoyunova; B.V. Senkovskiy; D.Yu. Usachov; D.V. Vyalikh; S.L. Molodtsov; I.I. Pronin (715-722).
Display OmittedA new method for synthesis of graphene-protected iron silicides has been tested, which consists in formation of graphene on Ni(111) followed by two-step intercalation of the system with Fe and Si. Characterization of the samples was performed in situ by low-energy electron diffraction, angular-resolved photoelectron spectroscopy, core-level photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in photoemission of Fe 3p electrons. It is shown, that at 400 °C the intercalation of graphene/Ni(111) with iron occurs in a range up to 14 ML. The graphene layer strongly interacts with the topmost Fe atoms and stabilizes the fcc structure of the film. The in-plane ferromagnetic ordering of the film has a threshold nature and arises after the intercalation of 5 ML Fe due to the thickness-driven spin reorientation transition. Subsequent intercalation of graphene/Fe/Ni(111) with Si leads to the formation of the inhomogeneous system consisted of intercalated and nonintercalated areas. The intercalated islands coalesce at 2 ML Si when a Fe-Si solid solution covered with the Fe3Si surface silicide is formed. The Fe3Si silicide is ferromagnetic and has an ordered (√3 × √3)R30° structure. The graphene layer is weakly electronically coupled to the silicide phase keeping its remarkable properties ready for use.
Keywords: Graphene; Intercalation; Iron silicides; Photoelectron spectroscopy; Ferromagnetic materials; Thin films;

Influence of hydrophobic and superhydrophobic surfaces on reducing aerodynamic insect residues by K. Ghokulla Krishnan; Athanasios Milionis; Eric Loth; Thomas E. Farrell; Jeffrey D. Crouch; Douglas H. Berry (723-731).
Display OmittedInsect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircrafts with laminar-flow surfaces. This study investigates the effectiveness of various hydrophobic and superhydrophobic surfaces in reducing residue of insects on an aerodynamic surface at relatively high impact speeds (about 45 m/s). An experimental setup consisting of a wind tunnel and a method to inject live flightless fruit flies was used to test the effectiveness of various surfaces against insect fouling. Insect fouling was analyzed based on residue area and height from multiple impacts. In general most of the residue area was due to the hemolymph spreading while most of the residue height was due to adhesion of exoskeleton parts. Hydrophobic and especially superhydrophobic surfaces performed better than a hydrophilic aluminum surface in terms of minimizing the residue area of various insect components (exoskeleton, hemolymph, and red fluid). Surfaces with reduced wettability and short lateral length scales tended to have the smallest residue area. Residue height was not as strongly influenced by surface wettability since even a single exoskeleton adhered to the surface upon impact was enough to produce a residue height of the order of one mm. In general, the results indicate that hemolymph spread needs to be avoided (e.g. by having reduced wettability and short lateral correlation lengths) in order to minimize the residue area, while exoskeleton adherence needs to be avoided (e.g. by having oleophobic properties and micro/nano roughness) in order to minimize the residue height. In particular, two of the superhydrophobic coatings produced substantial reduction in residue height and area, relative to the baseline surface of aluminum. However, the surfaces also showed poor mechanical durability on the high-speed insect impact location. This suggests that although low wettability materials show great insect anti-fouling behavior, their durability needs to be substantially improved in order to withstand harsh aerospace conditions.
Keywords: Fouling; Insect residue adhesion; Coating evaluation; Wetting; Superhydrophobic; Spray coating;

CrCuAgN PVD nanocomposite coatings: Effects of annealing on coating morphology and nanostructure by Xingguang Liu; Chanon Iamvasant; Chang Liu; Allan Matthews; Adrian Leyland (732-746).
Display OmittedCrCuAgN PVD nanocomposite coatings were produced using pulsed DC unbalanced magnetron sputtering. This investigation focuses on the effects of post-coat annealing on the surface morphology, phase composition and nanostructure of such coatings. In coatings with nitrogen contents up to 16 at.%, chromium exists as metallic Cr with N in supersaturated solid solution, even after 300 °C and 500 °C post-coat annealing. Annealing at 300 °C did not obviously change the phase composition of both nitrogen-free and nitrogen-containing coatings; however, 500 °C annealing resulted in significant transformation of the nitrogen-containing coatings. The formation of Ag aggregates relates to the (Cu + Ag)/Cr atomic ratio (threshold around 0.2), whereas the formation of Cu aggregates relates to the (Cu + Ag + N)/Cr atomic ratio (threshold around 0.5). The primary annealing-induced changes were reduced solubility of Cu, Ag and N in Cr, and the composition altering from a mixed ultra-fine nanocrystalline and partly amorphous phase constitution to a coarser, but still largely nanocrystalline structure. It was also found that, with sufficient Cu content (>12 at.%), annealing at a moderately high temperature (e.g. 500 °C) leads to transportation of both Cu and Ag (even at relatively low concentrations of Ag, ≤3 at.%) from inside the coating to the coating surface, which resulted in significant reductions in friction coefficient, by over 50% compared to that of the substrate (from 0.31 to 0.14 with a hemispherical diamond indenter, and from 0.83 to 0.40 with an alumina ball counterface, respectively). Results indicate that the addition of both Cu and Ag (in appropriate concentrations) to nitrogen-containing chromium is a viable strategy for the development of ‘self-replenishing’ silver-containing thin film architectures for temperature-dependent solid lubrication requirements or antimicrobial coating applications.
Keywords: Nanocomposite; PVD coatings; Annealing; Transportation; Phase transformation; Nanostructure;

The microscopic conformational change process of oil contaminants adhered onto perfect α-Al2O3 (0001) surface in aqueous solution was investigated by using all-atom classic molecular dynamics simulations. The change in removal mechanism of oil contaminants induced by surface coverage (surface area per molecule) was emphatically explored. Our simulation results strongly reveal that the increase in oil surface coverage induces an evident difference in microscopic detachment processes of oil contaminants. At a low surface coverage, oil contaminants can be thoroughly detached from solid surface. The whole detachment process could be divided into multi stages, including conformational change of oil contaminants on solid surface, dynamic motion of those in bulk solution and rapid migration of those from bulk solution to air/water interface. With surface coverage increasing, water diffusion becomes the key to induce conformational change and promote the detachment of oil contaminants. When oil surface coverage exceeds a threshold value, oil contaminants also undertake an evident conformational change process exhibiting typical characteristics but an incomplete detachment process occurs. All findings of the present study are helpful for the interpretation of the removal mechanism of oil contaminants on solid surface.
Keywords: Oil contaminants; Conformational change; Water diffusion; Molecular dynamics simulation; Surface coverage; Detachment;

The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach by Long Zhou; Fangyuan Xiu; Meng Qiu; Shuwei Xia; Liangmin Yu (760-767).
The optimized structure of hydrated goethite (010) surface with medium water coverage (water density about 6.7 H2O/nm2).Display OmittedUsing density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H2O is due to the formation of Fe―O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ3 ―O as an intermediate product; the proton belonged to μ3 ―O transferred to the neighbor surface μ2 ―O as the dissociative configuration.
Keywords: Density functional theory; Periodical boundary condition; Goethite; Water molecule; Chemical adsorption and dissociation;

Anti-corrosion film formed on HAl77-2 copper alloy surface by aliphatic polyamine in 3 wt.% NaCl solution by Yinzhe Yu; Dong Yang; Daquan Zhang; Yizhen Wang; Lixin Gao (768-776).
Display OmittedThe corrosion inhibition of a polyamine compound, N-(4-amino-2, 3-dimethylbutyl)-2, 3-dimethylbutane-1, 4-diamine (ADDD), was investigated for HAl77-2 copper alloy in 3 wt.% NaCl solution. Electrochemical measurements, scanning electron microscopy (SEM), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed for this research. The results show that ADDD strongly suppresses the corrosion of HAl77-2 alloy. The inhibition efficiency of ADDD is 98.6% at 0.5 mM, which is better than benzotriazole (BTAH) at the same concentration. Polarization curves indicate that ADDD is an anodic type inhibitor. Surface analysis suggests that a protective film is formed via the interaction of ADDD and copper. FT-IR reveals that the inhibition mechanism of ADDD is dominated by chemisorption onto the copper alloy surface to form an inhibition film. Furthermore, quantum chemical calculation and molecular dynamics (MD) simulations methods show that ADDD adsorbs on HAl77-2 surface via amino group in its molecule.
Keywords: Copper alloy; Corrosion; Electrochemical measurements; SEM; AFM;

MnO2 nanorods/3D-rGO composite as high performance anode materials for Li-ion batteries by Hongdong Liu; Zhongli Hu; Yongyao Su; Haibo Ruan; Rong Hu; Lei Zhang (777-784).
MnO2 nanorods/three-dimensional reduced graphene oxide (3D-rGO) composite has been synthesized by a simple in situ hydrothermal methord. The X-ray diffraction (XRD) pattern of the as-prepared composite reveals tetragonal structure of α-MnO2. Raman spectroscopic and X-ray photoelectron spectroscopy (XPS) of the samples confirm the coexistence of MnO2 and graphene. The Brunauer-Emmett-Teller (BET) analysis shows the large surface area of the composite. The electron microscopy images of the as-synthesized products reveals the MnO2 nanorods are homogeneously grown on 3D-rGO matrix. Electrochemical characterization exhibits the MnO2 nanorods/3D-rGO composite with large reversible capacity (595 mA h g−1 over 60 cycles at 100 mA g−1), high coulombic efficiency (above 99%), excellent rate capability and good cyclic stability. The superior electrochemical performance can be attributed to the turf-like nanostructure of composite, high capacity of MnO2 and superior electrical conductivity of 3D-rGO. It suggests that MnO2 nanorods/3D-rGO composite will be a promising anode material for Li-ion batteries.
Keywords: Li-ion batteries; MnO2; Reduced graphene oxide; Electrochemical performance;

Facile synthesis of mesostructured ZSM-5 zeolite with enhanced mass transport and catalytic performances by Chao Li; Yanqun Ren; Jinsheng Gou; Baoyu Liu; Hongxia Xi (785-794).
Display OmittedA mesostructured ZSM-5 zeolite with multilamellar structure was successfully synthesized by employing a tetra-headgroup rigid bolaform quaternary ammonium surfactant. It was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms, amines temperature programmed desorption (amines-TPD), and computer simulation. These results indicated that the dual-functional amphiphilic surfactants play a critical role for directing the multilamellar structure with high mesoporosity. The mass transport and catalytic performances of the zeolite were investigated by zero length column (ZLC) technique and aldol condensation reactions to evaluate the structure-property relationship. These results clearly indicated that the mass transport of selected molecules in hierarchical zeolite can be accelerated by introducing mesoporous structure with mesostructure with reduced diffusion length and an overall enhanced resistance against deactivation in reactions involving large molecules. Furthermore, the dual-functional surfactant approach of making hierarchical zeolite with MFI nanosheets framework would open up new opportunities for design and synthesis of hierarchical zeolites with controllable mesoporous structures.
Keywords: Mesoporous zeolite; Mass transport; Structure directing agents; Zero length column technique;

Electronic structure of Ar+ ion-sputtered thin-film MoS2: A XPS and IPES study by Antonino Santoni; Flaminia Rondino; Claudia Malerba; Matteo Valentini; Alberto Mittiga (795-800).
Polycrystalline MoS2 grown by Mo sulphurization was exposed to increasing doses of Ar+ ions at 250 eV starting from 2.2 × 1015 ions/cm2 to 3.92 × 1017 ions/cm2. Electronic structure changes were monitored by X-Ray Photoelectron Spectroscopy (XPS) and Inverse Photolectron Spectroscopy (IPES). No change in the Fermi level position was observed with Ar+ dosing. Ion bombardment resulted in a new visible feature at lower binding energy in the Mo3d core level, while the S2p lineshape showed little changes. The formation of a steady state from 2.49 × 1017 ions/cm2 has been detected. The investigation of the occupied and unoccupied states on the steady-state surface pointed to the simultaneous presence of metallic-like Mo with amorphous MoS2-x.
Keywords: MoS2; Sulphurization; CZTS; Ar+ ion sputtering; XPS; Inverse photoemission;

Effect of ZnO core electrodeposition conditions on electrochemical and photocatalytic properties of polypyrrole-graphene oxide shelled nanoarrays by A. Pruna; Q. Shao; M. Kamruzzaman; Y.Y. Li; J.A. Zapien; D. Pullini; D. Busquets Mataix; A. Ruotolo (801-809).
Novel hybrid core-shell nanoarchitectures were fabricated by a simple two-step electrochemical approach: first ZnO nanorod core was electrodeposited from Zn(NO3)2 solution; further, the core nanoarray was coated with a shell based on polypyrrole hybridized with graphene oxide by electropolymerization. The properties of the core/shell nanoarchitectures were studied as a function of the core properties induced by electrodeposition parameters. The ZnO nanostructures showed improved crystallinity and c-axis preferred orientation with increasing cathodic deposition potential while the increased deposition duration resulted in a morphology transition from nanorod to pyramidal shape. The electrochemical activity of the core/shell arrays was found to increase with the deposition potential of ZnO core but decreased when morphology changed from nanorod to pyramid shape. The photocatalytic results showed improved activity for the core/hybrid shell nanoarrays with respect to ZnO and ZnO/PPy ones. The degradation rate for methylene blue decreased with prolonged deposition duration of the core. The obtained results highlight the importance of electrochemical tuning of ZnO-based core/shell nanoarrays for improved performance in electrochemical and photocatalytic applications.
Keywords: ZnO; Graphene oxide; Polypyrrole; Core/shell; Nanorod; Pyramid;

Preparation of WO3/g-C3N4 composites and their application in oxidative desulfurization by Rongxiang Zhao; Xiuping Li; Jianxun Su; Xiaohan Gao (810-816).
Display OmittedThe WO3/g-C3N4 composite was successfully synthesized through directly calcining phosphotungstic and melamine. The WO3 is one of several good catalyst for oxidation desulfurization. But, the surface area of WO3 is small and short of active site. Taking into account the catalyst with large surface area generally has a high catalytic activity. The surface area of WO3/g-C3N4 composite is ten times as big as the WO3. The crystalline of WO3/g-C3N4 composites was obviously improved. Desulfurization experiment showed that the desulfurization rate of simulated oil can reach 91.2% under optimal conditions. Meanwhile, the activity of the catalyst was not significantly decreased after the 5 recycles. The result show that stability of catalyst is high.WO3/graphitic carbon nitride (g-C3N4) composites were successfully synthesized through direct calcining of a mixture of WO3 and g-C3N4 at 400 °C for 2 h. The WO3 was prepared by calcination of phosphotungstic acid at 550 °C for 4 h, and the g-C3N4 was obtained by calcination of melamine at 520 °C for 4 h. The WO3/g-C3N4 composites were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and Brunner−Emmett−Teller analysis (BET). The WO3/g-C3N4 composites exhibited stronger XRD peaks of WO3 and g-C3N4 than the WO3 and pure g-C3N4. In addition, two WO3 peaks at 25.7° and 26.6° emerged for the 36% −WO3/g-C3N4 composite. This finding indicated that WO3 was highly dispersed on the surface of the g-C3N4 nanosheets and interacted with the nanosheets, which resulted in the appearance of (012) and (022) planes of WO3. The WO3/g-C3N4 composite also exhibited a larger specific surface area and higher degree of crystallization than WO3 or pure g-C3N4, which resulted in high catalytic activity of the catalyst. Desulfurization experiments demonstrated that the desulfurization rate of dibenzothiophene (DBT) in model oil reached 91.2% under optimal conditions. Moreover, the activity of the catalyst was not significantly decreased after five recycles.
Keywords: WO3/g-C3N4; Composites; Oxidation desulfurization;

We report on the growth and characterization of self-assembled InAs/GaAs quantum dots (QDs). The influence of the systematically changed growth conditions on the opto-electronic and structural properties of the QDs were investigated. Combination of the amount of the deposited InAs, growth temperature and growth rate were optimized for low As/In flux ratio to obtain well-resolved ground and excited states in the low temperature photoluminescence (PL) spectra. SEM and TEM techniques were also used for the characterization of QDs. The results were evaluated simply through the conservation of mass approximation and the x-ray diffraction measurements with fitted curves. The extracted InAs and wetting layer thicknesses were brought out that the XRD analysis reflects the overall tendency of the QD density change and WL behaviors in response to the changes in growth conditions.
Keywords: Quantum dot; Self-assembled; Molecular beam epitaxy; Photoluminescence;

Effect of bias voltage on TiAlSiN nanocomposite coatings deposited by HiPIMS by Quansheng Ma; Liuhe Li; Ye Xu; Jiabin Gu; Lei Wang; Yi Xu (826-833).
TiAlSiN nanocomposite coatings were deposited onto cemented carbide (WC-10 wt.%, Co) substrates by high power impulse magnetron sputtering (HiPIMS). The effect of substrate bias voltage on plasma discharge characterization of HiPIMS, element concentration, deposition rate, microstructure, surface/cross-sectional morphology, hardness and adhesion strength of coatings were studied. Compared with those deposited with direct current magnetic sputtering (DCMS), HiPIMS-deposited TiAlSiN coatings show improvements in some properties, including the surface roughness, the grain size, the hardness and adhesion strength, but a decrease in the deposition rate. When the bias voltage increases, the discharge current rose up from 118A to 165A. HiPIMS-deposited TiAlSiN coatings show a shift of the preferred crystallographic orientation from (220) to (200) and decreases in surface roughness from 14.1 nm down to 7.4 nm and grain size from 10.5 nm to 7.4 nm. Meanwhile, a change in crystal morphology from columnar to equiaxial and a grain refinement, as well as an increase of hardness from 30 GPa up to 42 GPa of those TiAlSiN coatings were observed with the increasing bias voltage and a decrease in adhesion strength from HF2 to HF5 of those coatings were revealed by indentation adhesion test.
Keywords: TiAlSiN; HiPIMS; Bias voltage; Microstructure; Mechanical properties;

Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces by Isadora Berlanga; Álvaro Etcheverry-Berríos; Andy Mella; Domingo Jullian; Victoria Alejandra Gómez; Núria Aliaga-Alcalde; Victor Fuenzalida; Marcos Flores; Monica Soler (834-840).
Display OmittedWe investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.
Keywords: Curcumin derivatives; Curcuminoid; XPS; STM; Polycrystalline gold surface; Self-assembled monolayers (SAMs);

Organic functionalization of silicane with formaldehyde and propanaldehyde by Diego Morachis-Galindo; Pamela Rubio-Pereda; Noboru Takeuchi (841-848).
Display OmittedWe have studied the addition reaction of aldehydes on silicane by means of periodic density functional theory. The reaction is initiated at a dangling bond, formed by removing a hydrogen atom from the surface. An incoming unsaturated molecule can attach to the surface by reacting with the dangling bond and forming an intermediate carbon radical state. After abstraction of a neighboring H atom, the molecule becomes stable and a new dangling bond is formed. Thermodynamics and kinetics suggest that adsorption is highly probable to occur. Even more, comparisons with the addition reaction of aldehydes on H-Si(111) and the adsorption of hydrocarbons on silicane, suggest that reaction of aldehydes on silicane is even more favorable. This might be explained in terms of the enhanced polar ambient in silicane with respect to the H-Si(111) surface in the first case, and by the higher stability of Si-O bonds with respect to Si-C bonds in the later. Also, calculations suggest that the attachment of a second molecule is also favorable, indicating the possibility of a chain reaction.
Keywords: Silicene; Aldehydes; Organic functionalization;

Work function mediated by deposition of ultrathin polar FeO on Pt(111) by Shuangzan Lu; Zhihui Qin; Qinmin Guo; Gengyu Cao (849-853).
Significant work function changes from bare Pt(111) surface to 1 monolayer and 2 monolayers of ultrathin iron oxide (FeO) films on it are investigated by means of scanning tunneling microscopy/spectroscopy (STM/STS). With FeO layer-by-layer growth, a continuous reduction of the work function along with the surface vacuum level (VL) shifting is observed. We found that the compression of the electron spill-out at the metal-oxide interface and the substantial reconstruction of 2 ML FeO film, respectively, make major contributions to the first and the second reductions of the work function. The rectifying effect in FeO films is also observed, which is attributed to the downward shift of band alignment imposed by the total change in surface dipole. Our work shows that the polar oxide films play an important role to adjust surface electronic structures for enhancing device functionality.
Keywords: Polar FeO films; Work function tuning; STM/STS; Rectifying effect;

Understanding the shrinkage of optical absorption edges of nanostructured Cd-Zn sulphide films for photothermal applications by Md. Sohrab Hossain; Humayun Kabir; M. Mahbubur Rahman; Kamrul Hasan; Muhammad Shahriar Bashar; Mashudur Rahman; Md. Abdul Gafur; Shariful Islam; Amun Amri; Zhong-Tao Jiang; Mohammednoor Altarawneh; Bogdan Z. Dlugogorski (854-862).
Display OmittedIn this article Cd-Zn sulphide thin films deposited onto soda lime glass substrates via chemical bath deposition (CBD) technique were investigated for photovoltaic applications. The synthesized films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet visible (UV–vis) spectroscopic methodologies. A higher degree of crystallinity of the films was attained with the increase of film thicknesses. SEM micrographs exhibited a partial crystalline structure with a particulate appearance surrounded by the amorphous grain boundaries. The optical absorbance and absorption coefficient of the films were also enhanced significantly with the increase in film thicknesses. Optical band-gap analysis indicated a monotonic decrease in direct and indirect band-gaps with the increase of thicknesses of the films. The presence of direct and indirect transitional energies due to the exponential falling edges of the absorption curves may either be due to the lack of long-range order or to the existence of defects in the films. The declination of the optical absorption edges was also confirmed via Urbach energy and steepness parameters studies.
Keywords: XRD; SEM; UV–vis; Crystallinity; Band gap; Absorption edges;

Re-crystallization of ITO films after carbon irradiation by Muhammad Usman; Shahid Khan; Majid Khan; Turab Ali Abbas (863-866).
2.0 MeV carbon ion irradiation effects on Indium Tin Oxide (ITO) thin films on glass substrate are investigated. The films are irradiated with carbon ions in the fluence range of 1 × 1013 to 1 × 1015  ions/cm2. The irradiation induced effects in ITO are compared before and after ion bombardment by systematic study of structural, optical and electrical properties of the films. The XRD results show polycrystalline nature of un-irradiated ITO films which turns to amorphous state after 1 × 1013  ions/cm2 fluence of carbon ions. Further increase in ion fluence to 1 × 1014  ions/cm2 re-crystallizes the structure and retains for even higher fluences. A gradual decrease in the electrical conductivity and transmittance of irradiated samples is observed with increasing ion fluence. The band gap of the films is observed to be decreased after carbon irradiation.
Keywords: ITO; Ion irradiation; Carbon; Radiation damage;

Display OmittedThis study demonstrates that a laser-induced crystallization instrumented with Raman spectroscopy is, in general, an effective tool to study the thermally activated crystallization kinetics. It is shown, for the solid phase crystallization of an amorphous silicon thin film, that the integral intensity of Raman spectra corresponding to the crystalline phase grows linearly in the time-logarithmic scale. A mathematical model, which assumes random nucleation and crystal growth, was designed to simulate the crystallization process in the non-uniform temperature field induced by laser. The model is based on solving the Eikonal equation and the Arhenius temperature dependence of the crystal nucleation and the growth rate. These computer simulations successfully approximate the crystallization process kinetics and suggest that laser-induced crystallization is primarily thermally activated.

Dynamic contact interactions of fractal surfaces by Tamonash Jana; Anirban Mitra; Prasanta Sahoo (872-882).
Roughness parameters and material properties have significant influence on the static and dynamic properties of a rough surface. In the present paper, fractal surface is generated using the modified two-variable Weierstrass-Mandelbrot function in MATLAB and the same is imported to ANSYS to construct the finite element model of the rough surface. The force-deflection relationship between the deformable rough fractal surface and a contacting rigid flat is studied by finite element analysis. For the dynamic analysis, the contacting system is represented by a single degree of freedom spring mass-damper-system. The static force-normal displacement relationship obtained from FE analysis is used to determine the dynamic characteristics of the rough surface for free, as well as for forced damped vibration using numerical methods. The influence of fractal surface parameters and the material properties on the dynamics of the rough surface is also analyzed. The system exhibits softening property for linear elastic surface and the softening nature increases with rougher topography. The softening nature of the system increases with increase in tangent modulus value. Above a certain value of yield strength the nature of the frequency response curve is observed to change its nature from softening to hardening.
Keywords: Fractal surface; Contact; Nonlinear vibration; Tangent modulus; Yield strength;

Immunosensing by luminescence reduction in surface-modified microstructured SU-8 by Pinkie Jacob Eravuchira; Malgorzata Baranowska; Chris Eckstein; Francesc Díaz; Eduard Llobet; Lluis F. Marsal; Josep Ferré-Borrull (883-888).
SU-8, an epoxy based negative photoresist is extensively used as a structural material for the fabrication of microelectro-mechanical systems and in microelectronics technology. However, the possible applications of SU-8 for biosensing have not been explored much, mainly because of the photoluminescence SU-8 possesses in the near-UV and visible wavelength ranges which hinders fluorescent labelling of biorecognition events. In this study we demonstrate that photoluminescence of SU-8 can be employed itself as a sensing transduction parameter to produce a tool for immunosensing: the photoluminescence shows a systematic reduction upon modification of its surface chemistry, and in particular upon attachment of an antigen-antibody (aIgG-IgG) pair. We investigate the relation of the amount of reduction of photoluminescence on planar and microstructured surfaces, and we show that microstructuring leads to a higher reduction than a planar surface. Furthermore, we evaluated the dependence of photoluminescence reduction as a function of analyte concentration to prove that this magnitude can be applied to immunosensing.
Keywords: SU-8; Photolithography; Photoluminescence; Immunosensing;

Display OmittedThe production of H2 by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H2 by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO2/C nano-flakes, which was used as an efficient visible-light photocatalyst for H2 evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO2 nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m2  g−1 and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H2 production rate of 57.2 μmol h−1 under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO2 and carbon in this hybrid catalyst. This work highlights the potential of TiO2/C nano-flakes in the field of photocatalytic H2 evolution under visible-light irradiation.
Keywords: TiO2/C; Nano-flakes; Photocatalytic H2-production; Visible-light;

Three-dimensional mesoporous TiO2/graphene (TiO2/G) microspheres have been successfully synthesized through a simple UV-assisted method of reduced graphene oxide with hydrazine. The as-made surface modified mesoporous TiO2/G microspheres possess large surface area and exhibit a high initial discharge capacity of 220 mAh g−1 and retain 84% (∼185 mAh g−1) of reversible capacity over 100 cycles at a rate of 0.2C. In addition, TiO2/G microspheres display improved cyclic performance, excellent rate capability and enhanced electrical conductivity, which are superior to the bare TiO2 microspheres. Furthermore, TiO2/G microspheres can achieve a reversible capacity of 141 mAh g−1 upon 100 cycles even at the 1C rate. We believe that the mesoporous TiO2/G microspheres are expected to be a promising high performance anode material for the next generation lithium ion batteries.
Keywords: UV-assisted; TiO2; Graphene; Electrochemical performances;

Display OmittedNonlinear absorption and optical limiting properties of ZnFe2O4-rGO magnetic nanostructures was investigated by the Z-scan technique using Q-switched Nd:YAG laser (5 ns, 532 nm, 10 Hz) as an excitation source. Excited state absorption was the dominant process responsible for the observed nonlinearity in ZnFe2O4 decorated rGO which arises due to photo-generated charge carriers in the conduction band of zinc ferrite and increases in defects at the surface of rGO due to the incorporation of ZnFe2O4. The magnitude of the nonlinear absorption co-efficient was found to be in the order of 10−10  m/W. A noteworthy enhancement in the third-order NLO properties in ZnFe2O4-(15 wt%) rGO with those of individual counter parts and well known graphene composites was reported. Role of induced defects states (sp3) arising from the functionalization of rGO in the enhancement of NLO response was explained through Raman studies. Earlier incorporation and distribution of ZnFe2O4 upon GO through one-step hydrothermal method was analyzed by XRD and FTIR. Formation of (nanospheres/nanospindles) ZnFe2O4 along with reduction of graphene oxide was confirmed through TEM analysis. VSM studies showed zinc ferrite decorated rGO posseses superparamagnetic behavior. The tuning of nonlinear optical and magnetic behavior with variation in the content of spinel ferrites upon reduced graphene oxide provides an easy way to attain tunable properties which are exceedingly required in both optoelectronics and photothermal therapy applications.
Keywords: Z-scan; Two-photon absorption; Reverse saturable absorption; Superparamagnetic properties;

Electrochemically promoted electroless nickel-phosphorous plating on titanium substrate by Ce Gao; Lei Dai; Wei Meng; Zhangxing He; Ling Wang (912-919).
An electrochemically promoted electroless nickel–phosphorous plating process on titanium substrate is proposed. The influences of the temperature and current density on the phosphorous content, coating thickness and corrosion resistance are investigated. The results show that with the help of the electrochemical promotion, the uniform and amorphous nickel–phosphorous coatings with medium phosphorus content (6–8 wt%) are successfully prepared in the electroless bath at 40–60 °C. The phosphorous content of the coating increases with the temperature increasing, while decreases with current density increasing. Obvious passivation occurs for the nickel–phosphorous coatings during the anodic polarization in 3.5 wt% NaCl solution.
Keywords: Electroless plating; Electrochemical promotion; Nickel–phosphorous coating; Titanium; Corrosion electrochemical behaviour;

Display OmittedDensity functional theory (DFT) calculations were carried out to study the activation of methyl acetate and methanol on MgO(100) and MgO(501) surfaces and integrated in the context of transesterification, interesterification and glycerolysis reactions used in biodiesel industry. First results indicate the importance of including of dispersion forces in the calculations. On MgO(100) the reverse reactions steps of C―O and C―H dissociations and on MgO(501) the same reverse reaction step of C―H dissociations of methyl acetate are energetically favorable, while the dissociation of C―O bond into methoxide and acetate fragments on the edge of MgO(501) was found to be exothermic with a low activation energy. For methanol, the dissociation of O―H bond on MgO(100) surface in the presence of the second coadsorbed methanol molecule becomes more energetically favoured compared to the isolated molecule, due to the fact that the methoxide fragment is stabilized by intermolecular hydrogen bonding. This is reflected by the decrease of the activation energy of the forward reaction step and the increase of the activation energy of the backward reaction step, increasing the probability to have dissociated molecules among the undissociated ones. These results represent a step forward for better understanding from atomistic point of view the paths of these reactions on these surfaces for the corresponding catalytic processes.
Keywords: DFT; MgO surfaces; Methyl acetate dissociation; Methanol dissociation; Biodiesel;

Wetting characteristics of 3-dimensional nanostructured fractal surfaces by Ethan Davis; Ying Liu; Lijia Jiang; Yongfeng Lu; Sidy Ndao (929-935).
Display OmittedThis article reports the fabrication and wetting characteristics of 3-dimensional nanostructured fractal surfaces (3DNFS). Three distinct 3DNFS surfaces, namely cubic, Romanesco broccoli, and sphereflake were fabricated using two-photon direct laser writing. Contact angle measurements were performed on the multiscale fractal surfaces to characterize their wetting properties. Average contact angles ranged from 66.8° for the smooth control surface to 0° for one of the fractal surfaces. The change in wetting behavior was attributed to modification of the interfacial surface properties due to the inclusion of 3-dimensional hierarchical fractal nanostructures. However, this behavior does not exactly obey existing surface wetting models in the literature. Potential applications for these types of surfaces in physical and biological sciences are also discussed.
Keywords: Fractal; Wetting characteristics; Two-photon photolithography; Hierarchical;

Stability of Ptn cluster on free/defective graphene: A first-principles study by G.M. Yang; X.F. Fan; S. Shi; H.H. Huang; W.T. Zheng (936-941).
Display OmittedWith first-principles methods, we investigate the stability of isolated Ptn clusters from Sutton-Chen model and close-packed model, and their adsorption on defected graphene. The single-vacancy in graphene is found to enhance obviously the adsorption energy of Pt cluster on graphene due to the introduction of localized states near Fermi level. It is found that the close-packed model is more stable than Sutton-Chen model for the adsorption of Ptn cluster on single-vacancy graphene, except the magic number n = 13. The cluster Pt13 may be the richest one for small Pt clusters on defected graphene due to the strong adsorption on single-vacancy. The larger cluster adsorbed on defected graphene is predicted with the close-packed crystal structure. The charge is found to transfer from the Pt atom/cluster to graphene with the charge accumulation at the interface and the charge polarization on Pt cluster. The strong interaction between Pt cluster and single vacancy can anchor effectively the Pt nanoparticles on graphene and is also expected that the new states introduced near Fermi level can enhance the catalytic characteristic of Pt cluster.
Keywords: Stability; Pt cluster; Graphene; First-principles;

Molecular dynamics simulation of plasticity in VN(001) crystals under nanoindentation with a spherical indenter by Tao Fu; Xianghe Peng; Chen Wan; Zijun Lin; Xiaosheng Chen; Ning Hu; Zhongchang Wang (942-949).
We perform molecular dynamics simulations of the nanoindentation on VN (001) films with a spherical indenter to elucidate the initial plastic deformation and the formation mechanisms of dislocation loops during nanoindentation. We find that the nucleation and movement of partial dislocations are the main mechanism of the inelastic deformation at the initial plastic stage of nanoindentation, when the “dislocation flower” consisting of several {111} stacking fault planes and the 〈110〉 stair rod dislocation lines are observed. With the increase in indentation depth, the newly nucleated dislocations react with the existing ones, forming four kinds of dislocation loops. Moreover, we also conduct a systematic analysis of the formation process of the dislocation flower and the four kinds of dislocation loops.
Keywords: VN; Molecular dynamics simulation; Nanoindentation; Dislocation flower; Dislocation loops;

When poly(N-isopropyl acrylamide) (pNIPAM) is tethered to a surface, it can induce the spontaneous release of a sheet of mammalian cells. The release of cells is a result of the reversible phase transition the polymer undergoes at its lower critical solution temperature (LCST). Many techniques are used for the deposition of pNIPAM onto cell culture substrates. Previously, we compared two methods of deposition (plasma polymerization, and co-deposition with a sol-gel). We proved that although both were technically appropriate for obtaining thermoresponsive pNIPAM films, the surfaces that were co-deposited with a sol-gel caused some disruption in cell activity. The variation of cell behavior could be due to the delamination of pNIPAM films leaching toxic chemicals into solution. In this work, we assessed the stability of these pNIPAM films by manipulating the storage conditions and analyzing the surface chemistry using X-ray photoelectron spectroscopy (XPS) and contact angle measurements over the amount of time required to obtain confluent cell sheets. From XPS, we demonstrated that ppNIPAM (plasma polymerized NIPAM) films remains stable across all storage conditions while sol-gel deposition show large deviations after 48 h of storage. Cell response of the deposited films was assessed by investigating the cytotoxicity and biocompatibility. The 37 °C and high humidity storage affects sol-gel deposited films, inhibiting normal cell growth and proper thermoresponse of the film. Surface chemistry, thermoresponse and cell growth remained similar for all ppNIPAM surfaces, indicating these substrates are more appropriate for mammalian cell culture applications.
Keywords: pNIPAM; Isopropyl acrylamide; XPS; ESCA; Mammalian cells;

Crack-free CH3NH3PbI3 layer via continuous dripping method for high-performance mesoporous perovskite solar cells by Guo Chen; Jianghui Zheng; LingLing Zheng; Xin Yan; Huangding Lin; Fengyan Zhang (960-965).
Display OmittedThe past five years have witnessed the uniquely rapid emergence of the mixed organic-inorganic halide perovskite solar cells. Here, a modified deposition process, continuous dripping method, is reported for fabricating high-performance and reproducible perovskite solar cells. We have systematically investigated the impact of different molar ratio of lead iodide (PbI2) to dimethylsulfoxide (DMSO) on the growth, morphology and crystallinity of CH3NH3PbI3 (MAPbI3) films obtained via this process. The high power conversion efficiency (PCE) perovskite solar cell originates in crack-free and highly crystallographic perovskite films prepared with optimized ratio of PbI2 to DMSO in first precursor solution. The best PCE of 17.76% and an average PCE of 16.37 ± 0.51% were obtained via this process. Moreover, the conventional solution two steps method was also carried out as a comparison to this process. This work provides a new simple solution approach to obtain high quality of perovskite thin films for high-performance and reproducible PSCs.
Keywords: Perovskite solar cells; Two-step process; Continuous dripping method; Crack-free film; PbI2(DMSO)2 complex;

The effects of nonmetal dopants on the electronic, optical and chemical performances of monolayer g–C3N4 by first-principles study by S. Lu; C. Li; H.H. Li; Y.F. Zhao; Y.Y. Gong; L.Y. Niu; X.J. Liu; T. Wang (966-974).
Doping is an effective means to alter the electronic behavior of materials by forming new chemical bond and relaxing the surrounding chemical bonds. With the aid of first-principle studies, the effects of a series of nonmetal (NM) dopants on the geometric, thermodynamic, electronic and optical performances of monolayer g–C3N4 have been investigated. Results shown that, all considered NM atoms except Br and I atoms can be introduced into the monolayer g–C3N4 on account of the thermal stability, the supercell parameter and film thickness have been altered by the newly formed C―NM bonds and the relaxed chemical bonds around them, which have affected their electronic structure. The band gap values were altered less than ±0.14 eV. The optical absorption edge (and intensity) in visible light of all doped specimens red-shift 10–75 nm (and increase about 14%–71%) except for O– and S–doped specimens, and thus the NM dopants can enhance the visible-light response capability. Moreover, the highest occupied molecular orbital and lowest unoccupied molecular orbital of H–, B–, O–, S–, F– and As–doped specimens have been separated adequately, it can effectively separate the photogenerated e/h+ pairs and enhance the photocatalytic efficiency. Finally, we have confirmed six high efficiency monolayer g–C3N4 based photocatalysts by doping H, B, O, S, F and As atoms.
Keywords: Nonmetal doping; Monolayer g–C3N4; Chemical bond relaxation; Electronic structure and photocatalytic ability;

The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode.
Keywords: Poly (trimethylene terephthalate); Molecular dynamics; Conformation; Graphene; Carbon nanotube;

Perspective of laser-prototyping nanoparticle-polymer composites by Dongshi Zhang; Bilal Gökce (991-1003).
Display OmittedNanoparticle synthesis by laser ablation in liquids has attracted attention from researchers worldwide the past few years and the integration of these nanoparticles in functional materials such as nanoparticle-polymer composites, represents a natural next step. Such “nanointegration” into polymers can be achieved by the ex situ dispersion of laser-synthesized inorganic nanoparticles in polymer matrices and the in situ encapsulation/grafting of nanoparticles with polymers/monomers during synthesis. Because the nanoparticle shell and the polymer matrix may be identical, this method often does not require the use of dispersants or matrix binders and constitutes a new avenue for direct particle-polymer coupling. In this perspective review, we summarize the methodologies for in situ and ex situ laser prototyping of nanoparticle-polymer composites (LaNPC) and downstream bulk-processing techniques. The determinants of polymer-solvent-laser parametrization for aimed physical and chemical properties of the composites are discussed. By highlighting representative works related to a variety of promising applications, the advantageous features of this technique are demonstrated. Finally, the challenges and prospects of LaNPC are outlined and a perspective is given regarding how the recent research findings reviewed changed the research direction in the field.
Keywords: Laser ablation synthesis in liquid; Composites; Core-shell; Polymerization; Grafting; Encapsulation; Dispersion;

The effect of surface pre-treatment of pipe surface by green cerium compound and phosphoric acid solution on the fusion-bonded epoxy (FBE) coating performance was studied. The composition and surface morphology of the steel samples treated by acid and Ce solutions were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), equipped with energy dispersive spectroscopy (EDS). Also, the surface free energy was evaluated on these samples through contact angle measurements. In addition, the effect of Ce and acid washing procedures on the adhesion properties and corrosion protection performance of the FBE was examined by pull-off, salt spray and electrochemical impedance spectroscopy (EIS) tests. Results showed that compared to acid washing, the chemical treatment by Ce solution noticeably increased the surface free energy of steel, improved the adhesion properties of FBE, decreased the cathodic delamination rate of FBE, and enhanced the coating corrosion resistance compared to the acid washed samples.
Keywords: Corrosion resistance; Ce treatment; Cathodic delamination; XPS; SEM; EIS;

Display OmittedStructural and morphological features of the wetting layer formation and the transition to the three-dimensional Ge growth on (111) and (100) Si surfaces under quasi-equilibrium growth conditions were studied by means of scanning tunneling microscopy. The mechanism of the transition from the wetting layer to the three-dimensional Ge growth on Si was demonstrated. The principal differences and general trends of the atomic processes involved in the wetting layers formation on substrates with different orientations were demonstrated. The Ge growth is accompanied by the Ge atom redistribution and partial strain relaxation due to the formation of new surfaces, vacancies and surface structures of a decreased density. The analysis of three-dimensional Ge islands sites nucleation of after the wetting layer formation was carried out on the (111) surface. The transition to the three-dimensional growth at the Si(100) surface begins with single {105} facets nucleation on the rough Ge(100) surface.
Keywords: Stranski-Krastanow mechanism; Ge-Si; Surface reconstructions; Scanning tunneling microscopy; Molecular beam epitaxy;

Impact of the nanostructuration on the corrosion resistance and hardness of irradiated 316 austenitic stainless steels by E. Hug; R. Prasath Babu; I. Monnet; A. Etienne; F. Moisy; V. Pralong; N. Enikeev; M. Abramova; X. Sauvage; B. Radiguet (1026-1035).
Display OmittedThe influence of grain size and irradiation defects on the mechanical behavior and the corrosion resistance of a 316 stainless steel have been investigated. Nanostructured samples were obtained by severe plastic deformation using high pressure torsion. Both coarse grain and nanostructured samples were irradiated with 10 MeV 56Fe5+ ions. Microstructures were characterized using transmission electron microscopy and atom probe tomography. Surface mechanical properties were evaluated thanks to hardness measurements and the corrosion resistance was studied in chloride environment. Nanostructuration by high pressure torsion followed by annealing leads to enrichment in chromium at grain boundaries. However, irradiation of nanostructured samples implies a chromium depletion of the same order than depicted in coarse grain specimens but without metallurgical damage like segregated dislocation loops or clusters. Potentiodynamic polarization tests highlight a definitive deterioration of the corrosion resistance of coarse grain steel with irradiation. Downsizing the grain to a few hundred of nanometers enhances the corrosion resistance of irradiated samples, despite the fact that the hardness of nanocrystalline austenitic steel is only weakly affected by irradiation. These new experimental results are discussed in the basis of couplings between mechanical and electrical properties of the passivated layer thanks to impedance spectroscopy measurements, hardness properties of the surfaces and local microstructure evolutions.
Keywords: Stainless steel; Nanostructured grains; Irradiation resistance; High pressure torsion; Corrosion resistance;

Langmuir-Blodgett assembly of visible light responsive TiO2 nanotube arrays/graphene oxide heterostructure by Ying Chen; Hongyan Gao; Danming Wei; Xinju Dong; Yan Cao (1036-1042).
Display OmittedThe hybrid nanocomposites of titanium dioxide (TiO2) with graphene oxide (GO) have recently garnered much attention as electronic devices, energy conversion devices, photocatalysts and other applications. In this study, Langmuir-Blodgett (LB) assembly method was firstly reported to prepare a TiO2 nanotube arrays (TNA)-GO heterostructure. The as-prepared TNA-GO sample was characterized by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The promising characteristics of this TNA-GO material, the inexpensive, nontoxic and highly visible-light responsiveness, may raise the potential uses in many, various photocatalytic applications.
Keywords: TiO2 nanotube arrays; Graphene oxide; Langmuir-Blodgett assembly; Photoresponse;

Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy by W. Zhao; M. Steidl; A. Paszuk; S. Brückner; A. Dobrich; O. Supplie; P. Kleinschmidt; T. Hannappel (1043-1048).
Display OmittedFor well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H2-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H2 ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.
Keywords: (MO)CVD; MOVPE; Thermal deoxidation; Si(111); Hydrogen; III-V-on-Si heteroepitaxy;

In-situ monitoring of etching of bovine serum albumin using low-temperature atmospheric plasma jet by J. Kousal; A. Shelemin; O. Kylián; D. Slavínská; H. Biederman (1049-1054).
Display OmittedBio-decontamination of surfaces by means of atmospheric pressure plasma is nowadays extensively studied as it represents promising alternative to commonly used sterilization/decontamination techniques. The non-equilibrium atmospheric pressure plasmas were already reported to be highly effective in removal of a wide range of biological residual from surfaces. Nevertheless the kinetics of removal of biological contamination from surfaces is still not well understood as the majority of performed studies were based on ex-situ evaluation of etching rates, which did not allow investigating details of plasma action on biomolecules. This study therefore presents a real-time, in-situ ellipsometric characterization of removal of bovine serum albumin (BSA) from surfaces by low-temperature atmospheric plasma jet operated in argon. Non-linear and at shorter distances between treated samples and nozzle of the plasma jet also non-monotonic dependence of the removal rate on the treatment duration was observed. According to additional measurements focused on the determination of chemical changes of treated BSA as well as temperature measurements, the observed behavior is most likely connected with two opposing effects: the formation of a thin layer on the top of BSA deposit enriched in inorganic compounds, whose presence causes a gradual decrease of removal efficiency, and slight heating of BSA that facilitates its degradation and volatilization induced by chemically active radicals produced by the plasma.
Keywords: Atmospheric plasma; Plasma jet; Etching; Protein; In-situ; Ellipsometry;

Synthesis of ultra-thin tellurium nanoflakes on textiles for high-performance flexible and wearable nanogenerators by Wen He; Huynh Van Ngoc; Yong Teng Qian; Jae Seok Hwang; Ya Ping Yan; Hongsoo Choi; Dae Joon Kang (1055-1061).
We report that ultra-thin tellurium (Te) nanoflakes were successfully grown on a sample of a gold-coated textile, which then was used as an active piezoelectric material. An output voltage of 4 V and a current of 300 nA were obtained from the bending test under a driving frequency of 10 Hz. To test the practical applications, Te nanoflake nanogenerator (TFNG) device was attached to the subject’s arm, and mechanical energy was converted to electrical energy by means of periodic arm-bending motions. The optimized open-circuit voltage and short-circuit current density of approximately 125 V and 17 μA/cm2, respectively, were observed when a TFNG device underwent a compression test with a compressive force of 8 N and driving frequency of 10 Hz. This high-power generation enabled the instantaneous powering of 10 green light-emitting diodes that shone without any assistance from an external power source.
Keywords: Textile; Tellurium nanoflake; Bending; Compressing; Nanogenerators;

Display OmittedElectrically-conductive nanocrystalline carbon films, having non-toxic and non-immunogenic characteristics, are promising candidates for reusable medical devices. Here, the pure and N- doped nanocrystalline carbon films are deposited by the assistance of inductively coupled plasma (ICP) in an unbalanced facing target pulsed-DC magnetron sputtering process. Through the optical emission spectroscopy study, the role of ICP assistance and N-doping on the reactive components/radicals during the synthesis is presented. The N-doping enhances the three fold bonding configurations by increasing the ionization and energies of the plasma species. Whereas, the ICP addition increases the plasma density to control the deposition rate and film structure. As a result, sputtering-throughput (deposition rate: 31–55 nm/min), electrical resistivity (4–72 Ωcm) and water contact angle (45.12°–54°) are significantly tailored. Electric transport study across the surface microchannel confirms the superiority of N-doped carbon films for sterilization stability over the undoped carbon films.
Keywords: Carbon thin films; ICP; Sterilization; Electron transport; Surface morphology; Pulsed-DC plasma;

Display OmittedVarious weight loadings of Ag (1–10 wt.%) were introduced to mesoporous titania nanoparticles (MTN) via a direct in-situ electrochemical method. The catalysts were characterized by XRD, surface area analysis, FTIR, ESR, FESEM-EDX and TEM. Characterization results indicated that the introduction of Ag onto MTN decreased the particles size and band gap of the MTN while increasing the number of oxygen vacancies (OV) and Ti3+ site defects (TSD). The activity performance of Ag-MTN on photodegradation of 2-chlorophenol (2-CP) under visible light irradiation was in the following order: 5 wt% Ag-MTN> 1 wt% Ag-MTN > MTN > 10 wt% Ag-MTN, with degradation percentages of 97, 88, 80 and 63%, respectively. The synergistic effect between Ag0 and MTN seemed to play an important role in the system. The Ag0 acted as both an electron trap and a plasmonic sensitizer which suppressed the electron-hole recombination, while OV and TSD in the MTN accelerated the production of hydroxyl radicals for enhanced degradation of 2-CP. However, the formation of Ti-O-Ag in 10 wt% Ag-MTN was found to decrease the photoactivity due to the decrease in the formation of Ag0, TSD and OV as well as the increase in band gap energy. The photodegradation of 5 wt% Ag-MTN followed a pseudo-first-order Langmuir- Hinshelwood model and the catalyst was still stable after five cycles.
Keywords: Ag-MTN catalyst; Ag-Ti interaction; Visible light; Plasmonic resonance; Photoactivity;

Building of CoFe2/CoFe2O4/MgO architectures: Structure, magnetism and surface functionalized by TiO2 by M. Wang; Y.Q. Ma; X. Sun; B.Q. Geng; M.Z. Wu; G.H. Zheng; Z.X. Dai (1078-1087).
In order to expand the applications of magnetic nanoparticles, nanostructure CoFe2/CoFe2O4/MgO was synthesized. The CoFe2 core has the highest magnetization among all binary alloys, enhancing the response of magnetic nanoparticles to the external magnetic field; The CoFe2O4 shell protects CoFe2 core from oxidation and improve the stability and biocompatibility of magnetic nanoparticles. Some magnetic nanoparticles were functionalized by TiO2. The hollow rattle-type particles were obtained without the assistance of template and etchant, which has been generally used in previous reports. The photocatalytic performance was investigated for the functionalized magnetic nanoparticles. The rattle-type particles exhibited the strong absorption to methylene blue; The highest degradation efficiency reaches 93% for CoFe2/TiO2; CoFe2/TiO2 has the high magnetization, beneficial for the recovery of catalyst after degradation.Display OmittedWell-dispersed uniform CoFe2O4 nanoparticles were prepared and then coated by MgO through thermal decomposition of a metal–organic salt in organic solvent. Then CoFe2O4/MgO were reduced in a H2/N2 mixture gas and subsequently oxidized in an ambient atmosphere in order to build CoFe2/CoFe2O4/MgO architectures with high magnetization, good chemical stability and dispersivity, which are useful in some practical applications. MgO can be dissolved by the HCl solution. The surfaces of CoFe2O4, CoFe2/MgO, CoFe2 and CoFe2/CoFe2O4 magnetic particles were functionalized by TiO2 to prepare the magnetically separable photocatalysts. The rattle-type particles were obtained without the assistance of template and etchant. The photocatalytic activity of these photocatalysts in degradation of methylene blue and the magnetic separability were investigated: The nanosheet-shaped TiO2 and rattle-type particles exhibited good photocatalytic performance; The highest degradation efficiency reaches 93% for the CoFe2/TiO2 sample which has the highest magnetization value of 42 emu/g, beneficial for the recovery of catalyst after degradation.
Keywords: CoFe2/CoFe2O4/MgO architecture; Surface functionalization; TiO2; Rattle-type nanostructures; Photocatalyst;

Quasi-chemical approach for adsorption of mixtures with non-additive lateral interactions by O.A. Pinto; P.M. Pasinetti; A.J. Ramirez-Pastor (1088-1096).
Display OmittedThe statistical thermodynamics of binary mixtures with non-additive lateral interactions was developed on a generalization in the spirit of the lattice-gas model and the classical quasi-chemical approximation (QCA). The traditional assumption of a strictly pairwise additive nearest-neighbors interaction is replaced by a more general one, namely that the bond linking a certain atom with any of its neighbors depends considerably on how many of them are actually present (or absent) on the sites in the first coordination shell of the atom. The total and partial adsorption isotherms are given for both attractive and repulsive lateral interactions between the adsorbed species. Interesting behaviors are observed and discussed in terms of the low-temperature phases formed in the system. Comparisons with Monte Carlo simulations are performed in order to test the validity of the theoretical model.
Keywords: Equilibrium thermodynamics and statistical mechanics; Lattice-gas models; Non-additive lateral interactions; Gas mixture adsorption; Monte Carlo simulations;

The NiO nanocrystals were successfully prepared by calcinating Ni(OH)2 precursor synthesized via a facile ion diffusion controlled by ion exchange membrane without adding any solvent or template. X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) isotherm, X-ray photoelectron spectroscopy (XPS) and Ultraviolet–visible (UV–vis) analysis were used to investigate the crystallinity, morphology, surface and porosity characteristics, chemical composition and optical properties in more detail. The pseudocapacitive behavior of the NiO samples was investigated by cyclic voltammograms (CV) and galvanostatic charge-discharge tests in 2 M KOH. The results analysis reveals that both specific capacitance and surface area decrease with the increase of calcination temperatures. Among the NiO samples, the NiO-400 nanoflakes calcinated at 400 °C possess the highest specific capacitance of 381 F g−1 at a current density of 2 A g−1, but much lower than the Ni(OH)2 sample. In addition, the UV–vis analysis shows that there is a red shift of absorption peak for the three NiO samples with the increasing temperature and the NiO-400 has a broad band gap of 3.3 eV, which renders the material highly interesting for application in photocatalyst.
Keywords: Ion diffusion; Ion exchange membrane; β-Ni(OH)2 nanoflake; NiO nanoflakes; Supercapacitors;

Photocatalytic oxidation removal of Hg0 using ternary Ag/AgI-Ag2CO3 hybrids in wet scrubbing process under fluorescent light by Anchao Zhang; Lixiang Zhang; Xiaozhuan Chen; Qifeng Zhu; Zhichao Liu; Jun Xiang (1107-1116).
Display OmittedA series of ternary Ag/AgI-Ag2CO3 photocatalysts synthesized using a facile coprecipitation method were employed to investigate their performances of Hg0 removal in a wet scrubbing reactor. The hybrids were characterized by N2 adsorption-desorption, XRD, SEM-EDS, HRTEM, XPS, DRS and ESR. The photocatalytic activities of Hg0 removal were evaluated under fluorescent light. The results showed that AgI content, fluorescent light irradiation, reaction temperature all showed significant influences on Hg0 removal. NO exhibited significant effect on Hg0 removal in comparison to SO2. Among these ternary Ag/AgI-Ag2CO3 hybrids, Ag/AgI(0.1)-Ag2CO3 showed the highest Hg0 removal efficiency, which could be ascribed to the effective separation of photogenerated electron-hole pairs between AgI and Ag2CO3 and the surface plasmon resonance (SPR) effect in the visible region by metallic silver nanoparticles (Ag0 NPs). The trapping studies of reactive radicals showed that the superoxide radicals (•O2 ) may play a key role in Hg0 removal under fluorescent light. According to the experimental and characterization results, a possible photocatalytic oxidation mechanism for enhanced Hg0 removal over Ag/AgI(0.1)-Ag2CO3 hybrid under fluorescent light was proposed.
Keywords: Photocatalytic oxidation; Hg0 removal; Ag/AgI-Ag2CO3 photocatalysts; Wet scrubbing process; Fluorescent light;

High adhesion transparent conducting films using graphene oxide hybrid carbon nanotubes by Shi-Xun Da; Jie Wang; Hong-Zhang Geng; Song-Lin Jia; Chun-Xia Xu; Lin-Ge Li; Pei-Pei Shi; Guangfen Li (1117-1125).
The GO hybrid CNTs to fabricate TCFs could dramatically enhance the conductivity, adhesion, flatness, and wettability of the films, all these improvements are advantageous for optoelectronic applications.Display OmittedFlexible transparent conducting films (TCFs) with carbon nanotubes (CNTs) have attracted more and more attention for their wide range of potential applications. While, there are still some problems to be solved on several aspects. In this study, a graphene oxide/carbon nanotube (GO/CNT) hybrid TCF was fabricated through the simple spray coating method. GO sheets were introduced to form new electron transporting channels. It was found that the best optoelectronic property films were fabricated when the ratio of GO/CNT is 1.5:1.0, which the sheet resistance of the film was found to be 146 Ω/sq at the transmittance of 86.0%. Due to the two-dimensional structure and the oxidation groups of GO sheets, flatness and wettability of the electrode surface was improved obviously. Adhesion factor of the TCFs was calculated by the change of transparent and sheet resistance after trial test, the addition of GO sheets enhanced the adhesion dramatically and the mechanism was analyzed. Improvements of conductivity, flatness, wettability and adhesion above are all advantageous for the solution-based processing of organic electronics for spraying and printing.
Keywords: Carbon nanotube; Graphene oxide; Hybrid; Transparent conducting films;

Display OmittedRemarkable improvement in antibacterial activity and durability of different cellulosic substrates namely cotton, linen, viscose and lyocell was achieved by pre-surface modification using N2-plasma to create new active and binding sites, –NH2 groups, onto the modified fabric surfaces followed by subsequent loading of biosynthesized silver nanoparticles (Ag NPs) alone and in combination with certain antibiotics using exhaustion method. The imparted antibacterial activity against both G+ve (S. aureus) and G−ve (E. coli) pathogens was governed by type of substrate, extent of modification and subsequent loading of antibacterial agent, synergistic effect, and antibacterial activity as well as type of harmful bacteria. A remarkable antibacterial activity still retained even after 15 washings.In addition, incorporation of Ag NPs into pigment printing paste and into acid dyeing bath for combined coloration and functionalization of O2-plasma and N2-plasma pre-modified substrates respectively were successfully achieved.Moreover, both SEM images and EDS spectra of selected substrates revealed the change in surface morphology as well as the presence of the loaded Ag element onto the post-treated substrates.
Keywords: Cellulosic substrates; Antibacterial functionalization; Plasma pretreatment; Biosynthesized Ag NPs; Antibiotics; Combined coloration and functionalization;

Enhancement of ZnO-rGO nanocomposite thin films by gamma radiation for E. coli sensor by Noor Azwen Noor Azmy; Ahmad Ashrif A. Bakar; Norhana Arsad; Sarada Idris; Abdul Rahman Mohmad; Aidil Abdul Hamid (1134-1143).
The fabricated E. coli sensor of ZnO-rGO nanocomposite thin films by gamma radiation was investigated. Nanocomposite films were prepared via sol–gel method and were irradiated at 10 kGy at room temperature. The surface characteristic of as-prepared samples have been characterized by x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The proposed structure shows that exposed gamma radiation may change the microstructure of the films occurs as a result of their flexible structure. Uv–vis spectra of nanocomposite were studied to investigate the optical behavior of ZnO-rGO films and the optical energy band gap and Urbach energy were found to be gamma dose dependent. The sensing properties were identified by measuring the changes of conductivity of film using I-V measurement. Upon exposure to E. coli, the radiated ZnO-rGO films (1.00 vol% GO) exhibited higher sensitivity, as much as 4.62 × 10−3, than un-radiated films, 1.04 × 10−3. This enhancement of the I-V response was attributed to a positive influence of the gamma radiation in these films. The results prove that our ZnO-rGO nanocomposites thin films by gamma radiation demonstrate a strong performance for the detection of microbiological organisms in water.
Keywords: Gamma radiation; ZnO-rGO nanocomposite; Thin films; E. coli sensor;

Double hollow MoS2 nano-spheres: Synthesis, tribological properties, and functional conversion from lubrication to photocatalysis by Yueru Liu; Kunhong Hu; Enzhu Hu; Jianhua Guo; Chengliang Han; Xianguo Hu (1144-1152).
Molybdenum disulfide (MoS2) has extensive applications in industries as solid lubricants and catalysts. To improve the lubricating performance of MoS2, novel double-hollow-sphere MoS2 (DHSM) nanoparticles with an average diameter of approximately 90 nm were synthesized on sericite mica (SM). When the DHSM/SM composite was used as an additive in polyalphaolefin oil, friction and wear decreased by 22.4% and 63.5% respectively. The low friction and wear were attributed to the easy exfoliation of DHSM. The DHSM/SM composite was then rubbed under 40 MPa for 1 h to investigate the exfoliation and functional conversion behaviors of DHSM. Results showed that DHSM (lubricating structure) on SM could be completely exfoliated into nanosheets (catalytic structure) by rubbing. The nanosheets exfoliated from DHSM presented good photocatalytic activity for the removal of organic compounds from waste water. This work provided both a novel solid lubricant for industrial applications and a possible approach to designing a novel green lubricant for use as a photocatalyst in organic-waste treatment after lubricating service life.
Keywords: Molybdenum disulfide; Solid lubricant additives; Photocatalysis; Nanoparticles; Double hollow nanostructure;

Atomistic simulations were used to investigate the plastic deformation behavior of bicrystalline silver nanowires with Σ3 asymmetric tilt grain boundaries at 0.1 K. The calculated grain boundary energies of Σ3 asymmetric tilt grain boundaries corresponded well with the energies measured in experiments and predicted by the theoretical description. The Σ3 asymmetric tilt grain boundaries with low inclination angles were composed of a replication of twin boundary segments separated by small ledges. The results demonstrated that the combination effect of Schmid factor and non-Schmid factors could explain dislocations emission into grain 1 only in models with low inclination angles (Ф < 64.76°). At the latter stage of plastic deformation, free surfaces served as additional dislocation sources. Parallelly arranged operative slip systems were the fundamental features of plastic deformation. In addition, a number of stacking faults and multiple stacking faults were formed during plastic deformation. The hindrance of stacking faults to dislocation motion and the interactions between dislocations leaded to the observed strain hardening in nanowires with inclination angles at and above 29.50°. The low stacking fault energy of silver was responsible for the appearance of strain hardening. Dislocations emitted from grain 2 interacted with each other contributing to the observed strain hardening. Grain boundaries were completely eliminated by successive emission of dislocations from grain boundaries in nanowires with an inclination angle of 35.26° and 54.74°. A detailed understanding of the relationship between strength and grain boundary structures as well as specific plastic deformation would push forward the application of nanocrystalline materials and provide insights into the synthesis of nanocrystalline materials with superior strength and ductility.
Keywords: Plastic deformation; Tension; Inclination angle; Bicrystals; Atomistic simulation; Plasticity;

Influence of O2 exposure on the interaction between CH4 and amorphous AlYB14 by Oliver Hunold; Martin Wiesing; Teresa de los Arcos; Denis Music; Guido Grundmeier; Jochen M. Schneider (1165-1172).
The influence of surface oxidation on the interaction between CH4 and amorphous AlYB14 (a-AlYB14) has been studied theoretically by using density functional theory and experimentally by ultra-high vacuum atomic force microscopy (UHV-AFM). CH4 mimics the –CH3 termination and aliphatic subunits of a polymer chain. Low-energy ion scattering measurements of magnetron sputtered thin films suggest that the bonding at the surfaces of pristine a-AlYB14 and O2 exposed a-AlYB14 (O2//a-AlYB14) is metal-boron and metal-oxygen dominated, respectively. Based on the ab initio calculations the adsorption energies of CH4 on a-AlYB14 and O2//a-AlYB14 decreases from −0.07 to −0.30 eV, respectively. This trend is consistent with experimental data obtained by colloidal probe UHV-AFM studies with a polyethylene sphere, where larger adhesion forces for the O2 exposed surface as compared to the pristine a-AlYB14 surface were measured. No charge transfer takes place between CH4 and the pristine as well as the O2 exposed a-AlYB14. Oxygen chemisorption induces changes in surface bonding. States at the Fermi level are depleted upon oxidation, hence the surface bonding becomes more semiconducting causing a charge redistribution within the adsorbed CH4 molecule. Hence, these data serve as proof of concept for exploring the effect of O2 exposure on the interaction between aliphatic polymers and a-AlYB14 using a correlative experimental and theoretical research approach.
Keywords: Ab initio molecular dynamics; Atomic force microscopy; O2 exposure; Adsorption; Amorphous AlYB14; Thin films;

Optimal process parameters for phosphorus spin-on-doping of germanium by Virginia Boldrini; Sara Maria Carturan; Gianluigi Maggioni; Enrico Napolitani; Daniel Ricardo Napoli; Riccardo Camattari; Davide De Salvador (1173-1180).
Display OmittedThe fabrication of homogeneously doped germanium layers characterized by total electrical activation is currently a hot topic in many fields, such as microelectronics, photovoltaics, optics and radiation detectors. Phosphorus spin-on-doping technique has been implemented on Ge wafers, by developing a protocol for the curing process and subsequent diffusion annealing for optimal doping. Parameters such as relative humidity and curing time turned out to affect the surface morphology, the degree of reticulation reached by the dopant source and the amount of dopant available for diffusion. After spike annealing in a conventional furnace, diffusion profiles and electrical properties have been measured. Ge loss from the surface during high-temperature annealing, due to diffusion into the source film, has been observed and quantified.
Keywords: Germanium; Spin-on-doping; Curing; Phosphorus diffusion; Electrical activation; Surface corrosion;

Copper spherical cavity arrays: Fluorescence enhancement in PFO films by Edna R. Spada; Gustavo T. Valente; Marcelo A. Pereira-da-Silva; Maria L. Sartorelli; Francisco E.G. Guimarães; Roberto M. Faria (1181-1186).
This manuscript addresses the use of a well-ordered antidot copper nanostructure as a active substrate for surface enhancement fluorescence (SEF). The antidot array was produced by electrodeposition and nanosphere lithography and characterized by microscopy technique, its successful application as SEF-active substrates was verified using polyfluorene (PFO) as a probe layer. Atomic force microscopy (AFM) was used to evaluate the regularity of the metal surface as well PFO coated process and confocal laser fluorescence microscopy (CLSM) to determine the behavior exhibited by the fluorescent layer due to the existence of the nanostructured surface. No accumulation PFO in the cavities was detected and the more intense emission regions coincides with the position of the cavities and is at about one order of magnitude higher.
Keywords: Nanosphere lithography; Electrodeposition; Surface-enhancement fluorescence;