Applied Surface Science (v.360, #PB)
Editorial Board (ii).
Layer-by-layer assembly of polyelectrolyte and gold nanoparticle for highly reproducible and stable SERS substrate by Zhicheng Liu; Zhaodong Yan; Lu Bai (437-441).
Building high-quality surface-enhanced Raman spectroscopy (SERS) substrates has attracted considerable attention from both fundamental and applied research. In this work, a simple layer-by-layer assembly of polyelectrolytes and gold nanoparticles was utilized to obtain multilayer thin films with tunable SERS performances. A relative uniform distribution of gold nanoparticles in the films was observed. Moreover, the SERS signals collected from the constructed substrates showed excellent reproducibility and stability. The obtained SERS substrates have a promising future in the field of sensing.
Keywords: Layer-by-layer; Gold nanoparticle; SERS; Reproducibility; Polyelectrolyte;
Anodized ZnO nanostructures for photoelectrochemical water splitting by Mao-Chia Huang; TsingHai Wang; Bin-Jui Wu; Jing-Chie Lin; Ching-Chen Wu (442-450).
Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO3)2. Potentiostatic anodization was conducted at two potentials (−0.7 V in the passive region and −1.0 V in the active region vs. SCE) which are higher than the open circuit potential (−1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at −0.7 V vs. SCE were composed of nanowires at while those obtained at −1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm2 at 0.5 V vs. SCE under 100 mW/cm2 illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.
Keywords: ZnO; Electrochemical anodic deposition; Photoelectrochemical water splitting;
STM observation of a box-shaped graphene nanostructure appeared after mechanical cleavage of pyrolytic graphite by Rostislav V. Lapshin (451-460).
A description is given of a three-dimensional box-shaped graphene (BSG) nanostructure formed/uncovered by mechanical cleavage of highly oriented pyrolytic graphite (HOPG). The discovered nanostructure is a multilayer system of parallel hollow channels located along the surface and having quadrangular cross-section. The thickness of the channel walls/facets is approximately equal to 1 nm. The typical width of channel facets makes about 25 nm, the channel length is 390 nm and more. The investigation of the found nanostructure by means of a scanning tunneling microscope (STM) allows us to draw a conclusion that it is possible to make spatial constructions of graphene similar to the discovered one by mechanical compression, bending, splitting, and shifting graphite surface layers. The distinctive features of such constructions are the following: simplicity of the preparation method, small contact area between graphene planes and a substrate, large surface area, nanometer cross-sectional sizes of the channels, large aspect ratio. Potential fields of application include: ultra-sensitive detectors, high-performance catalytic cells, nanochannels for DNA manipulation, nanomechanical resonators, electron multiplication channels, high-capacity sorbents for hydrogen storage.
Keywords: Graphite; Highly oriented pyrolytic graphite; HOPG; Cleavage; Exfoliation; Graphene; Graphene nanostructure; Nanochannel; Nanopore; Scanning tunneling microscopy; STM; Nanotechnology;
Effects of sintering and mixed oxide growth on the interface cracking of air-plasma-sprayed thermal barrier coating system at high temperature by Bowen Lv; Hua Xie; Rong Xu; Xueling Fan; Weixu Zhang; T.J. Wang (461-469).
Sintering and mixed oxide (MO) growth significantly affect the thermal and mechanical properties of thermal barrier coating system (TBCs) in gas turbine at high temperature. In this work, we numerically analyzed the effects of sintering and MO growth on the interface cracking of TBCs. A thermal-elasto-viscoplastic constitutive model was introduced, in which the effect of sintering was studied using a spherical shell model. Based on the same spherical shell model and our previous experimental observations, we theoretically derived the evolution of relative density and applied this constitutive model to the sintering of ceramic coating. The numerical results showed that viscosity, initial porosity of ceramic and the growth rate of MO had significant effects on interface cracking. In contrast, the influence of initial pore size of ceramic coating was neglectable. Suggestions were also made for the choice of material during TBCs design.
Keywords: Thermal barrier coating; Sintering; Mixed oxide; Interface crack; Constitutive model; Finite element method;
Adsorption behavior and mechanism of Cr(VI) using Sakura waste from aqueous solution by Wenfang Qi; Yingxin Zhao; Xinyi Zheng; Min Ji; Zhenya Zhang (470-476).
The main chemical components of Sakura leaves are cellulose 16.6%, hemicellulose 10.4%, lignin 18.3%, ash 11.4%, and others 43.3%. The adsorption capacity of Cr(VI) onto Sakura leaves can achieve 435.25 mg g1, much higher than other similar agroforestry wastes.A forestall waste, Sakura leave, has been studied for the adsorption of Cr(VI) from aqueous solution. The materials before and after adsorption were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). To investigate the adsorption performance of Sakura waste, batch experiments were conducted under different adsorbent dosage, contact time, initial concentration of Cr(VI), and co-existing ions. Results showed the data fitted pseudo-second-order better than pseudo-first-order kinetic model. Equilibrium data was analyzed with Langmuir, Freundlich and RedlichPeterson isotherm models at temperature ranges from 25 °C to 45 °C. The maximum adsorption capacity from the Langmuir model was 435.25 mg g1 at pH 1.0. The presence of Cl, SO4 2 and PO4 3 would lead to an obvious negative effect on Cr(VI) adsorption, and their influence order follows PO4 3 > SO4 2 > Cl. The study developed a new way to reutilize wastes and showed a great potential for resource recycling.
Keywords: Hexavalent chromium; Adsorption; Kinetic; Isotherm; Selectivity; Mechanism;
Differences between GaAs/GaInP and GaAs/AlInP interfaces grown by movpe revealed by depth profiling and angle-resolved X-ray photoelectron spectroscopies by M.C. López-Escalante; M. Gabás; I. García; E. Barrigón; I. Rey-Stolle; C. Algora; S. Palanco; J.R. Ramos-Barrado (477-484).
GaAs/GaInP and GaAs/AlInP interfaces have been studied using photoelectron spectroscopy tools. The combination of depth profile through Ar+ sputtering and angle resolved X-ray photoelectron spectroscopy provides reliable information on the evolution of the interface chemistry. Measurement artifacts related to each particular technique can be ruled out on the basis of the results obtained with the other technique. GaAs/GaInP interface spreads out over a shorter length than GaAs/AlInP interface. The former could include the presence of the quaternary GaInAsP in addition to the nominal GaAs and GaInP layers. On the contrary, the GaAs/AlInP interface exhibits a higher degree of compound mixture. Namely, traces of P atoms in a chemical environment different to the usual AlInP coordination were found at the top of the GaAs/AlInP interface, as well as mixed phases like AlInP, GaInAsP or AlGaInAsP, located at the interface.
Keywords: IIIV semiconductors; GaInP; AlInP; ARXPS; Depth profiling; Interfaces;
Femtosecond laser surface texturing of titanium as a method to reduce the adhesion of Staphylococcus aureus and biofilm formation by Alexandre Cunha; Anne-Marie Elie; Laurent Plawinski; Ana Paula Serro; Ana Maria Botelho do Rego; Amélia Almeida; Maria C. Urdaci; Marie-Christine Durrieu; Rui Vilar (485-493).
The aim of the present work was to investigate the possibility of using femtosecond laser surface texturing as a method to reduce the colonization of Grade 2 Titanium alloy surfaces by Staphylococcus aureus and the subsequent formation of biofilm. The laser treatments were carried out with a Yb:KYW chirped-pulse-regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. Two types of surface textures, consisting of laser-induced periodic surface structures (LIPSS) and nanopillars, were produced. The topography, chemical composition and phase constitution of these surfaces were investigated by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Surface wettability was assessed by the sessile drop method using water and diiodomethane as testing liquids. The response of S. aureus put into contact with the laser treated surfaces in controlled conditions was investigated by epifluorescence microscopy and scanning electron microscopy 48 h after cell seeding. The results achieved show that the laser treatment reduces significantly the bacterial adhesion to the surface as well as biofilm formation as compared to a reference polished surfaces and suggest that femtosecond laser texturing is a simple and promising method for endowing dental and orthopedic titanium implants with antibacterial properties, reducing the risk of implant-associated infections without requiring immobilized antibacterial substances, nanoparticles or coatings.
Keywords: Femtosecond lasers; Laser surface texturing; Dental and orthopedic implants; Wettability; Bacteria adhesion; Biofilm;
On-chip nanostructuring and impedance trimming of transparent and flexible ITO electrodes by laser induced coherent sub-20 nm cuts by Maziar Afshar; Moritz Leber; Wigand Poppendieck; Karsten König; Helmut Seidel; Dara Feili (494-501).
In this work, the effect of laser-induced nanostructuring of transparent indium tin oxide (ITO) electrodes on flexible glass is investigated. Multi-electrode arrays (MEA) for electrical and optical characterization of biological cells were fabricated using standard MEMS technologies. Optimal sputter parameters concerning oxygen flow, sputter power and ambient pressure for ITO layers with both good optical and electrical properties were determined. Afterwards, coherent sub-20 nm wide and 150 nm deep nanocuts of many micrometers in length were generated within the ITO electrodes by a sub-15 femtosecond (fs) pulsed laser. The influence of laser processing on the electrical and optical properties of electrodes was investigated. The electrochemical impedance of the manufactured electrodes was measured before and after laser modification using electrochemical impedance spectroscopy. A small reduction in electrode impedance was observed. These nanostructured electrodes show also polarizing effects by the visible spectrum.
Keywords: Nanostructuring; Laser trimming; Microelectrodes; Indium tin oxide; Nanocuts; Impedance spectroscopy;
The structure evolution mechanism of electrodeposited porous Ni films on NH4Cl concentration by Xiangtao Yu; Mingyong Wang; Zhi Wang; Xuzhong Gong; Zhancheng Guo (502-509).
NH4Cl was an important component for the electrodeposition of porous metal films through hydrogen bubble template approach. The effects of NH4Cl concentrations on pore formation and structure evolution of the electrodeposited porous Ni films were studied. It was found that Ni films electrodeposited from solutions with 0.250.35 M NH4Cl were compact. When NH4Cl concentrations were 0.40.75 M and 0.853 M, porous Ni films with dish-like and honeycomb-like pores were electrodeposited, respectively. To form porous structure, the critical amounts of Ni in mass deposited onto the electrode must be achieved. However, at lower NH4Cl concentration, Ni electrodeposition was interrupted after about 15 s due to Ni2+ hydrolysis. The critical amounts of Ni in mass were not reached, and compact Ni films were obtained. When NH4Cl concentrations exceeded 0.4 M, Ni2+ hydrolysis was inhibited due to the enhanced buffer ability of solution and Ni(NH3) n 2+ (2 n 6) complexes became the discharged ions. Ni electrodeposition proceeded continuously and reached the critical amounts of Ni in mass, and porous Ni films were formed. At higher NH4Cl concentration, hydrogen was produced mainly by the electrochemical reduction of NH4 +. pH near cathode was hardly changed, and Ni2+ ions with low overpotential were reduced. The rough Ni films were formed, which led to smaller break-off diameter of bubbles. Therefore, the pore sizes of Ni films were decreased.
Keywords: Electrodeposition; Nickel films; Hydrogen bubbles; NH4Cl; Porous structure;
Electrochemical characterization of chromia- and alumina-forming nickel-based superalloys in molten silicates by Tuti Katrina Abdullah; Carine Petitjean; Pierre-Jean Panteix; Stéphane Mathieu; Christophe Rapin; Michel Vilasi; Zuhailawati Hussain; Afidah Abdul Rahim (510-518).
A comparison of the corrosion behaviour of simplified chromia- and alumina-forming alloys (Ni30Cr and Ni8Al28Cr) in molten glass is performed via electrochemical methods. A pre-oxidation treatment in air prior to immersion ensured the formation of a 2-μm-thick oxide scale of Cr2O3 or Al2O3. The lifetime of Ni30Cr depended on the competition between the oxide growth and its dissolution in the melt. For Ni8Al28Cr, the high solubility of alumina in the melt studied here led to severe aluminium loss in a few minutes and clearly demonstrated the higher efficiency of chromia-forming alloys for molten glass applications.
Keywords: Molten silicates; Superalloys; High temperature corrosion; Passivity; Electrochemical characterization;
Physical and electrical characteristics of NiFe thin films using ultrasonic assisted pulse electrodeposition by K. Asa Deepthi; R. Balachandran; B.H. Ong; K.B. Tan; H.Y. Wong; H.K. Yow; S. Srimala (519-524).
Nickel iron (NiFe) thin films were prepared on the copper substrate by ultrasonic assisted pulse electrodeposition under galvanostatic mode. Careful control of the thin films deposition is essential as the electrical properties of the films could be greatly affected, particularly if low quality films are produced. The preparation of NiFe/Cu thin films was aimed to reduce the grain size of NiFe particles, surface roughness and electrical resistivity of the copper substrates. Various parameters were systematically studied including current magnitude, deposition time and ultrasonic bath temperature. The optimized conditions to obtain NiFe permalloy, which subsequently applied to all investigated samples, were found at a current magnitude of 70 mA deposited for a duration of 2 min under ultrasonic bath temperature of 27 °C. The composition of NiFe permalloy was as close as Ni 80.71% and Fe 19.29% and the surface roughness was reduced from 12.76 nm to 2.25 nm. The films electrical resistivity was decreased nearly sevenfold from an initial value of 67.32 μΩ cm to 9.46 μΩ cm.
Keywords: NiFe/Cu thin films; Pulse electrodeposition; Surface morphology; Electrical characteristics;
Polypropylene nonwoven surface modified through introducing porous microspheres: Preparation, characterization and adsorption by Xiao Du; Junfu Wei; Wei Liu; Xiangyu Zhou; Danyang Dai (525-533).
A new porous fabric adsorbent (PM/PP nonwoven) was prepared by hydrogen bonding self-assembly method, in which poly(divinylbenzene-co-4-vinylpyridine) microspheres were introduced onto the surface of PP-g-AA (polypropylene grafted acrylic acid) nonwoven. The effects of the main conditions for self-assembly reaction such as mass ratio of microsphere to nonwoven, pH and the grafting degree of acrylic acid were studied. In addition, the adsorption mechanisms and interactions for three VOCs (styrene, cyclohexane, acetone) were systematically elucidated. The resulting 28.2% PM/PP nonwoven obtained a higher adsorption amount (52.8 mg/g) of styrene vapor, which was 88 times greater than that of original PP nonwoven. Meanwhile, the kinetic studies suggested that the Yoon and Nelson model is suitable to describe the adsorption mechanism of styrene over the modified nonwovens. Adsorption and pressure drop data showed that PM/PP nonwoven had good adsorption ability and air permeability due to its abundant functional groups and porous structures. Taken together, it is expected that PM/PP nonwoven would be a promising adsorbent for removal of VOCs from the gas streams.
Keywords: Polypropylene nonwoven; Surface modification; Porous microspheres; Self-assembly; VOCs adsorption;
Synthesis of NiO@MnO2 core/shell nanocomposites for supercapacitor application by Junjiao Chen; Ying Huang; Chao Li; Xuefang Chen; Xiang Zhang (534-539).
In this work, NiO@MnO2 core/shell nanocomposites were fabricated by a two-step method. The morphology and structure of the nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis and thermal gravity analysis. In addition, the supercapacitive performances were examined by cyclic voltammogram (CV), galvanostatic chargedischarge and electrochemical impedance spectroscopy (EIS). The electrochemical results indicate that the composite exhibits a specific capacitance of 266.7 F g1 at 0.5 A g1 and excellent cycling stability (81.7% retention after 2000 cycles at 1 A g1). Therefore, this wok offers meaningful reference for supercpacitor applications in the future.
Keywords: NiO tube; MnO2 nanosheets; Supercapacitor; Nanocomposites;
Chemical vapor deposition of low reflective cobalt (II) oxide films by Eliane Amin-Chalhoub; Thomas Duguet; Diane Samélor; Olivier Debieu; Elisabeta Ungureanu; Constantin Vahlas (540-546).
Low reflective CoO coatings are processed by chemical vapor deposition from Co2(CO)8 at temperatures between 120 °C and 190 °C without additional oxygen source. The optical reflectivity in the visible and near infrared regions stems from 2 to 35% depending on deposition temperature. The combination of specific microstructural features of the coatings, namely a fractal cauliflower morphology and a grain size distribution more or less covering the near UV and IR wavelength ranges enhance light scattering and gives rise to a low reflectivity. In addition, the columnar morphology results in a density gradient in the vertical direction that we interpret as a refractive index gradient lowering reflectivity further down. The coating formed at 180 °C shows the lowest average reflectivity (2.9%), and presents an interesting deep black diffuse aspect.
Keywords: Optical reflectivity; MOCVD; Refractive index gradient; CoO; Cobalt oxide;
Surface reconstruction: An effective method for the growth of mismatched materials by Yu Sun; Beining Zheng; Xiaofeng Wu; Long Yuan; Jie Wu; Hongping Guo; Keke Huang; Shouhua Feng (547-552).
High quality thin film of GaSb was fabricated with molecular beam epitaxy technique on the reconstructed Si(1 1 1) surface.The crystalline quality of epitaxial films depends on the degree of lattice match between substrates and films. Here, we report a growth strategy for large mismatched epi-films to grow GaSb films on Si(1 1 1) substrates. The epitaxial strategy can be influenced by controlling the surface reconstructions of Sb-treated Si(1 1 1). The film with the best quality was grown on Si(1 1 1)-(53 ÿ 53)-Sb surface due to the stress release and the formation of a self-assembled 2D fishbone structure. Controlled surface engineering provides an effective pathway towards the growth of the large mismatched materials.
Keywords: Heteroepitaxy; Mismatched materials; Surface reconstruction;
Improvement of NiMoNb to polyimide adhesion by inductively coupled nitrogen plasma treatment by S.-H. Bang (553-558).
In this study, the effect of sputtering power on the peel strength of the flexible copper clad laminate (FCCL) was evaluated before and after heat treatment using 180° peel test. An increase in the sputtering powers from 200 W to 600 W increased film density and improved peel strength. To enhance peel strength much more, an inductively coupled plasma (ICP) was treated on the PI surface using N2 gas with Ar as a function of RF power. A dramatic enhancement of the peel strength, 923 N/m was achieved, especially after heat treatment by changing ICP power from 200 W to 900 W. The reduction ratio of the peel strength for the 900 W plasma-treated FCCL was only 12%, whereas that for the 200 W plasma-treated FCCL was 43%. The root mean square (RMS) surface roughness with PIs exposed to both 200 W and 900 W plasma treatments was rarely changed, while X-ray photoelectron spectroscopy (XPS) showed the substantial increase of CN functional groups. To obtain insight the film characteristics, the NiMoNb/PI interfaces were investigated by a high resolution transmission electron microscopy (HR-TEM).
Keywords: NiMoNb; Peel strength; ICP treatment; Film density;
Single- and dual-wavelength laser pulses induced modification in 10ÿ(Al/Ti)/Si multilayer system by B. SalatiĿ; S. PetroviĿ; D. Peruško; M. Ŀekada; P. Panjan; D. PanteliĿ; B. JelenkoviĿ (559-565).
The surface morphology of the ablation craters created in the multilayer 10ÿ(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.253.5 ÿ 109 W cm2. Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1:10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10ÿ(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems.
Keywords: Dual-wavelength pulses; Laser ablation; Crater formation; Nanostructures;
Hydrogen permeability degradation of Pd-coated NbTiNi alloy caused by its interfacial diffusion by Naofumi Ohtsu; Kazuhiro Ishikawa; Yoshihiro Kobori (566-571).
Pd-coated Nb40Ti30Ni30 (NbTiNi) is considered a promising material for hydrogen-permeable membranes because of the low usage of Pd metal. This paper reports the degradation of hydrogen permeability occurring during the permeation experiment above 773 K. Surface analysis using X-ray photoelectron spectroscopy revealed that interdiffusion between the Pd coating and the constituent elements of Nb and Ti progressed during the permeation experiment. The diffused Ti was concentrated near the topmost surface and then formed TiO2, which resulted in a decrease in the Pd concentration at the topmost surface. However, the diffused Nb was observed to bind to Pd in the surface and formed a PdNb alloy beneath the topmost surface. We concluded that these changes caused the decline of the hydrogen permeability at high-temperature conditions.
Keywords: XPS; Hydrogen permeable membrane; Nb-based alloy; Decline of permeability; Interdiffusion;
Thermal post-deposition treatment effects on nanocrystalline hydrogenated silicon prepared by PECVD under different hydrogen flow rates by Sana Ben Amor; Hosny Meddeb; Ridha Daik; Afef Ben Othman; Sonia Ben Slama; Wissem Dimassi; Hatem Ezzaouia (572-578).
At high annealing temperatures, many atoms do not suffer the attraction of surface species due to the thermal agitation and consequently few atoms are adsorbed.As the temperature is lowered the adsorption is more efficient to the point that is no more atoms in the gas phase. Indeed at relatively low temperatures, the atoms have too little energy to escape from the surface or even to vibrate against it. They lost their degree of freedom in the direction perpendicular to the surface. But this does not prevent the atoms to diffuse along the surface. As a result, the layer's thickness decrease with increasing the annealing temperature.In this paper, hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited on mono-crystalline silicon substrate by plasma enhanced chemical vapor deposition (PECVD) under different hydrogen flow rates followed by a thermal treatment in an infrared furnace at different temperature ranging from 300 to 900 °C. The investigated structural, morphological and optoelectronic properties of samples were found to be strongly dependent on the annealing temperature. Raman spectroscopy revealed that nc-Si:H films contain crystalline, amorphous and mixed structures as well. We find that post-deposition thermal treatment may lead to a tendency for structural improvement and a decrease of the disorder in the film network at moderate temperature under 500 °C. As for annealing at higher temperature up to 900 °C induces the recrystallization of the film which is correlated with the grain size and volume fraction in the layer. We demonstrate that high annealing temperature can lead to a decrease of siliconhydrogen bonds corresponding to a reduction of the amorphous matrix in the layer promoting the formation of covalent SiSi bonds. The effusion of the hydrogen from the grown film leads to increase its density and therefore induces a decrease in the thickness of the layer. For post-deposition thermal treatment in temperature range under 700 °C, the post-deposition anneal seems to be crucial for obtaining good passivation quality as expressed by a minority carrier lifetime of 17 μs, as it allows a significant reduction in defect states at the layer/substrate interface. While for a temperature higher than 900 °C, the lifetime reduction is obtained because of hydrogen effusion phenomenon, thus a tendency for crystallization in the grown film.
Keywords: Nanocrystalline hydrogenated silicon; PECVD; Hydrogen flow rates; Thermal treatment;
Determination of adsorptive and catalytic properties of copper, silver and iron contain titanium-pillared bentonite for the removal bisphenol A from aqueous solution by Fatma Tomul; Funda Turgut Basoglu; Hale Canbay (579-593).
Ti-pillared bentonite, Cu, Ag and Fe modified Ti-pillared bentonite and Cu/Ti- and Fe/Ti-mixed pillared bentonite were synthesized using different titanium sources by direct synthesis or by modification after synthesis. The effects of synthesis conditions on the surface characteristics, pore structure and acidity of the pillared bentonites were investigated by SEMEDS, XPS, XRD, N2-adsorption/desorption and FTIR analyses before and after ammonia adsorption. The results of EDS, XPS and XRD analysis confirmed that titanium, copper, silver and iron were incorporated into the bentonite structure. In the XRD patterns, the formation of delaminated structure reflecting the non-parallel distribution of the bentonite layers by pillaring with Ti, Cu/Ti and Fe/Ti-pillars was observed. XPS spectra indicated the presence of TiO2, CuO, Ag and Ag2O and Fe2O3 species depending on the source of active metals in the synthesized samples. In the FTIR spectra, an increase in the Bronsted/Lewis peak intensity was observed with the loading of copper and iron, whereas a decrease in Lewis and Bronsted acidities was observed with incorporation of silver. Adsorption studies indicated that the adsorption capacity of the sample synthesized using titanium (IV) propoxide and incorporating iron to the structure by ion exchange (Fe-PTi-PILC) were higher than those in other samples. The adsorption of BPA (bisphenol A) by all tested samples was found to fit the Langmuir isotherm. In the catalytic wet peroxide oxidation (CWPO) over PTi-PILC (prepared by titanium (IV) propoxide), Fe-PTi-PILC and Cu-PTi-PILC (prepared by copper impregnated Ti-pillared bentonite) samples, BPA values close to complete conversion were achieved within 30 min at 25 °C, pH 4 and 5 g/L m cat. CWPO results showed that increasement of pH causes a decrease the rate of oxidation. On the other hand, by the time catalyst and BPA concentration is increased, the rate of oxidation is increased as well.
Keywords: Ti-pillared bentonite; Copper; Silver and iron; Impregnation; Ion exchange; Direct synthesis; Surface characteristics; Acidity; Adsorption; Catalytic wet peroxide oxidation;
A novel reducing graphene/polyaniline/cuprous oxide composite hydrogel with unexpected photocatalytic activity for the degradation of Congo red by Jie Miao; Anjian Xie; Shikuo Li; Fangzhi Huang; Juan Cao; Yuhua Shen (594-600).
Excellent photocatalytic activity of the RGO/PANI/Cu2O composite hydrogel for CR degradation under UVvis light irradiation.In this work, a novel reducing graphene/polyaniline/cuprous oxide (RGO/PANI/Cu2O) composite hydrogel with a 3D porous network has been successfully prepared via a one-pot method in the presence of cubic Cu2O nanoparticles. The as-synthesized ternary composites hydrogel shows unexpected photocatalytic activity such that Congo red (CR) degradation efficiency can reaches 97.91% in 20 min under UVvis light irradiation, which is much higher than that of either the single component (Cu2O nanoparticles), or two component systems (RGO/Cu2O composite hydrogel and PANI/Cu2O nanocomposites). Furthermore, the ternary composite hydrogel exhibits high stability and do not show any significant loss after five recycles. Such outstanding photocatalytic activity of the RGO/PANI/Cu2O composite hydrogel was ascribed to the high absorption ability of the product for CR and the synergic effect among RGO, PANI and Cu2O in photocatalytic process. The product of this work would provide a new sight for the construction of UVvis light responsive photocatalyst with high performance.
Keywords: RGO/PANI/Cu2O; Composite hydrogel; Photocatalyst; Congo red;
A review on plasmonic metalTiO2 composite for generation, trapping, storing and dynamic vectorial transfer of photogenerated electrons across the Schottky junction in a photocatalytic system by L. Gomathi Devi; R. Kavitha (601-622).
A review on noble metal deposited titania heterostructure for energy and environmental application: an exploration on site specific interaction, electrostatic effects, surface adsorption, metallic nature, size of the deposits and oxidation state of the metal.The titania based nanomaterials are an attractive candidates for energy and environmental applications. TiO2 is one of the most important photocatalyst for its special multiple characteristics like high reactivity, low toxicity, low cost, high flexibility, long term stability especially in aqueous medium, shows relatively high energy conversion efficiency, easy to prepare several modifications with various morphologies, with good recycle ability, favorable band edge positions and superior physicochemical and optoelectronic properties. However, large band gap of titania and massive charge carrier recombination impairs its wide photocatalytic applications. As an alternative to various strategies reported extensively in literature, noble metal deposition on the titania surface seems to be effective and reliable method for increasing the life time of excitonic pairs and to extend the band gap absorption to visible range of the solar spectrum. In this focused review, we discuss the fundamental and critical issues in the photocatalytic activity of metal deposited titania taking into consideration the influence of various parameters like preparation methods, metal dispersion on titania, formation of heterojunctions and optimum metal loadings on the interfacial charge carrier dynamics. The metal deposition onto the varied hierarchical morphology, crystal structure, defective surface of titania along with extended modification like simultaneous doping and heterostructure coupling with other semiconductors is also highlighted. It was revealed that deposited metal is involved in multiple crucial roles like; (i) it serves as passive electron sink with high capacity to store electrons to suppress photogenerated charge carrier recombination; (ii) it facilitates rapid dioxygen reduction to generate reactive free radicals; (iii) visible light response for titania can be achieved through surface plasmon resonance effect; (iv) direct excitation of metal nanoparticles especially under visible light and vectorial electron transfer to the TiO2 CB. This review attempts to provide a comprehensive update of design and fabrication of metallization on the surface of TiO2 semiconductor particles highlighting some of the advancements made in the energy and environment applications.
Keywords: Metal deposition; Surface plasmon resonance; Schottky barrier; Vectorial charge transfer dynamics; Photocatalysis;
SEM-EDX analysis and TOF-SIMS 3D imaging of a textile/rubber interface undergoing fatigue loading by C. Valantin; R. Benoit; M.P. D.; F. Lacroix; E. Gomez; P. Phalip; J. Morcel; D. Tricoche; N. Aït Hocine (623-633).
Unidirectional textilerubber composites must exhibit a strong interface to reach admissible lifetime expectancy. Usually, this is achieved by coating the textile with Resorcinol-Formaldehyde-Latex (RFL). Nevertheless, former SEM observations of our composite revealed microcracks at the RFL/rubber interface. They appeared to propagate through fatigue loading, in correlation with hardening of RFL and interfacial rubber, both highlighted by nanoindentation tests. This mechanical damage was not correlated to chemical structure degradation which limited the development of more reliable interfacial materials formulations. In this perspective, EDX and ToF-SIMS are used in the present study to characterize RFL coated textile and composite's textile/rubber interface compositions, before and after different numbers of cycles of fatigue loading. Those analyses allow the identification of textile contaminants, potentially responsible for composite's initial interfacial microcracks: inorganic grains, polysiloxanes, fatty acids, latex surfactants and esters contaminants, attributed to diffusion from the RFL layer or from textile sizing. Concerning RFL hardening, four potential mechanisms can be raised: VP-latex complexation with metallic ions coming from rubber formulation, RF post-condensation or disproportion, migration of latex surfactants and thermo-oxidative degradations. This last mechanism seems to be the main one responsible for the hardening of interfacial rubber.
Keywords: Polyamide cordrubber composite; Fatigue damage; Interphase analysis; ToF-SIMS; SEM-EDX; Nanoindentation;
Mesoporous anatase TiO2 microspheres with interconnected nanoparticles delivering enhanced dye-loading and charge transport for efficient dye-sensitized solar cells by Liang Chu; Zhengfei Qin; Qiaoxia Zhang; Wei Chen; Jian Yang; Jianping Yang; Xingao Li (634-640).
The photoelectrodes of DSSCs consisted of mesoporous anatase TiO2 microspheres with interconnected nanoparticles. The interconnected nanoparticles enhance dye-loading capacity and charge transport.Mesoporous anatase TiO2 microspheres with interconnected nanostructures meet both large surface area and connected-structure for electron transfer as ideal nano/micromaterials for application in solar cells, energy storage, catalysis, water splitting and gas sensing. In this work, mesoporous anatase TiO2 microspheres consisting of interconnected nanoparticles were synthesized by template-free, one-step fast solvothermal process, where urea was used as capping agent to control phase and promote oriented growth. The morphology was assembled by nucleation-growth-assembly-mechanism. The mesoporous anatase TiO2 microspheres with interconnected nanoparticles were further utilized as efficient photoelectrodes of dye-sensitized solar cells (DSSCs), which were beneficial to capacity of dye loading and charge transfer. The power conversion efficiency (PCE) based on the optimized thickness of TiO2 photoelectrodes was up to 7.13% under standard AM 1.5 G illumination (100 mW/cm2).
Keywords: Mesoporous anatase TiO2 microspheres; Interconnected nanoparticles; Photoelectrodes; Dye-sensitized solar cells;
Atmospheric-pressure DBD plasma-assisted surface modification of polymethyl methacrylate: A study on cell growth/proliferation and antibacterial properties by Fatemeh Rezaei; Babak Shokri; M. Sharifian (641-651).
This paper reports polymethyl methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid–base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.
Keywords: Cold atmospheric plasma; PMMA surface modification; Surface analysis; ATR-FTIR; Cell viability; Antibacterial property;
Visible-light activated ZnO/CdSe heterostructure-based gas sensors with low operating temperature by Bin Wu; Zhangqing Lin; Minqi Sheng; Songyan Hou; Jifang Xu (652-657).
Three-dimensional ZnO/CdSe heterostructure (ZnO/CdSe HS) was fabricated with large scale and its gas-sensing application with low operating temperature was explored. Combining cost-effective chemical vapor deposition with solution growth methods, ZnO nanorods were grown on the surface of CdSe nanoribbons. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were employed to confirm the formation of ZnO/CdSe HS. The ZnO/CdSe HSs were fabricated as gas sensors in the detection of ethanol at the optimum operating temperature of 160 °C. Compared with ZnO-based gas sensors, the optimum operating temperature of the ZnO/CdSe HS-based sensor was approximately 100 °C lower, while the sensitivity was 20-fold higher in the dark and 3-fold higher under visible light illumination condition. The enhancement of sensing properties was attributed to the advanced heterostructure and visible light activated CdSe.
Keywords: ZnO/CdSe; Gas sensor; Visible light illumination; Low operating temperature;
Novel hierarchical three-dimensional ammonium vanadate nanowires electrodes for lithium ion battery by Dong Fang; Yunhe Cao; Ruina Liu; Weilin Xu; Suqin Liu; Zhiping Luo; Chaowei Liang; Xiaoqing Liu; Chuanxi Xiong (658-665).
Ammonium vanadate (NH4V4O10) nanowire flowers and nanowires on titanium (Ti) foils are synthesized by hexamethylenetetramine (HMTA)-assisted hydrothermal reactions as a cathode material for lithium-ion battery. The as-prepared NH4V4O10 nanowires are about 50 nm in diameter and several micrometers in length. The effects of reaction time, temperature and additive concentration on the resulting morphology are investigated. Reversible lithium intercalation behavior of the nanowires has been evaluated by cyclic voltammetry and galvanostatic dischargecharge cycling. The NH4V4O10 nanowires on Ti foil deliver a high discharge capacity of 168.5 mA h g1 after 100 cycles between 2.0 and 4.0 V at 50 mA g1. A high rate capability is obtained with a remaining discharge capacity of about 182.6 mA h g1 after 35 cycles at various rates. Further, the NH4V4O10 nanowires on Ti foil have a higher discharge capacity of 330.5 mA h g1 after 100 cycles at 0.84.0 V at 50 mA g1.
Keywords: Ammonium vanadate; Lithium-ion battery; Nanowires; Hydrothermal reaction;
Effect of Mn doping on the structural and electrical properties of periodic Ba0.9Sr0.1TiO3 multilayers by Xuekun Hong; Tan Shao; Tao Wang; Yushen Liu; Debao Zhang; Yawei Kuang; Jinfu Feng (666-670).
Undoped and Mn-doped periodic BST multilayers have been prepared by chemical solution deposition method. Mn2+ tends to substitute for Ti4+ in the BST lattice and introduces more oxygen vacancies, which leads to the reduction of the concentration of electrons and the downward shift of the Fermi level. As a result, improved electrical properties, such as lower frequency dispersion of the dielectric constant, lower dielectric loss and leakage current were found for Mn-doped samples. However, excessive Mn leads to the coexistence of Mn2+ and Mn3+ (or Mn4+), which is believed to degenerate the electrical performance of BST multilayers. 1 mol% Mn-doped BST multilayer exhibits the best electrical performance, with leakage current density of 2.1 × 10−5 A/cm2 (at 100 kV/cm), dielectric loss of ∼0.08 (at 10 kHz) and the minimum frequency dispersion of the dielectric constant.
Keywords: BST; Multilayer; Mn-doped; Oxygen vacancy;
Regeneration of LOHC dehydrogenation catalysts: In-situ IR spectroscopy on single crystals, model catalysts, and real catalysts from UHV to near ambient pressure by Max Amende; Andre Kaftan; Philipp Bachmann; Richard Brehmer; Patrick Preuster; Marcus Koch; Peter Wasserscheid; Jörg Libuda (671-683).
The Liquid Organic Hydrogen Carrier (LOHC) concept offers an efficient route to store hydrogen using organic compounds that are reversibly hydrogenated and dehydrogenated. One important challenge towards application of the LOHC technology at a larger scale is to minimize degradation of Pt-based dehydrogenation catalysts during long-term operation. Herein, we investigate the regeneration of Pt/alumina catalysts poisoned by LOHC degradation. We combine ultrahigh vacuum (UHV) studies on Pt(111), investigations on well-defined Pt/Al2O3 model catalysts, and near-ambient pressure (NAP) measurements on real coreshell Pt/Al2O3 catalyst pellets. The catalysts were purposely poisoned by reaction with the LOHC perhydro-dibenzyltoluene (H18-MSH) and with dicyclohexylmethane (DCHM) as a simpler model compound. We focus on oxidative regeneration under conditions that may be applied in real dehydrogenation reactors. The degree of poisoning and regeneration under oxidative reaction conditions was quantified using CO as a probe molecule and measured by infrared reflection-absorption spectroscopy (IRAS) and diffuse reflectance Fourier transform IR spectroscopy (DRIFTS) for planar model systems and real catalysts, respectively. We find that regeneration strongly depends on the composition of the catalyst surface. While the clean surface of a poisoned Pt(111) single crystal is fully restored upon thermal treatment in oxygen up to 700 K, contaminated Pt/Al2O3 model catalyst and coreshell pellet were only partially restored under the applied reaction conditions. Whereas partial regeneration on facet-like sites on supported catalysts is more facile than on Pt(111), carbonaceous deposits adsorbed at low-coordinated defect sites impede full regeneration of the Pt/Al2O3 catalysts.
Keywords: Infrared spectroscopy; Liquid Organic Hydrogen Carrier; Model catalysis; Real catalysis; Pressure gap; Materials gap;
Effects of pore sizes and oxygen-containing functional groups on desulfurization activity of Fe/NAC prepared by ultrasonic-assisted impregnation by Song Shu; Jia-Xiu Guo; Xiao-Li Liu; Xue-Jiao Wang; Hua-Qiang Yin; De-Ming Luo (684-692).
A series of Fe-loaded activated carbons treated by HNO3 (Fe/NAC) were prepared by incipient impregnation method with or without ultrasonic assistance and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy disperse spectroscope (SEM-EDS), transmission electron microscopy (TEM) and N2 adsorption/desorption. The desulfurization activities were evaluated at a fixed bed reactor under a mixed gas simulated from flue gas. The results showed that desulfurization activity from excellent to poor is as follows: Fe/NAC-60 > Fe/NAC-80 > Fe/NAC-30 > Fe/NAC-15 > Fe/NAC-0 > Fe/NAC-100 > NAC. Fe/NAC-60 exhibits the best desulfurization activity and has breakthrough sulfur capacity of 319 mg/g and breakthrough time of 540 min. The introduction of ultrasonic oscillation does not change the form of Fe oxides on activated carbon but can change the dispersion and relative contents of Fe3O4. The types of oxygen-containing functional groups have no obvious change for all samples but the texture properties show some differences when they are oscillated for different times. The fresh Fe/NAC-60 has a surface area of 1045 m2/g and total pore volume of 0.961 cm3/g with micropore volume of 0.437 cm3/g and is larger than Fe/NAC-0 (823 m2/g, 0.733 and 0.342 cm3/g). After desulfurization, surface area and pore volume of all samples decrease significantly, and those of the exhausted Fe/NAC-60 decrease to 233 m2/g and 0.481 cm3/g, indicating that some byproducts deposit on surface to cover pores. Pore size distribution influences SO2 adsorption, and fresh Fe/NAC-60 has more pore widths centralized at about 0.7 nm and 1.02.0 nm and corresponds to an excellent desulfurization activity, showing that micropore is conducive to the removal of SO2.
Keywords: Activated carbon; Iron; Ultrasonic oscillation; Impregnation; Desulfurization;
ZnO/a-Si distributed Bragg reflectors for light trapping in thin film solar cells from visible to infrared range by Aqing Chen; Qianmin Yuan; Kaigui Zhu (693-697).
Display OmittedDistributed Bragg reflectors (DBRs) consisting of ZnO and amorphous silicon (a-Si) were prepared by magnetron sputtering method for selective light trapping. The quarter-wavelength ZnO/a-Si DBRs with only 6 periods exhibit a peak reflectance of above 99% and have a full width at half maximum that is greater than 347 nm in the range of visible to infrared. The 6-pair reversed quarter-wavelength ZnO/a-Si DBRs also have a peak reflectance of 98%. Combination of the two ZnO/a-Si DBRs leads to a broader stopband from 686 nm to 1354 nm. Using the ZnO/a-Si DBRs as the rear reflector of a-Si thin film solar cells significantly increases the photocurrent in the spectrum range of 4001000 nm, in comparison with that of the cells with Al reflector. The obtained results suggest that ZnO/a-Si DBRs are promising reflectors of a-Si thin-film solar cells for light trapping.
Keywords: ZnO/a-Si DBRs; Light trapping; Thin-film solar cells;
Correlation between donating or accepting electron behavior of the adsorbed CO or H2 and its oxidation over TiO2 under ultraviolet light irradiation by Xiaoying Peng; Zhoujun He; Kai Yang; Xun Chen; Xuxu Wang; Wenxin Dai; Xianzhi Fu (698-706).
Although both H2 and CO can be thermodynamically oxidized by O2 over TiO2 under UV irradiation, only CO was oxidized by O2 over TiO2 due to its donating electrons to TiO2, while H2 was not oxidized by O2 under the same condition due to its accepting electrons from TiO2.Although both H2 and CO can be thermodynamically oxidized by O2 over TiO2 under ultraviolet light (UV) irradiation, it was found that CO not H2 could be oxidized over an anatase TiO2 in this work. The chemisorption results of CO and H2 at TiO2 surface under UV irradiation, investigated by a gas sensing testing, showed that CO adsorption at TiO2 would cause the decrease of TiO2 surface impedance, whereas H2 adsorption would cause its increase. It is proposed that the CO adsorbed at TiO2 donate electrons to TiO2 (as a process of CO pre-oxidation), resulting in its oxidation. In contrast, the H2 adsorbed at TiO2 accept electrons from TiO2 (as a process of H2 pre-reduction), which makes it difficult to be oxidized. This result indicates that the photocatalytic oxidation of a reactant over TiO2 not only depends on the formation of the photo-generated carriers and the subsequent activated oxidizing species, but maybe also depends on the electron transfer behavior at the interface of the adsorbed reactant and TiO2.
Keywords: TiO2; Photocatalytic oxidation; Photo-assisted gas sensitivity; Electron transfer; Chemisorption;
First-principles simulations on the new hybrid phases of germanene with alkali metal atoms coverage by Jianmei Yuan; Chan Tang; Jianxin Zhong; Yuliang Mao (707-714).
We present first-principles calculations of a new type hybrid phases composed by buckled germanene with saturated or half-saturated alkali metal atoms adsorption. Our energetics and electronic structure analysis suggests that adsorbed alkali metal atoms (Li, Na, K) can be used as covered adatoms to synthesize germanene-based new phases in two dimensional. The predicted new phases of Ge2X2 and Ge2X1 (X = Li, Na, K) relative to the single germanene sheet could exist at room temperature. The formation energy of Ge2Li2 configuration obtained from complete lithiation is even more favorable than that of germanane. Charge transfer is significant between the alkali metal atoms and Ge, indicating the ionic interactions between them. Furthermore, our charge density analysis indicates that covalent component in some extent exists in Ge2X2 and Ge2X1 (X = Li, Na, K) 2D phases, which even leads the complete lithiated germanene into a semiconductor with an energy gap of 0.14 eV. We report that 2D phases of Ge2X1 (X = Li, Na, K) are metallic with weak polarization on the Fermi level and in unoccupied states. It is found that half-lithiated germanene exhibits local magnetic moments of 0.48 μB on the Ge atoms neighbored with Li adatoms.
Keywords: Germanene; Hybrid phase; Alkali metal atom; First-principles;
The molecular understanding of interfacial interactions of functionalized graphene and chitosan by Hong-ping Zhang; Xue-gang Luo; Xiao-yan Lin; Xiong Lu; Youhong Tang (715-721).
The type of the functional groups can be used to modulating interactions between graphene sheet and chitosan.Graphene-reinforced chitosan scaffolds have been extensively studied for several years as promising hard tissue replacements. However, the interfacial interactions between graphene and chitosan are strongly related to the solubility, processability, and mechanical properties of graphene-reinforced chitosan (GC) composites. The functionalization of graphene is regarded as the most effective way to improve the abovementioned properties of the GC composite. In this study, the interfacial interactions between chitosan and functionalized graphene sheets with carboxylization (COOH-), amination (NH2-), and hydroxylation (OH-) groups were systematically studied at the electronic level using the method of ab initio simulations based on quantum mechanics theory and the observations were compared with reported experimental results. The covalent linkages between COOH-modified graphene and the chitosan units were demonstrated and the combination of multi-functionalization on graphene could regulate the interfacial interactions between graphene and the chitosan. The interfacial interactions between chitosan and properly functionalized graphene are critical for the preparation of GC-based composites for tissue engineering scaffolds and other applications.
Keywords: Graphene; Chitosan; DFT; Interfacial interactions;
Synthesis and structural features of resorcinolformaldehyde resin chars containing nickel nanoparticles by M.V. Galaburda; V.M. Bogatyrov; J. Skubiszewska-ZiĿba; O.I. Oranska; D. Sternik; V.M. Gunko (722-730).
A series of meso- and microporous carbons containing magnetic Ni nanoparticles (Ni/C) with a variety of Ni loadings were synthesized by a simple one-pot procedure through carbonization of resorcinolformaldehyde polymers containing various amounts of nickel(II) acetate. Such composite materials were characterized by N2 sorption, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscope (TEM). The XRD patterns reveal peaks corresponding to face centered cubic nickel with the average size of crystallites of 1718 nm. SEM and TEM results reveal that the formation of the nanoparticles took place mainly in the carbon spheres (12 μm in size) and on the outer surface as well. The as-prepared composites are characterized by a coreshell structure with well-crystallized graphitic shells about 815 nm in thickness. The Raman spectra show that Ni content influences the structure of the carbon. It was also shown that the morphology (particle shape and sizes) and porosity (pore volume and pore size distribution) of the chars are strongly dependent on water and nickel contents in the blends. One of the applications of Ni/C was demonstrated as a magnetically separable adsorbent.
Keywords: Resorcinolformaldehyde polymers; Carbonnickel composites; Magneto-sensitive sorbents; Coreshell structure; Char; Particle morphology; Composite structure; Texture; Graphite;
Structural and gas sensing properties of ex-situ oxidized Sn grown by thermal evaporation by A. Amutha; S. Amirthapandian; B. Sundaravel; A.K. Prasad; B.K. Panigrahi; P. Thangadurai (731-737).
SnO2 thin films were obtained by ex-situ oxidation of Sn metal film deposited by thermal evaporation. The oxidation of the Sn film was carried out at 600, 700 and 900 °C for 2 h in a controlled oxygen atmosphere. GIXRD confirmed the tetragonal rutile phase of SnO2 which was further confirmed by Raman spectroscopy. The RBS measurements provided the thickness and chemical information of the film. Thickness of the film was in the range of 612 nm and the presence of Sn and oxygen in the films are shown. Scanning electron microscopy revealed spherical particles of different sizes for films annealed at different temperatures. The SnO2 thin film oxidized at 900 °C was tested for methane gas sensing. A sensing response of 78.46% for 100 ppm of methane at an operating temperature of 100 °C which is one of lowest reported was obtained.
Keywords: SnO2 thin films; GIXRD; Rutherford backscattering; Raman spectroscopy; Methane gas sensor;
High yield production of reduced TiO2 with enhanced photocatalytic activity by Jian Tian; Xiaolin Hu; Hongru Yang; Yanli Zhou; Hongzhi Cui; Hong Liu (738-743).
The reduced TiO2 nanobelts are prepared through reduction of pure nanobelts by utilizing NaBH4. Compared with pure TiO2 nanobelts, the reduced TiO2 nanobelts present enhanced UV and visible photocatalytic performance in decomposing methyl orange (MO) and water splitting for hydrogen production. Experimental results and theoretical calculations show that the improved performance is due to the generation of Ti3+ and oxygen vacancy, which can increase the visible light absorption, promote charge carrier trapping, and improve photogenerated electronhole separation efficiency, thus the photocatalytic property is improved. Moreover, the reduced TiO2 nanobelts with high ratio of Ti3+ (55.8%) present better photocatalytic properties than that of reduced TiO2 nanobelts with lower ratio of Ti3+ (9.8%), which indicates that a certain high ratio of Ti3+ will facilitate photocatalysis. The results show that the reduced TiO2 represent an effective strategy in improving the visible photocatalytic properties.
Keywords: NaBH4 reduction; TiO2 nanobelts; Photocatalytic; Ti3+ ions; UVvisible;
The large-area CdTe thin film for CdS/CdTe solar cell prepared by physical vapor deposition in medium pressure by Run Luo; Bo Liu; Xiaoyan Yang; Zheng Bao; Bing Li; Jingquan Zhang; Wei Li; Lili Wu; Lianghuan Feng (744-748).
The Cadmium telluride (CdTe) thin film has been prepared by physical vapor deposition (PVD), the Ar + O2 pressure is about 0.9 kPa. This method is a newer technique to deposit CdTe thin film in large area, and the size of the film is 30 ÿ 40 cm2. This method is much different from the close-spaced sublimation (CSS), as the relevance between the source temperature and the substrate temperature is weak, and the gas phase of CdTe is transferred to the substrate by Ar + O2 flow. Through this method, the compact and uniform CdTe film (30 ÿ 40 cm2) has been achieved, and the performances of the CdTe thin film have been determined by transmission spectrum, SEM and XRD. The film is observed to be compact with a good crystallinity, the CdTe is polycrystalline with a cubic structure and a strongly preferred (1 1 1) orientation. Using the CdTe thin film (3 ÿ 5 cm2) which is taken from the deposited large-area film, the 14.6% efficiency CdS/CdTe thin film solar cell has been prepared successfully. The structure of the cell is glass/FTO/CdS/CdTe/graphite slurry/Au, short circuit current density (J sc) of the cell is 26.9 mA/cm2, open circuit voltage (V oc) is 823 mV, and filling factor (FF) is 66.05%. This technique can be a quite promising method to apply in the industrial production, as it has great prospects in the fabricating of large-area CdTe film.
Keywords: Large-area CdTe thin film; CdS/CdTe solar cell; Physical vapor deposition; Medium pressure;
Fabrication of TiO2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment by Yingjia Qian; Lina Chi; Weili Zhou; Zhenjiang Yu; Zhongzhi Zhang; Zhenjia Zhang; Zheng Jiang (749-757).
Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO2, we successfully fixed TiO2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti4+. The TiO2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.
Keywords: Ultrafiltration; Polytetrafluoroethylene membrane; Titanium dioxide (TiO2); Plasma-induced graft polymerization;
Thermally stable anomalous Hall behavior in perpendicular Co/Pt multilayers sandwiched by HfO2 layers by Shao-Long Jiang; Xu-Jing Li; Yi-Wei Liu; Xi Chen; Qian-Qian Liu; Gang Han; Guang Yang; Dong-Wei Wang; Jing-Yan Zhang; Jiao Teng; Guang-Hua Yu (758-761).
The effect of annealing on the anomalous Hall effect (AHE) in perpendicular Co/Pt multilayers sandwiched by HfO2 layers has been studied. It was found that thermally stable AHE features can be obtained in perpendicular Co/Pt multilayers with the introduction of two Co/HfO2 interfaces, leading to the improvement of the skew scattering contribution to the AHE after annealing. On the contrary, thermally stable AHE behavior cannot be observed in Co/Pt multilayers sandwiched by Pt layers or MgO layers because of Co–Pt interdiffusion during annealing.
Keywords: Thermally stable anomalous Hall effect; Co/Pt multilayers; The Co/HfO2 interfaces;
Tailoring the emissive properties of photocathodes through materials engineering: Ultra-thin multilayers by Daniel Velázquez; Rachel Seibert; Hasitha Ganegoda; Daniel Olive; Amy Rice; Kevin Logan; Zikri Yusof; Linda Spentzouris; Jeff Terry (762-766).
We report on an experimental verification that emission properties of photocathodes can be manipulated through the engineering of the surface electronic structure. Ultrathin multilayered MgO/Ag(0 0 1)/MgO films were grown by pulsed laser deposition, tuning the thickness n of the flanking MgO layers to 0, 2, 3, and 4 monolayers. We observed an increase in quantum efficiency and simultaneous decrease in work function with layer thickness. The scale and trend direction of measurements are in good but not excellent agreement with theory. Angle resolved photoemission data for the multilayered sample n = 3 showed that the emission profile has a metallic-like momentum dispersion. Deviations from theoretical predictions [K. Németh et al., PRL 104, 046801 (2010)] are attributed to imperfections of real surfaces in contrast with the ideal surfaces of the calculation. Photoemissive properties of cathodes are critical for electron beam applications such as photoinjectors for Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). An ideal photoemitter has a high quantum efficiency, low work function, low intrinsic emittance and long lifetime. It has been demonstrated here that emission properties may be systematically tailored by control of layer thickness in ultrathin multilayered structures. The reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.
Keywords: Pulsed laser deposition; RHEED; Epitaxy; Photocathode; Work function; Quantum efficiency;
Tetra methyl substituted Cu(II) phthalocyanine as alternative hole transporting material for organometal halide perovskite solar cells by Georgia Sfyri; Challuri Vijay Kumar; Yu-Long Wang; Zong-Xiang Xu; C.A. Krontiras; Panagiotis Lianos (767-771).
Copper phthalocyanine is a promising hole transporting material, which can be employed with solid state perovskite solar cells. Tetra methyl substituted copper phthalocyanine was presently studied as a hole transporting material and demonstrated improved performance with respect to unsubstituted copper phthalocyanine. This material shows a strong absorption in the Visible and Near IR part of the electromagnetic spectrum contributing to the absorption of photons. Its LUMO and HOMO level are favourably positioned for injecting electrons and scavenging holes. Methyl substitution facilitates closer molecular packing leading to a stronger extinction coefficient, stronger ϿϿ interaction and higher charge carrier mobility.
Keywords: Hole transporting material; Perovskite solar cells; Copper phthalocyanine;
Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution by Junyan Jiang; Yuantao Zhang; Chen Chi; Fan Yang; Pengchong Li; Degang Zhao; Baolin Zhang; Guotong Du (772-776).
KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 ÿ 1017 cm3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.
Keywords: N-polar GaN; Wet etching; Strain; Doping;
Double layer approach to create durable superhydrophobicity on cotton fabric using nano silica and auxiliary non fluorinated materials by Danushika Charyangi Manatunga; Rohini M. de Silva; K.M. Nalin de Silva (777-788).
Creation of differential superhydrophobicity by applying different non-fluorinated hydrophobization agents on a cotton fabric roughened with silica nanoparticles was studied. Cotton fabric surface has been functionalized with silica nanoparticles and further hydrophobized with different hydrophobic agents such as hexadecyltrimethoxy silane (HDTMS), stearic acid (SA), triethoxyoctyl silane (OTES) and hybrid mixtures of HDTMS/SA and HDTMS/OTES. The cotton fabrics before and after the treatment were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). The wetting behavior of cotton samples was investigated by water contact angle (WCA) measurement, water uptake, water repellency and soil repellency testing. The treated fabrics exhibited excellent water repellency and high water contact angles (WCA). When the mixture of two hydrophobization agents such as HDTMS/OTES and HDTMS/SA is used, the water contact angle has increased (145°160°) compared to systems containing HDTMS, OTES, SA alone (130°140°). It was also noted that this fabricated double layer (silica + hydrophobization agent) was robust even after applying harsh washing conditions and there is an excellent anti-soiling effect observed over different stains. Therefore superhydrophobic cotton surfaces with high WCA and soil repellency could be obtained with silica and mixture of hydrophobization agents which are cost effective and environmentally friendly when compared with the fluorosilane treatment.
Keywords: Superhydrophobicity; Silica nanoparticles; Hydrophobization agents; Cotton fabrics;
A self-modification approach toward transparent superhydrophobic glass for rainproofing and superhydrophobic fiberglass mesh for oilwater separation by Xiaojiang Liu; Yan Wang; Zao Chen; Keyang Ben; Zisheng Guan (789-797).
A method employing one kind of material both for the construction of rough morphology and the chemical modification is called self-modification by us, which has not been reported in fabricating superhydrophobic surfaces so far. In this paper, taking candle soot as an intermediate, we created rough, superhydrophilic and transparent surfaces on glass trough calcination of polydimethylsiloxane (PDMS) at 550 °C. Subsequently, a novel chemical vapour deposition (CVD) modification was conducted by heating PDMS at 330 °C in air to give the surfaces a water contact angle (WCA) of 170° ± 0.5° and a sliding angle (SA) of 0°. This CVD modification is expected to be a valuable way of modification because of its simple operation, low cost and short time consumption. Results indicate that the high temperature calcination and the moderate temperature CVD modification can drastically improve the stability of the surperhydrophobic surfaces through controlling the morphology and the surface chemical composition. The as-prepared glass surfaces are capable of bearing heavy rains, keeping the sight clear in the rain and being used at a high temperature (<400 °C) or in water. Besides, superhydrophobic fiberglass mesh was prepared and applied in oilwater separation.
Keywords: Self-modification; Superhydrophobic; PDMS; Transparent; Rainproof; Oilwater separation;
Removal of rhodamine 6G dye contaminant by visible light driven immobilized Ca1x Ln x MnO3 (Ln = Sm, Ho; 0.1 x 0.4) photocatalysts by B. Barrocas; S. Sério; A. Rovisco; Y. Nunes; M.E. Melo Jorge (798-806).
Visible-light-driven Ca1x Ln x MnO3 (Ln = Sm, Ho; 0.1 x 0.4) films were grown by RF-magnetron sputtering onto fused silica substrates. The effects of Ca2+ substitution for Ho3+ or Sm3+ in Ca1x Ln x MnO3 on the structural, morphological and photocatalytic properties for rhodamine 6G dye degradation under visible light irradiation were investigated. XRD showed a pure typical perovskite phase for all the prepared films, except for Ca0.9Ho0.1MnO3 and a decrease of the crystallite size with the increase of the amount of ion substituted. SEM and AFM revealed that the films surface is dense, with low roughness. UVvis spectroscopy indicated for the two series band gaps in the range of 1.62.8 eV, being lower for the films containing holmium. The results showed that some Ca1x Ho x MnO3 and Ca1x Sm x MnO3 films present higher photocatalytic activity for Rh6G degradation in comparison with TiO2 films and for the same x value the Ho-films exhibited higher photocatalytic activity. For both films series the maximal degradation rate was obtained for x = 0.2; above this content the degradation percentage exhibits a decreasing trend with the increase of Ho or Sm substitution, except for x = 0.4 in the case of Ho system, which is observed again an increase in the degradation rate. The Rh6G photocatalytic degradation followed a pseudo first-order reaction kinetics. XRD and SEM of the used photocatalysts evidenced high photochemical stability.
Keywords: Mixed-valence manganites films; RF-magnetron sputtering; Rhodamine 6G; Photocatalytic activities; Visible light irradiation;
The composite capacitive behaviors of the N and S dual doped ordered mesoporous carbon with ultrahigh doping level by Deyi Zhang; Longyan Lei; Yonghua Shang; Kunjie Wang; Yi Wang (807-815).
Heteroatoms doping provides a promising strategy for improving the energy density of supercapacitors based on the carbon electrodes. In this paper, we present a N and S dual doped ordered mesoporous carbon with ultrahigh doping level using dimethylglyoxime as pristine precursor. The N doping content of the reported materials varies from 6.6 to 15.6 at.% dependent on the carbonization temperature, and the S doping content varies from 0.46 to 1.01 at.%. Due to the ultrahigh heteroatoms doping content, the reported materials exhibit pronounced pseudo-capacitance. Meanwhile, the reported materials exhibit high surface areas (640869 m2 g1), large pore volume (0.711.08 cm2 g1) and ordered pore structure. The outstanding textual properties endow the reported materials excellent electrical double-layer capacitance (EDLC). By effectively combining the pseudo-capacitance with EDLC, the reported materials exhibit a surprising energy storage/relax capacity with the highest specific capacitance of 565 F g1, which value is 3.3 times higher than that of pristine CMK-3, and can compete against some conventional pseudo-capacitance materials.
Keywords: Composite capacitive behaviors; Heteroatoms doped carbon; Utrahigh doping level;
Influence of the composition and crystalline phase of electrodeposited CoNi films in the preparation of CoNi oxidized surfaces as electrodes for urea electro-oxidation by J. Vilana; E. Gómez; E. Vallés (816-825).
Oxidized species of CoNi have been obtained by means of electrodeposition of CoNi films and posterior electro-oxidation, to obtain electrodes able to be catalysts of oxidative reactions in alkaline medium. The products of electro-oxidation formed, which depend on the composition and the crystal phase of CoNi deposits, have been identified; for this, Co-fcc, Co-hcp, Co7Ni3-fcc, Co7Ni3-hcp, Co5Ni5-fcc and Ni-fcc films have been electrodeposited and oxidized. The influence of the crystalline phase of the films in the nature of the superficial oxides formed has been demonstrated: the electrodes prepared from CoNi-fcc films contained β-Co x Ni(1x)(OH)2, while those prepared from Co7Ni3-hcp films contained Co2NiO4 and β-Co x Ni(1x)(OH)2. The catalytic behaviour of the electro-oxidized electrodes for urea electro-oxidation was evaluated. Separate tests were performed to differentiate the influence of the composition and the crystalline structure of the initial films and, therefore, of the different oxidized species formed. The electrodes prepared by electro-oxidation of the Co7Ni3-hcp films show better electro-catalytic performance for urea's oxidation than those obtained by oxidation of the Co7Ni3-fcc, because they induce higher intensity, lower onset potential and lesser simultaneous oxygen evolution, becoming a good anode for urea electro-oxidation in urea electrolysis for hydrogen production or waste water treatment.
Keywords: CoNi oxidized surfaces; Electrodeposition; Catalytic substrates in basic media; Urea electro-oxidation;
Influence of the tensile strain on CH4 dissociation on Cu(1 0 0) surface: A theoretical study by Feng He; Kai Li; Guangyou Xie; Ying Wang; Menggai Jiao; Hao Tang; Zhijian Wu (826-832).
Tensile strain is widespread on the catalyst surface due to the lattice mismatch between the catalyst and substrate, such as Cu/MgO in this work. Thus, it is important to investigate the influence of tensile strain on the catalytic properties. In this study, we have investigated the CH4 dissociation on Cu(1 0 0) surface by considering the tensile strain. Our results showed that compared with the unstrained Cu(1 0 0) surface, the most stable sites for dissociation species CH x (x = 03) and H adsorption on strained surface remain unchanged. The surface strain strengthens CH x (x = 03) adsorption, while weakens H adsorption. The elementary reaction for CH4 dissociation with the largest electronic energy barrier changes from CH C + H on the unstrained surface to CH4 CH3 + H on the strained surface (for strain equal to and larger than 3%), in agreement with the experimental observation that CH4 dissociation into CH3 and H is the most difficult reaction. The tensile strain accelerates C migration while has no obvious influence for C polymerization. Both DFT calculations and microkinetic model demonstrated that the strain hinders the CH4 dissociation process on Cu(1 0 0) surface. CH4 dissociation rate depends sensitively on the magnitude of the surface tensile strain.
Keywords: Tensile strain; CH4 activation; Catalytic activity; DFT-D2; Microkinetic model;
Materials processing with superposed Bessel beams by Xiaoming Yu; Carlos A. Trallero-Herrero; Shuting Lei (833-839).
We report experimental results of femtosecond laser processing on the surface of glass and metal thin film using superposed Bessel beams. These beams are generated by a combination of a spatial light modulator (SLM) and an axicon with >50% efficiency, and they possess the long depth-of-focus (propagation-invariant) property as found in ordinary Bessel beams. Through micromachining experiments using femtosecond laser pulses, we show that multiple craters can be fabricated on glass with single-shot exposure, and the 1+(1) superposed beam can reduce collateral damage caused by the rings in zero-order Bessel beams in the scribing of metal thin film.
Keywords: Materials processing; Femtosecond laser; Spatial lightmodulator; Beam-shaping; Glass; Thin film solar cell;
Microwave-assisted synthesis of reduced graphene oxide/titania nanocomposites as an adsorbent for methylene blue adsorption by Huan Wang; Haihuan Gao; Mingxi Chen; Xiaoyang Xu; Xuefang Wang; Cheng Pan; Jianping Gao (840-848).
In this study microwave-assisted reduction (MrGO) and direct reduction of graphene oxide (rGO) by Ti powders were established, and the effect of the reaction conditions on the reduction were discussed. The results showed that GO can be effectively reduced by both methods, however, microwave assistance can greatly shorten the reduction time. The produced Ti ions from the reaction of Ti powder with GO were transferred to TiO2 by hydrolysis and formed MrGO/TiO2 and rGO/TiO2. They were used as adsorbents for the removal of methylene blue (MB). MrGO/TiO2 showed a higher adsorption capacity (q max, 845.6 mg/g) than rGO/TiO2 (q max, 467.6 mg/g). Investigation on the adsorption MB onto MrGO/TiO2 was conducted and demonstrated that adsorption kinetics followed the pseudo second-order kinetics model and the adsorption isotherm was well described by the Langmuir isotherm model. The recycling of MrGO/TiO2 was achieved by photocatalytic degradation of MB catalyzed by MrGO/TiO2 itself.
Keywords: Microwave; Reduction; Graphene; Titania; Adsorption; Methylene blue;
Effect of nano-additives on microstructure, mechanical properties and wear behaviour of FeCrB hardfacing alloy by Junfeng Gou; Pengpeng Lu; You Wang; Saiyue Liu; Zhiwei Zou (849-857).
Wear rate of the hardfacing layers with different nano-additives content and the counterpart GCr15 steel balls under conditions: normal load = 15 N, rotating speed = 400 rpm, total sliding time = 20 min.FeCrB hardfacing alloys with different nano-additives content were investigated. The effects of nano-additives on the microstructures of hardfacing alloy were studied by using optical microscope, scanning electron microscope, X-ray diffractometer. The hardness and the fracture toughness of hardfacing alloys were measured, respectively. The sliding wear tests were carried out using a ball-on-disc tribometer. The experimental results showed that primary carbide of hardfacing alloys was refined and its distribution became uniform with content of nano-additives increased. The hardfacing alloys are composed of Cr7C3, Fe7C3, α-Fe and Fe2B according to the results of X-ray diffraction. The hardness of hardfacing alloys increased linearly with the increase of nano-additives. The hardness of the hardfacing alloy with 1.5 wt.% nano-additives increased 54.8% than that of the hardfacing alloy without nano-additives and reached to 1011HV. The K IC of the hardfacing alloy with 0.65 wt.% nano-additives was 15.4 MPam1/2, which reached a maximum. The value increased 57.1% than that of the hardfacing alloy without nano-additives. The wear rates of the hardfacing layer with 0.65 wt.% and 1.0 wt.% nano-additives decreased about 88% than that of the hardfacing layer without nano-additives. The main wear mechanism was adhesion wear.
Keywords: Hardfacing alloys; Hardness; Fracture toughness; Sliding wear;
Enhancement of growth and osteogenic differentiation of MC3T3-E1 cells via facile surface functionalization of polylactide membrane with chitooligosaccharide based on polydopamine adhesive coating by Huihua Li; Chuang Luo; Binghong Luo; Wei Wen; Xiaoying Wang; Shan Ding; Changren Zhou (858-865).
To develop a chitooligosaccharide(COS)-functionalized poly(d,l-lactide) (PDLLA) membrane to enhance growth and osteogenic differentiation of MC3T3-E1 cells, firstly a thin polydopamine (PDOPA) layer was adhered to the PDLLA membrane via the self-polymerization and strong adhesion behavior of dopamine. Subsequently, COS was immobilized covalently on the resultant PDLLA/PDOPA composite membrane by coupling with PDOPA active coating. The successful immobilization of the PDOPA and COS was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) results indicated that the surface topography and roughness of the membranes were changed, and the root mean square increased from 0.613 nm to 6.96 and 7.12 nm, respectively after coating PDOPA and COS. Water contact angle and surface energy measurements revealed that the membrane hydrophilicity was remarkably improved by surface modification. In vitro cells culture results revealed that the PDOPA- and COS-functionalized surfaces showed a significant increase in MC3T3-E1 cells adhesion, proliferation, osteogenic differentiation and alkaline phosphate activity compared to the pristine PDLLA substrate. Furthermore the COS-functionalized PDLLA membrane was more effectively at enhancing osteoblast activity than the PDOPA-functionalized PDLLA membrane.
Keywords: Poly(d,l-lactide); Dopamine; Chitooligosaccharide; Surface modification; Osteogenic differentiation;
Preparation of bactericidal cationic PDMS surfaces using a facile and efficient approach by Nasreddine Kébir; Irène Kriegel; Marc Estève; Vincent Semetey (866-874).
Two cationic polymers containing vinyl and quaternary ammonium groups were successfully grafted on silicone surfaces containing Si―H groups. The reaction was carried out by straightforward hydrosilylation reaction in water without using exogenous catalyst and without doping the surface with Si―H groups. The Si―H content was varied by changing the curing time or the ratio between silicone components. The surfaces obtained exhibited quaternary ammonium densities ranging from 1.8 ÿ 1014 to 2.8 ÿ 1015 charge/cm2 and higher polarity and hydrophilicity in comparison with non grafted surfaces. Bactericidal effects of these surfaces against Escherichia coli and Staphylococcus epidermidis were evidenced. This study have evidenced also the fouling of the poly(quaternary ammonium) (PQA) surfaces by contact with plasmatic proteins probably limiting their use in some biomedical field (e.g. implantable medical devices).
Keywords: Bactericidal surfaces; Surface charge density; Cationic polymers; Silicones; Hydrosilylation; Protein adsorption;
Resistance switching properties of Cu2S film by electrochemical deposition by Yongming Yan; C.P. Yang; K. Bärner; V.V. Marchenkov; Yun Zeng (875-879).
In this work, the Cu2S film was prepared by electrochemical deposition. Further, the EPIR effect and IV characteristics of Ag/Cu2S/Ag and Ag/Cu2S/Ag sandwich devices are demonstrated. These devices present resistive switching behaviors at room temperature.Electric pulse-induced resistance (EPIR) effect in metaloxidemetal devices is a fascinating phenomenon toward next generation universal nonvolatile memories. Herein, the cuprous sulfide (Cu2S) film was prepared by electrochemical deposition. Further, the resistive switching (RS) behaviors of Ag/Cu2S/Ag and Ag/Cu2S/Cu sandwich structures were observed and compared. Ag/Cu2S/Ag device shows a reversible, high ratio (103) RS effect. However, Ag/Cu2S/Cu device displays a low operation voltage (0.5 V) and a more consistent high resistance. Our data suggest that the RS effect in Ag/Cu2S/Ag device results from formation or annihilation of conductive filaments. Moreover, a space charge barrier at the interface of Ag/Cu2S film is used to explain the RS effect in Ag/Cu2S/Cu device. This study is useful for exploring the sulfide materials and their applications in nonvolatile memory devices.
Keywords: Cuprous sulfide; Electrochemical deposition; Interfacial effects; EPIR effect; Resistive memory;
Effect of liquid properties on laser ablation of aluminum and titanium alloys by Peixuan Ouyang; Peijie Li; E.G. Leksina; S.V. Michurin; Liangju He (880-888).
In order to study the effect of liquid properties on laser ablation in liquids, aluminum 5A06 and titanium TB5 targets were irradiated by single-pulse infrared laser in isopropanol, distilled water, glycerin and as a comparison, in air, respectively. Craters induced by laser ablation were characterized using scanning electron and white-light interferometric microscopies. The results show that for liquid-mediated ablation, craters with porous surface structures were formed in aluminum target through phase explosion, while no micro-cavities were formed in titanium target owing to high critical temperature of titanium. In addition, ablation rates of aluminum and titanium targets vary with types of ambient media in accordance with such sequence: air < isopropanol < water < glycerin. Further, the influence of liquid properties on material-removal mechanisms for laser ablation in liquid is discussed. It is concluded that the density, thermal conductivity and acoustical impedance of liquid play a dominant role in laser ablation efficiency.
Keywords: Laser ablation; Surface morphology; Ablation rate; Liquid properties; Material-removal mechanisms;
Facile mesoporous template-assisted hydrothermal synthesis of ordered mesoporous magnesium silicate as an efficient adsorbent by Qingshan Lu; Qiang Li; Jingjing Zhang; Jingfeng Li; Jinhua Lu (889-895).
Mesoporous materials with unique structure as well as special morphology have potential applications in pollutant adsorption. In this work, using mesoporous silica SBA-15 filled with carbon (C@SBA-15) as both silicon source and assisted template, the ordered mesoporous magnesium silicate (Mg3Si4O9(OH)4) has been fabricated at 140 °C by a novel and facile hydrothermal method. During the hydrothermal process, the magnesium silicate grew along the silica walls at the expense of consuming silica and deposited on the carbon surface of the C@SBA-15. Meanwhile, the rigid carbon inside the pores of the SBA-15 supported the magnesium silicate as mesoporous walls under hydrothermal condition. The obtained magnesium silicate possessed ordered mesoporous structure, high specific surface area of 446 m2/g, large pore volume of 0.84 cm3/g, and hierarchical structure assembled with ultrathin nanosheets of 15 nm in thickness. These characteristics endow the ordered mesoporous magnesium silicate with the fast adsorption rate and high adsorption capacity of 382 mg/g for methylene blue. In addition, this synthesis method opens a new approach to fabricate other ordered mesoporous silicates.
Keywords: Magnesium silicate; Mesostructure; Hydrothermal method; Mesoporous template;
Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate by Changxin Xie; Xiaohong Li; Kaijun Liu; Min Zhu; Rong Qiu; Qiang Zhou (896-903).
The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, Ͽ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the SipeDrude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised SipeDrude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.
Keywords: Laser-induced periodic surface structures (LIPSSs); Near sub-wavelength ripples; Deep sub-wavelength ripples; Femtosecond laser pulses; Monocrystalline silicon;
Controllable wettability and morphology of electrodeposited surfaces on zinc substrates by Binyan Zhang; Shixiang Lu; Wenguo Xu; Yuanyuan Cheng (904-914).
Superhydrophobic surfaces combining hierarchical micro/nanostructures were fabricated on zinc substrates by etching, electrodeposition of ZnO coatings and annealing. Such superhydrophobic surfaces offer possibilities for chemical, biological, electronic and microfluidic applications.Superhydrophobic surfaces combining hierarchical micro/nanostructures were fabricated on zinc substrates by etching in hydrochloric acid solution, electrodeposition of ZnO coatings and subsequent thermal annealing. The optimal coatings were electrodeposited at 1.25 V for 900 s on the etched zinc substrates and then annealed at 200 °C for 60 min, which could achieve a maximum water contact angle of 170 ± 2° and an ultra-low sliding angle of approximately 0°. By conducting SEM and water CA analysis, we found that the morphology and wettability of prepared samples were controllable by the fabrication process. Interestingly, even without any additional modification, the samples prepared under different electrodeposition conditions (including Zn(CH3COO)2 concentration from 5 mM to 40 mM and deposition time from 300 s to 1500 s) exhibited superhydrophobic character. The influences of the Zn(CH3COO)2 concentration, deposition time, annealing temperature and annealing time on the wetting behaviors were also discussed in detail. Such superhydrophobic surfaces possess long-term stability, and good corrosion resistance as well as self-cleaning ability. In addition, the anti-icing properties of the ZnO films were investigated. These surfaces could be rapidly and reversibly switched between superhydrophobicity and superhydrophilicity by alternating UV illumination and dark storage or thermal annealing. The intelligent switchable surfaces with controllable wettability and morphology offer possibilities for chemical, biological, electronic and microfluidic applications.
Keywords: Electrodeposition; Wettability; Controllable morphology; ZnO microstructures; Anti-icing properties;
Potential enhancement of antibacterial activity of graphene oxide-silver nanocomposite by introducing C2 carbon chain linkage by Hyosuk Yun; Mohammad Shamsuddin Ahmed; Kyungmi Lee; Seungwon Jeon; Chul Won Lee (915-920).
Various carbon chain linkages were introduced during the process of synthesizing silver-nanoparticles (AgNPs)-decorated graphene nanocomposites [referred to as GO-C x -Ag where, HS-(CH2) x -SH = C x and x = 0, 2, or 4] to evaluate antibacterial properties. The nano-structures of GO-C x -Ag were characterized using TEM and XPS, revealing that GO-C 2 -Ag comprises well-dispersed and smaller AgNPs anchored onto the surface of graphene sheets than the GO-C 0 -Ag and GO-C 4 -Ag. The antibacterial activities of those nanocomposites were assessed using paper-disk diffusion and minimal inhibitory concentration (MIC) methods against Gram-negative and Gram-positive bacteria. The results showed that carbon chain linkers enhanced the antibacterial activity against Gram-negative Salmonella typhimurium and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. In particular, GO-C 2 -Ag showed higher antibacterial activity than GO-C 0 -Ag and GO-C 4 -Ag due to nearly eight times higher reactive oxygen species (ROS) formation which determined by fluorescence-based ROS detection experiment. Also, LC-inductively coupled plasma mass spectrometer (LC-ICP-MS) demonstrated that the Ag release from GO-C x -Ag was insignificant (0.03%). However, the higher ROS formation from GO-C 2 -Ag was facilitated by higher dispersion, smaller size, and well attachment of AgNPs with AgO species onto graphene sheets. These results suggest that the medium length carbon chain linkers in between Ag and GO can be utilized to improve antibacterial activity.
Keywords: Antibacterial materials; Carbon nanostructures; Grafted graphene; Silver nanoparticles;
Influence of grain refinement on the electrochemical behavior of AISI 430 ferritic stainless steel in an alkaline solution by A. Fattah-alhosseini; S. Vafaeian (921-928).
In this paper, the effect of grain refinement on the electrochemical behavior of AISI 430 ferritic stainless steel in 0.1 M NaOH solution was investigated. Potentiodynamic polarization curves showed that fine-grained samples have less corrosion potential, higher corrosion current density, and less protective passive film in comparison to coarse-grained samples. Electrochemical impedance spectroscopy (EIS) analysis revealed that implementing the thermomechanical operation led to lower polarization resistance. Also, MottSchottky analysis revealed that the passive films on both fine-grained and coarse-grained samples behave as n-type and p-type semiconductors and the semiconductor character of the passive films did not change by grain refinement. Moreover, it was found that the calculated donor and acceptor densities increased with grain refinement. Thus, the presented results indicated that grain refinement weakens the corrosion and passivation behavior of AISI 430 stainless steel in this alkaline solution.
Keywords: Grain refinement; Thermomechanical; Passive film; Alkaline solution;
Fabrication and physico-mechanical properties of thin magnetron sputter deposited silver-containing hydroxyapatite films by A.A. Ivanova; M.A. Surmeneva; A.I. Tyurin; T.S. Pirozhkova; I.A. Shuvarin; O. Prymak; M. Epple; M.V. Chaikina; R.A. Surmenev (929-935).
As a measure of the prevention of implant associated infections, a number of strategies have been recently applied. Silver-containing materials possessing antibacterial activity as expected might have wide applications in orthopedics and dentistry. The present work focuses on the physico-chemical characterization of silver-containing hydroxyapatite (Ag-HA) coating obtained by radio frequency (RF) magnetron sputtering. Mechanochemically synthesized Ag-HA powder (Ca10x Ag x (PO4)6(OH)2x , x = 1.5) was used as a precursor for sputtering target preparation. Morphology, composition, crystallinity, physico-mechanical features (Young's modulus and nanohardness) of the deposited Ag-HA coatings were investigated. The sputtering of the nanostructured multicomponent target at the applied process conditions allowed to deposit crystalline Ag-HA coating which was confirmed by XRD and FTIR data. The SEM results revealed the formation of the coating with the grain morphology and columnar cross-section structure. The EDX analysis confirmed that Ag-HA coating contained Ca, P, O and Ag with the Ca/P ratio of 1.6 ± 0.1. The evolution of the mechanical properties allowed to conclude that addition of silver to HA film caused increase of the coating nanohardness and elastic modulus compared with those of pure HA thin films deposited under the same deposition conditions.
Keywords: RF magnetron sputtering; Thin films; Silver-containing hydroxyapatite; Nanohardness; Young's modulus;
Fabrication of silica-decorated graphene oxide nanohybrids and the properties of composite epoxy coatings research by Yu Ma; Haihui Di; Zongxue Yu; Ling Liang; Liang Lv; Yang Pan; Yangyong Zhang; Di Yin (936-945).
With the purpose of preparing anticorrosive coatings, solvent-based epoxy resins often serve as raw material. Unfortunately, plentiful micro-pores are fabricated via solvent evaporation in the resin curing process, which is an intrinsic shortcoming and it is thus necessary to obstacle their micro-pore for enhancing antiseptic property. To reduce the intrinsic defect and increase the corrosion resistance of coating, we synthesize a series of SiO2GO hybrids through anchoring silica (SiO2) on graphene oxide (GO) sheets with the help of 3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane, and disperse the hybrids into epoxy resin at a low weight fraction of 2%. Furthermore, we investigate the appropriate preparation proportion of SiO2GO hybrids (namely: SiO2GO (1:5)). The electrochemical impedance spectroscopy (EIS) test and coatings morphology monitoring in corrosion process reveal that the anticorrosive performance of epoxy coatings is significantly enhanced by incorporation of SiO2GO (1:5) hybrids to epoxy compared with neat epoxy and other nanofillers including SiO2 or GO at the same contents. The superiority of the SiO2GO (1:5) hybrids is related to their excellent dispersion in resin and sheet-like structure.
Keywords: Graphene oxide; Silica; Epoxy coatings; Corrosion resistance; Sheet-like structure;
Molecular dynamics study of the interactions of incident N or Ti atoms with the TiN(001) surface by Zhenhai Xu; Quanren Zeng; Lin Yuan; Yi Qin; Mingjun Chen; Debin Shan (946-952).
The interaction processes between incident N or Ti atoms and the TiN(001) surface are simulated by classical molecular dynamics based on the second nearest-neighbor modified embedded-atom method potentials. The simulations are carried out for substrate temperatures between 300 and 700 K and kinetic energies of the incident atoms within the range of 0.510 eV. When N atoms impact against the surface, adsorption, resputtering and reflection of particles are observed; several unique atomic mechanisms are identified to account for these interactions, in which the adsorption could occur due to the atomic exchange process while the resputtering and reflection may simultaneously occur. The impact position of incident N atoms on the surface plays an important role in determining the interaction modes. Their occurrence probabilities are dependent on the kinetic energy of incident N atoms but independent on the substrate temperature. When Ti atoms are the incident particles, adsorption is the predominant interaction mode between particles and the surface. This results in the much smaller initial sticking coefficient of N atoms on the TiN(001) surface compared with that of Ti atoms. Stoichiometric TiN is promoted by N/Ti flux ratios larger than one.
Keywords: TiN; Atomic deposition; Adsorption; Resputtering; Reflection; Molecular dynamics;
Fabrication of phase and morphology controlled pure rutile and rutile/anatase TiO2 nanostructures in functional ionic liquid/water by Satwant Kaur Shahi; Navneet Kaur; Vasundhara Singh (953-960).
In this paper, pure rutile and anatase-rutile TiO2 nanoparticles have been successfully synthesised via a green route by hydrolysis of titanium tetrachloride with room temperature acidic ionic liquid 3-methyl-1-(3-sulfonylpropyl) imidazolium trifluoromethanesulfonate [HO3S(CH2)3MIM][CF3SO3] in aqueous medium. The influence of pH of the solution by varying molar ratio of substrate and ionic liquid has been investigated in both solgel and hydrothermal synthesis of TiO2 with significant variation in phase, phase composition (ratio of rutile to anatase) and morphology as indicated by various structural analysis such as XRD, TEM, BET, Raman and UVvis absorption spectroscopy. The results indicate formation of a bunch of aligned thin flaky nano-rods of TiO2 which look like nano-flowers with a crystal size of 35 nm by solgel method, while in case of hydrothermal method well-defined rutile solid nanorods of TiO2 were formed with variable length in the range of 120170 nm and 2024 nm in width. The photocatalytic activity of the prepared TiO2 samples has been determined by the photodegradation of methyl orange dye (20 ppm) under UV light. Best photocatalytic activity was exhibited by sample S-2 prepared via solgel method.
Keywords: Titanium dioxide; Functional ionic liquid; Rutile; Photocatalytic degradation; Methyl orange;
In vitroin vivo performance of bare and drug loaded silica gel synthesized via optimized process parameters by Suparna Chakraborty; Supratim Biswas (961-969).
Silica xerogel as a potential drug carrier system for the in vivo as well as in vitro delivery of andrographolide was tested. The present study aims to optimize the effective experimental parameters; volume of ethanol, volume of water and drying temperature by applying response surface methodology coupled with BoxBehnken experimental design. The in vitro drug release in simulated body fluid at 37 οC from the selected formulation was significantly highest (44.83 ± 0.9%) among rest of the formulations. Results indicate that solgel method is useful for entrapping andrographolide in the silica gel and for releasing the same via diffusion through the porous matrix under the in vitro/in vivo conditions. Silica gel exhibited slow matrix degradation as well as sustained release of andrographolide within the experimental time frame of 168 h. In vivo study was performed with three increasing doses [2 mg (S1), 8 mg (S2), and 16 mg (S3)] of silica. Histological fates of different organs were executed with those doses.
Keywords: BoxBehnken design; Response surface methodology; Drug release; Optimization; Matrix degradation; Histology;
Oxidation resistance and mechanical properties of HfC nanowire-toughened ultra-high temperature ceramic coating for SiC-coated C/C composites by Jincui Ren; Yulei Zhang; Heng Hu; Tian Fei; Hejun Li (970-978).
To improve the oxidation resistance of carbon/carbon (C/C) composites, a dense HfC nanowire-toughened ultra-high temperature ceramic multiphase coating was prepared on SiC-coated C/C composites by chemical vapor deposition (CVD) and pack cementation. The microstructure, mechanical and oxidation resistance properties of the coating were investigated. The results show that the HfC nanowires in the coating could suppress the cracking of the coating and then improve the toughness of the coating. The flexural property, thermal shock and isothermal oxidation resistance of the coating were all improved due to the incorporation of HfC nanowires.
Keywords: Carbon/carbon composite; Ultra-high temperature ceramic coating; HfC nanowires; Mechanical property; Oxidation resistance;
Adsorption of nucleotides on biomimetic apatite: The case of adenosine 5⿲ triphosphate (ATP) by Khaled Hammami; Hafed El-Feki; Olivier Marsan; Christophe Drouet (979-988).
ATP is a well-known energy supplier in cells. The idea to associate ATP to pharmaceutical formulations/biotechnological devices to promote cells activity by potentially modulating their microenvironment thus appears as an appealing novel approach. Since biomimetic nanocrystalline apatites have shown great promise for biomedical applications (bone regeneration, cells diagnostics/therapeutics, ), thanks to a high surface reactivity and an intrinsically high biocompatibility, the present contribution was aimed at exploring ATP/apatite interactions. ATP adsorption on a synthetic carbonated nanocrystalline apatite preliminarily characterized (by XRD, FTIR, Raman, TG-DTA and SEM-EDX) was investigated in detail, pointing out a good agreement with Sips isothermal features. Adsorption characteristics were compared to those previously obtained on monophosphate nucleotides (AMP, CMP), unveiling some specificities. ATP was found to adsorb effectively onto biomimetic apatite: despite smaller values of the affinity constant K S and the exponential factor m, larger adsorbed amounts were reached for ATP as compared to AMP for any given concentration in solution. m < 1 suggests that the ATP/apatite adsorption process is mostly guided by direct surface bonding rather than through stabilizing intermolecular interactions. Although standard ο G ads ° was estimated to only 4 kJ/mol, the large value of N max led to significantly negative effective οG ads values down to 33 kJ/mol, reflecting the spontaneous character of adsorption process. Vibrational spectroscopy data (FTIR and Raman) pointed out spectral modifications upon adsorption, confirming chemical-like interactions where both the triphosphate group of ATP and its nucleic base were involved. The present study is intended to serve as a basis for future research works involving ATP and apatite nanocrystals/nanoparticles in view of biomedical applications (e.g. bone tissue engineering, intracellular drug delivery, ).
Keywords: Nanocrystalline apatite; Adenosine triphosphate; Adsorption; Nucleotide; Vibrational spectroscopy;
Controllable giant magnetoresistance effect by the δ-doping in a magnetically confined semiconductor heterostructure by Mao-Wang Lu; Xue-Li Cao; Xin-Hong Huang; Ya-Qing Jiang; Shi-Peng Yang (989-993).
We propose theoretically an alternative method to effectively manipulate a GMR device by the δ-doping, which is based on a magnetically confined semiconductor heterostructure. It is found that the magnetoresistance ratio is tunable by changing weight and/or position of the δ-doping. Thus, a structurally controllable GMR device can be obtained for magnetoelectronics applications.We report on a theoretical study of the influence of a δ-doping on a giant magnetoresistance (GMR) device based on a magnetically confined GaAs/Al x Ga1x As heterostructure. The δ-doping dependent transmission and conductance of the device are calculated. It is shown that there still exists an obvious GMR effect even the inclusion of a δ-doping. It is also shown that the magnetoresistance ratio (MR) of the device can be switched by changing the weight and/or position of the δ-doping. These interesting features provide an alternative way to manipulate a GMR device, and the structure can be employed as a structurally controllable GMR device for magnetoelectronics applications.
Keywords: Magnetically confined semiconductor heterostructure; The δ-doping; GMR effect; Magnetoresistance ratio; Controllable GMR device;
Study on the surface speciation of Fe-pillared montmorillonite and mechanism of its photocatalytic effect on degradation of ionic dye rhodamine-B by Jimin Fang; Xiuyan Huang; Qian Zhang; Junhong Chen; Xun Wang (994-998).
The surface protonation constants of Na-montmorillonite (abbreviated as Namt) and Fe-pillared montmorillonite (abbreviated as Femt) were obtained from experimental determination and then fitted with Protfit 2.1 software. The values of pK a1, pK a2 and Nt as well as the iron content of Femt are higher than those of Namt. The surface speciation of the sample presents lagging performance as the pH changes. The adsorption amount and catalytic decolorization rate of Femt for rhodamine-B are higher than that of Namt at the same pH. When the pH value increases, the adsorption amount and catalytic decolorization rate of Femt for rhodamine-B decline. The content of >FeOH2 + on the surface of Femt is positively correlated with the adsorption amount and catalytic decolorization rate for the dye. The mechanism of >FeOH2 + for the photocatalytic degradation of rhodamine-B may be interpreted as follows: after >FeOH2 + effectively captures hydrogen peroxide and photoelectrons in the valence band of >FeOH2 +, hydroxyl radicals are produced. Hydroxyl radicals are also produced by electron holes on the valence band of >FeOH2 + absorbing OH. The interrupted electrostatic field produced by >FeOH2 + on the surface of Femt can prevent the electronhole recombination, which improves the catalytic efficiency of the Femt. Rhodamine-B is photocatalytically degraded by hydroxyl radicals.
Keywords: Photo-Fenton-like; Ionic dye; Surface speciation; Quinoid structure; Electron capture;
Periodic nanostructures fabricated on GaAs surface by UV pulsed laser interference by Wei Zhang; Dayun Huo; Xiaoxiang Guo; Chen Rong; Zhenwu Shi; Changsi Peng (999-1002).
In this paper, periodic nanostructures were fabricated on GaAs wafers by four-beam UV pulsed laser interference patterning. Significant different results were observed on epi-ready and homo-epitaxial GaAs substrate surfaces, which suggests GaAs oxide layer has an important effect on pulsed laser irradiation process. In the case of two-pulse patterning, a noticeable morphology transformation induced by the second pulse was observed on homo-epitaxial GaAs substrate. Based on photo-thermal mode, temperature distribution on sample surface as a function of time and position was calculated by solving the heat diffusion equations.
Keywords: Periodic nanostructures; GaAs; Laser interference patterning;
Electron irradiation induced buckling, morphological transformation, and inverse Ostwald ripening in nanorod filled inside carbon nanotube by Anshika Singh; Reetu Kumari; Vinay Kumar; Lucky Krishnia; Zainab Naqvi; Amrish K. Panwar; Umananda M. Bhatta; Arnab Ghosh; P.V. Satyam; Pawan K. Tyagi (1003-1008).
The present study aims to deduce the in-situ response of iron carbide (Fe3C) nanorod filled inside carbon nanotube (CNT) under electron irradiation. Electron irradiation on Fe3C filled-CNT at both high and room temperature (RT) has been performed inside transmission electron microscope. At high temperature (HT), it has been found that γ-Fe atoms in lattice of Fe3C nanorod accumulate first and then form the cluster. These clusters follow the inverse Ostwald ripening whereas if e-irradiation is performed at RT then only the morphological changes in both carbon nanotube as well as nanorod are observed. Compression generated either by electron beam heating or by shrinkage of CNT walls is observed to be a decisive factor.
Keywords: Filled-carbon nanotube; Electron-irradiation; Nano-engineering; shape-alteration; In situ transmission electron microscopy;
Characteristics of fluorinated CNTs added carbon foams by Ji-Hyun Kim; Do Young Kim; Euigyung Jeong; Young-Seak Lee (1009-1015).
To fabricate carbon foams with high compressive strength and thermal conductivity, carbon foams were prepared by curing and heat treatment of a polymer solution containing CMC, isotropic pitch and fluorinated CNTs. The CNTs were fluorinated at different fluorine gas pressures (F2:N2 = 3:7, 5:5, and 7:3). The highly heat-treated carbon foams containing fluorinated CNTs prepared with F2:N2 = 5:5 had the highest thermal conductivity of 3.18 ± 0.01 W/mK, and compressive strength of 2.42 ± 0.22 MPa, which were approximately 15% and 133% higher, respectively, than those of the highly heat-treated carbon foams containing un-fluorinated CNTs due to increased crystallinity of CNTs and their adhesion with pitches in highly heat-treated carbon foams through fluorination of CNTs.
Keywords: Fluorination; CNTs; Carbon foam; Apparent density; Compressive strength; Thermal conductivity;
Boron doped g-C3N4 with enhanced photocatalytic UO2 2+ reduction performance by Changhai Lu; Rongyue Chen; Xi Wu; Meifeng Fan; Yunhai Liu; Zhanggao Le; Shujuan Jiang; Shaoqing Song (1016-1022).
Tuning the band gap and absorption intensity of visible-light by element doping is an attractive strategy to enhance the photocatalytic activity of semiconductor materials. Here we doped boron into g-C3N4 to construct highly efficient photocatalysts (B-g-C3N4) for the photocatalytic reduction of UO2 2+. Characterization and photocatalysis tests showed the band gap of B-g-C3N4 was narrowed, and the absorption intensity of visible-light was enhanced with increasing the formed N-B-C (BCN) of B-g-C3N4, which is consistent with the trend of the photocatalytic performance of B-g-C3N4. The optimized B-g-C3N4 photocatalyst with BCN content of 1.01 at.% exhibited excellent removal efficiency of UO2 2+ and good photocatalytic stability. Therefore, these results may lead to a new strategy for exploring the advanced photocatalysts based on the carbon nanomaterials with abundant BCN for the photocatalytic reduction of U(VI) pollutant.
Keywords: Graphitic carbon nitride; Boron doping; Photocatalysis; UO2 2+ reduction;
Ge deposition on Si(1 0 0) in the conditions close to dynamic equilibrium between islands growth and their decay by A.A. Shklyaev; A.E. Budazhapova (1023-1029).
The formation of islands arrays during Ge deposition on Si(1 0 0) at high temperatures is studied using scanning tunneling and electron microscopies. It is found that the island size and shape distributions, which are known to be bimodal at growth temperatures below 700 °C, become monomodal at temperatures above 800 °C. The obtained data suggest that the processes such as island nucleation and Ostwald ripening become less significant in the surface morphology formation, giving the advantage to selective attachment of deposited Ge atoms to island sidewalls and spatially inhomogeneous Si-Ge intermixing, as the temperature increases. At 900 °C, the islands exhibit a tendency to form laterally ordered arrays when the growth conditions approach the dynamic equilibrium between the growth of islands and their decay by means of Si-Ge intermixing. The islands ordering is accompanied by their shape transformation into the cone with shallow sidewalls inclined from (1 0 0) by angles of around 10°.
Keywords: Ge growth on Si(1 0 0); Monomodal island distribution; Dynamic equilibrium; Islands lateral ordering;
A facial approach combining photosensitive solgel with self-assembly method to fabricate superhydrophobic TiO2 films with patterned surface structure by Zongfan Duan; Zhen Zhao; Dan Luo; Maiqun Zhao; Gaoyang Zhao (1030-1035).
Superhydrophobic TiO2 films with micro-patterned surface structure was prepared through a facial approach combining photosensitive solgel method with following surface modification by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTCS). The patterned surface possessed quasi micro-lens array structure resembling processus mastoideus of lotus, leading to excellent hydrophobicity. The relationship between hydrophobic performance and the period of the micro-patterned TiO2 surface was investigated. The water contact angles (CAs) of micro-patterned TiO2 surface increased with the decrease of the periods, and the patterned surface with the lowest period of 0.83 μm showed the highest CA of 163°. It suggests that this approach would offer an advantage to control the wettability properties of superhydrophobic surfaces by adjusting the fine pattern structure. Furthermore, the superhydrophobic state could be converted to the state of superhydrophilicity under ultraviolet (UV) illumination as a result of the photocatalytic decomposition of the PFOTCS monolayer on the micro-patterned TiO2 Surface.
Keywords: Thin film; Surfaces; Superhydrophobic; Superhydrophilic; TiO2; Pattern;
Strengthening of porous TiB2SiC ceramics by pre-oxidation and crack-healing by Rubing Zhang; Changshou Ye; Yaoyao Zhang (1036-1040).
Crack-healing behavior of low porosity ceramics was firstly investigated by pre-oxidizing the samples. From the curves, the strength of porous ceramics obviously improved after pre-oxidation, with a maximum increase in strength of 134.4% for samples pre-oxidized at 800 °C for 240 min.Low porosity TiB2SiC ceramics were prepared by Cold Isostatic PressingPressureless Sintering (CIPPS). The crack-healing behavior of these ceramics was investigated by pre-oxidizing the samples at 8001200 °C in air for various durations ranging from 5 to 240 min. The effects of pre-oxidation temperature and time on the microstructure and mechanical properties of porous TiB2SiC ceramics were studied. The strength of porous ceramics obviously improved after pre-oxidation, with a maximum increase in strength of 134.4% for samples pre-oxidized at 1200 °C for 120 min. The strengthening mechanism of porous TiB2SiC ceramics after pre-oxidation was also investigated and discussed. This study provides a novel concept for improving the strength and structural integrity of porous ceramics in practical applications.
Keywords: Porous ceramics; Crack-healing; Pre-oxidation; TiB2; Mechanical properties;
Chemisorption of NO on Pt-decorated graphene as modified nanostructure media: A first principles study by Ali Shokuhi Rad; Ehsan Abedini (1041-1046).
We used density functional theory calculations (DFT) to search the potential of pristine as well as Pt-decorated graphene sheets as adsorbent/gas sensors for NO by considering the electronic properties of NO on these two surfaces. We found much higher adsorption energy, higher charge transfer, lower connecting distance, and higher orbital hybridizing of NO gas molecule on Pt-decorated graphene than pristine graphene. We used orbital analysis including density of states as well as frontier molecular orbital study for NO-surface systems because of more understanding of the kind of interaction. Our results reveal physisorption of NO on pristine graphene with adsorption energy of 24 kJ mol1while in contrast much higher adsorption energy of 199 kJ mol1 is achieved upon adsorption of NO on Pt-decorated graphene which is in the range of chemisorption.
Keywords: Nanostructure sensor; Pt-decorated graphene; Density functional study; Gas sensor; Density of states;
Structural and optical characterization of mechanically milled Mg-TiO2 and nitrided Mg-TiO x -N y nanostructures: Possible candidates for gas sensing application by A.S. Bolokang; B.P. Dhonge; H.C. Swart; C.J. Arendse; T.F.G. Muller; D.E. Motaung (1047-1058).
We report for the first time on the gas sensing properties of novel ball milled and nitrided Mg-TiO2 prepared powder. Ball milling was performed on an Mg-TiO2 powder mixture for 60 hours (h), yielding a reduction in crystallite sizes. The milled powder was annealed in nitrogen at 650 °C, and crystalized into two face centred cubic (FCC) phases with different lattice parameters. The nitrided powder sample exhibited various morphologies including nanorods, as well as nanoparticles showing porous behaviour. The AFM and BET analyses showed high roughness and surface area for 60 h milled Mg-TiO2 nanostructures. The Mg-TiO2 60 h and Mg-TiO2-60 h-N2 materials were tested for their sensing performance towards H2, NH3 and CH4 gases at various temperatures. The Mg-TiO2 60 h sensing material showed high sensing response to NH3, disclosing fast response-recovery time and high selectivity to NH3.
Keywords: Mg-TiO2; Mechanical milling; Nanostructures; Nitridation; Gas sensing;
Synthesis of porous SnO2 nanocubes via selective leaching and enhanced gas-sensing properties by Yining Li; Qi Wei; Peng Song; Qi Wang (1059-1065).
Porous SnO2 nanocubes have been successfully fabricated via a selective leaching strategy, which exhibited high response, short responserecovery times and good selectivity to ethanol gas.Porous micro-/nanostructures are of great interest in many current and emerging areas of technology. In this paper, porous SnO2 nanocubes have been successfully fabricated via a selective leaching strategy using CoSn(OH)6 as precursor. The structure and morphology of as-prepared samples were investigated by several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimeter analysis (TGDSC), transmission electron microscopy (TEM) and N2 adsorptiondesorption analyses. On the basis of those characterizations, the mechanism for the formation of porous SnO2 nanocubes has been proposed. Owing to the well-defined and uniform porous structures, porous SnO2 nanocubes possessing more adsorbent amount of analytic gas and accelerate the transmission speed so as to enhance the gas-sensing properties. Gas sensing investigation showed that the sensor based on porous SnO2 nanocubes exhibited high response, short responserecovery times and good selectivity to ethanol gas.
Keywords: Tin dioxide; Porous nanocubes; Selective leaching; Gas sensor;
Study on Pt-structured anodic alumina catalysts for catalytic combustion of toluene: Effects of competitive adsorbents and competitive impregnation methods by Qi Zhang; Hongjuan Luan; Tao Li; Yongqiang Wu; Yanhui Ni (1066-1074).
Novel competitive impregnation methods were used to prepare high dispersion Pt-structured anodic alumina catalysts. It is found that competitive adsorbents owning different acidity result in different Pt loading amount and also exert great effects on Pt distribution, particle size and redox ability. The suitable adsorption ability of lactic acid led to its best activity for catalytic combustion of toluene. Co-competitive and pre-competitive impregnation methods were also compared and the mechanisms of two competitive methods were proposed. Co-competitive impregnation made Pt distribute more uniformly through pore channels and resulted in better catalytic activity, because of the weaker spatial constraint effect of lactic acid. Furthermore, the optimized Pt-structured anodic alumina catalyst also showed a good chlorine-resistance under moisture atmosphere, because water could promote the reaction of dichloromethane (DCM) transformation and clean chloride by-products to release more active sites.
Keywords: Toluene; Competitive adsorbent; Competitive method; Chlorine-resistance;
Interfacial properties of the enhanced visible-light plasmonic Ag/Bi2WO6 (0 0 1) nanocomposite by Fang Wang; Kun Cao; Yi Wu; Kun-Hao Zhang; Ying Zhou (1075-1079).
First principle calculations are performed to study the interfacial photoelectric properties of Ag n /Bi2WO6 (0 0 1) (n = 1, 2, 3, 4) hybrid photocatalyst. The parallel adsorption of Ag cluster leads to more energetic favorable structures due to stronger interfacial interactions. The positive charged Ag cluster may act as excited electron traps and facilitate the electronhole separation. In particular, hybridization between Ag 5s and O 2p leads to the formation of isolated energy levels above the valence bands, and they become more dispersed with broader bandwidth with the increment of silver cluster size, which is responsible for the enhanced absorption in visible-light region. In the deep valence region, Ag 4d orbital turns more delocalized and hybrid with O 2p states as the cluster size increases, which contributes to more covalent bond feature of AgO. Moreover, optical spectra demonstrate obvious red-shifts of the absorption edge with the increment of silver content, which enhances efficiently the visible-light photocatalytic activities of Bi2WO6 (0 0 1). The study provides insights into the enhanced photocatalyic mechanism of Ag/Bi2WO6 (0 0 1) and aids in the design of noble metal loaded visible-light plasmonic photocatalyst.
Keywords: Plasmonic photocatalyst; First principle calculation; Interfacial property;
On the passivation mechanism of Fe3O4 nanoparticles during Cr(VI) removal from water: A XAFS study by F. Pinakidou; M. Katsikini; K. Simeonidis; E. Kaprara; E.C. Paloura; M. Mitrakas (1080-1086).
X-Ray Absorption Spectroscopies (XAFS) are employed in order to gather a thorough insight on the uptake mechanism of Cr(VI) by Fe3O4 nanoparticles under water treatment conditions. The XANES measurements identify that the reducing potential of Fe3O4 activates the precipitation of Cr(VI) in the form of insoluble and non-toxic Cr(III). However, electron donation from Fe(II) is responsible for its gradual consumption, resulting in the presence of a surface maghemite layer and the formation of structural vacancies. EXAFS analysis reveal that adsorption of Cr(III)-oxyanions occurs on sorption sites provided by the vacancies in the maghemite layer, where Cr(III) is involved in a bidentate binuclear (2E) geometry with Fe-octahedra while it also forms monodentate (1V) complexes with the Fe(III)O4 tetrahedra. The surface maghemitization along with the reduced Cr(III) adsorption into the vacancies, tracks the degree of Cr-reduction, since this surface structural modifications hinder Cr(VI) access to the Fe(II) ions of the magnetite nanoparticles. Thus, high surface coverage leads to the passivation of the reduction ability since physisorbed Cr(VI) is also detected through the formation of outer sphere complexes.
Keywords: Cr(VI) removal; Fe3O4 nanoparticles; Water treatment; EXAFS; XANES;