Applied Surface Science (v.364, #C)

Green synthesis of nickel species in situ modified hollow microsphere TiO2 with enhanced photocatalytic activity by Qi Wang; Zenan Qin; Jie Chen; Baosheng Ren; Qifeng Chen; Yanchuan Guo; Xiaofeng Cao (1-8).
A green solvothermal approach was proposed to synthesize highly crystallized hollow microsphere TiO2 in the presence of oxalic acid and the products exhibited high photocatalytic activity compared with the counterpart of solid microsphere and particulate TiO2.A green template-free solvothermal approach was developed to synthesize hollow microsphere TiO2-modified in situ with nickel species (Ni2+/Ni3+). Oxalic acid played a pivotal role in the formation of hollow architecture, acting as chelating agent, structure-directing reagent, and acidity-modulation reagent, while isopropyl alcohol ensured the formation of spherical structure. The microstructure and composition of the products were characterized with various techniques, and the results showed that the products exhibited not only highly crystallized anatase phase, large specific surface areas, and the mesoporous shell and hollow architecture, but also the coexistence of Ni2+/Ni3+. The unique structure and composition of the photocatalysts resulted in improved UV and visible photocatalytic activity for degradation of Rhodamine-B and 2,4-dichlorophenol.
Keywords: Green synthesis; Hollow microsphere TiO2; Nickel species modification; High crystallinity; Photocatalytic activity;

Improvement of corrosion resistance of Ni―Mo alloy coatings: Effect of heat treatment by R. Mousavi; M.E. Bahrololoom; F. Deflorian; L. Ecco (9-14).
In this paper, Ni―Mo alloy coatings were deposited from bath containing sodium citrate, nickel sulphate, and sodium molybdate. Essentially, this work is divided into two mains parts: (i) the optimization on the coatings deposition parameters and (ii) the effect of the heat treatment. Polarization curves and electrochemical impedance spectroscopy were acquired using potentiostat/galvanostat and a frequency response analyzer, respectively. Morphology and chemical composition of the coatings were investigated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Polarization curves at different condition revealed that electroplating at temperature 40  oC, pH 9 provides a dense coating with high efficiency. Following the optimization of the deposition parameters, the coatings were annealed at 200, 400, and 600  oC for 25 min. The results showed that the coatings obtained at temperature 40  oC, pH 9, and annealing at 600  oC has the highest corrosion resistance and microhardness.
Keywords: Ni―Mo coating; Electrochemical impedance spectroscopy; Diffusion control; Annealing;

Hydrophobic conjugated microporous polymers for sorption of human serum albumin by Chunli Zheng; Miaomiao Du; Shanshan Feng; Hanxue Sun; An Li; Chi He; TianCheng Zhang; Qiaorui Wang; Wei Wei (15-20).
Conjugated microporous polymers (CMPs) exhibit an excellent sorbency for human serum albumin.This paper investigated the sorption of human serum albumin (HSA) from water by three kinds of conjugated microporous polymers (CMPs) with surface hydrophobicity and intrinsic porosity. It was found that the three CMPs captured HSA with fast sorption kinetics and good working capacity. Equilibrium was obtained at 80 min for all the tests, and the maximum sorption quantity (q m) ranged from 0.07 to 0.14 mg/mg. With the increase in the particle external surface area of the CMPs, a greater extent of HSA sorption was achieved. Moreover, promoting the dispersion of CMPs in HSA aqueous solution was also beneficial to the extraction. Attenuated Total Reflection Fourier Transform Infrared spectroscopy verified the interactions between the CMPs and the N―H, C=O, and C―N groups of HSA. This paper might provide fundamental guidance for the practical application of CMPs to proteins separation and recovery.
Keywords: Human serum albumin; Conjugated microporous polymers; Sorption; Protein;

Fabrication and characterization of a sandpaper-based flexible energy storage by Jen-Yu Shieh; Cheng-Hung Wu; Sung-Ying Tsai; Hsin Her Yu (21-28).
A sandpaper-based supercapacitor was assembled from two graphene/CNTs-coated fine-sandpaper electrodes and a PVA porous separator enclosed with H3PO4/PVA gel electrolyte, then packaged between two PET sheets by hot pressing. The galvanostatic charge/discharge curves obtained at a current of 0.10 mA over about 3000 cycles. The capacitance retention rates remained over 91% after this period, indicating the electrochemical stability of the supercapacitor. Thus, the supercapacitor based on the fine sandpaper electrode has a long lifetime and good cycling stability.In this paper, graphene and carbon nanotubes dispersed in a pectin solution are examined as a precursor for electrode fabrication for supercapacitor applications. The carbon nanotubes not only prevent the stacking of graphene sheets, but also act as spacers and binders. Dropping the hybrid conductive suspension onto sandpaper is found to form a sandpaper-based electrode that improves the specific capacitance of a subsequently fabricated supercapacitor because of its high surface area. In particular, the large contact surface of the sandpaper allows it to absorb more electrolyte ions and increases the number of ions assembled on the electrode surface. For the supercapacitor fabrication, replacing the liquid or solid electrolyte with a gel electrolyte prevents leakage and contact discontinuity. Therefore, a high-performance supercapacitor can be constructed with one separator coated with a gel electrolyte inserted between two fine-sandpaper-based electrodes, which can be assembled into a sandwich structure by hot pressing. Electrochemical analysis shows excellent cycle stability and flexibility of the fine-sandpaper-based supercapacitor. Because of the simple and low-cost assembly of this flexible and lightweight supercapacitor, it has potential applications in many energy storage fields, including wearable electronics and flexible products.
Keywords: Sandpaper; Flexible supercapacitor; Gel electrolyte; Microporous separator; Energy storage;

Halides are often present at electrochemical environment, they can directly influence the electrode potential or zero charge potential through the induced work-function change. In this work, we focused in particular on the halogen-induced work function change as a function of the coverage of fluorine, chlorine, bromine and iodine on Al2Au and Al2Pt (110) surfaces. Results show that the real relation between work function change and dipole moment change for halogens adsorption on intermetallic surfaces is just a common linear relationship rather than a directly proportion. Besides, the different slopes between fitted lines and the theoretical slope employed in pure metal surfaces demonstrating that the halogens adsorption on intermetallic surfaces are more complicated. We also present a weight parameter β to describe different factors effect on work function shift and finally qualify which factor dominates the shift direction.
Keywords: Halogens; Intermetallic surface; Work function; Dipole moment; Charge transfer; Polarization effect;

Hierarchically structured self-supported latex films for flexible and semi-transparent electronics by Anni Määttänen; Petri Ihalainen; Björn Törngren; Emil Rosqvist; Markus Pesonen; Jouko Peltonen (37-44).
Different length scale alterations in topography, surface texture, and symmetry are known to evoke diverse cell behavior, including adhesion, orientation, motility, cytoskeletal condensation, and modulation of intracellular signaling pathways. In this work, self-supported latex films with well-defined isotropic/anisotropic surface features and hierarchical morphologies were fabricated by a peel-off process from different template surfaces. In addition, the latex films were used as substrates for evaporated ultrathin gold films with nominal thicknesses of 10 and 20 nm. Optical properties and topography of the samples were characterized using UV–vis spectroscopy and Atomic Force Microscopy (AFM) measurements, respectively. The latex films showed high-level transmittance of visible light, enabling the fabrication of semi-transparent gold electrodes. Electrochemical impedance spectroscopy (EIS) measurements were carried out for a number of days to investigate the long-term stability of the electrodes. The effect of 1-octadecanethiol (ODT) and HS(CH2)11OH (MuOH) thiolation and protein (human serum albumin, HSA) adsorption on the impedance and capacitance was studied. In addition, cyclic voltammetry (CV) measurements were carried out to determine active medicinal components, i.e., caffeic acid with interesting biological activities and poorly water-soluble anti-inflammatory drug, piroxicam. The results show that the fabrication procedure presented in this study enables the formation of platforms with hierarchical morphologies for multimodal (optical and electrical) real-time monitoring of length-scale-dependent biomaterial-surface interactions.
Keywords: Transparent conducting electrodes; Thin film; 3D surface topography; Latex; Evaporated gold;

Pd surface activation via a sonochemical approach was studied by varying Pd precursor status in the aqueous solution. By aging a K2PdCl6 activation solution overnight with added NH4OH, the chlorinated Pd complex was changed to an ammonia-based Pd complex. The Pd surface activation carried out with the NH4OH complexing agent resulted in improved surface condition following Cu electroless deposition. The Cu thin film deposited on a substrate sonochemically activated with the aged, ammonia-based Pd complex showed improved surface roughness and resistivity compared to that for Cu films deposited via two other precursors (chlorinated Pd complex and ammonia-based complex) without aging. In addition, nitrogen purging during sonochemical activation improved Cu film quality.
Keywords: Sonochemistry; Palladium; Surface activation; Electroless deposition; Ammonium hydroxide;

A remarkable enhancement in the hydrophilic nature of titanium dioxide (TiO2) films is obtained by surface modification in DC-glow discharge plasma. Thin transparent TiO2 films were coated on glass substrate by sol–gel dip coating method, and exposed in DC-glow discharge plasma. The plasma exposed TiO2 film exhibited a significant change in its wetting property contact angle, which is a representative of wetting property, has reduced to considerable limits 3.02° and 1.85° from its initial value 54.40° and 48.82° for deionized water and ethylene glycol, respectively. It is elucidated that the hydrophilic property of plasma exposed TiO2 films dependent mainly upon nanometer scale surface roughness. Variation, from 4.6 nm to 19.8 nm, in the film surface roughness with exposure time was observed by atomic force microscopy (AFM). Analysis of variation in the values of contact angle and surface roughness with increasing plasma exposure time reveal that the surface roughness is the main factor which makes the modified TiO2 film superhydrophilic. However, a contribution of change in the surface states, to the hydrophilic property, is also observed for small values of the plasma exposure time. Based upon nanometer scale surface roughness and dangling bonds, a variation in the surface energy of TiO2 film from 49.38 to 88.92 mJ/m2 is also observed. X-ray photoelectron spectroscopy (XPS) results show change in the surface states of titanium and oxygen. The observed antifogging properties are the direct results of the development of the superhydrophilic wetting characteristics to TiO2 films.
Keywords: TiO2 thin films; Sol–gel dip coating method; Contact angel measurement; Antifogging property;

Microstructural changes of Zr702 induced by pulsed laser surface treatment by Linjiang Chai; Baofeng Chen; Shuyan Wang; Ning Guo; Can Huang; Zhiming Zhou; Weijiu Huang (61-68).
In this work, the surface of a fully recrystallized Zr702 is treated by pulsed laser following which microstructural changes are investigated by use of electron backscatter diffraction and electron channeling contrast imaging techniques. The pulsed laser treatment results in three distinctly different microstructural features from the surface to the substrate: fine α plates with a few hundred nanometers in width (zone I), irregular-shaped grains with varied sizes (zone II), and essentially unchanged equiaxed grains (zone III). The α plates result from rapid phase transformation due to easy heat extraction of the pulsed laser with dense nanoscale twins inside those plates closer to the surface. The origin of the irregular-shaped grains is found to be related to insufficient recrystallization of antecedently formed α plates near the substrate. Hardness tests reveal highest value (∼356.7 HV) near the surface in zone I and the lowest value (∼165.2 HV) in zone II. Reasons accounting for the difference are discussed in terms of various microstructural characteristics induced by the pulsed laser surface treatment.
Keywords: Zr alloy; Surface treatment; Microstructure; Electron backscatter diffraction;

Decorative black TiC x O y film fabricated by DC magnetron sputtering without importing oxygen reactive gas by Katsushi Ono; Masao Wakabayashi; Yukio Tsukakoshi; Yoshiyuki Abe (69-74).
Novel fabrication of decorative black TiC x O y film by dc magnetron sputtering at high pressure using no oxygen gas.Decorative black TiC x O y films were fabricated by dc (direct current) magnetron sputtering without importing the oxygen reactive gas into the sputtering chamber. Using a ceramic target of titanium oxycarbide (TiC1.59O0.31), the oxygen content in the films could be easily controlled by adjustment of total sputtering gas pressure without remarkable change of the carbon content. The films deposited at 2.0 and 4.0 Pa, those are higher pressure when compared with that in conventional magnetron sputtering, showed an attractive black color. In particular, the film at 4.0 Pa had the composition of TiC1.03O1.10, exhibited the L* of 41.5, a* of 0.2 and b* of 0.6 in CIELAB color space. These values were smaller than those in the TiC0.29O1.38 films (L* of 45.8, a* of 1.2 and b* of 1.2) fabricated by conventional reactive sputtering method from the same target under the conditions of gas pressure of 0.3 Pa and optimized oxygen reactive gas concentration of 2.5 vol.% in sputtering gas. Analysis of XRD and XPS revealed that the black film deposited at 4.0 Pa was the amorphous film composed of TiC, TiO and C. The adhesion property and the heat resisting property were enough for decorative uses. This sputtering process has an industrial advantage that the decorative black coating with color uniformity in large area can be easily obtained by plain operation because of unnecessary of the oxygen reactive gas importing which is difficult to be controlled uniformly in the sputtering chamber.
Keywords: TiC x O y coatings; Decorative black films; DC magnetron sputtering;

Gold catalysts supported on nanosized iron oxide for low-temperature oxidation of carbon monoxide and formaldehyde by Zheng Tang; Weidong Zhang; Yi Li; Zuming Huang; Huishan Guo; Feng Wu; Jinjun Li (75-80).
This study aimed to optimize synthesis of gold catalyst supported on nanosized iron oxide and to evaluate the activity in oxidation of carbon monoxide and formaldehyde. Nanosized iron oxide was prepared from a colloidal dispersion of hydrous iron oxide through a dispersion–precipitation method. Gold was adsorbed onto nanosized iron oxide under self-generated basic conditions. Characterization results indicate that the iron oxide consisted of hematite/maghemite composite with primary particle sizes of 6–8 nm. Gold was highly dispersed on the surface of the support. The catalysts showed good activity in the oxidation of airborne carbon monoxide and formaldehyde. The optimal pH for their synthesis was ∼7. The catalytic performance could be enhanced by extending the adsorption time of gold species on the support within 21 h. The optimized catalyst was capable of achieving complete oxidation of 1% carbon monoxide at −20 °C and 33% conversion of 450 ppm formaldehyde at ambient temperature. The catalyst may be applicable to indoor air purification.
Keywords: Iron oxide nanoparticle; Gold catalyst; Catalytic oxidation; Carbon monoxide; Formaldehyde;

Washable and antibacterial superhydrophbic fabric by Junfei Ou; Zhile Wang; Fajun Wang; Mingshan Xue; Wen Li; Alidad Amirfazli (81-85).
Inspired by the high adherence of mussel and the excellent water repellency of lotus leaf, superhydrophobic fabric is fabricated via the sequential deposition of polydopamine, Ag2O, and 1H,1H,2H,2H-perfluorodecanethiol, which shows excellent washability and high anti-bacterial activity due to the strong interfacial interaction and the surface silver species as well as the non-wettability, respectively.
Keywords: Superhydrophobic fabric; Stability; Anti-bacterial; Polydopamine;

SEM images of APSG, PAMAM-1.0SSASG, PAMAM-2.0SSASG, PAMAM-3.0SSASG and PAMAM-4.0SSASG.Silica-gel adsorbents PAMAM-n.0SSASG (n  = 1–4) with dendrimer-like polyamidoamine (PAMAM) and 5-sulfosalicylic acid as functional groups were prepared and characterized with FTIR, SEM, TG, elemental analysis and porous structure analysis. Micro-column enrichment and measurement of Pb2+ with graphite furnace atomic absorption spectroscopy (GFAAS) was studied with PAMAM-n.0SSASG (n  = 1–4) as adsorbent. It was emphasized to investigate the relationship between dynamic adsorption/desorption rates, adsorption capacities, and grafting percentage of PAMAM onto silica-gel surface. Experiments showed that the generation increase of grafted PAMAM changed the pore diameter distribution of adsorbent and obviously improved adsorption/desorption property for Pb2+. Adsorption capacity of PAMAM-n.0SSASG (n  = 1–4) was 14.04, 17.43, 20.07 and 25.05 mg g−1 for Pb2+ respectively. An enrichment factor of 200 was obtained with PAMAM-4.0SSASG as adsorbent and with 2000 mL Pb2+ solution (1.0 ng mL−1). The priority of adsorption property of PAMAM-4.0SSASG was explained by steric hindrance effect of PAMAM on adsorption/desorption, and selective adsorption of 5-sulfosalicylic acid with Pb2+. With PAMAM-4.0SSASG as adsorbent, GFAAS method for analysis of Pb2+ combined with micro-column enrichment was proposed and applied to the determination of Pb2+ of standard reference sample and sea water sample.
Keywords: Silica gel; 5-Sulfosalicylic acid; Dendrimer-like polyamidoamine; Pb2+; Preconcentration;

Fractal properties of worn surface of Fe-based alloy coatings during rolling contact process by Shu-ying Chen; Hai-dou Wang; Guo-zheng Ma; Jia-jie Kang; Bin-shi Xu (96-102).
The rolling contact fatigue (RCF) failure procedure of Fe-based alloy coating, fabricated by high efficient plasma spray (PS) technology, was investigated by a double-roller test machine with oil lubrication under pure rolling contact condition. The fractal dimension (FD) was utilized to quantitatively characterize the profile of the worn surface at different experiment stage and the failure mechanism of the coating was discussed. The results indicated that the nonlinear morphologies of the worn surface of Fe–Cr alloy coating possessed excellent fractal properties. The failure procedure could be divided into four stages according to the value and change rule of FD, i.e. (1) running-in stage, (2) stable abrade stage, (3) accelerated damage stage, (4) unstable removal stage.
Keywords: Fractal; Rolling contact fatigue; Surface morphology; Fe-based alloy coating;

Nano silica particle was modified to produce hydrophobic surface with contact angle of 107° using the water soluble SDS as a modifier through a new route. The grafted density reached 1.82–2 nm. Brønsted acid sites supply proton to react with SDS via generating carbocation, forming a Si–O–C structure.Hydrophobic silica particles were prepared using the surfactant sodium dodecyl sulfate (SDS) as a modifier by a new route comprising three processes, namely, aqueous mixing, spray drying and thermal treatment. Since SDS dissolves in water, this route is free of an organic solvent and gave a perfect dispersion of SDS, that is, there was excellent contact between SDS and silica particles in the modification reaction. The hydrophobicity of the modified surface was verified by the contact angle of the nano-sized silica particles, which was 107°. The SDS grafting density reached 1.82 nm−2, which is near the highest value in the literature. The optimal parameters of the SDS/SiO2 ratio in the aqueous phase, process temperature and time of thermal treatment were determined to be 20%, 200 °C and 30 min, respectively. The grafting mechanism was studied by comparing the modification with that on same sized TiO2 particles, which indicated that the protons of the Brønsted acid sites on the surface of SiO2 reacted with SDS to give a carbocation which then formed a Si–O–C structure. This work showed that the hydrophilic surface of silica can be modified to be a hydrophobic surface by using a water soluble modifier SDS in a new modification route.
Keywords: Nano-silica particle; Surface modification; Sodium dodecyl sulfate; Hydrophobic; Grafting;

A facile, self-reduction and size controlled synthesis method has been explored to fabricate silver nanoparticles (Ag NPs) on carbon nanosphere (CNs) under mild conditions. Without using predeposition of seed metals and reducing agent, a uniform and complete layer of Ag NPs was formed through grafting a molecular layer on CNs surfaces under UV irradiation. The size and thickness of Ag NPs were effectively tuned by adjusting the UV irradiation time. This direct formation of Ag NPs was attributed to self seed in aqueous Ag(NH3)2 + complex solution through a triazine-based silane coupling agent molecular layer, even at 25 °C. Scanning electron microscopy (SEM), Transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the Ag NPs’ properties. A substantial conductivity improvement of prepared Ag NPs on carbon nanosphere was demonstrated. The presented method is simple and environmentally friendly and thus should be of significant value for the industrial fabrication of Ag NPs on carbon nanosphere in conduct electricity paint and coating applications.
Keywords: Self-reduction; Size control; Silver nanoparticles; Carbon nanosphere; Triazine molecular layer; Conductivity;

In situ synthesis of mesoporous polyvinyl alcohol/hydroxyapatite composites for better biomedical coating adhesion by Riaz Hussain; Sobia Tabassum; Mazhar Amjad Gilani; Ejaz Ahmed; Ahsan Sharif; Faisal Manzoor; Asma Tufail Shah; Anila Asif; Faiza Sharif; Farasat Iqbal; Saadat Anwar Siddiqi (117-123).
Hydroxyapatite (HA) shows diverse biomedical applications as bone filler and coating material for metal implants to enhance osteoconduction. Four different PVAHA composites were synthesized in situ by an economical co-precipitation wet methodology. The FTIR spectra of PVAHA composites showed characteristic signals of HA and PVA. The BET surface area of PVAHA composites were in range of 41.3–63.7 m2/g. The composites showed type IV nitrogen adsorption/desorption isotherm, a characteristic for mesoporous material. The pore diameter range (6.3–8.1 nm) of PVAHA composites also confirmed their mesoporous nature. The Barrett–Joyner–Halenda (BJH) pore size distribution curves indicated a narrow pore size distribution. To obtain a homogeneous crack free coating with EPD on stainless steel (SS) plates, different parameters such as PVA percentages in PVAHA composites, solvent, deposition time and voltage were optimized. The PVAHA composites were stable after EPD as confirmed by FTIR spectra recorded before and after EPD. The SEM images of the coating showed a homogeneous morphology. The thickness of the coating was controlled by varying voltage and time. The best results were obtained with c-PVAHA composite at 30 volts for 5–10 min and current density was around 4.5 to 5 mA. The adhesion strength of c-PVAHA coating was measured by using ASTM standard F1044-99. The average value was approximately 9.328 ± 1.58 MPa.
Keywords: Polyvinyl alcohol; Hydroxyapatite; Electrophoretic deposition; Biomedical coating;

Functionalization of cellulose nanowhiskers (CNW) was performed by means of chemical synthesis involving polymerization of polyaniline in emeraldine salt form (PAni SE) in the presence of CNW. Thermal, chemical and morphological samples properties were evaluated. Polymeric coatings were obtained with epoxy, aminopropyltriethoxysilane (APS), CNW and CNW/PAni SE applied on carbon steel with a conversion coating of zirconia (Zr) and the mechanical properties were evaluated. With regard to CNW functionalization the sample was encapsulated with PAni SE as observed by FTIR and morphologic analysis, with decreased thermal stability. Regarding the mechanical properties of CNW and CNW/PAni SE polymeric coatings, improvements in flexibility and hardness properties using the APS and Zr layer were observed. The adherence of polymer coatings improved by the incorporation of CNW and CNW/PAni SE. Through morphological analysis it was observed that CNW shows good dispersion in the polymer matrix without agglomerates formation.
Keywords: Nanocomposites; Cellulose nanowhiskers; Polyaniline; Epoxy; Polymer coatings;

Investigation on femto-second laser irradiation assisted shock peening of medium carbon (0.4% C) steel by Jyotsna Dutta Majumdar; Evgeny L. Gurevich; Renu Kumari; Andreas Ostendorf (133-140).
In the present study, the effect of femtosecond laser irradiation on the peening behavior of 0.4% C steel has been evaluated. Laser irradiation has been conducted with a 100 μJ and 300 fs laser with multiple pulses under varied energy. Followed by laser irradiation, a detailed characterization of the processed zone was undertaken by scanning electron microscopy, and X-ray diffraction technique. Finally, the residual stress distribution, microhardness and wear resistance properties of the processed zone were also evaluated. Laser processing leads to shock peening associated with plasma formation and its expansion, formation of martensite and ferrito–pearlitic phase in the microstructure. Due to laser processing, there is introduction of residual stress on the surface which varies from high tensile (140 MPa) to compressive (−335 MPa) as compared to 152 MPa of the substrate. There is a significant increase in microhardness to 350–500 VHN as compared to 250 VHN of substrate. The fretting wear behavior against hardened steel ball shows a significant reduction in wear depth due to laser processing. Finally, a conclusion of the mechanism of wear has been established.
Keywords: Femtosecond laser; Microstructure; Residual stress; Wear; Steel;

Electrochemical preparation of MnO2 nanobelts through pulse base-electrogeneration and evaluation of their electrochemical performance by Mustafa Aghazadeh; Mohammad Ghannadi Maragheh; Mohammad Reza Ganjali; Parviz Norouzi; Farnoush Faridbod (141-147).
Cathodic electrodeposition of MnO2 from a nitrate solution, via pulsed base (OH) electrogeneration was performed for the first time. The deposition experiments were performed in a pulse current mode in typical on-times and off-times (i.e. t on  = 1 s and t off  = 1 s) with a peak current density of 2 mA cm−2 (I a  = 2 mA cm−2). The structural characterizations conducted by XRD and FTIR techniques revealed that the prepared MnO2 is composed of both α and γ phases. Morphological observation by SEM and TEM showed that the prepared MnO2 is made up of nanobelts with uniform shapes (an average diameter and length of 50 nm and 1 μm, respectively). Further electrochemical measurements by cyclic voltammetry and charge–discharge techniques revealed that the prepared MnO2 nanostructures have excellent capacitive behaviors, like a specific capacitance of 235.5 F g−1 and capacity retention of 91.3% after 1000 cycling at the scan rate of 25 mV s−1.
Keywords: MnO2; Pulse electrodeposition; Nanobelts; Supercapacitors;

Facile solution deposition of Cu2ZnSnS4 (CZTS) nano-worm films on FTO substrates and its photoelectrochemical property by Yaohan Huang; Guangli Li; Qingfei Fan; Meili Zhang; Qi Lan; Ximei Fan; Zuowan Zhou; Chaoliang Zhang (148-155).
In this work, Cu2ZnSnS4 (CZTS) nanoworm films have been directly deposited on fluorine-doped tin oxide (FTO) conductive glass substrates by a solvothermal method using polyethylene glycol 400 (PEG-400) as the solvent and structure-directing agent. The as-obtained CZTS thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectrum (XPS), UV–vis spectra and photoelectrochemical measurement. The synthetic conditions, such as reaction temperature, reaction time, solvents, were investigated to know the formation of CZTS thin films. The results showed that PEG-400 plays a key role in the formation of the nanoworms by affecting the crystal growth process. The p-type CZTS nanoworm film with the band gap of 1.62 eV was synthesized at 180 °C for 22 h and the photovoltaic performance was studied by forming a photoelectrochemical cell.
Keywords: Cu2ZnSnS4 films; Solvothermal method; PEG; Photovoltaic performance;

Tetragonal Gd-doped BiVO4 having enhanced photocatalytic activity have been synthesized by a facile microwave hydrothermal method. The structural analysis indicates that Gd doping can induce the phase transition from monoclinic to tetragonal BiVO4. The reaction results in precursor solutions imply that tetragonal GdVO4 seeds as crystal nucleus are the original and determined incentives to force the formation of tetragonal Gd-BiVO4. The influences of the surface defect, band structure, and BET surface area on the improved photocatalytic activities of tetragonal Gd-doped BiVO4 are investigated systematically. The results demonstrate that the more surface oxygen deficiencies as active sites and the excellent mobility and separation of photogenerated electrons and holes are beneficial to the enhancement of the photocatalytic performance of tetragonal Gd-BiVO4. The RhB photodegradation experiments indicate that the contribution of high photocatalytic activities under simulated sun-light is mainly from UV-light region due to the tetragonal structure feature. The best photocatalytic performance is obtained for tetragonal 10 at% Gd-BiVO4, of which the RhB degradation rate can reach to 96% after 120 min simulated sun-light irradiation. The stable tetragonal Gd-BiVO4 with efficient mineralization will be a promising photocatalytic material applied in water purification.
Keywords: Gd-doped BiVO4; Phase transition; Formation mechanism; Photocatalytic activity; Sun-light;

Capability of defective graphene-supported Pd13 and Ag13 particles for mercury adsorption by Jittima Meeprasert; Anchalee Junkaew; Chompoonut Rungnim; Manaschai Kunaseth; Nawee Kungwan; Vinich Promarak; Supawadee Namuangruk (166-175).
Defective graphene (DG) supported Ag13 and Pd13 nanoparticles acts as sorbents for elementary mercury (Hg0) adsorption. Hg is inert to DG surface, but it moderately adsorbs on deposited Ag13-DG and strongly adsorbs on deposited Pd13-DG.Reactivity of single-vacancy defective graphene (DG) and DG-supported Pd n and Ag n (n  = 1, 13) for mercury (Hg0) adsorption has been studied using density functional theory calculation. The results show that Pd n binds defective site of DG much stronger than the Ag n , while metal nanocluster binds DG stronger than single metal atom. Metal clustering affects the adsorption ability of Pd composite while that of Ag is comparatively less. The binding strength of −8.49 eV was found for Pd13 binding on DG surface, indicating its high stability. Analyses of structure, energy, partial density of states, and d-band center (ɛd) revealed that the adsorbed metal atom or cluster enhances the reactivity of DG toward Hg adsorption. In addition, the Hg adsorption ability of M n -DG composite is found to be related to the ɛd of the deposited M n , in which the closer ɛd of M n to the Fermi level correspond to the higher adsorption strength of Hg on M n -DG composite. The order of Hg adsorption strength on M n -DG composite are as follows: Pd13 (−1.68 eV) >> Ag13 (−0.67 eV) ∼ Ag1 (−0.69 eV) > Pd1 (−0.62 eV). Pd13-DG composite is therefore more efficient sorbent for Hg0 removal in terms of high stability and high adsorption reactivity compared to the Ag13. Further design of highly efficient carbon based sorbents should be focused on tailoring the ɛd of deposited metals.
Keywords: Mercury; DFT; Palladium; Silver; Nanoparticle; Graphene;

Polyaniline/carbon nanotube/CdS quantum dot composites with enhanced optical and electrical properties by Mrinmoy Goswami; Ranajit Ghosh; Takahiro Maruyama; Ajit Kumar Meikap (176-180).
A new kind of polyaniline/carbon nanotube/CdS quantum dot composites have been developed via in-situ polymerization of aniline monomer in the presence of dispersed CdS quantum dots (size: 2.7–4.8 nm) and multi-walled carbon nanotubes (CNT), which exhibits enhanced optical and electrical properties. The existences of 1st order, 2nd order, and 3rd order longitudinal optical phonon modes, strongly indicate the high quality of synthesized CdS quantum dots. The occurrence of red shift of free exciton energy in photoluminescence is due to size dependent quantum confinement effect of CdS. The conductivity of the composites (for example PANI/CNT/CdS (2 wt.% CdS)) is increased by about 7 of magnitude compared to that of pure PANI indicating a charge transfer between CNT and polymer via CdS quantum dots. This advanced material has a great potential for high-performance of electro-optical applications.
Keywords: Polyaniline; Carbon nanotube; Cadmium sulfide; Quantum dots; Composites;

Modulating electronic, magnetic and chemical properties of MoS2 monolayer sheets by substitutional doping with transition metals by Dongwei Ma; Weiwei Ju; Tingxian Li; Xiwei Zhang; Chaozheng He; Benyuan Ma; Yanan Tang; Zhansheng Lu; Zongxian Yang (181-189).
TM doping can significantly modify the electronic and magnetic properties of MoS2 monolayer sheets and their chemical activity toward the O2 molecule, which may provide a route to extend their applications in the fields of nanospintronics, gas sensing and catalysis.Based on first-principles calculations, the effects of substitutional doping with transition-metal (TM) atoms (Co, Ni, Ru, Rh, Pd, Ir, Pt and Au) were investigated on the electronic structure, magnetic property and chemical activity of the molybdenum disulfide (MoS2) monolayer sheet. It is found that all the considered TM atoms are strongly bonded to the sulfur defects. The magnetic properties of MoS2 monolayer sheets can be modulated by embedding TM atoms. The introduced spin magnetic moments are 1.00, 1.00, 1.00, 0.99, and 2.00μ B, respectively, for Ir, Rh, Co, Au and Ru doping. The electronic properties of MoS2 monolayer sheets are also significantly changed due to the induced impurity states in the band gap. The chemical activity of the TM-doped MoS2 monolayer sheet (TM-MoS2) is significantly enhanced compared with the undoped sheet. Most TM-MoS2 can strongly adsorb and thus effectively activate the adsorbed O2. It is proposed that the partially occupied d orbitals of the doped TM atoms localized in the vicinity of the Fermi level play a crucial role in adsorbing and activating the adsorbed O2. The adsorption of O2 can in turn modify the electronic structures and magnetic properties of TM-MoS2.
Keywords: First-principles calculation; Transition metal; Substitutional doping; O2 adsorption; MoS2;

Study of nanoindentation mechanical response of nanocrystalline structures using molecular dynamics simulations by Jia Li; Jiawen Guo; Hao Luo; Qihong Fang; Hong Wu; Liangchi Zhang; Youwen Liu (190-200).
Molecular dynamics (MD) simulations are performed to study the nanoindentation onto three different crystal structures including the single crystalline, polycrystalline, and nanotwinned polycrystalline copper. To reveal the effects of crystal structure and twin-lamellae-thickness on the response of nanoindentation, we evaluate the evolution of crystalline structure, dislocation, strain, indentation force, temperature, hardness, and elastic recovery coefficient in the deformation zone. The results of MD simulations show that the hardness, elastic recovery ratio and temperature of those three nanocrystalline copper strongly depend on crystal structure and twin-lamellae-thickness. It is also revealed that as nanoindenter goes deeper, the extent of plastic zone becomes substantially larger. Initial dislocation always nucleates at the beneath of indenter, and the discrete drops of indentation force observed at certain indentation depths, indicates dislocation bursts during the indentation process. In particular, the twining and detwining are dominant over the dislocation nucleation in driving plasticity in nanotwinned polycrystalline during nanoindentation, which are in good agreement with the previous work. Furthermore, we find that plastic deformation has a strong dependence on crystal structure. The plastic deformation of the single crystalline copper relies on the generation, propagation and reaction of dislocations, that of the polycrystalline copper depends on the dislocation–grain boundary (GB) interactions, and that of the nanotwinned polycrystalline copper relies upon the dislocation–twin boundary (TB) interactions as well as twining/detwining. This work not only provides insights into the effects of crystal structure and two-lamellae-thickness on the mechanical properties of copper under nanoindentation, but also shed lights onto the guideline of understanding other FCC nanocrystalline materials.
Keywords: Molecular dynamics simulation; Nanoindentation; Mechanical property; Polycrystalline; Twin;

Vmh2 hydrophobin layer entraps glucose: A quantitative characterization by label-free optical and gravimetric methods by B. Della Ventura; I. Rea; A. Caliò; P. Giardina; A.M. Gravagnuolo; R. Funari; C. Altucci; R. Velotta; L. De Stefano (201-207).
Hydrophobins (HFBs) are peculiar proteins which self-assemble at hydrophilic-hydrophobic interfaces into amphipathic membranes, and some of them (class I HFB) are able to form much more stable amyloid-like layers. This feature makes them suitable for many purposes, particularly when stable surface functionalization is required, also in view of their versatility in binding different kinds of molecules. For instance, it has been shown that Vmh2 from Pleurotus ostreatus (a class I HFB) is able to bind molecules like glucose, thus offering the perspective of using Vmh2 as a surface functionalization tool in bio-hybrid devices. In this paper a quantitative analysis of glucose interaction with the Vmh2 layer is reported; in particular, it is shown that Vmh2 layer swells by almost doubling its thickness as a result of glucose diffusion and each Vmh2 monomer is able to bind approximately 30 glucose molecules. These results have been achieved by self-assembling multi-layers of Vmh2 on a gold substrate and, subsequently, measuring both the mass of the bound glucose and the thickness of the resulting layer through two different and complementary techniques: quartz crystal-microbalance and ellipsometry. The data provided by the two techniques are in a satisfactory agreement and offer a plausible description of the mechanisms underlying the interaction of glucose with Vmh2 layer. This facile and versatile coating is of interest for biomedical applications of gold surfaces and particles.
Keywords: Hydrophobin; Self-assembly; Glucose binding proteins; Quartz crystal microbalance;

Surface modification of cotton fabrics by gas plasmas for color strength and adhesion by inkjet ink printing by Porntapin Pransilp; Meshaya Pruettiphap; Worawan Bhanthumnavin; Boonchoat Paosawatyanyong; Suda Kiatkamjornwong (208-220).
Surface properties of cotton fabric were modified by three types of gas plasma pretreatment, namely, oxygen (O2), nitrogen (N2) and sulfur hexafluoride (SF6), to improve ink absorption of water-based pigmented inkjet inks and color reproduction of the treated surfaces. Effects of gas plasma exposure parameters of power, exposure time and gas pressure on surface physical and chemical properties of the treated fabrics were investigated. XPS (X-ray photoelectron spectroscopy) was used to identify changes in functional groups on the fabric surface while AFM (atomic force microscopy) and SEM (scanning electron microscopy) were used to reveal surface topography of the fabric. Color spectroscopic technique was used to investigate changes in color strength caused by different absorptions of the printed fabrics. The O2 plasma treatments produced new functional groups, ―O―C―O/C=O and O―C=O while N2 plasma treatments produced additionally new functional groups, C―N and O=C―NH, onto the fabric surface which increased hydrophilic properties and surface energy of the fabric. For cotton fabric treated with SF6 plasma, the fluorine functionalization was additionally found on the surface. Color strength values (K/S) increased when compared with those of the untreated fabrics. SF6 plasma-treated fabrics were hydrophobic and caused less ink absorption. Fabric surface roughness caused by plasma etching increased fabric surface areas, captured more ink, and enhanced a larger ink color gamut and ink adhesion. Cotton fabrics exhibited higher ink adhesion and wider color gamut after the O2 plasma treatment comparing with those after N2 plasma treatment.
Keywords: Oxygen plasma; Nitrogen plasma; Sulfur hexafluoride plasma; Water-based inkjet ink; Ink adhesion; Color gamut; Color strength;

The ability of alumina (Al2O3) nanoparticles in adsorption of heavy metals was employed in improving the copper removal efficiency of PES membranes. Mixed matrix membranes were prepared using PES and different amounts of alumina nanoparticles by phase inversion method. The fabricated membranes were characterized in terms of morphology and performance using scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses, water contact angle and porosity measurements, determination of pure water flux, copper ion removal, and reusability test. Mixed matrix membranes revealed higher water permeation compared with the pristine PES membrane just by adding small amounts of nanoparticles ≤ 1.0 wt. % as a result of increasing the membrane porosity and hydrophilicity after addition of alumina nanoparticles into the membrane matrix. Moreover, copper ion removal efficiency of alumina mixed membranes was improved. Membrane performance tests as well as adsorptive nature of alumina nanoparticles proposed that adsorption was the most possible separation mechanism by mixed matrix membranes. Reusability test of membrane confirmed the durability of removal efficiency even after four cycles of filtration.
Keywords: Nanocomposite membrane; γ-Alumina (Al2O3) nanoparticles; Water treatment; Copper removal;

Optical, electrical and electrochemical evaluation of sputtered platinum counter electrodes for dye sensitized solar cells by R.S. Moraes; E. Saito; D.M.G. Leite; M. Massi; A.S. da Silva Sobrinho (229-234).
Charge transfer resistance results show that even platinum thin films (short deposition times) present acceptable values to counter-electrodes (red dashed line corresponds to commercial platinum charge transfer resistance), besides reducing platinum consumption.Since Grätzel and O’Regan started in 1991, dye-sensitized solar cells (DSSC) have been extensively studied around the world. In addition to increasing efficiency, their characteristics such as low cost materials and inexpensive manufacturing processes are attractive for organic solar cells. Several parts of DSSC devices are being researched such as semiconductor engineering, low cost counter electrodes, electrolytes, and dyes. In this work, platinum (Pt) thin films were deposited by sputtering technique to produce counter electrodes for DSSC. The films were characterized by profilometry, elipsometry, four-point probe sheet resistance, spectrophotometry, and electrochemical impedance spectroscopy. The electrode response was also compared to that built from a commercial platinum solution. The results allow us to determine the minimum Pt film thickness necessary to achieve a relevant reduction of the sheet resistance and charge transfer resistance, which preserve a significant electrode transparency. The 22 nm and 24.8 nm thick films combined low charge transfer resistance and good transparency. The 122 nm Pt film presented the lowest charge transfer resistance.
Keywords: Energy conversion; Solar energy; DSSC counter electrode; Platinum catalytic thin film;

Display OmittedThe controlled growth of organic layers on surfaces is still waiting for an in-situ reliable technique that would allow their quality to be monitored and improved. Here we show that the growth of a perylene monolayer deposited on Ag(1 1 0) at room temperature can be tracked with low energy atoms in a regime where the energy perpendicular to the layer is less than 0.1 eV and below the organic film damage threshold. The image processing required for this atom triangulation technique is described in detail.
Keywords: Organic layer on surface; On-line monitoring of growth and organisation;

DFT calculations were used to investigate the properties of the atomic copper embedded in the surface of graphene (Cu/dG) and the catalytic reaction pathway for the CO2 hydrogenation to formic acid (FA). The Cu/dG was active for the adsorption of the hydrogen molecule (H2), and provided a reaction site for the heterolytic cleavage of H2, leading to the formation of Cu-H deposited on a singly hydrogenated vacancy graphene (Cu-H/H-dG). The protonation of CO2 takes place facilely over the generated metal-hydride species (Cu-H). Under the dilution of H2, the catalytic process would be hampered by the formation of copper-formate deposited on the H-dG due mainly to the very high energy demand for the transformation of the copper-formate to FA through the protonation from the H-dG. It was further found that the presence of H2 in the system plays a significant role in producing the FA on the Cu/dG catalyst. The copper-formate species can be converted into formic acid via the heterolytic cleavage of the second hydrogen molecule, yielding the FA and Cu-H species.
Keywords: CO2 hydrogenation; Graphene; Copper; Catalysis; DFT;

In present work, MoS2/a-C composite films were synthesized by r.f. sputtering of MoS2 and graphite targets, and the influence of C dopant on the structure, morphology, mechanical and the tribological properties of composite films in vacuum, ambient air and mutually alternated atmospheres were discussed in detail. Increasing the sputtering power applied on graphite target from 0 to 400 W, the film hardness increases significantly by one order of magnitude, and the optimized lubricant performance were obtained at 300 W. After sliding tests the morphology and structure of tribofilm and debris were investigated by using optical spectroscopy and Raman spectroscopy. The results reveal that the adaptive release of non-lubricant phase from tribofilm is a critical issue for determining the tribological performance of MoS2/a-C composite films in different sliding atmospheres. The more exhaustive release of non-lubricant phase, the lower friction of rubbed counterparts can be obtained. More interestingly, the lubricant mechanism of tribofilms formed in alternated atmospheres is partially affected by their initial composition established at the beginning of sliding.
Keywords: MoS2/a-C composite films; Structure; Properties; Tribofilm; Lubricant mechanism;

Enhanced catalytic performance of Pt/TNTs composite electrode by reductive doping of TNTs by Huazhen Cao; Kailu Huang; Liankui Wu; Guangya Hou; Yiping Tang; Guoqu Zheng (257-263).
This paper introduced a novel method to fabricate Pt/TiO2 nanotube arrays (TNTs) composite electrode with enhanced catalytic performance toward methanol oxidation. The TNTs supports were pretreated by reductive doping, and Pt nanoparticles were subsequently implanted in the TNTs by electrochemical deposition. Effects of the reductive doping on the microstructure and electrocatalytic activity of Pt/TNTs composite electrode were studied. The results show that Ti3+ is produced by the reductive doping of TNTs, which makes the resistance of TNTs efficiently decreased. The increased conductivity of TNTs facilitated the subsequent electrodeposition of Pt nanoparticles, leading to the smaller size of Pt particles and higher deposition rate. The Pt/reductive doped TNTs electrode prepared from 4 h electrodeposition exhibit excellent electrocatalytic activity, for which the peak current density is as high as 76.6 mA cm−2 and the mass transfer coefficient is obviously increased.
Keywords: TiO2 nanotube arrays; Reductive doping; PT nanoparticles; Catalytic electrode; Methanol oxidation;

Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel–tungsten composite coatings by Swarnima Singh; M. Sribalaji; Nitin P. Wasekar; Srikant Joshi; G. Sundararajan; Raghuvir Singh; Anup Kumar Keshri (264-272).
Silicon carbide (SiC) reinforced nickel–tungsten (Ni–W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni–W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni–W–5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni–W–5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, E corr) compared to Ni–W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni–W–5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.
Keywords: Pulse electrodeposition; Nickel–tungsten alloy; Silicon carbide; Surface morphology; Phase evolution; Corrosion;

Effect of annealing conditions on structural and luminescencent properties of Eu3+-doped Gd2Ti2O7 thin films by Željka Antić; K. Prashanthi; Sanja Ćulubrk; Katarina Vuković; Miroslav D. Dramićanin; Thomas Thundat (273-279).
Here we report on preparation of Eu3+-doped Gd2Ti2O7 pyrochlore luminescent thin films by pulsed laser deposition technique and their structural, morphological and optical characterization. The influence of annealing temperature and background gas (air vs. argon) on film photoluminescence is examined for the optimization of post-deposition annealing conditions. As-deposited amorphous films become pure pyrochlore crystalline after calcination at temperatures higher than 1000 °C. Atomic force microscopy showed increase in the grain size from ∼20 nm in the as-deposited to ∼60 nm in the crystalline sample annealed at 1100 °C. Scanning electron microscopy showed dense films with the uniform thickness of about 700 nm. Luminescence spectra of crystalline films were complex and composed of better resolved emission lines than in the amorphous sample. Emission spectra showed that symmetry of Eu3+ sites become disturbed in annealed films due to the extrinsic thermal stress. Films treated in argon displayed similar emission and excitation spectral features like air-treated ones, but with better resolved emission lines. Calculated quantum efficiency of emission showed that optimization of annealing conditions led to an enhancement of films luminescence. The highest quantum efficiency of emission and the longest lifetime is found for the sample annealed at 1100 °C in presence of argon.
Keywords: Thin films; Pulsed laser deposition; Luminescence; Pyrochlores; Rare earths;

The surface roughness (R a) dropped from 38.23 nm to 16.13 nm after plasma treatment. No cracks appeared around crater c, which indicated preferable vertical adhesion was achieved through the transition layer.An amorphous carbon (a-C) film is deposited on the plasma-treated UHMWPE substrate using a closed field unbalanced magnetron sputtering to improve its tribological properties. During the plasma treatment period, a transition layer is prepared by high energy ion bombardment at a bias voltage of −500 V to enhance the adhesion between the a-C film and the substrate. The mechanical and tribological properties of the a-C film were evaluated by nano-indentation and ball-on-disk tribometer. After deposition of a-C film with a thickness 900 nm, the nano-hardness of UHMWPE significantly increases from 47 MPa to 720 MPa and the wear rate decreases from 9.82 × 10−15  m3  N−1  m−1 to 4.78 × 10−15  m3  N−1  m−1 in bovine calf serum solution. The formation of the transition layer is believed to be the reason why the vertical adhesion between the a-C film and the UHMWPE substrate is enhanced.
Keywords: a-C film; Transition layer; UHMWPE substrate; Tribological property;

Fullerene-like hydrogenated carbon (FL-C:H) films as carbon materials were prepared by direct current plasma enhanced chemical vapor deposition (dc-PECVD) technique. The content of FL nanostructure was confirmed by high-resolution transmission electron microscopy (HRTEM), visible Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The effect of fullerene-like nanostructure on the friction behavior of the films was studied using a reciprocating ball-on-flat tribometer in humid environment. It is concluded that the curved FL nanostructure provide the film excellent mechanical properties and friction performance. Interestingly, combining with the results of Raman analyses of the wear debris, we find that new FL nanostructure form during the friction process. These new FL nanostructure may originate from the rapid annealing and stress relaxation of unstable carbon clusters.
Keywords: Fullerene-like; Carbon materials; Mechanical properties; Friction performance; Rapid annealing; Stress relaxation;

In order to improve the interfacial adhesion between hydrophilic ramie fibers and hydrophobic polypropylene (PP) matrices, ramie fibers are modified by atmospheric pressure dielectric barrier discharge (DBD) plasma with our continuous ethanol flow technique in helium environment. A central composite design of experiments with different plasma processing parameter combinations (treatment current, treatment time and ethanol flow rate) is applied to find the most influential parameter and to obtain the best modification effect. Field emission scanning electron microscope (SEM) shows the roughened surfaces of ramie fibers from the treated groups due to plasma etching effect. Dynamic contact angle analysis (DCAA) demonstrates that the wettability of the treated fibers drastically decreases. Microbond pullout test shows that the interfacial shear strength (IFSS) between treated ramie fibers and PP matrices increases significantly. Residual gas analysis (RGA) confirms the creation of ethyl groups during plasma treatment. This study shows that our continuous ethanol flow technique is effective in the plasma modification process, during which the ethanol flow rate is the most influential parameter but all parameters have simultaneous influence on plasma modification effect of ramie fibers.
Keywords: Dielectric barrier discharge; Response surface; Ramie fibers; Ethanol vapor; Interfacial adhesion;

Influence of heat generated by a Raman excitation laser on the structural analysis of thin amorphous silicon film by P. Novák; J. Očenášek; L. Prušáková; V. Vavruňková; J. Savková; J. Rezek (302-307).
In the present work we investigate thin amorphous silicon film fabricated by plasma enhanced chemical vapor deposition. In particular, we analyze changes in the recorded Raman spectra caused by excitation laser irradiation. Solid phase crystallization, hydrogen diffusive outflow and Raman spectra peak shifts have been observed experimentally and analyzed numerically. The role of film thickness on all these features is pointed out. The study involves laser powers between 0.1 mW and 10 mW focused to a spot diameter of ∼1 μm and film thicknesses between 50 and ∼2000 nm. Additionally, the laser induced temperature fields were analyzed by means of numerical simulation and the Raman spectral shift trough Balkanski model. Results are correlated to structural analysis by Raman spectroscopy, optical microscopy, scanning electron microscopy and atomic force microscopy. It was found that the hydrogen content and solid phase fraction identified by Raman spectroscopy are highly sensitive to the applied excitation laser power.
Keywords: Hydrogenated amorphous silicon; Raman spectroscopy; Structure; PECVD; Thermal field;

Factors affecting the spontaneous adsorption of Bi(III) onto Pt and PtRu nanoparticles by Ehab N. El Sawy; M. Akhtar Khan; Peter G. Pickup (308-314).
The influence of Bi(III) concentration and pH on the spontaneous adsorption of Bi species onto Pt nanoparticles has been systematically investigated in order to identify the adsorbing species, determine whether the nature of the adsorbing species changes, and investigate whether the activities of the resulting Bi decorated particles for formic acid oxidation can be influenced. The adsorption of Bi follows a Temkin-type isotherm, with a pH dependence indicating that the adsorbing species is [Bi6O4(OH)4]6+. Activities of Bi decorated Pt nanoparticles for formic acid oxidation are strongly influenced by the Bi coverage, with a maximum enhancement of a factor of ca. 60 at a coverage of 70%, but not by the Bi(III) concentration or pH used to adsorb the Bi species, other than through their influence on Bi coverage. These results support the conclusion that the adsorbing species is [Bi6O4(OH)4]6+ under all conditions investigated. Adsorbed Bi also activates PtRu nanoparticles for formic acid oxidation, although the effect is not as strong as for Pt. The maximum enhancement observed was only a factor of ca. 7. This has been attributed to attenuation of the effects of Bi adatoms that are adsorbed at Ru sites.
Keywords: Adsorption; Bismuth; Platinum; Nanoparticles; Electrocatalysis; Formic acid;

Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.
Keywords: Boriding; Ternary boride; Thin-film; Cemented carbide; Tungsten carbide;

NiO nanosheet/TiO2 nanorod-constructed pn heterostructures for improved photocatalytic activity by Bin Sun; Guowei Zhou; Tingting Gao; Huaijin Zhang; Haohai Yu (322-331).
NiO nanosheet/acid-corroded TiO2 nanorod (A-TiO2 nanorod) heterostructures with high photocatalytic activity were successfully fabricated via a facile and low-cost hydrothermal route. The as-prepared heterostructures featured NiO nanosheets with uniformly assembled A-TiO2 nanorods and a rough surface. The morphology, structure, and photoelectric properties of the pristine NiO nanosheets and TiO2-based nanomaterials were characterized in detail, and results revealed that secondary NiO nanosheets were successfully grown on TiO2 nanorod substrates to achieve a pn heterostructure between the cubic structure NiO and the TiO2 anatase phase. In comparison with P25, NiO nanosheets, TiO2 nanorods, and A-TiO2 nanorods, the proposed heterostructures exhibited markedly enhanced photocatalytic activity for the degradation of methyl orange under UV light irradiation. Specifically, the NiO nanosheet/A-TiO2 nanorod heterostructures exhibited the best photocatalytic activity, achieving 100% photocatalytic efficiency within 20 min. The observed enhancement in photocatalytic activity was attributed to the synergetic contributions of pn heterostructures and the large specific surface area of the catalyst, which may improve the separation of photogenerated electron–hole pairs and prolong the lifetime of charge carriers. The heterostructures could be easily recycled without observable decreases in photocatalytic activity because of their one-dimensional nanostructural property.
Keywords: TiO2 nanorods; Acid-corroded; NiO nanosheets; pn heterostructure; Synergetic contribution; Photocatalytic activity;

A superparamagnetic Fe3O4-graphene oxide nanocomposite for enrichment of nuciferine in the extract of Nelumbinis Folium (Lotus leaf) by Jie-Ping Fan; Bing Zheng; Yu Qin; Dan Yang; Dan-Dan Liao; Xiao-Kang Xu; Xue-Hong Zhang; Jian-Hang Zhu (332-339).
In this work, a superparamagnetic Fe3O4-graphene oxide (MGO) nanocomposite was prepared by one-step chemical co-precipitation method, and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), powder X-ray diffraction (PXRD), Raman spectroscopy and nitrogen adsorption–desorption curve. The as-prepared MGO was used to adsorb nuciferine, and the adsorption kinetic, isotherm and reusability of MGO were also investigated. The results showed that the adsorption of nuciferine on MGO reached its equilibrium very quickly (within 10 min) due to the two-dimensional carbon nanostructure of GO. In comparison with MGO, five conventional sorbents, i.e., macroporous resin D-101, silica gel, reverse phase silica gel (RP-C18) and cation exchange resin and polyamide, were also used to evaluate their adsorption capabilities. Therefore, MGO combined the advantages of both superparamagnetic particle and GO, i.e., easy separation and high absorption capacity. Finally, MGO was successfully applied to enrichment and separation of nuciferine in the extract of Nelumbinis Folium (Lotus leaf).
Keywords: Superparamagnetic; Graphene oxide; Separation; Nuciferine; Nelumbinis Folium;

We report characteristics of MoO3 graded ITO anodes prepared by a RF/DC graded sputtering for acidic poly(3,4-ethylene dioxylene thiophene):poly(styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs). Graded sputtering of the MoO3 buffer layer on top of the ITO layer produced MoO3 graded ITO anodes with a sheet resistance of 12.67 Ω/square, a resistivity of 2.54 × 10−4  Ω cm, and an optical transmittance of 86.78%, all of which were comparable to a conventional ITO anode. In addition, the MoO3 graded ITO electrode showed a greater work function of 4.92 eV than that (4.6 eV) of an ITO anode, which is beneficial for hole extraction from an organic active layer. Due to the high work function of MoO3 graded ITO electrodes, the acidic PEDOT:PSS-free OSCs fabricated on the MoO3 graded ITO electrode exhibited a power conversion efficiency 3.60% greater than that of a PEDOT:PSS-free OSC on the conventional ITO anode. The successful operation of PEDOT:PSS-free OSCs indicates simpler fabrication steps for cost-effective OSCs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable OSCs.
Keywords: MoO3 graded ITO; Acidic PEDOT:PSS; Transparent anode; Work function; Organic solar cells;

Corrosion behaviour of super-hydrophobic electrodeposited nickel–cobalt alloy film by S. Khorsand; K. Raeissi; F. Ashrafizadeh; M.A. Arenas; A. Conde (349-357).
Hierarchical super-hydrophobic Ni–Co film with enhanced corrosion resistance was fabricated on a copper substrate by one-step electrodeposition process. The contact angle and water repellence properties of the Ni–Co film were measured to determine its wettability. The Ni–Co film exhibited excellent super-hydrophobic properties with a static water contact angle of 158° and a sliding angle of ≤5°. The corrosion performance of the super-hydrophobic surface (SHS) was investigated by electrochemical potentiodynamic measurements and electrochemical impedance spectroscopy in NaCl solution (3.5 wt.%). Moreover, to study the long-term stability of the super-hydrophobic film, SHS samples were immersed into NaCl solution and their corrosion behaviour was investigated by the electrochemical impedance spectroscopy. Additionally, the changes of surface wettability were also monitored over the whole immersion time up to 11 days. Experimental results indicated that super-hydrophobic samples had much more corrosion resistance in comparison with freshly prepared samples or the bare substrate.
Keywords: Super-hydrophobic; Hierarchical structure; Corrosion resistance; Long-term stability; EIS;

The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO4. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.
Keywords: Electrochemical atomic layer deposition; Underpotential deposition; Surface-limited redox replacement; Cu film; Cu(Mn) film; Cu interconnects;

On the growth of conductive aluminum doped zinc oxide on 001 strontium titanate single crystals by L.M. Trinca; A.C. Galca; G. Aldica; R. Radu; I. Mercioniu; L. Pintilie (365-370).
Display OmittedAluminum doped zinc oxide (AZO) thin films were obtained by pulsed laser deposition on (001) SrTiO3 (STO) on a range of substrate temperatures during ablation between 300 °C and 600 °C. A hexagonal system lying on a cubic one should be difficult to be obtained in epitaxial form. The geometrical selection of the AZO growth on (001) STO is not giving a unique preferential orientation. Two orientations, c-axis (along [001]) and 110, have been observed experimentally with different ratios at different substrate temperature. Discussions are made with respect to the temperature dependence of lattice mismatch between the two cases and the cubic surface of the substrate, and to the substrate surface morphology and terminating atomic layer composition. The 110 AZO is the main phase at deposition temperature of 550 °C, while for other substrate temperatures the 001 is the preferential orientation. The conductive character of 110 AZO thin film have been inferred from both ellipsometry spectra and current–voltage measurements. Excepting the samples deposited at 300 °C, the lowest resistivity is recorded for the samples with 110 AZO as the main phase.
Keywords: Al:ZnO; Pulsed laser deposition; X-ray diffraction; Transparent conductive oxides;

Hydrothermal synthesis of hierarchical SnO2 nanostructures made of superfine nanorods for smart gas sensor by Xinliang Kuang; Tianmo Liu; Dongfeng Shi; Wenxia Wang; Mingping Yang; Shahid Hussain; Xianghe Peng; Fusheng Pan (371-377).
We report synthesis of hierarchical SnO2 nanostructures by a facile hydrothermal method. Extensive structural characterizations demonstrate that the well-defined hierarchical nanostructures are composed of numerous one-dimensional nanorods, the diameter and density of which can be precisely tailored by adjusting the dosage of NaOH. Interestingly, with more NaOH added, smaller and denser nanorods are formed, which is consistent with the assumption. We proposed that the nucleation process was facilitated in such case leading to all-direction rapider growth. Moreover, the nucleation process could be started by the decomposition of preformed ZnSn(OH)6 induced by alkali etching. Based on the comparative experiments, a possible growth mechanism for hierarchical SnO2 nanostructures has been proposed and discussed in detail. The gas sensing properties of the as-prepared hierarchical SnO2 nanostructures were all tested. It was found that the S3 sample which assembled with smallest and densest nanorods showed the excellent sensitivities toward ethanol.
Keywords: SnO2; Hydrothermal method; Nanorods; Gas sensor; Ethanol;

Effect of different parameters on machining of SiC/SiC composites via pico-second laser by Weinan Li; Ruoheng Zhang; Yongsheng Liu; Chunhui Wang; Jing Wang; Xiaojun Yang; Laifei Cheng (378-387).
Pico-second laser plays an important role in modern machining technology, especially in machining high hardness materials. In this article, pico-second laser was utilized for irradiation on SiC/SiC composites, and effects of different processing parameters including the machining modes and laser power were discussed in detail. The results indicated that the machining modes and laser power had great effect on machining of SiC/SiC composites. Different types of surface morphology and structure were observed under helical line scanning and single ring line scanning, and the analysis of their formulation was discussed in detail. It was believed that the machining modes would be responsible to the different shapes of machining results at the same parameters. The processing power shall also influence the surface morphology and quality of machining results. In micro-hole drilling process, large amount of debris and fragments were observed within the micro-holes, and XPS analysis showed that there existed Si–O bonds and Si–C bonds, indicating that the oxidation during processing was incomplete. Other surface morphology, such as pores and pits were discussed as well.
Keywords: SiC/SiC composites; X-ray photoelectron spectroscopy (XPS); Scanning electron microscopy (SEM); Laser processing;

The composite of graphene and a perovskite-type oxide (PTO) should be an attractive new material, owing to the special properties of graphene and the flexibility of PTO. Both graphene and PTO are promising support for some metallic nanoparticles. Therefore, in this work, taking LaFeO3 as the representative for PTO, a novel composite of graphene sheets-LaFeO3 has been prepared by using hydrothermal synthesis, and bimetallic nanoparticles of Cu-Co have been loaded on the composite. The resultant catalyst is applied to higher alcohols synthesis (HAS) from syngas. The morphology, structure and the state of the bimetallic composite catalyst are characterized by using techniques of SEM, TEM, AFM, XRD, TPR, Raman and N2 adsorption–desorption. For the graphene-LaFeO3 support, the graphene sheets are embedded into the bulk LaFeO3 or uniformly deposited on the surface of the LaFeO3 grains, resulting in high specific surface area. And the mass transferring ability of the bimetallic catalyst is optimized by uniform mixing of graphene and LaFeO3 and the formation of the mesopores. For the active component, the Cu-Co alloy nanoparticles are highly dispersed on the graphene-LaFeO3 composite, which leads to the high activity, high selectivity and excellent stability to higher alcohols.
Keywords: Graphene; LaFeO3; Perovskite-type oxide; CuCo alloy; Higher alcohols synthesis;

Fourier transform infrared and Raman spectroscopy studies on magnetite/Ag/antibiotic nanocomposites by Olena Ivashchenko; Justyna Jurga-Stopa; Emerson Coy; Barbara Peplinska; Zuzanna Pietralik; Stefan Jurga (400-409).
This article presents a study on the detection of antibiotics in magnetite/Ag/antibiotic nanocomposites using Fourier transform infrared (FTIR) and Raman spectroscopy. Antibiotics with different spectra of antimicrobial activities, including rifampicin, doxycycline, cefotaxime, and ceftriaxone, were studied. Mechanical mixtures of antibiotics and magnetite/Ag nanocomposites, as well as antibiotics and magnetite nanopowder, were investigated in order to identify the origin of FTIR bands. FTIR spectroscopy was found to be an appropriate technique for this task. The spectra of the magnetite/Ag/antibiotic nanocomposites exhibited very weak (for doxycycline, cefotaxime, and ceftriaxone) or even no (for rifampicin) antibiotic bands. This FTIR “invisibility” of antibiotics is ascribed to their adsorbed state. FTIR and Raman measurements show altered C―O, C=O, and C―S bonds, indicating adsorption of the antibiotic molecules on the magnetite/Ag nanocomposite structure. In addition, a potential mechanism through which antibiotic molecules interact with magnetite/Ag nanoparticle surfaces is proposed.
Keywords: Magnetite; Silver; Antibiotic; FTIR spectroscopy; Raman spectroscopy;

In the present work, self-ordered MoO3-TiO2 nanotube layers have been fabricated from Ti-Mo (7 wt.% Mo) alloy through anodization, and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and photoelectrochemical measurements. In comparison with pure TiO2 nanotubes, the synthesized MoO3-TiO2 nanotubes showed an enhanced donor concentration, lower electron transfer resistance, and longer electron lifetime. Moreover, photoinduced-carrier-separation efficiency also improved remarkably on addition of MoO3 to the TiO2 nanotube matrix. It was also shown that these beneficial properties led to higher photocatalytic water splitting activity and photocurrent response in the MoO3-TiO2 nanotubes.
Keywords: MoO3-TiO2 nanotubes; anodization; photoinduced carriers behavior; water splitting activity;

Enhancement of photocatalytic reduction of CO2 to CH4 over TiO2 nanosheets by modifying with sulfuric acid by Zhiqiao He; Juntao Tang; Jie Shen; Jianmeng Chen; Shuang Song (416-427).
TiO2 nanosheets modified with various concentrations of sulfuric acid have been synthesized through hydrothermal treatment at 240 °C followed by heat treatment at 105 °C. Compared with untreated TiO2 nanosheets, the H2SO4-modified samples exhibited markedly improved quantum yield (QY), energy returned on energy invested (EROEI), and turnover number (TON) for CO2 reduction to CH4 under visible-light irradiation. As supported by physical-chemical characterization, the enhanced photocatalytic activities can be attributed to acidification promoting the formation of hydroxyl groups (Brønsted acidic sites) and oxygen vacancies/Ti3+ species. Thus, efficient charge separation and transfer to the TiO2 surface for both CO2 reduction and the accompanying H2O oxidation is facilitated. The highest activity for CO2 photoreduction to CH4 was obtained with TiO2 nanosheets with 0.5 mol L−1 H2SO4, with QY, EROEI, and TON of 0.726‰, 0.335‰, and 83.124, respectively. Furthermore, the catalyst maintained stable performance throughout five successive recyclability test runs.
Keywords: Surface protonation; {0 0 1} facets dominated TiO2; CO2 photoreduction; CH4 formation; Visible light;

Use of Raman spectroscopy to assess the efficiency of MgAl mixed oxides in removing cyanide from aqueous solutions by Daniel Cosano; Carlos Esquinas; César Jiménez-Sanchidrián; José Rafael Ruiz (428-433).
Calcining magnesium/aluminium layered double hydroxides (Mg/Al LDHs) at 450 °C provides excellent sorbents for removing cyanide from aqueous solutions. The process is based on the “memory effect” of LDHs; thus, rehydrating a calcined LDH in an aqueous solution restores its initial structure. The process, which conforms to a first-order kinetics, was examined by Raman spectroscopy. The metal ratio of the LDH was found to have a crucial influence on the adsorption capacity of the resulting mixed oxide. In this work, Raman spectroscopy was for the first time use to monitor the adsorption process. Based on the results, this technique is an effective, expeditious choice for the intended purpose and affords in situ monitoring of the adsorption process. The target solids were characterized by using various instrumental techniques including X-ray diffraction spectroscopy, which confirmed the layered structure of the LDHs and the periclase-like structure of the mixed oxides obtained by calcination.
Keywords: Layered double hydroxides; Cyanide removal; Raman spectroscopy; Memory effect;

Controllable synthesis of branched hierarchical ZnO nanorod arrays for highly sensitive hydrazine detection by Jie Hu; Zhenting Zhao; Yongjiao Sun; Ying Wang; Pengwei Li; Wendong Zhang; Kun Lian (434-441).
An sensitive hydrazine electrochemical sensor was fabricated by using branched hierarchical ZnO nanorod arrays.In this paper, three different kinds of ZnO nanostructures were successfully synthesized on Au/Glass (Au/G) substrate by electrochemical deposition method. The morphology and crystalline structures of the obtained samples were characterized using SEM, XRD and HRTEM. Electrochemical responses of the as-prepared ZnO based sensors to hydrazine in 0.1 M phosphate buffer solution (PBS, pH 7.4) were analyzed by cyclic voltammetry and single-potential amperometry. The results confirmed that the electrochemical performances of ZnO sensors are strongly dependent on the specific surface area. Especially, the branched hierarchical ZnO nanorod arrays shows the highest sensitivity of 5.35 μA μM−1  cm−2, a short response time of 3 s, a low detection limit of 0.08 μM with a linear hydrazine concentration response range from 0.8 μM to 101 μM, and it also exhibits excellent anti-interference, stability and reproducibility abilities, which provide great potential method of ZnO branched hierarchical structures in the development of high-performance electrochemical sensor.
Keywords: Electrochemical sensor; Branched hierarchical ZnO; Electrodeposition; Hydrazine;

The fabrication of microlens array (MLA) on silicon surface is focused in this paper by taking advantage of a novel micromachining approach, the electrochemical wet stamping (E-WETS). The E-WETS allows the direct imprinting of MLA on an agarose stamp into substrate through a selective anodic dissolution process. The pre-patterned agarose stamp can direct and supply the solution preferentially on the contact area between the agarose stamp and the substrate, to which the electrochemical reaction is confined. The anodic potential vs. saturated calomel electrode is optimized and 1.5 V is chosen as the optimum value for the electrochemical polishing of p-Si. A refractive MLA on an PMMA mold is successfully transferred onto p-Si surface. Display OmittedThis paper focuses on the fabrication of microlens array (MLA) on silicon surface by taking advantage of a novel micromachining approach, the electrochemical we stamping (E-WETS). The E-WETS allows the direct imprinting of MLA on an agarose stamp into the substrate through a selective anodic dissolution process. The pre-patterned agarose stamp can direct and supply the solution preferentially on the contact area between the agarose stamp and the substrate, to which the electrochemical reaction is confined. The anodic potential vs. saturated calomel electrode is optimized and 1.5 V is chosen as the optimum value for the electrochemical polishing of p-Si. A refractive MLA on a PMMA mold is successfully transferred onto the p-Si surface. The machining deviations of the fabricated MLA from those on the mold are 0.44% in diameter and 2.1% in height respectively, and the machining rate in HF is around 1.1 μm/h. The surface roughness of the fabricated MLA is less than 12 nm owing to the electrochemical polishing process. The results demonstrate that E-WETS is a promising approach to fabricate MLA on p-Si surface with high accuracy and efficiency.
Keywords: Microlens array; Electrochemical wet stamping; Agarose stamp; Anodic dissolution; Silicon;

Sc and C co-doped TiO2 nanoparticles were synthesized through simple sol–gel method, which decreased the crystallite size of the nanoparticles and increased the lifetime of the photo-induced charge carriers. The Sc and C co-doped samples showed significantly high photoactivity as compared to the single C-doped TiO2 nanoparticles.Scandium and carbon co-doped TiO2 catalyst was prepared through a simple sol–gel synthesis method by using scandium nitrate as scandium dopant precursor, glucose as carbon precursor and tetrabutyl orthotitanate as titanium precursor and calcined them at 450 °C for 3 h. The characterizations of the prepared samples were accomplished through X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence spectroscopy (PL), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET). The X-ray diffraction results of the samples showed the decrease in the crystal size of the sample with the subsequent increase in the specific surface area as shown by Brunauer–Emmett–Teller. The UV–visible diffuse reflectance spectroscopy displayed the blue shift in the absorption together with the photoluminescence spectroscopy revealed the decrease in the recombination of electrons and holes by the addition of the scandium and then after the certain optimum value, the further increase of the scandium further increased the recombination of electrons and holes. The photo-catalytic activity of the samples was investigated with the help of photo-catalytic degradation of Acid orange 7 under visible light irradiation. The degradation of Acid orange 7 was highly increased for the Sc and C co-doped samples compared to the single C doped sample. And the sample 0.2 Sc/C-TiO2 had the maximum increase. The enhanced photo-catalytic performance was due the decrease of the crystal size, increase of the surface area, increase in the surface hydroxyl groups, and increase of the lifetime of the electrons and holes because of the synergistic effect of the Sc and C co-doping in TiO2.
Keywords: Titanium dioxide; Photo-catalysis; Sol–gel method; Scandium; Carbon;

The changes in composition of the corrosion products of electrodeposited ternary Zn–Co–Mo alloy coatings on AISI 1015 steel during exposure to 0.5 mol dm−3 NaCl solution were investigated. XPS studies demonstrated that at the initial stage of corrosion on the surface of Zn–Co–Mo coating zinc hydroxide layer is formed. Hydroxyl groups react with chloride and carbonate ions which lead to the formation of zinc hydroxy carbonates and zinc hydroxy chlorides. The share of these compounds in the oxidation products is initially large. However, with time zinc hydroxy compounds slowly changes to zinc oxide, which is more stable corrosion product. It was estimated that after 24 h of exposure to NaCl solution nearly 60% of zinc detected on the surface of Zn–Co–Mo coating was present in the ZnO form, 18% in the form of zinc hydroxy chloride, and more than 21% as zinc hydroxy carbonate. XPS analyses revealed that the amount of zinc hydroxy chloride increases as the exposure time lengthens and it is significantly higher than at the surface of binary Zn–Co coating. The presence of crystalline zinc chloride hydroxide as a stable product of corrosion of ternary Zn–Co–Mo alloy coating in a 0.5 mol dm−3 NaCl solution was confirmed by XRD analysis. According to XRD and FTIR other zinc corrosion products like: ZnO, Zn(OH)2 and Zn5(CO3)2(OH)6 were also present. The results of XPS and EIS measurements allow us to assume that in the presence of Mo in the alloy, on the surface of ternary Zn–Co–Mo alloy (3.4 wt.% Co, 2.7 wt.% Mo) coating more zinc hydroxy chloride is formed, which favors higher corrosion resistance of this coating.
Keywords: Zn–Co coating; Zn–Co–Mo coating; Passive layer; Zinc corrosion; XPS; EIS;

This paper presents an investigation on the ablation characteristics of excimer laser (λ  = 248 nm, τ  = 15 ns) and femtosecond laser (λ  = 800 nm, τ  = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F th  = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (F th  = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α −1  = 223 nm) than that for femtosecond laser ablation (α −1  = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas C=C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the C=C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (C―O and C=O bond) and nitrogen-rich (C―N) functional groups.
Keywords: Excimer laser; Femtosecond laser; Ablation; ABS; Polymer;

Printed biotin-functionalised polythiophene films as biorecognition layers in the development of paper-based biosensors by Petri Ihalainen; Markus Pesonen; Pernilla Sund; Tapani Viitala; Anni Määttänen; Jawad Sarfraz; Carl-Erik Wilén; Ronald Österbacka; Jouko Peltonen (477-483).
Display OmittedThe integration of flexible electronic sensors in clinical diagnostics is visioned to significantly reduce the cost of many diagnostic tests and ultimately make healthcare more accessible. This study concentrates on the characterisation of inkjet-printed bio-functionalised polythiophene films on paper-based ultrathin gold film (UTGF) electrodes and their possible application as biorecognition layers. Physicochemical surface properties (topography, chemistry, and wetting) and electrochemical characteristics of water-soluble regioirregular tetraethylene-glycol polythiophene (TEGPT) and biotin-functionalised TEGPT (b-TEGPT) films were examined and compared. In addition, their specificity towards streptavidin protein was tested. The results show that stable supramolecular biorecognition layers of insulating b-TEGPT and streptavidin were successfully fabricated on a paper-based UTGF by inkjet-printing. Good adhesion of thiophene to UTGF can be attributed to covalent linkage between sulphur and gold, whereas the stability of the streptavidin layer is due to the high affinity between biotin and streptavidin. The device introduced can be utilised in the development of biosensors for clinically relevant analytes e.g. for detecting complementary DNA oligomers or antibody–antigen complexes.
Keywords: Bio-recognition layer; Polythiophene; Inkjet printing; Streptavidin; Ultrathin gold film; Paper substrate;

TEM and HRTEM images with insets showing the diffraction pattern and IFFT, and EDX spectrum of a single SiNW.Silicon nanowires (SiNWs) have been synthesized on gold layer-coated silicon substrates via plasma enhanced chemical vapor deposition method (PECVD). Various thicknesses of Au layers were coated on Si (111) substrates using radio frequency magnetron sputtering. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to characterize the morphology, compositions, and structures of the samples. The results show that the sample consisted of single-crystalline SiNWs with the diameters ranging from 40 to 160 nm and length up to 3 μm. It was observed that the diameter of SiNWs increases with increasing of Au catalyst layers thickness. Raman spectra display peaks with narrow and asymmetric shape at 518 cm−1 for the SiNWs, indicating the high crystalline nature of the samples. A possible growth mechanism is proposed for the formation of nanowires (NWs). It has been found that the features of SiNWs depend on the thickness of Au layers.
Keywords: Au nanolayers; Silicon nanowires; PECVD;

SEM results demonstrate that microcracks are remarkably removed from the Al–17.5Si alloy surface after HCPEB treatment due to Nd element, and they decrease in length at high pulse number, showing a decrease in the stress concentration in the primary Si phase during the cooling process of HCPEB, as shown in Fig. 1. Therefore, the microcrack elimination is attributed to reducing the stress concentration.In the present work, the effect of Nd on the microcracks generated on an Al–17.5Si alloy surface by a high current pulsed electron beam (HCPEB) was investigated. By a newly proposed site-fixed observation, the propagation of microcracks with increasing pulsed numbers first increases and then decreases due to the Nd element. The crack density decreases from 0.0669 mm/mm2 of 5 pulses to 0.00687 mm/mm2 of 50 pulses. EPMA analysis results indicate that Nd is uniformly distributed on the HCPEB-treated alloy surface. Nano-silicon particles and nano-Al cellular structures were formed by TEM observation, showing grain refinement of the alloy surface. The microcrack elimination is attributed to a decrease in the stress concentration in the primary Si phase during the cooling process of HCPEB. The electrochemical measurement shows that the corrosion current density decreases sharply by two magnitudes as the pulsed number increases after adding the Nd element, thus indicating an improved corrosion resistance. In contrast, in the HCPEB-irradiated sample without Nd, this value increases conversely due to the presence of numerous microcracks, thereby demonstrating a decreased corrosion resistance.
Keywords: High current pulsed electron beam; Al–17.5Si alloy; Microcracks; Site-fixed observation; Electrochemical measurement;

Scheme of adsorption of water (a) and methanol (b) on the surface of the WO3 films.Here it has been reported on aging of the nanosized WO3 film, which is revealed is continuous reduction of the photochromic sensitivity over time. Water molecules physically adsorbed on the film surface from ambient air form donor–acceptor and hydrogen bonds, changing gradually the adsorption state to chemisorption which prevents an access of organic molecules that serve as hydrogen donors by the photochromism. The mechanism of the process has been investigated and discussed. The role of water in the photochromism has been highlighted. The difference in the efficiency for being of a hydrogen donor in the photochromic process between water and organic molecules is discussed.
Keywords: Photochromism; Photocatalysis; Hydrogen; Water; Hydrogen bronzes;

Enhanced visible light photocatalytic activity by Cu2O-coupled flower-like Bi2WO6 structures by Li Liu; Lan Ding; Yongguang Liu; Weijia An; Shuanglong Lin; Yinghua Liang; Wenquan Cui (505-515).
Cu2O nanodots decorated flower-like Bi2WO6 were prepared via an interfacial self-assembly method. The Cu2O nanodots, with an average diameters of 20 nm, were dispersed on the surface of Bi2WO6 uniformly, as evidenced by characterization of the structure and composition. The as-prepared Cu2O/Bi2WO6 hybrid photocatalysts revealed the lower charge-transfer resistance, higher photocurrent intensity and the outstanding photocatalytic activity. The 3 wt% Cu2O/Bi2WO6 composites showed the highest degrade rate for methylene blue (MB), which was 2.14 and 12.25 times that of the pure Bi2WO6 and Cu2O, respectively. Significantly, the superior stability was also observed in the five cyclic runs. The enhanced photocatalytic performance was attributed to the enhancement of visible light absorption efficiency as well as the efficient photo-generated charge separation originated from a strong interaction in the intimately contact interface, which was confirmed by the results of photocurrent and EIS measurements. Based on the experimental results, a mechanisms on enhancement of photocatalytic activity have been emphasized.
Keywords: Photocatalysis; Bi2WO6; Cu2O nanodots; Interfacial self-assembly method;

Tunable surface morphology of electrospun PMMA fiber using binary solvent by Zhi Liu; Jiang-hui Zhao; Peng Liu; Ji-huan He (516-521).
Superhydrophobic–superoleophilic fibrous polymethyl methacrylate (PMMA) membranes were prepared by electrospinning technique. The membranes exhibited a high water contact angle up to 153.9° and nearly zero oil contact angle. This super wettability property is attributed to hierarchical macro- and nanostructure on surface of PMMA membrane and can be conveniently tuned by adjusting the weight ratio of binary solvent of N,N-dimethylacetamide and acetone. Resultant fibrous PMMA membranes with superhydrophobic–superoleophilic property can be used in water treatment. This facile one-step strategy shows an alternative approach to produce special wettability surface and will benefit this material.
Keywords: Binary solvent; Electrospinning; PMMA; Phase separation; Superhydrophobic;

Adsorption of CO and formation of carbonates at steps of pure and Co-doped SrTiO3 surfaces by DFT calculations by Silvia Carlotto; Marta M. Natile; Antonella Glisenti; Andrea Vittadini (522-527).
A reconstructed SrTiO3 (1 1 0) surface, whose facets are oriented along the {1 0 0} planes, is used to study the reactivity of steps at the (1 0 0) surface. With this aim, we studied the interaction of CO on pure and Co-doped SrTiO3 (1 1 0) facetted surfaces using density functional theory calculations. Results show that steps have peculiar properties: at variance to their terrace counterparts, step-edge O ions can absorb CO molecules. Furthermore, the interaction of CO with co-adsorbed O2 easily gives rise to stable monodentate and bidentate carbonate species, which hamper the formation/desorption of CO2. In this context, Co impurities play a double role: on one hand, they stabilize oxygen vacancies, on the other, they (partially) contrast the formation of carbonate species.
Keywords: SrTiO3; Steps; DFT calculations; Adsorption; CO oxidation;

Study on hierarchical structured PDMS for surface super-hydrophobicity using imprinting with ultrafast laser structured models by Bin Liu; Wenjun Wang; Gedong Jiang; Xuesong Mei; Zibao Wang; Kedian Wang; Jianlei Cui (528-538).
We report a simple and inexpensive method for producing super-hydrophobic surfaces through direct replication of micro/nano-structures on polydimethylsiloxane (PDMS) from a replication master prepared by ultrafast-laser texturing process. Gratings were obtained on 304L stainless steel plate using picosecond laser ablation. It has been used as a master with grating areas of different structural features. PDMS negative replica was prepared from the masters, and PDMS positive replica was prepared from the negative replica thereafter. Wettability of samples of the steel master, negative and positive replicas was distinguished using the apparent contact angle (CA) of water drop. Relationships between the CAs on three kinds of samples and structural features were presented. Super-hydrophobic behavior with self-cleaning, exhibited by a water contact angle of 164.5° and sliding angle of 8.44°, was observed on the PDMS negative replica surface. The negative and positive replicas were sputtered on gold films, which were used to metalized PDMS and eliminate the submicron/nano-structures in hierarchical structures. Results prove that submicro/nano-structures of hierarchical structures enhance the hydrophobicity of material surface remarkably. This replication method can be applied for large scale production of micro/nano textured super-hydrophobic surfaces for commercial applications.
Keywords: Ultrafast laser; Surface texture; PDMS templating; Super-hydrophobic surface; Submicro/nano-structures;

High efficient preparation of carbon nanotube-grafted carbon fibers with the improved tensile strength by Wenxin Fan; Yanxiang Wang; Chengguo Wang; Jiqiang Chen; Qifen Wang; Yan Yuan; Fangxu Niu (539-551).
An innovative technique has been developed to obtain the uniform catalyst coating on continuously moving carbon fibers. Carbon nanotube (CNT)-grafted carbon fibers with significantly improved tensile strength have been succeeded to produce by using chemical vapor deposition (CVD) when compared to the tensile strength of untreated carbon fibers. The critical requirements for preparation of CNT-grafted carbon fibers with high tensile strength have been found, mainly including (i) the obtainment of uniform coating of catalyst particles with small particle size, (ii) the low catalyst-induced and mechano-chemical degradation of carbon fibers, and (iii) the high catalyst activity which could facilitate the healing and strengthening of carbon fibers during the growth of CNTs. The optimum growth temperature was found to be about 500 °C, and the optimum catalyst is Ni due to its highest activity, there is a pronounced increase of 10% in tensile strength of carbon fibers after CNT growth at 500 °C by using Ni catalyst. Based on the observation from HRTEM images, a healing and crosslink model of neighboring carbon crystals by CNTs has been formulated to reveal the main reason that causes an increase in tensile strength of carbon fibers after the growth of CNTs. Such results have provided the theoretical and experimental foundation for the large-scale preparation of CNT-grafted carbon fibers with the improved tensile strength, significantly promoting the development of CNT-grafted carbon fiber reinforced polymer composites.
Keywords: CVD; Carbon fibers; Carbon nanotubes; Tensile strength; Healing and crosslink model;

Antimicrobial and antioxidant surface modification toward a new silk-fibroin (SF)-l-Cysteine material for skin disease management by Frederico Nogueira; Luíza Granadeiro; Claudia Mouro; Isabel C. Gouveia (552-559).
A novel dressing material – silk fibroin fabric (SF)-l-Cysteine (l-Cys) – is here developed to be used as standard treatment for atopic dermatitis (AD), which combines comfort, thermic, and tensile strength properties of silk materials with antioxidant and antimicrobial effects of l-Cys. A careful understanding about the linking strategies is needed in order not to compromise the bioavailability of l-Cys and deplenish its bioactivity. Durability was also addressed through washing cycles and compared with hospital requirements, according to international Standard EN ISO 105-C06:2010. The present research also analyze the interactions between Staphylococcus aureus and SF-l-Cys under simulating conditions of AD and demonstrated the effectiveness of a double covalent grafting, with the importance of SF tyrosine (Tyr) covalent linkage with l-Cys (SF-g-l-Cys/Tyr-g-l-Cys) even after several washing cycles, twenty five, whereas for a disposable application a single covalent mechanism of grafting l-Cys proved to be sufficient (SF-g-l-Cys). Results showed effective antimicrobial activities exhibiting higher inhibition ratios of 98.65% for SF-g-l-Cys after 5 washing cycles, whereas 97.55% for SF-g-l-Cys/Tyr-g-l-Cys after 25 washing cycles, both at pH 9.5 grafting strategy. Furthermore, it is also reported a non-protumoral effect of l-Cys. A new advance is herein achieved at the world of medical antimicrobial textiles tailored to address wound moisture environment and exudate self-cleaning, which may open novel applications as complementary therapy for AD disease.
Keywords: l-Cysteine (l-Cys); Antimicrobial applications; Medical textiles; Atopic dermatitis (AD); Staphylococcus aureus;

First-principle study of SO2 molecule adsorption on Ni-doped vacancy-defected single-walled (8,0) carbon nanotubes by Wei Li; Xiao-Min Lu; Guo-Qing Li; Juan-Juan Ma; Peng-Yu Zeng; Jun-Fang Chen; Zhong-Liang Pan; Qing-Yu He (560-566).
These two figures reflect the orbital bonding between SO2 molecule and the SV-2-CNT and Ni-SV-2-CNT. Which indicated the feasibility of making the sensors for SO2 molecule detecting with introducing vacancies, Ni atoms or combination of them.To explore the possible way of detecting the poisonous gas SO2, we have investigated the interactions between SO2 molecule and modified (8,0) single-walled carbon nanotubes by using the density functional theory (DFT) method. The adsorption energies, interaction distances, changes of geometric and electronic structures were all analyzed to investigate the sensitivity of variety of models of CNTs with Ni doping, vacancies, and a combination of them toward SO2 molecule. From our investigations, we found that SO2 molecule was more likely to be absorbed on vacancy-defected CNTs with relatively higher adsorption energy and shorter binding distance compared with the perfect CNTs. In addition, after doping Ni atom on the vacancies, the modified CNTs which were not very much sensitivity to SO2 molecule could become much sensitivity to it. In other words, the number of sensitive adsorption sites increased. The partial density of states (PDOS) and the electron concentration of the adsorption systems suggested the strong electrons interaction between SO2 molecule and defected or Ni-doped defected CNTs. Therefore the vacancies and Ni-doped vacancies CNTs had the potential capacities to make the sensors for SO2 molecule detecting.
Keywords: Ni-doped carbon nanotubes; Vacancy; Adsorption; SO2;

Investigation of interdiffusion and depth resolution in Cu/Ni multilayers by means of AES depth profiling by X.L. Yan; Y. Liu; H.C. Swart; J.Y. Wang; J.J. Terblans (567-572).
The interdiffusion upon annealing Cu/Ni multilayers structures at 325 °C, 350 °C and 375 °C for 30 min were investigated by Auger electron spectroscopy (AES) depth profiling. The Cu/Ni multilayers structures were deposited on a SiO2 substrate by means of electron beam evaporation in a high vacuum. The measured AES depth profiles of the as-deposited and annealed samples were quantitatively fitted by the Mixing-Roughness-Information depth model assuming that the roughness parameter has linearly increased with the sputtered depth. The roughness values extracted from the depth profiling data fits agreed well with those measured by atomic force microscopy. The depth-dependent interdiffusion coefficients of the annealed samples and depth resolution upon depth profiling of the as-deposited sample were quantitatively evaluated accordingly.
Keywords: AES depth profiling; Interdiffusion coefficient; Cu/Ni multilayers; Depth resolution; MRI model;

Ytterbium oxide nanodots via block copolymer self-assembly and their efficacy to dye-sensitized solar cells by Kwang-Won Park; Sungwoo Ahn; Sung-Hwan Lim; Ming Hao Jin; Jeemin Song; Seung-Young Yun; Hyeon Mo Kim; Gi Jeong Kim; Kang Min Ok; Jongin Hong (573-578).
In this study, we develop a novel phosphor, Yb2O3, to be used as the spectral converter in dye-sensitized solar cells (DSSCs) for the efficient capture of ultraviolet light via down-conversion. These zero-dimensional nanodots with a high refractive index also allow more light to be trapped and can prevent charge recombination at the interfaces in the DSSCs. Compared to DSSCs without the nanodots, the DSSCs fabricated with the Yb2O3 nanodots exhibits higher power-conversion efficiencies for both the N719 (10.5%) and CSD-01 (20.5%) dyes. The multifunctionality of the Yb2O3 nanodots provides a new route for improving the performance of DSSCs.
Keywords: Ytterbium oxide; Block copolymer; Spectral converter; Dye-sensitized solar cell;

In this paper, a new core-shell composite of nordihydroguaiaretic acid (NDGA) molecularly imprinted polymers layer-coated silica gel (MIP@SiO2) was prepared through sol–gel technique and applied as a material for extraction of NDGA from Ephedra. It was synthesized using NDGA as the template molecule, γ-aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTEOS) as the functional monomers, tetraethyl orthosilicate (TEOS) as the cross-linker and ethanol as the porogenic solvent in the surface of silica. The non-imprinted polymers layer-coated silica gel (NIP@SiO2) were prepared with the same procedure, but with the absence of template molecule. In addition, the optimum adsorption affinity occurred when the molar ratio of NDGA:APTS:MTEOS:TEOS was 1:6:2:80. The prepared MIP@SiO2 and NIP@SiO2 were analyzed by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform-infrared spectroscopy (FT-IR). Their affinity properties to NDGA were evaluated through dynamic adsorption, static adsorption, and selective recognition experiments, and the results showed the saturated adsorption capacity of MIP@SiO2 could reach to 5.90 mg g−1, which was two times more than that of NIP@SiO2. High performance liquid chromatography (HPLC) was used to evaluate the extraction of NDGA from the medicinal plant ephedra by the above prepared materials, and the results indicated that the MIP@SiO2 had potential application in separation of the natural active component NDGA from medicinal plants.
Keywords: Nordihydroguaiaretic acid; Surface molecularly imprinted polymers; Sol–gel; Selectivity recognition; Ephedra;

Attapulgite-CeO2/MoS2 ternary nanocomposite for photocatalytic oxidative desulfurization by Xiazhang Li; Zuosong Zhang; Chao Yao; Xiaowang Lu; Xiaobing Zhao; Chaoying Ni (589-596).
Novel attapulgite(ATP)-CeO2/MoS2 ternary nanocomposites were synthesized by microwave assisted assembly method. The structures of the nanocomposites were characterized by XRD, FT-IR, UV–vis, XPS and in situ TEM. The photocatalytic activities of ATP-CeO2/MoS2 composites were investigated by degradating dibenzothiophene (DBT) in gasoline under visible light irradiation. The effect of the mass ratio of CeO2 to MoS2 on photocatalytic activity was investigated. The results indicate that the three-dimensional network structure is firmly constructed by ATP skeleton, CeO2 particles and MoS2 nanosheet which effectively increase the surface area of the composites and promote the separation of electrons and holes by resulting electronic transmission channels of multi-channel in space. The degradation rate of DBT can reach 95% under 3 h irradiation when the mass ratio of CeO2/MoS2 is 4/10. A plausible mechanism for the photocatalytic oxidative desulfurization of this nanocomposite is put forward.
Keywords: Attapulgite; MoS2; CeO2; Photocatalytic oxidation; Desulfurization;

When an interface exists between a liquid and a solid, the angle between the surface of the liquid and the outline of the contact surface is described as the contact angle. The size of the contact angle is the metrics of the hydrophobicity of the surface. The prediction of the contact angle has significant effect on the design of hydrophobic surface and improvement of hydrophobicity. In this paper, a prediction model for contact angle has been proposed based on minimum Gibbs free energy. It considers the effects of unilateral force and area constraints of the droplets. The effect of micro-structural parameters on contact angle has also been investigated. Micro-milling experiments have been conducted to fabricate the hydrophobic surface in order to validate the predictive capability of the contact angle model. Results revealed that the established prediction model could estimate the contact angle of hydrophobic surface. The contact angle could be increased by increasing concave width or reducing convex. The outcome of this research will lead to new methodologies for preparing hydrophobic surfaces with micro-machining technology.
Keywords: Hydrophobic surface; Contact angle; Energy method; Micro-milling;

Novel magnetically separable BiOBr/CoFe2O4 microspheres were prepared and acted as a high-performance and recyclable material for efficient water purification.Novel magnetically separable BiOBr/CoFe2O4 microspheres assembled from nanoparticles were successfully fabricated by a facile solvothermal method at 160 °C for 12 h. Then, BiOBr/CoFe2O4 microspheres were characterized via XRD, TEM, SEM, EDS and VSM. Congo red (CR) was selected as a pollutant model to evaluate the photocatalytic activities of BiOBr/CoFe2O4 microspheres. The value of coercivity (232 Oe) and the saturation magnetization (33.79 emu g−1) were obtained, which indicated that BiOBr/CoFe2O4 microspheres can be separated and recovered easily from the treated solution. What is more, by calculation, the initial rate constants of BiOBr/CoFe2O4 microspheres is about 1.45 times higher than that of the pure BiOBr, which resulted from superior adsorption and transfer performance to organic contaminants in aqueous systems. Four consecutive regeneration cycles demonstrated that the BiOBr/CoFe2O4 microspheres had high photostability under simulated solar light irradiation. According to the radical trapping experiments, the h + radicals and O2 radicals were the two main active species that drive the photocolorization of CR pollutant by BiOBr/CoFe2O4 microspheres under simulated solar light irradiation. This work suggests that the BiOBr/CoFe2O4 microspheres may be a promising photocatalyst for photodegrading organic pollutants and environmental remediation.
Keywords: Bismuth oxybromide; Cobalt ferrite; Photocatalysis; Decolorization; Congo red; Magnetic separation;

The optimal reaction pathways for the dissociation of CH3OH on Pd (100) surface.Density functional theory (DFT) method was employed to investigate the adsorption and decomposition mechanisms of CH3OH on Pd (100) surface. Different kinds of possible adsorption modes of relevant intermediates on the surface were identified. It was found that CH3OH and CH2OH prefers to adsorb on the top site, CH3O, CHOH and CO occupy preferentially on the bridge site, while CH2O, CHO, COH and H species adsorb on the hollow site. The adsorption energies of all species exhibit the following trend: CH3OH < CH2O < CH3O < CO < CH2OH < H < CHO < CHOH < COH. Subsequently, four possible dissociation pathways of CH3OH via initial O―H and C―H bond scissions were proposed and studied systematically. The transition states, energy barriers and reaction energies were calculated to explore the dehydrogenation mechanisms of CH3OH on Pd (100) surface. It was indicated that the scission of C―H bond is more favorable for CH3OH and CH2OH and the H―O bond cleavage is easier for CHOH. The path 2 (CH3OH―CH2OH―CHOH―CHO―CO) is the most possible dehydrogenation pathway, where the highest energy barrier of CH3OH dissociation makes it to be the rate-determining step of the whole dehydrogenation reaction.
Keywords: Density functional theory; Pd (100) surface; Methanol; Adsorption; Decomposition;

The oxygenous functional groups located at the edges of on GO sheets mainly participated in the complexation of Pb(II). And the Pb(II) might bridged different GO sheets through simultaneously binding the hydroxyl or carboxyl groups at the edges.Comparative study has been performed on the adsorption of Pb(II) on graphene oxides (GOs) prepared from flaky, lump and amorphous graphites with the Hummers method in this work. The GOs were characterized by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, Chemical analysis, Raman spectroscopy and Atomic force microscope. The results indicated that GO prepared from amorphous graphite had lower C/O ratio and more thin layers (less than 2 nm in thickness) than those prepared from the other two natural graphites. The adsorption process was well described by the pseudo-second-order kinetics model, and the equilibrium data agreed precisely with the Langmuir model. The hydroxyl and carboxyl located at the edges of GO sheets mainly participated in the complexation of Pb(II), and different GO sheets were bridged by Pb(II) through simultaneously bonding the marginal oxygenous groups.
Keywords: Natural graphite; Crystalline morphology; Graphene oxide; Lead ion; Adsorption sites;

Novel ferroferric oxide/polystyrene/silver core–shell magnetic nanocomposite microspheres as regenerable substrates for surface-enhanced Raman scattering by Bo Liu; Chong Bai; Dan Zhao; Wei-Liang Liu; Man-Man Ren; Qin-Ze Liu; Zhi-Zhou Yang; Xin-Qiang Wang; Xiu-Lan Duan (628-635).
A novel Ag-coated Fe3O4@Polystyrene core–shell microsphere has been designed via fabrication of Fe3O4@Polystyrene core–shell magnetic microsphere through a seed emulsion polymerization, followed by deposition of Ag nanoparticles using in-situ reduction method. Such magnetic microspheres can be utilized as sensitive surface-enhanced Raman scattering (SERS) substrates, using Rhodamine 6G (R6G) as a probe molecule, with both stable and reproducible performances. The SERS detection limit of R6G decreased to 1 × 10−10 M and the enhancement factor of this substrate on the order of 106 was obtained. In addition, owing to possessing excellent magnetic properties, the resultant microspheres could be separated rapidly by an external magnetic field and utilized repeatedly for three times at least. Therefore, the unique renewable property suggests a new route to eliminate the single-use problem of traditional SERS substrates and will be promising for the practical application.
Keywords: Core–shell microspheres; In-situ reduction; SERS substrate; Stability; Reproducibility;

This paper reports the green and in-situ preparation of the Cu/Fe3O4 magnetic nanocatalyst synthesized using Morinda morindoides leaf extract without stabilizers or surfactants. The catalyst was characterized by XRD, SEM, EDS, UV–visible, TEM, VSM and TGA-DTA. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4-nitrophenol (4-NP), Congo red (CR) and Rhodamine B (RhB) in an environmental friendly medium at room temperature. The catalyst was recovered using an external magnet and reused several times without appreciable loss of its catalytic activity. In addition, the stability of the recycled catalyst has been proved by SEM and EDS techniques.
Keywords: Cu/Fe3O4; Reduction; Magnetic catalyst; Catalytic properties;

Undoped nanodiamond (ND) supported PtRu (PtRu/ND) electrocatalyst for methanol oxidation reactions (MOR) in direct methanol fuel cells was prepared by a microwave-assisted polyol reduction method. Sp3-bonded ND possesses high electrochemical stability but low conductivity, while sp2-bonded carbon nanomaterials with high conductivity are prone to oxidation. Therefore, the functions of the supporting material were separated in this study. ND (sp3), as a support, and AB or CNTs (sp2), as a conductive additive, were combined to form the hybrid electrocatalysts PtRu/ND + AB and PtRu/ND + CNT for MOR. The morphology of the electrocatalysts was characterized by scanning electron microscopy and electrochemical measurements were performed using an electrochemical workstation. The results indicated that the electrocatalytic activity of PtRu/ND for MOR was improved with the addition of AB or CNTs as a conductive additive. Moreover, adding CNTs to PtRu/ND as a conductive additive showed better electrocatalytic activities than adding AB, which can be ascribed to the better electron-transfer ability of CNTs.
Keywords: Undoped nanodiamond; Conductive additives; Acetylene black; Carbon nanotubes; Methanol oxidation reaction;

Tailored lithium storage performance of graphene aerogel anodes with controlled surface defects for lithium-ion batteries by Hui Shan; Dongbin Xiong; Xifei Li; Yipeng Sun; Bo Yan; Dejun Li; Stephen Lawes; Yanhua Cui; Xueliang Sun (651-659).
Three dimensional self-assembled graphene aerogel (GA) anode materials with some surface defects have been successfully generated through a facile hydrothermal procedure using graphene oxide as precursor. The morphologies and textural properties of as-obtained GA were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman and other spectroscopy techniques. The surface defects and electrical conductivities of GA can be controlled by adjusting the hydrothermal reaction time. The results indicate that GA with a reaction time of 6 h exhibits extremely high reversible capacity (1430 mAh g−1 at the current density of 100 mA g−1) and superior rate capability (587 mAh g−1 at 800 mA g−1) with excellent cycling stability (maintaining a reversible capacity of 960 mAh g−1 at 100 mA g−1 after 100 cycles). It is demonstrated that the 3D porous network with increased defect density, as well as the considerable electrical conductivity, results in the excellent electrochemical performance of the as-made GA anodes in lithium-ion batteries.
Keywords: Hydrothermal self-assembly; Graphene aerogel; Defects; Lithium ion batteries; Anode materials;

Contribution of oligomer/carbon dots hybrid semiconductor nanoribbon to surface-enhanced Raman scattering property by Guiyang Zhang; Lin Hu; Kerong Zhu; Manqing Yan; Jian Liu; Jiaxiang Yang; Hong Bi (660-669).
The hybrid Ag-(PS-PSS)/C-dots nanobelts (NBs) have been prepared by decorating Ag nanoparticles (NPs) on surface of the ultra-long, semiconducting (PS-PSS)/C-dots nanoribbons (NRs) via an electroless plating method. The as-prepared Ag-(PS-PSS)/C-dots NB has been demonstrated to be an excellent substrate for surface-enhanced Raman scattering (SERS) with a detection limit of 10−14  M and an enhancement factor of 3.35 × 108 while using rhodamine 6G as probe molecules. Moreover, we have investigated the application of Ag-(PS-PSS)/C-dots NBs as SERS substrate for detection of coumarins. Further, the Ag-(PS-PSS)/C-dots NB could be used as a sacrificial template to form a novel kind of hollow porous Ag nanotubes (NTs) by simply removing the inner NR in tetrahydrofuran. However, the obtained Ag NTs show a weaker SERS effect compared to that of the Ag-(PS-PSS)/C-dots NBs, which indicates that the inner organic/C-dots NR plays an essential role in SERS property of the Ag-(PS-PSS)/C-dots NBs. Here the organic (PS-PSS)/C-dots NR not only acts as a dielectric support for Ag NPs to reduce the surface plasmon damping at the Ag-NR interface due to the high electrical conductivity but also their large surface area are favorable for creating more “hot-spots”. In addition, the embedded sp2-hybridized C-dots in NR can adsorb more aromatic R6G molecules via π–π interaction, which also drives R6G molecules approaching to the “hot-spots”, thus enhancing the SERS signals. Based on our results, it is believed that the employment of semiconducting organic (PS-PSS)/C-dots ribbon-like structures to fabricate sensitive SERS substrates is an interesting new approach.
Keywords: Semiconductor; Carbon dots; Nanostructure; Surface-enhanced; Raman scattering (SERS); Rhodamine 6G;

A high power ZnO thin film piezoelectric generator by Weiwei Qin; Tao Li; Yutong Li; Junwen Qiu; Xianjun Ma; Xiaoqiang Chen; Xuefeng Hu; Wei Zhang (670-675).
A highly efficient and large area piezoelectric ZnO thin film nanogenerator (NG) was fabricated. The ZnO thin film was deposited onto a Si substrate by pulsed laser ablation at a substrate temperature of 500 °C. The deposited ZnO film exhibited a preferred c-axis orientation and a high piezoelectric value of 49.7 pm/V characterized using Piezoelectric Force Microscopy (PFM). Thin films of ZnO were patterned into rectangular power sources with dimensions of 0.5 × 0.5 cm2 with metallic top and bottom electrodes constructed via conventional semiconductor lithographic patterning processes. The NG units were subjected to periodic bending/unbending motions produced by mechanical impingement at a fixed frequency of 100 Hz at a pressure of 0.4 kg/cm2. The output electrical voltage, current density, and power density generated by one ZnO NG were recorded. Values of ∼95 mV, 35 μA cm−2 and 5.1 mW cm−2 were recorded. The level of power density is typical to that produced by a PZT NG on a flexible substrate. Higher energy NG sources can be easily created by adding more power units either in parallel or in series. The thin film ZnO NG technique is highly adaptable with current semiconductor processes, and as such, is easily integrated with signal collecting circuits that are compatible with mass production. A typical application would be using the power harvested from irregular human foot motions to either to operate blue LEDs directly or to drive a sensor network node in mille-power level without any external electric source and circuits.
Keywords: Nanogenerator; ZnO thin film; Pulsed laser ablation; Piezoelectric efficiency;

Nb2O5 coated hierarchical TiO2 nanowire-sheet arrays photoanode was synthesized on Ti-mesh substrate by using a hydrothermal approach for fully flexible dye-sensitized solar cells which exhibited well photovoltaic efficiency of 4.55%.Nb2O5 coated hierarchical TiO2 nanowire-sheet arrays photoanode was synthesized on flexible Ti-mesh substrate by using a hydrothermal approach. The effect of TiO2 morphology and Nb2O5 coating layer on the photovoltaic performance of the flexible dye sensitized solar cells (DSSCs) based on Ti-mesh supported nanostructures were systematically investigated. Compared to the TiO2 nanowire arrays (NWAs), hierarchical TiO2 nanowire arrays (HNWAs) with enlarged internal surface area and strong light scattering properties exhibited higher overall conversion efficiency. The introduction of thin Nb2O5 coating layers on the surface of the TiO2 HNWAs played a key role in improving the photovoltaic performance of the flexible DSSC. By separating the TiO2 and electrolyte (I/I3 ), the Nb2O5 energy barrier decreased the electron recombination rate and increased electron collection efficiency and injection efficiency, resulting in improved J sc and V oc. Furthermore, the influence of Nb2O5 coating amounts on the power conversion efficiency were discussed in detail. The fully flexible DSSC based on Nb2O5 coated TiO2 HNWAs films with a thickness of 14 μm displayed a well photovoltaic property of 4.55% (J sc  = 10.50 mA cm–2, V oc  = 0.75 V, FF = 0.58). The performance enhancement of the flexible DSSC is largely attributed to the reduced electron recombination, enlarged internal surface area and superior light scattering ability of the formed hierarchical nanostructures.
Keywords: Ti mesh; TiO2 HNWAs; Nb2O5 coating layers; Flexible dye-sensitized solar cells;

Iron oxide (Fe2O3) nanoparticles were grown on graphene oxide (GO) using a simple microwave-assisted method. The effects of urea concentration on Fe2O3 nanoparticles and GO/Fe2O3 composite were examined. The as-prepared samples were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The Fe2O3 nanoparticles were uniformly developed on GO sheets. The results showed that urea affects both Fe2O3 morphology and particle size. In the absence of urea, the Fe2O3 nanostructures exhibited a rod-like morphology. However, increasing urea concentration altered the morphology and decreased the particle size. The Raman results of GO/Fe2O3 showed that the intensity ratio of D band to G band (I D/I G) was decreased by addition of urea, indicating that urea can preserve the GO sheets during synthesis of the composite from exposing more defects. The surface area and thermal stability of GO/Fe2O3 and Fe2O3 were compared using the Brunauer–Emmett–Teller method and thermal gravimetric analysis, respectively. The results showed that the increased concentration of urea induced a larger surface area with more active sites in the Fe2O3 nanoparticles. However, the increase in urea concentration led to decreased thermal stability of the Fe2O3 nanoparticles. The magnetic properties of Fe2O3 nanoparticles were characterized by a vibrating sample magnetometer and results revealed that the magnetic properties of Fe2O3 nanoparticles are affected by the morphology.
Keywords: Maghemite; Hematite; Nanoparticle; Composite; Urea; Morphology;

Synthesis of MoS2/g-C3N4 nanosheets as 2D heterojunction photocatalysts with enhanced visible light activity by Juan Li; Enzhou Liu; Yongning Ma; Xiaoyun Hu; Jun Wan; Lin Sun; Jun Fan (694-702).
TEM image and schematic diagram of photocatalytic mechanism of 2D MoS2/g-C3N4 composites.g-C3N4 nanosheets coupled with MoS2 nanosheets as 2D heteroconjuction were prepared via a facile impregnation and calcination method. The structure characterization clearly indicated that MoS2 nanosheets were successfully horizontal loaded on g-C3N4 nanosheets. The investigation indicated that the formation of 2D heterojunction between the g-C3N4 nanosheets and MoS2 nanosheets promoted the charge transfer and enhanced separation efficiency of photoinduced electron–hole pairs. Furthermore, the measurement of photocatalytic activity for the degradation of rhodamine B and methyl orange revealed that the as-prepared 2D MoS2/g-C3N4 heterojunction exhibited the significantly enhanced photocatalytic activity and considerable stability under visible light irradiation. The 2D MoS2/g-C3N4 heterojunction prepared with 3 wt% of MoS2 exhibited the optimal photodegradable efficiency. The present work shows that the formation of 2D heterojunction should be a good strategy to design efficient photocatalysts.
Keywords: g-C3N4 nanosheets; MoS2 nanosheets; 2D heterojunction; Photocatalysis;

A novel and sensitive electrochemical biosensor based on hybrid nanocomposite consisting of copper oxide nanowires (CuO NWs) and carboxyl-functionalized single-walled carbon nanotubes (SWCNTs-COOH) was first developed for the detection of the specific-sequence target DNA. This schematic represents the fabrication procedure of our DNA biosensor.Here, we developed a novel and sensitive electrochemical biosensor to detect specific-sequence target DNA. The biosensor was based on a hybrid nanocomposite consisting of copper oxide nanowires (CuO NWs) and carboxyl-functionalized single-walled carbon nanotubes (SWCNTs-COOH). The resulting CuO NWs/SWCNTs layers exhibited a good differential pulse voltammetry (DPV) current response for the target DNA sequences, which we attributed to the properties of CuO NWs and SWCNTs. CuO NWs and SWCNTs hybrid composites with highly conductive and biocompatible nanostructure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry (CV). Immobilization of the probe DNA on the electrode surface was largely improved due to the unique synergetic effect of CuO NWs and SWCNTs. DPV was applied to monitor the DNA hybridization event, using adriamycin as an electrochemical indicator. Under optimal conditions, the peak currents of adriamycin were linear with the logarithm of target DNA concentrations (ranging from 1.0 × 10−14 to 1.0 × 10−8  M), with a detection limit of 3.5 × 10−15  M (signal/noise ratio of 3). The biosensor also showed high selectivity to single-base mismatched target DNA. Compared with other electrochemical DNA biosensors, we showed that the proposed biosensor is simple to implement, with good stability and high sensitivity.
Keywords: Electrochemical; CuO nanowire; Single-walled carbon nanotube; Adriamycin; Differential pulse voltammetry; DNA biosensor;

Two-step synthesis of highly emissive C/ZnO hybridized quantum dots with a broad visible photoluminescence by Liangjie He; Shiliang Mei; Qiuhang Chen; Wanlu Zhang; Jie Zhang; Jiatao Zhu; Guoping Chen; Ruiqian Guo (710-717).
The formation schematics of the C/ZnO hybridized QDs.In situ growth of ZnO layer on the surface of carbon dots was realized via a two-step method, which resulted in an enhancement of the broad visible emission with a high quantum yield. Influence of the refluxing time, the temperature and the oleylamine/octadecene ratio was investigated to address the key factors on the preparation of the carbon dots. Under the optimal conditions, the carbon dots with an average diameter of 3.4 ± 0.4 nm and a photoluminescence quantum yield of 29.3% were achieved. Remarkable improvements of photoluminescence were achieved by the hybridization of the ZnO layer, which can eliminate the surface-trap from the C cores and form the new centers of emission. The synergistic effect arising from the C/ZnO hybridized structure obviously broadened the visible emission and enhanced their photoluminescence quantum yield from 29.3% to 47.3%. The as-prepared highly emissive quantum dots exhibited a broad and stable emission with the Commission Internationaled ‘E’ clairage chromaticity coordinate of (0.23, 0.34), which could offer a promising solution for the future-generation white light emitting diodes.
Keywords: Carbon dots; ZnO; Hybridized quantum dots; Two-step method; Photoluminescence enhancement;

Controllable resistive switching in Au/Nb:SrTiO3 microscopic Schottky junctions by Yuhang Wang; Xiaolan Shi; Kehan Zhao; Guanlin Xie; Siyu Huang; Liuwan Zhang (718-725).
The reversible resistive switching effect at oxide interface shows promising applications in information storage and artificial intelligence. However, the microscopic switching mechanism is still elusive due to the difficulty of direct observation of the electrical and chemical behavior at the buried interface, which becomes a major barrier to design reliable, scalable, and reproducible devices. Here we used a gold-coated AFM tip as a removable electrode to investigate the resistive switching effect in a microscopic Au/Nb:SrTiO3 Schottky junction. We found that unlike the inhomogeneous random resistive switching in the macroscopic Schottky junctions, the high and low resistance states can be reversibly switched in a controllable way on the Nb-doped SrTiO3 surface by the conductive tip. The switching between the high and low resistance states in vacuum is accompanied by the reversible shift of the surface Fermi level. We indicate that the transfer of the interface oxygen ion in a double-well potential is responsible for the resistive switching in both macroscopic and microscopic Schottky junctions. Our findings provide a guide to optimize the key performance parameters of a resistive switching device such as operation voltage, switching speed, on/off ratio, and state retention time by proper electrode selection and fabrication strategy.
Keywords: Resistive switching; Nb-doped SrTiO3; Schottky junction; Scanning probe microscopy; Oxygen vacancy; First principle calculation;

Facile preparation of MnO2 nanorods and evaluation of their supercapacitive characteristics by Mustafa Aghazadeh; Maryam Asadi; Mohammad Ghannadi Maragheh; Mohammad Reza Ganjali; Parviz Norouzi; Farnoush Faridbod (726-731).
The first time pulsed base (OH) electrogeneration to the cathodic electrodeposition of MnO2 in nitrate bath was applied and MnO2 nanorods were obtained. The deposition experiments were performed under a pulse current mode with typical on-times and off-times (t on  = 10 ms and t off  = 50 ms) and a peak current density of 2 mA cm−2 (I a  = 2 mA cm−2). The structural characterization with XRD and FTIR revealed that the prepared MnO2 is composed of both α and γ phases. Morphological evaluations through SEM and TEM revealed that the prepared MnO2 contains nanorods of relative uniform structures (with an average diameter of 50 nm). The electrochemical measurements through cyclic voltammetry and charge–discharge techniques revealed that the prepared MnO2 nanostructures reveal an excellent capacitive behavior with specific capacitance values of 242, 167 and 98 F g−1 under the applied current densities of 2, 5 and 10 A g−1, respectively. Also, excellent long-term cycling stabilities of 94.8%, 89.1%, and 76.5% were observed after 1000 charge–discharge cycles at the current densities of 2, 5 and 10 A g−1.
Keywords: MnO2; Pulse electrodeposition; Heat-treatment; Supercapacitors;

Phase dependent photocatalytic activity of Ag loaded TiO2 films under sun light by V. Madhavi; P. Kondaiah; Habibuddin Shaik; G. Mohan Rao (732-739).
Well-crystallized anatase and mixed (anatase–rutile) phase TiO2 thin films were deposited by DC magnetron sputtering technique at various DC powers in the range of 80–140 W. Pure anatase phase was observed in the TiO2 films deposited at low power of 80 W. Films deposited at 120 W were composed of both anatase and rutile phases. At higher power of 140 W, the films are rutile dominated and the rutile percentage increased from 0 to 82% with increase of DC power. The same results of phase change were confirmed by Raman studies. The surface morphology of the TiO2 films showed that the density of the films increased with increase of sputter power. The optical band gap of the films varied from 3.35 to 3.14 eV with increase of DC power. The photocatalytic activity of the TiO2 films increased with increasing DC power up to 120 W and after that it decreases. We found that the TiO2 films deposited at 120 W with 48% of rutile phase, exhibited high photocatalytic activity (43% of degradation) under UV light compared with other TiO2 films. After loading the optimized Ag nanoparticles on the mixed phase TiO2 films, the photocatalytic activity shifted from UV to visible region with enhancement of photocatalytic activity (55% of degradation).
Keywords: Sputtering; XRD; Surface plasmons; Photo catalysis;

The content of Ni phase, which is the main ferromagnetic phase in Ni–P–La coating, is almost increased linearly with the concentration of La in plating solution.Ni–P–La coatings were prepared on Si substrate by electroless plating method under different La content, pH value, plating temperature and plating time. The surface morphology, chemical composition, structure and magnetic properties of coatings were observed and determined by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). The results showed that Ni–P–La coating is smooth and uniform with a cellular morphology grown in columnar manner. With the increase of La content, pH value and plating time, the thickness and saturation magnetization of coating are increased continuously, but the stability of plating bath is decreased greatly with La content and pH value. Under higher plating temperature, the thickness and saturation magnetization of coatings are obviously enhanced. But too high plating temperature is harmful to the plating bath and coating. The optimum plating conditions for Ni–P–La coating is La2O3 addition of 10 mg L−1, pH value of 5.0, plating temperature of 75 °C and plating time of 45 min. The role of La element is to benefit the deposition of Ni element, promote the formation of Ni phase during the annealing process, and thus improve the magnetic properties of Ni–P–La coating.
Keywords: Ni–P–La coating; Electroless plating; Rare earth element; Preparation; Magnetic properties;

HfO2 gate dielectric on Ge (1 1 1) with ultrathin nitride interfacial layer formed by rapid thermal NH3 treatment by Khushabu S. Agrawal; Vilas S. Patil; Anil G. Khairnar; Ashok M. Mahajan (747-751).
Interfacial properties of the ALD deposited HfO2 over the surface nitrided germanium substrate have been studied. The formation of GeON (∼1.7 nm) was confirmed by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron spectroscopy (HRTEM) over the germanium surface. The effect of post deposition annealing temperature was investigated to study the interfacial and electrical properties of hafnium oxide/germanium oxynitride gate stacks. The high-k MOS devices with ultrathin GeON layer shows the good electrical characteristics including higher k value ∼18, smaller equivalent oxide thickness (EOT) around 1.5 nm and smaller hysteresis value less than 170 mV. The Q eff and D it values are somewhat greater due to the (1 1 1) orientation of the germanium and may be due to the presence of nitrogen at the interface. The Fowler–Northeim (FN) tunneling of Ge MOS devices has been studied. The barrier height Φ B extracted from the plot is ∼1 eV.
Keywords: PEALD; HfO2; Passivation; XPS; Current conduction mechanism;

Improvement of the stability and activity of immobilized glucose oxidase on modified iron oxide magnetic nanoparticles by Mahboube Abbasi; Razieh Amiri; Abdol-Kalegh Bordbar; Elnaz Ranjbakhsh; Ahmad-Reza Khosropour (752-757).
Immobilized proteins and enzymes are widely investigated in the medical field as well as the food and environmental fields. In this study, glucose oxidase (GOX) was covalently immobilized on the surface of modified iron oxide magnetic nanoparticles (MIMNs) to produce a bioconjugate complex. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to the size, shape and structure characterization of the MIMNs. Binding of GOX to these MIMNs was confirmed by using FT-IR spectroscopy. The stability of the immobilized and free enzyme at different temperature and pH values was investigated by measuring the enzymatic activity. These studies reveal that the enzyme's stability is enhanced by immobilization. Further experiments showed that the storage stability of the enzyme is improved upon binding to the MIMNs. The results of kinetic measurements suggest that the effect of the immobilization process on substrate and product diffusion is small. Such bioconjugates can be considered as a catalytic nanodevice for accelerating the glucose oxidation reaction for biotechnological purposes.
Keywords: Enzymatic activity; Glucose oxidase; Immobilization; Iron oxide magnetic nanoparticles; Stability;

Water adsorption and dissociation on solid surfaces play a key role in a variety of industrial processes, a detailed comprehension of this process and the effect of the surface structure will assist in developing the improved catalysts. In this study, the adsorption and dissociation of H2O on three different types of CuO(111) surfaces, including the stoichiometric, oxygen-vacancy and oxygen-rich surfaces, have been systematically investigated and compared using density functional theory methods. All possible initial configurations of H2O adsorbed on those surfaces with only one coverage have been identified. Our results show that the adsorption ability of H2O is substantially weaker than that of the dissociated species (HO, H and O). H2O chemisorbs at the CuSUB, Cu2 and CuSUB sites of the stoichiometric, oxygen-vacancy and oxygen-rich surfaces, respectively; subsequently, the chemisorption H2O dissociates into OH and H species. The dissociation mechanisms of chemisorption H2O and the single OH group leading to the final O and H species suggest that the dissociation of single OH species occurs at a higher barrier compared to the dissociation of OH in the presence of neighboring H atom (produced from the initial step of H2O dissociation), namely, the presence of H is in favor of OH dissociation, which agrees with the results of charge transfer. However, owing to the significantly high barrier of OH dissociation compared to the initial dissociation step of H2O, OH species is considered as the dominant product on those surfaces. Oxygen-rich surface is the most favorable for the initial dissociation of H2O both thermodynamically and kinetically than other two surfaces. The calculated vibrational frequencies for the adsorbed H2O and OH species on CuO(111) surfaces can be applied to guide the experimental research of surface vibrational spectroscopy. In addition, our results may provide a basis for the study of H2O interaction with other metal oxide surfaces.
Keywords: Water; CuO(111); Adsorption; Dissociation; Density functional theory;

We proposed an electron cyclotron resonance microwave hydrogen–nitrogen mixed plasma (HNP) pretreatment for 4H–SiC surface combined with post-oxidation annealing (POA) to improve the SiO2/SiC interface properties. Results revealed that HNP surface pretreatment effectively reduced the density of interface traps (D it ), which was closely correlated with interface flattening because of surface flattening, surface state (contaminants, adsorbates, and dangling bonds) reduction, and suppressed generation of interface defects during oxidation. Combined with POA, D it was further decreased because of passivation of the formed defects after oxidation. The correlation among passivation, SiC surface properties, SiO2/SiC interface properties, and defect levels was established.
Keywords: SiC semiconductor; SiO2/SiC interface; Density of interface traps; Surface pretreatment; Surface states;

A facile hydrothermal route to self-assembled ZnGa2O4 particles and their microwave application by Mingjia Lu; Xin Ouyan; Songping Wu; Rongyun Ge; Rui Xu (775-782).
Self-assembled porous ZnGa2O4 particles were synthesized through a facile hydrothermal route in this work. The phase evolution and microstructure of specimens were identified by XRD and SEM. Various morphologies (i.e. porous, nanorods or spherical particles) and size (nano or micro-sized) could be rationally designed through altering the reaction conditions. Hydrothermal ZnGa2O4 particles exhibited an outstanding microwave dielectric performance, i.e. a dielectric constant of 9.93, a Q  ×  f value of 73 000 GHz, and a τ f value of –68.7 ppm/ °C. What is more, the ZnGa2O4 ceramics displayed a stable quality factor in the high temperature region (1400–1500 °C) due to the unique frame-structured ZnGa2O4 particles. Therefore, they can be regarded as potential candidate materials for millimeter-wave device.
Keywords: Self-assembly; Porous ZnGa2O4; Hydrothermal route; Dielectric materials/properties;

Single domain CoFe2O4 nanoparticles with different amount of defects/strain have been synthesized by varying the growth temperature in the hydrothermal method. Nanoparticles grown at lower temperature are of larger size and exhibit more planar defects and oxygen vacancies as compared to nanoparticles grown at higher temperatures which are of smaller sizes and exhibit less planar defects and oxygen vacancies. The nanoparticles with larger amount of defects also possess a higher value of intrinsic strain as compared to nanoparticles with fewer defects. The presence of intrinsic strain in the nanoparticles is found to shift the cationic distribution at the tetrahedral and octahedral sites. The saturation magnetization (M s ) of the nanoparticles is found to depend upon both the intrinsic strain and size of the nanoparticles. The M s increases with the decrease in the nanoparticles size from 32 nm to 20 nm, and this is correlated to the inverse of spin canting effect due to decrease in the intrinsic strain which leads to shifting of Co2+ ions from tetrahedral to octahedral sites. However, with further decrease in the size of the nanoparticles (16 nm), the size effect dominates over the strain effect leading to decrease in M s . The coercivity is found to be higher in the nanoparticles with larger amount of defects/strain and has been attributed to strain induced strong spin canting and pinning due to defect sites. The variation of coercivity with particle size (D) exhibits deviation from D 3/2 dependence for the nanoparticles with larger amount of strain/defects.
Keywords: CoFe2O4; Defects; Strain; Single domain; Inverse spin canting;

Self-limiting atomic layer deposition of conformal nanostructured silver films by Zahra Golrokhi; Sophia Chalker; Christopher J. Sutcliffe; Richard J. Potter (789-797).
The controlled deposition of ultra-thin conformal silver nanoparticle films is of interest for applications including anti-microbial surfaces, plasmonics, catalysts and sensors. While numerous techniques can produce silver nanoparticles, few are able to produce highly conformal coatings on high aspect ratio surfaces, together with sub-nanometre control and scalability. Here we develop a self-limiting atomic layer deposition (ALD) process for the deposition of conformal metallic silver nanoparticle films. The films have been deposited using direct liquid injection ALD with ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) and propan-1-ol. An ALD temperature window between 123 and 128 °C is identified and within this range self-limiting growth is confirmed with a mass deposition rate of ∼17.5 ng/cm2/cycle. The effects of temperature, precursor dose, co-reactant dose and cycle number on the deposition rate and on the properties of the films have been systematically investigated. Under self-limiting conditions, films are metallic silver with a nano-textured surface topography and nanoparticle size is dependent on the number of ALD cycles. The ALD reaction mechanisms have been elucidated using in-situ quartz crystal microbalance (QCM) measurements, showing chemisorption of the silver precursor, followed by heterogeneous catalytic dehydrogenation of the alcohol to form metallic silver and an aldehyde.
Keywords: Atomic layer deposition; Silver; Thin films; Nanoparticles; Self-limiting;

Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13C, 29Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide important insights into the fabrication of advanced polymer nanocomposites for dielectric applications.
Keywords: Barium titanate; Nanocomposite; Silane modification; Dielectric properties; Breakdown strength;

Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO2 (Pt-P25) catalysts with and without adsorbed halogen ions (including F, Cl, Br, and I) were prepared through impregnation and ion modification. Pt-TiO2 samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO2 sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO2. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.
Keywords: Halogen poisoning; Pt-TiO2; Formaldehyde; Catalytic oxidation;

Polydimethylsiloxane (PDMS) and SU-8 are both widely used for microfluidic system. However, it is difficult to permanently seal SU-8 microfluidic channels using PDMS with conventional methods. Previous efforts of combining these two materials mainly employed oxygen plasma modified PDMS. The nitrogen plasma modification of PDMS bonding with SU-8 is rarely studied in recent years. In this work, the mechanism of nitrogen plasma modified PDMS bonding with SU-8 was investigated. The fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle of a water droplet were used to analyze the nitrogen plasma modified surface and the hydrophilic stability of PDMS samples. Pull-off tests were used for estimating the bonding effect of interface between nitrogen plasma modified PDMS and SU-8.
Keywords: SU-8; PDMS; Nitrogen plasma treatment; Contact angle; FTIR; XPS; Pull-off test;

Water adsorption on two-dimensional silica films by M.T. Nayakasinghe; A. Chakradhar; N. Sivapragasam; U. Burghaus (822-828).
In the meanwhile several inorganic low-dimensional crystals (analog to the prototypical organic graphene) are known. A technological important example is two-dimensional (2D) silica films (silicatene); their molecular structure is well described in the literature. However, much less is known about the surface chemistry. We present experimental data to characterize water adsorption on silicatene using several known synthesis procedures. The wettability of the 2D films did in our study depend on details of the film preparation. Therefore, the hydrophobicity could be used as a simple diagnostics tool to verify the quality of silicatene films. In addition, wettability of the precursors to silicatene namely Mo(112), and O-Mo(112) were characterized.
Keywords: crystalline 2D silica; water; kinetics; wetting; hydrophobic; hydrophilic;

N–F codoped and molecularly imprinted TiO2 were prepared by simple ethanol–water solvothermal method. Their mechanism of high adsorption capacity, preferable photocatalytic degradation activity, good selectivity and excellent reusability for target contaminants were identified and discussed.N–F codoped and molecularly imprinted TiO2 (MIP-NFTs) were successfully prepared by simple ethanol–water solvothermal method using 2-nitrophenol (2NP) and 4-nitrophenol (4NP) as template molecules (target contaminants), respectively. The surface structure and properties of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption measurements (BET), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra (UV–vis DRS). In comparison with non-imprinted N–F codoped TiO2 nanocomposites (NIP-NFTs), MIP-NFTs show a higher adsorption, good selectivity and preferable degradation capacity toward the target contaminants. The adsorption amounts of 2NP and 4NP over the corresponding MIP-NFTs are about 1.78 and 2.21 times of that over NIP-NFTs, respectively. MIP-NFTs show a much higher adsorption capacity and selectivity for target contaminants in the mixed solution. Degradation selectivity experiments demonstrate that the selectivity coefficient (R) of degradation of 2NP relative to 4NP over 2NP/MIP-NFTs and 4NP relative to 2NP over 4NP/MIP-NFTs are 1.93 and 1.61, respectively. The enhancement about adsorption capacity and selectivity can be attributed to the chemical interaction and size matching between target contaminants and imprinted cavities. The apparent rate constants for the photodegradation of 2NP and 4NP over the corresponding MIP-NFTs are 0.05233 min−1 and 0.03734 min−1, being 267% and 198% of that over NIP-NFTs under simulated solar light. Moreover, MIP-NFTs exhibit excellent reusability due to their inorganic framework.
Keywords: N–F codoped TiO2; Molecular imprinting; Adsorption; Selectivity; Degradation; Nitrophenol;

Fabrication and reducing gas detection characterization of highly-crystalline p-type zinc chromite oxide thin film by Yuan-Chang Liang; Yu-Ru Cheng; Hao-Yuan Hsia; Cheng-Chia Chung (837-842).
A p-type ternary ZnCr2O4 (ZCO) thin film was fabricated using rf sputtering on a sapphire substrate. Microstructural analyses revealed that the ZCO thin film had a high crystalline quality. Surface morphology investigations showed that the ZCO film had a rugged surface because of a distinct columnar grain feature. A gas sensor composed of the ZCO thin film exhibited marked acetone and NH3 gas-sensing responses. These acetone and NH3 gas-sensing responses reached an optimal value at operating temperatures of 250 °C and 300 °C, respectively. The ZCO sensor showed satisfactory repeatability when operated under dynamic conditions. The stable gas-sensing behavior of the p-type ZCO thin film to acetone and NH3 gases broadens the design of oxide gas sensors incorporated with this ternary oxide.
Keywords: ZnCr2O4; Sputtering; Oxide films; Gas detection;

The change in roughness of various thicknesses Ga-doped ZnO (GZO) thin films deposited by magnetron reactive sputtering on glass substrates at room temperature was measured by atomic force microscopy (AFM). Multi-resolution signal decomposition based on wavelet transform and fractal geometry was applied to process surface profiles, to evaluate the roughness trend of relevant frequency resolution. The results give a six-level decomposition and the results change with deposited time and surface morphology. Also, it is found that fractal dimension is closely connected to the underside diameter (grain size) and the distance between adjacent grains that affect the change rate of surface and the increase of the defects such as abrupt changes lead to a larger value of fractal dimension.
Keywords: GZO; Atomic force microscopy; Surface roughness; Wavelet; Fractal;

Facile preparation of nitrogen-doped hierarchical porous carbon with high performance in supercapacitors by Kun Yan; Ling-Bin Kong; Kui-Wen Shen; Yan-Hua Dai; Ming Shi; Bing Hu; Yong-Chun Luo; Long Kang (850-861).
Preparing and activating process of nitrogen-doped hierarchical porous carbon (NHPC).The nitrogen-doped hierarchical porous carbon (NHPC) material was successfully prepared through a simple carbonization procedure of well-defined diblock copolymer precursor containing nitrogen-enriched carbon source, i.e., polyacrylonitrile (PAN), and asacrificial block, i.e., polymethylmethacrylate (PMMA). PAN-b-PMMA diblock copolymer was synthesized by atom transfer radical polymeriation (ATRP) with narrow molecular weight distribution. The as-obtained NHPC possessed nitrogen-doped hierarchical porous structure with high BET surface area of 257 m2  g−1 and Nonlocal density functional theory (NLDFT) mesopore size of 14.61 nm. Surface activated nitrogen-doped hierarchical porous carbon (A-NHPC) materials were obtained by subsequent surface activation with HNO3 solution. The effects of activation conditions on supercapacitive behavior were systematically studied, a maximum specific capacitance of 314 F g−1 at a current density of 0.5 A g−1 was achieved in 2 M KOH aqueous electrolyte. Simultaneously, it exhibited excellent rate capability of 67.8% capacitance retention as the current density increased from 0.5 to 20 A g−1 and superior cycling performance of 90% capacitance retention after 10,000 cycles at the current density of 2 A g−1.
Keywords: Diblock copolymer; Atom transfer radical polymerization; Carbonization; Nitrogen-doped hierarchical porous carbon; Surface activation;

In this study, the geometric structures and electronic properties of two widely used organophosphorus pesticides, diazinon and hinosan, boron nitride nanotubes (BNNTs) and Fe doped boron nitride nanotubes (FeBNNTs) as adsorbents of these pesticides are studied by density functional theory calculation as well as dispersion correction by Grimme method. The results show that Fe doping in boron nitride nanotubes structures increases the potency of nanotubes to adsorb mentioned pesticides, especially when Fe atom located instead of N atom. Comparing the adsorption energies of diazinon on FeBNNTs with ones for hinosan demonstrate that the adsorption of hinosan is energetically more favorable by FeBNNTs. Assessment of adsorption energies in aqueous solution confirmed significant decrease in their values compared to ones in gaseous phase. However, the adsorption of diazinon and hinosan on both BNNTs and FeBNNTs are exothermic. So, BNNTs and FeBNNTs may be promising candidates as appropriate adsorbents for adsorbing diazinon and hinosan. Also, the results of calculations have revealed that van der Waals interaction energies are remarkably large in adsorption of diazinon and hinosan on all boron nitride nanotubes.
Keywords: Diazinon; Hinosan; Boron nitride nanotube (BNNT); Density functional theory; PBE/DNP; Van der Waals;

Conducting this study has demonstrated that not only SEM-EDX but also XPS can be an efficient tool for characterising watercolour paint surfaces. We find that surface effects are mediated by water. Once the powdered components in the watercolour come into contact with water they dramatically transform their chemical structures at the surface and show the presence of pigment components with a random dispersion within the gum layer. Hence the topmost surface of the paint is confirmed as being composed of the gum binder components. This result is difficult to confirm using just one analytical technique (either XPS or SEM-EDX). In addition, peak fitting of C1s XPS spectra suggests that the gum binder in the commercial watercolour paints is probably gum arabic (by comparison with the reference materials). This identification is not conclusive, but the combination techniques of XPS and SEM shows the surface structure with material distribution of the gum binder and the other ingredients of the watercolour paints. Therefore as a unique technique, XPS combined with SEM-EDX may prove a useful method in the study of surface structure for not only watercolour objects but also other art objects; which may in future help in the conservation for art.
Keywords: Organic synthetic pigment; Watercolour paint; XPS; Polysaccharide binders; Gum arabic; Gum tragacanth;

Self-assembled thin film of imidazolium ionic liquid on a silicon surface: Low friction and remarkable wear-resistivity by Rashi Gusain; Sho Kokufu; Paramjeet S. Bakshi; Toru Utsunomiya; Takashi Ichii; Hiroyuki Sugimura; Om P. Khatri (878-885).
Imidazolium-hexafluorophosphate (ImPF6) ionic liquid thin film is prepared on a silicon surface using 3-chloropropyltrimethoxysilane as a bifunctional chemical linker. XPS result revealed the covalent grafting of ImPF6 thin film on a silicon surface. The atomic force microscopic images demonstrated that the ImPF6 thin film is composed of nanoscopic pads/clusters with height of 3–7 nm. Microtribological properties in terms of coefficient of friction and wear-resistivity are probed at the mean Hertzian contact pressure of 0.35–0.6 GPa under the rotational sliding contact. The ImPF6 thin film exhibited low and steady coefficient of friction (μ  = 0.11) along with remarkable wear-resistivity to protect the underlying silicon substrate. The low shear strength of ImPF6 thin film, the covalent interaction between ImPF6 ionic liquid thin film and underlying silicon substrate, and its regular grafting collectively reduced the friction and improved the anti-wear property. The covalently grafted ionic liquid thin film further shows immense potential to expand the durability and lifetime of M/NEMS based devices with significant reduction of the friction.
Keywords: Ionic liquid; Thin film; Self-assembly; Friction; Wear-resistivity;

Design and fabrication of UV band-pass filters based on SiO2/Si3N4 dielectric distributed bragg reflectors by Jiangping Dai; Wang Gao; Bin Liu; Xianlei Cao; Tao Tao; Zili Xie; Hong Zhao; Dunjun Chen; Han Ping; Rong Zhang (886-891).
We have designed one kind of optical filters based on double stacks of 13.5-pairs SiO2/Si3N4 dielectric distributed Bragg reflector (DDBR) structures, to realize the passband with different central wavelengths in ultraviolet (UV) range. These SiO2/Si3N4 multi-layers have been successfully fabricated on (0001) sapphire substrates by plasma-enhanced chemical vapor deposition (PECVD). The reflectance spectra measured by the UV–visible spectrometer manifest that a series of band-pass filters with fixed passband width of ∼30 nm and central passband varied from 310 nm to 370 nm have been obtained successfully. Besides, the other series of filters with passband width varied from 30 nm to 45 nm can be achieved. With good control of PECVD deposition parameters, all samples exhibit smooth surface with root mean square roughness less than 4.5 nm. Moreover, cross-section scanning electron microscope (SEM) images show these DDBR structures have good periodicity in accordance with the design, indicating that these band-pass filter structures are suitable for wavelength-window-selection UV photodetectors.
Keywords: Distributed Bragg reflector; Ultraviolet band-pass filter; Plasma-enhanced chemical deposition; Surface and section morphology; X-ray photoelectron spectroscopy; Finite-different time-domain method;

Electrical properties of SiO2/SiC interfaces on 2°-off axis 4H-SiC epilayers by M. Vivona; P. Fiorenza; T. Sledziewski; M. Krieger; T. Chassagne; M. Zielinski; F. Roccaforte (892-895).
In this paper, the electrical properties of the SiO2/SiC interface on silicon carbide (4H-SiC) epilayers grown on 2°-off axis substrates were studied. After epilayer growth, chemical mechanical polishing (CMP) allowed to obtain an atomically flat surface with a roughness of 0.14 nm. Metal-oxide-semiconductor (MOS) capacitors, fabricated on this surface, showed an interface state density of ∼1 × 1012  eV−1  cm−2 below the conduction band, a value which is comparable to the standard 4°-off-axis material commonly used for 4H-SiC MOS-based device fabrication. Moreover, the Fowler–Nordheim and time-zero-dielectric breakdown analyses confirmed an almost ideal behavior of the interface. The results demonstrate the maturity of the 2°-off axis material for 4H-SiC MOSFET device fabrication.
Keywords: 4H-SiC; 2°-Off axis; Interface states; SiO2/SiC; MOS;

Protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating characterized using quartz crystal microbalance by Shyam V. Vaidya; Min Yuan; Alfredo R. Narváez; David Daghfal; James Mattzela; David Smith (896-908).
The protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating (Dursan®) were compared to that of an amorphous fluoropolymer (AF1600) coating and bare 316L grade stainless steel by studying non-specific adsorption of various proteins onto these surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D). A wash solution with nonionic surfactant, polyoxyethyleneglycol dodecyl ether (or Brij 35), facilitated 100% removal of the adsorbed bovine serum albumin (BSA), mouse immunoglobulin G (IgG), and normal human plasma proteins from the Dursan surface and of the adsorbed normal human plasma proteins from the AF1600 surface, whereas these proteins remained adsorbed on the bare stainless steel surface. Mechanical stress in the form of sonication demonstrated durability of the Dursan coating to mechanical wear and showed no negative impact on the coating's ability to prevent adsorption of plasma proteins. Surface delamination was observed in case of the sonicated AF1600 coating, which further led to adsorption of normal human plasma proteins.
Keywords: Carboxysilane coating; Protein; Adsorption; Biofouling; Dursan; QCM-D;

This study used the sol–gel method to prepare Cu2ZnSnS4 thin films containing oxygen and explored the composition, structural, and optoelectronic properties of the films. The non-vacuum process enabled the oxygen content of the Cu2ZnSnS4 films to be 8.89 at% and 10.30 at% for two different annealing conditions. In the crystal structure, oxygen was substituted at the positions of sulfur and appeared in the interstitial sites of the lattice. The compositions of the thin films deviated from the stoichiometric ratio. Both films had kesterite structures with no secondary phase structure. The kesterite CZTS film possessed a composite microstructure of crystallite and crystalline states. The microstructure of the Cu2ZnSnS4 film with higher oxygen content was denser and the average grain size was smaller. Incorporating oxygen atoms into crystalline Cu2ZnSnS4 changed the energy band structure: the direct energy band gaps were, respectively, 2.75 eV and 2.84 eV; the thin films mainly adsorbed photons with wavelengths less than 500 nm; and the absorption coefficients increased from 104  cm−1 to 105  cm−1. The films had a comparatively high absorptive capacity for photons less than 350 nm. Increasing the oxygen content of the film lowered the resistivity. Thus, the oxygen-containing Cu2ZnSnS4 thin film could be a candidate for the p-type absorber layer material required in multi-junction solar cells.
Keywords: Cu2ZnSnS4; Oxygen; Thin film; Structure; Band gap; Absorption coefficient;

Biodegradable hydrogel nanocomposites (HNC) of gum karaya (GK) grafted with poly(acrylic acid) (PAA) incorporated silicon carbide nanoparticles (SiC NPs) were synthesized using the in situ graft copolymerization method and tested for the adsorption of cationic dyes from aqueous solution. The structure and morphology of the HNC were characterized using different spectroscopic and microscopic techniques. The results showed that the surface area and porosity of the hydrogel polymer significantly increased after nanocomposite formation with SiC NPs. The HNC was employed for the removal of cationic dyes, i.e., malachite green (MG) and rhodamine B (RhB) from the aqueous solution. The HNC was found to remove 91% (MG) and 86% (RhB) of dyes with a polymer dose of 0.5 and 0.6 g l−1 in neutral medium, respectively. The adsorption process was found to be highly pH dependent and followed the pseudo-second-order rate model. The adsorption isotherm data fitted well with the Langmuir adsorption isotherm with a maximum adsorption capacity of 757.57 and 497.51 mg g−1 for MG and RhB, respectively. Furthermore, the HNC was demonstrated as a versatile adsorbent for the removal of both cationic and anionic dyes from the simulated wastewater. The HNC showed excellent regeneration capacity and was successfully used for the three cycles of adsorption–desorption. In summary, the HNC has shown its potential as an environment friendly and efficient adsorbent for the adsorption of cationic dyes from contaminated water.
Keywords: Gum karaya; Silicon carbide NPs; Nanocomposite; Adsorption; Malachite green; Rhodamine B;

High performance hybrid rGO/Ag quasi-periodic mesh transparent electrodes for flexible electrochromic devices by A.S. Voronin; F.S. Ivanchenko; M.M. Simunin; A.V. Shiverskiy; A.S. Aleksandrovsky; I.V. Nemtsev; Y.V. Fadeev; D.V. Karpova; S.V. Khartov (931-937).
A possibility of creating a stable hybrid coating based on the hybrid of a reduced graphene oxide (rGO)/Ag quasi-periodic mesh (q-mesh) coating has been demonstrated. The main advantages of the suggested method are the low cost of the processes and the technology scalability. The Ag q-mesh coating is formed by means of the magnetron sputtering of silver on the original template obtained as a result of quasi-periodic cracking of a silica film. The protective rGO film is formed by low temperature reduction of a graphene oxide (GO) film, applied by the spray-deposition in the solution of NaBH4. The coatings have low sheet resistance (12.3 Ω/sq) and high optical transparency (82.2%). The hybrid coatings are characterized by high chemical stability, as well as they show high stability to deformation impacts. High performance of the hybrid coatings as electrodes in the sandwich-system «electrode–electrochromic composition–electrode» has been demonstrated. The hybrid electrodes allow the electrochromic sandwich to function without any visible degradation for a long time, while an unprotected mesh electrode does not allow performing even a single switching cycle.
Keywords: Quasi-periodic mesh transparent electrode; self-organized template; Reduced graphene oxide (rGO); Flexible electrochromic device;