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Applied Surface Science (v.257, #24)

Electrodeposition from ZnO nano-rods to nano-sheets with only zinc nitrate electrolyte and its photoluminescence by Bai Xue; Yi Liang; Liu Donglai; Nie Eryong; Sun Congli; Feng Huanhuan; Xu jingjing; Jin Yong; Jiao Zhifeng; Sun Xiaosong (pp. 10317-10321).

► ZnO nano-sheets can be evolved from ZnO nano-rods on ITO glass substrates by using electro-chemical-deposition process in the sole Zn(NO₃)₂·6H₂O electrolyte without any capping agents used. ► An electrolyte concentration-induced growth mechanism has been discussed. ► Room temperature photoluminescence properties of ZnO nanostructures are investigated.This very paper focuses on the synthesis of ZnO nano-structures by means of electro-chemical-deposition process. The crystalline structure and morphologies of the prepared ZnO were characterized with X-ray diffraction and scanning electronic microscopy, respectively. It is found that in case of low Zn(NO₃)₂·6H₂O electrolyte concentration the fast growth mode in the c-axis direction leaded to the formation of 1D nanostructure of ZnO. On the other hand, at high concentration, this fast growth mode was restricted because the absorbed NO₃⁻ on (0001) plane would bond with Zn²⁺ ions, which, therefore, resulted in the formation of 2D nanostructure of ZnO. Room temperature photoluminescence performances of different ZnO structures were also investigated. A blue shift of 15nm for ZnO nano-sheets has been found as the shapes of ZnO evolved from nano-rods to nano-sheets.

Keywords: ZnO; Electrochemical deposition; Morphology evolution; Growth mechanism; Photoluminescence

Adsorption CO₂ on the perfect and oxygen vacancy defect surfaces of anatase TiO₂ and its photocatalytic mechanism of conversion to CO by Waranyu Pipornpong; Raina Wanbayor; Vithaya Ruangpornvisuti (pp. 10322-10328).

Display Omitted► Adsorption energies for physisorption and chemisorption of CO₂ on perfect and oxygen vacancy defect surfaces of anatase TiO₂ were obtained. ► The photocatalytic mechanism of CO₂ conversion to CO has been presented. ► Photoexcitation in TiO₂ surfaces has been described and discussed in detail.The adsorption energies for physisorption and the most stable chemisorption of CO₂ on the neutral charge of perfect anatase [TiO₂] (001) are −9.03 and −24.66kcal/mol on the spin-unpolarized and −12.98 and −26.19kcal/mol on the spin-polarized surface. The small activation barriers of 1.67kcal/mol on the spin-unpolarized surface and of 6.66kcal/mol on the spin-unpolarized surface were obtained. The adsorption mechanism of CO₂ on the oxygen vacancy defect [TiO₂+V_O] surface of anatase TiO₂ using density functional theory calculations was investigated. The energetically preferred conversion of CO₂ to CO was found either on the spin-unpolarized or spin-polarized surfaces of oxygen vacancy defect surface [TiO₂+V_O] as photocatalyst.

Keywords: Carbon dioxide; Carbon monoxide; Physisorption and chemisorption; Perfect anatase; Oxygen vacancy defect surface; Photocatalyst; TiO; ₂; DFT

Room temperature magnetic properties of Fe and C implanted ZnO films by Y.H. Xue; X.D. Zhang; X.L. Zhang; Y.Y. Shen; F. Zhu; L.H. Zhang; J. Wang; C.L. Liu (pp. 10329-10332).

► RT ferromagnetism was observed in all ZnO films treated differently. ► Fe or C ion implantation induces slight decrease of the magnetism. ► Sequential implantation of Fe and C into ZnO film increases the magnetic moment. ► Effect of magnetic enhancement has been tentatively interpreted.ZnO films prepared by radio frequency magnetron sputtering were singly or sequentially implanted with 120keV Fe ions at a fluence of 5×10¹⁶ions/cm² and 20keV C ions at a fluence of 3×10¹⁵ions/cm². Magnetic and optical properties as well as structures of the films have been investigated using various techniques. Magnetic measurements show that the as-deposited ZnO film presents room temperature ferromagnetism. Single Fe or C ion implantation has no contribution to enhancement in the film magnetism, while magnetic moment increases distinctly in the Fe and C ions sequentially implanted film. Results from structural measurements reveal that Fe nanoparticles are formed in the Fe singly implanted ZnO film. The post C implantation induces dissolution of Fe nanoparticles and promotes Fe atoms to substitute Zn atoms in the lattice. Based on the structural results, the effect of magnetic enhancement has been tentatively interpreted.

Keywords: ZnO thin film; Ion-implantation; Optical properties; Room-temperature magnetism

Improvement of orthodontic friction by coating archwire with carbon nitride film by Songbo Wei; Tianmin Shao; Peng Ding (pp. 10333-10337).

► CNx film is coated on the surface of archwire to reduce wire-bracket friction in orthodontic application. ► The CNx film has sp² carbon dominated structures and diversiform bonds coexist in the film. ► This CNx film with sp² rich structures remarkably reduces the wire-bracket friction both in ambient air and in artificial saliva. ► The reduction of friction of the CNx coated wire is more significant at large angulation than that at small angulation.In order to reduce frictional resistance between archwire and bracket during orthodontic tooth movement, carbon nitride (CNx) thin films were deposited on the surface of archwires with ion beam assisted deposition (IBAD). The energy-dispersive X-ray spectrometer (EDS) analysis showed that the CNx film was successfully deposited on the surface of the orthodontic wires. X-ray photoelectron spectroscopy (XPS) analysis suggested that the deposited CNx film was sp² carbon dominated structures, and diversiform bonds (NC, NC, et al.) coexisted in the film. The friction tests indicated that the CNx film significantly reduced the wire-bracket friction both in ambient air and in artificial saliva. The sp²C rich structure of the CNx film as well as its protection function for the archwire was responsible for the low friction of the wire-bracket sliding system.

Keywords: Friction; CNx film; Ion beam assisted deposition; Orthodontic archwire

Effects of the substrate temperature on the properties of CuIn₅S₈ thin films by M. Gannouni; M. Kanzari (pp. 10338-10341).

► In this work, CuIn5S8 thin films were successfully prepared by thermal evaporation onto different substrate temperatures. ► Which have significant effect on their physico-chemical properties. ► The obtained films present an amorphous structure in nature and become polycrystalline only by heat treatment from 200 ̊C with an enhancement in the intensity of the (311) main peak.Structural, optical and electrical properties of CuIn₅S₈ thin films grown by thermal evaporation have been studied relating the effects of substrate heating conditions of these properties. The CuIn₅S₈ thin films were carried out at substrate temperatures in the temperature range 100–300°C. The effects of heated substrate on their physico-chemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), optical transmission and hot probe method. X-ray diffraction revealed that the films are strong preferred orientation along the (311) plane upon substrate temperature 200°C and amorphous for the substrate temperatures below 200°C. No secondary phases are observed for all the films. The composition is greatly affected by heated substrate. From the optical transmission and reflection, an important absorption coefficient exceeds 10⁵cm⁻¹ at 800nm was found. As increasing the substrate temperature, the optical energy band gap decreases from 1.70eV for the unheated films to 1.25eV for the deposited films at 300°C. It was found that CuIn₅S₈ thin film is an n-type semiconductor at 250° C.

Keywords: CuIn; ₅; S; ₈; Spinel structure; Structural properties; Optical properties; Electrical properties

Optical waveguide with homogeneous refractive index profile in LiNbO₃ by double-low-energy Oxygen ion implantation by S.-M. Zhang; K.-M. Wang; X.-H. Liu; X.-B. Ming (pp. 10342-10345).

► The waveguide was formed by 550keV O ion followed by 250keV O ion implantation. ► A nearly homogeneous damage layer was formed in the annealed waveguide. ► A homogeneous near-field intensity profile was obtained from the waveguide. ► The estimated propagation loss is about 0.5dB/cm.We report on the formation of the planar waveguide by 550keV O ion followed by 250keV O ion implantation in lithium niobate (LiNbO₃), at fluences of 6×10¹⁴ions/cm² and 3×10¹⁴ions/cm², respectively. The Rutherford backscattering/channeling spectra have shown the atomic displacements in the damage region before and after annealing. A broad and nearly homogeneous damage layer has been formed by double-energy ion implantation after annealing. Both the dark mode spectra and the data of refractive index profile verified that the extraordinary refractive index was enhanced in the ion implanted region of LiNbO₃. A homogeneous near-field intensity profile was obtained by double-low-energy ion implantation. There is a reasonable agreement between the simulated modal intensity profile and the experimental data. The estimated propagation loss is about 0.5dB/cm.

Keywords: Planar waveguides; Lithium niobate; Integrated optics devices; Ion radiation effects

Converting ultrasonic induction heating deposited monetite coating to Na-doped HA coating on H₂O₂-treated C/C composites by a two-step hydrothermal method by Xiong Xin-bo; Hung Jian-feng; Zeng Xie-rong; Chu Cen-cen (pp. 10346-10350).

► A Na-doped HA coating was successfully prepared on C/C by a two-step hydrothermal method. ► The achieved Na-doped HA coating on C/C showed a bonding strength of 115.7N and a nanohardness of 2.08GPa. ► Incorporation of Na into HA lattice can enhance the mechanical performances.a monetite coating on H₂O₂-treated C/C composites was prepared by ultrasonic induction heating (UIH) technology. Subsequently, this coating was subjected to an ammonia hydrothermal treatment to form a undoped hydroxyapatite (U-HA) coating. Finally, the as-prepared U-HA coating was placed in a NaOH solution and hydrothermally treated to produce the other hydroxyapatite (Na-HA) coating. The structure, morphology and chemical composition of the two HA coatings were characterized by XRD, FTIR, SEM and EDS, the adhesiveness and local mechanical properties, e.g. nanohardness and Young's modulus of the two HA coatings to C/C composites was evaluated by a scratch test and nanoindentation technique respectively. The results showed that the two HA coatings had the alike morphology and crystallization. But, compared with the U-HA coating, the Na-HA coating was doped with Na ions, and gave a Ca/P ratio close to a stoichiometric hydroxyapatite, and thus showed a higher nano-indentation value, Young's modulus, and larger bonding strength. These results verified the strengthened effect of Na ion in hydroxyapatite coating on carbon/carbon (C/C) composities.

Keywords: Carbon/carbon composites; Hyroxyapatite; Coating; Induction heating deposition

Effect of Cr incorporation on the structural and optoelectronic properties of TiO₂:Cr deposited by means of a magnetron co-sputtering process by A. Hajjaji; M. Gaidi; B. Bessais; M.A. El Khakani (pp. 10351-10357).

► In this work, we report on the effect of Cr incorporation on the microstructural and optical properties of TiO₂:Cr thin films deposited by the RF-magnetron sputtering method. ► The structural, morphological, chemical bonding and optoelectronic properties of the sputter-deposited TiO₂:Cr films were systematically investigated, as a function the incorporated Cr content ► We were thus able to demonstrate that by varying P_Cr from 8W to 150W, the Cr content of the TiO₂:Cr films can be fairly controlled from ∼2at.% to ∼18at.% and their associated bandgap engineered from 3.3eV to 1.5eV.In this work, we report on the effect of Cr incorporation on the microstructural and optical properties of TiO₂:Cr thin films deposited by the RF-magnetron sputtering method. The structural, morphological, chemical bonding and optoelectronic properties of the sputter-deposited TiO₂:Cr films were systematically investigated, as a function the incorporated Cr content, by means of various techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-Transform Infra-Red (FTIR) absorption, X-ray Photoelectron Spectroscopy (XPS) and ellipsometry. The Cr incorporation into the TiO₂ films was controlled by adjusting the RF power ( P_Cr) on the Cr target during the co-sputtering process of TiO₂ and Cr. We were thus able to demonstrate that by varying P_Cr from 8W to 150W, the Cr content of the TiO₂:Cr films can be fairly controlled from ∼2at.% to ∼18at.% and their associated bandgap engineered from 3.3eV to 1.5eV. The room-temperature deposited TiO₂:Cr are mainly amorphous with the presence of some TiO₂ nanocrystallites, and their density increases as their Cr content is increased. The Cr inclusions were found to coexist under both metallic and oxidized forms in the films. By subjecting the TiO₂:Cr films to post-annealing treatment (at 550°C), their crystalline structure was found to be sensitive to their Cr content. Indeed, an anatase-to-rutile phase transformation has been pointed out to occur at a Cr content of ∼7at.%. Likewise, the Cr-content dependence of the bandgap of annealed TiO₂:Cr films undergoes a transition around the 7at.% of Cr. Our results demonstrate the ability to control the Cr-content of TiO₂:Cr films, which leads to tune their optoelectronic properties, such as bandgap or optical absorption edge.

Keywords: Titanium oxide films; Cr; Magnetron sputtering; Bandgap engineering; Phase transition

Effects of growth duration on the structural and optical properties of ZnO nanorods grown on seed-layer ZnO/polyethylene terephthalate substrates by Y.I. Jeong; C.M. Shin; J.H. Heo; H. Ryu; W.J. Lee; J.H. Chang; C.S. Son; J. Yun (pp. 10358-10362).

► ZnO nanorods were well-formed for up to 5h, but leaned and agglomerated after 5h of growth. ► The structural and optical properties of ZnO nanorods were improved after 5 and 6h, respectively. ► The growth properties of ZnO nanorods are dependent on growth duration in hydrothermal method.Well-aligned single crystalline zinc oxide (ZnO) nanorods were successfully grown, by hydrothermal synthesis at a low temperature, on flexible polyethylene terephthalate (PET) substrates with a seed layer. Photoluminescence (PL), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) measurements were used to analyze the optical and structural properties of ZnO nanorods grown for various durations from 0.5h to 10h. Regular and well-aligned ZnO nanorods with diameters ranging from 62nm to 127nm and lengths from 0.3μm to 1.65μm were formed after almost 5h of growth. The growth rate of ZnO grown on PET substrates is lower than that grown on Si (100) substrates. Enlarged TEM images show that the tips of the ZnO nanorods grown for 6h have a round shape, whereas the tips grown for 10h are sharpened. The crystal properties of ZnO nanorods can be tuned by using the growth duration as a growth condition. The XRD and PL results indicate that the structural and optical properties of the ZnO nanorods are most improved after 5h and 6h of growth, respectively.

Keywords: Zinc oxide (ZnO); Hydrothermal synthesis; Polymer substrate; HRTEM; XRD; PL; Structural properties; Optical properties

Numerical and experimental investigations of splat geometric characteristics during oblique impact of plasma spraying by Chang-Wei Kang; Jiak Kwang Tan; Lunsheng Pan; Cheng Yee Low; Ahmed Jaffar (pp. 10363-10372).

► Time history of droplet evolution has been carried out via CFD software FLOW-3D^®. ► Splats are obtained experimentally and characterized by SEM and WYKO^® optical surface profiler. ► Experiments and simulations are conducted for four substrate inclination angles and fair agreements are obtained. ► Simulation provides more insights into the dynamics of droplet impact. ► Simulation shows that droplet spreading is completed earlier than solidification.Splats are obtained on the substrates inclined at different angles (0°, 20°, 40° and 60°) by plasma spraying process and characterized by SEM and WYKO^® optical surface profiler. Numerical model is developed using CFD software FLOW-3D^® to simulate the process of droplet impact, spreading and solidification onto the substrates. Splat characteristics such as spread factor, aspect ratio and fractional factor are defined and compared between simulation and experiment. Fair agreements are obtained. In addition, the impacting behavior including spreading and solidification are analyzed in details from the simulation results. The rates of reduction in droplet kinetic energy during impact, spreading and solidification are also compared between different inclination angles.

Keywords: Splat; Oblique impact; Spreading; Solidification and inclined substrate

Characterization and properties Ti–Al–Si–N nanocomposite coatings prepared by middle frequency magnetron sputtering by C.W. Zou; J. Zhang; W. Xie; L.X. Shao; L.P. Guo; D.J. Fu (pp. 10373-10378).

► TiN-containing amorphous Ti–Al–Si–N (nc–TiN/a–Si₃N₄ or a–AlN) nanocomposite coatings were deposited by using a modified closed field twin unbalanced magnetron sputtering system. ► The hardness of the Ti–Al–Si–N coatings deposited at Si targets currents of 5, 8, 10, and 12A were 45, 47, 54 and 46GPa, respectively. ► The friction coefficient of coatings deposited at 5, 8, 10 and 12A were 0.85, 0.76, 0.75 and 0.69, respectively.TiN-containing amorphous Ti–Al–Si–N (nc–TiN/a–Si₃N₄ or a–AlN) nanocomposite coatings were deposited by using a modified closed field twin unbalanced magnetron sputtering system which is arc assisted and consists of two circles of targets, at a substrate temperature of 300°C. XRD, XPS and High-resolution TEM experiments showed that the coatings contain TiN nanocrystals embedded in the amorphous Si₃N₄ or AlN matrix. The coatings exhibit good mechanical properties that are greatly influenced by the Si contents. The hardness of the Ti–Al–Si–N coatings deposited at Si targets currents of 5, 8, 10, and 12A were 45, 47, 54 and 46GPa, respectively. The high hardness of the deposited Ti–Al–Si–N coatings may be own to the plastic distortion and dislocation blocking by the nanocrystalline structure. On the other hand, the friction coefficient decreases monotonously with increasing Si contents. This result would be caused by tribo-chemical reactions, which often take place in many ceramics, e.g. Si₃N₄ reacts with H₂O to produce SiO₂ or Si(OH)₂ tribolay-layer.

Keywords: Ti–Al–Si–N nanocomposite coatings; Middle-frequency magnetron sputtering; Friction coefficient; Hardness

One step synthesis and characterization of CdS nanorod/graphene nanosheet composite by Kejie Zhang; Xiaoheng Liu (pp. 10379-10383).

► CdS nanorod/graphene nanosheet nanocomposite was synthesized by one-step pyrolysis process. ► Well-dispersed and coated CdS nanorods were obtained by acid treatment method. ► The acid-treated nanocomposite presented remarkable fluorescence quenching effect.In this work, an one-step approach to synthesize a CdS nanorod/graphene nanosheet (CdS/GNS) nanocomposite by the pyrolysis of a single-source precursor (bis(2-mercaptobenzothiazolato)-cadmium (II)) under nitrogen atmosphere were reported. X-ray diffraction result showed that the CdS nanorods belong to hexagonal crystal system. Transmission electron microscopy observations demonstrated that the CdS nanorods were coated by the graphene nanosheets effectively. Furthermore, the optical properties of the CdS/GNS nanocomposite were characterized by fluorescence spectroscopy. The nanocomposite displayed remarkable fluorescence quenching effect, implying that there was a high-efficiency energy transfer between graphene nanosheets and coated CdS nanorods, which could be applied in new optoelectronic or photovoltaic devices.

Keywords: One-step synthesis; CdS nanorods; Graphene nanosheet; Nanocomposite; Fluorescence quenching

Versatile functionalization of Fe₃O₄ nanoparticles via RAFT polymerization and click chemistry by Yang Zhou; Shixing Wang; Keqiang Xie; Yongnian Dai; Wenhui Ma (pp. 10384-10389).

• Fe₃O₄ NPs can be modified simultaneously by RAFT polymerization and click chemistry. • The results showed that PEGMA was successfully grafted onto the surface of Fe₃O₄ NPs by RAFT polymerization and click coupling reaction. • The functionalized Fe₃O₄ NPs have the larger saturation magnetization, which enables them very susceptible to magnetic fields and consequently makes the liquid phase separate easily.Azide-functionalized chain transfer agent (CTA) was synthesized and subsequently employed to mediate the reversible addition fragmentation transfer (RAFT) polymerization of poly(ethylene glycol) monomethacrylate (PEGMA) on the alkyne-functionalized Fe₃O₄ nanoparticles surface together with click chemistry. In a single pot procedure, azide-functionalized CTA, alkyne-functionalized Fe₃O₄ and PEGMA were combined to produce the desired product. Fourier transformed infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results showed that PEGMA chains were grafted to Fe₃O₄ nanoparticles using RAFT polymerization and click chemistry.

Keywords: Fe; ₃; O; ₄; nanoparticles; Poly(ethylene glycol) monomethacrylate; Click chemistry; Reversible addition fragmentation chain transfer polymerization

Structural evolution of self-ordered alumina tapered nanopores with 100nm interpore distance by Juan Li; Congshan Li; Xuefeng Gao (pp. 10390-10394).

► Profiles of alumina taper-pores evolve with cyclic anodizing and etching. ► Matched cyclic times, anodizing and etching time is vital to high-quality taper-pore. ► Overmuch etching can cause side effects such as wall-breaking and thinning. ► Roles of anodizing and etching and their co-effects on taper-pore are revealed.We in-detail investigated the profile evolution processes of highly ordered alumina under the cyclic treatment of mild anodizing of aluminum foils in oxalic acid followed by etching in phosphoric acid. With the cyclic times increasing, the profiles of nanopores were gradually evolved into the parabola-like, trumpet-like and conical shape. Although the inserted etching itself nearly had no impact on the growth rate of the nanopores due to the rapid recovering of thinned barrier layer at the initial stage of next anodizing, overmuch etching could bring apparent side effects such as wall-breaking, thinning and taper-removing from the top down. The anodizing and etching kinetics and their synergetic effects in modulating different aspect ratios and open sizes of conical pores were studied systematically. These findings are helpful to tailor high-quality anodic alumina taper-pores with tunable profiles.

Keywords: Porous anodic alumina; Tapered; Conical; Anodizing; Etching

Surfactant-assisted synthesis of Ag nanostructures and their self-assembled films on copper and aluminum substrate by Yujiang Zhuo; Wendong Sun; Lihong Dong; Ying Chu (pp. 10395-10401).

Silver nanostructures with controlled morphologies, such as assembly of plates, rods, belts and sheets have been prepared on copper and aluminum substrates by a surfactant-assisted colloidal chemical method.Display Omitted► A facile surfactant-assisted chemical solution approach was exploited. ► Control the release rate of Ag atoms from AgNO₃ and the reaction rate in the solution. ► A cooperative effect of surfactant and chloride ion had great impact on the morphologies of Ag nanostructures on aluminum substrate.In this paper, silver nanostructures with controlled morphologies, such as plates, rods, belts, sheets and their self-assembled films have been prepared on copper and aluminum substrates by a surfactant-assisted colloidal chemical method. The X-ray powder diffraction (XRD) and the selected area electron diffraction (SAED) patterns indicated that the Ag nanostructures grew on the substrates with cubic symmetry and single-crystalline in nature. An oriented attachment with surfactant-assisted mechanism and a cooperative effect of surfactant and chloride ion on the morphology of Ag nanostructures were investigated systematically and synthetically.

Keywords: Surfactant-directed; Ag nanostructures; Self-assembled nanoparticles film; Chemical synthesis

Investigation of crystal structure and new ellipsometric properties of hexagonal CdS epilayers by D.J. Kim; Y.D. Choi; J.W. Lee; J.C. Sur (pp. 10402-10407).

High quality hexagonal CdS epilayer was grown on GaAs (111) substrates by the hot-wall epitaxy method. The crystal structure of the grown CdS epilayers was confirmed to be the hexagonal structure by X-ray diffraction pattern and scanning electron microscopy image. The optical properties of the hexagonal CdS epilayers were investigated in a wide photon energy range between 2.0 and 8.5eV using spectroscopic ellipsometry (SE) at room temperature. The data obtained by SE were analyzed to find the critical points of the pseudodielectric function spectra, 〈 ɛ( E)〉=〈 ɛ₁( E)〉+ i〈 ɛ₂( E)〉, such as E₀, E_1A, E_1B,E0′, F₁, and two E₂ structures. In addition, the second derivative spectra, d² ɛ( E)/ dE², of the pseudodielectric function of hexagonal CdS epilayers were numerically calculated to determine the critical structures. Four structures, such asE0′ F₁, and two E₂ structures, from 6.0eV to 8.0eV were observed, for the first time, at 300K by ellipsometric measurements for the hexagonal CdS epilayers.

Keywords: Hexagonal-CdS; Spectroscopic ellipsometry; Hot-wall epitaxy; SEM image; Pseudodielectric function

Electrocatalysis of oxygen reduction reaction on Nafion/platinum/gas diffusion layer electrode for PEM fuel cell by Sekineh Chabi; Mehdi Kheirmand (pp. 10408-10413).

► New gas diffusion electrode based on Pt-coated Nafion membrane was fabricated. ► Electroless method was used to deposit platinum on Nafion membrane. ► Electrochemical and chemical results showed good deposition of platinum particles on Nafion membrane. ► Compared with traditional electrode, new electrode based on Pt-coated Nafion membrane exhibited improved polarization performance.In this work a new membrane electrode based on Pt-coated Nafion membrane was fabricated. Chemical deposition process was used to coat platinum on Nafion 117 membrane and then Pt-coated Nafion membrane was hot pressed on gas diffusion layer (GDL) to make new membrane electrode. The electrochemical and chemical studies of the Pt-coated Nafions were investigated by electrochemical techniques, X-ray diffraction and scanning electron microscopy. The electrochemical results indicated that as the concentration of H₂PtCl₆ increased, the oxygen reduction reaction rate increased until the concentration was reached where the reduction reaction was limited by the problem of mass transport. The electrochemical results for oxygen reduction reaction showed that the new electrode which prepared by plating Nafion membrane with 0.06M H₂PtCl₆ in electroless plating solution, has a higher performance than other electrodes. The XRD results showed that the average platinum particle size of the best sample was about 3nm. The loading of platinum for this electrode was 0.153mgcm⁻².

Keywords: Platinum; Electroless plating; Oxygen reduction reaction; Nafion membrane; Gas diffusion electrode; Proton exchange membrane fuel cell

Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings by Zhiming Li; Shiqiang Qian; Wei Wang (pp. 10414-10420).

► The roughness of the NiCoCrAlY coating increases with the increasing of substrate roughness. ► The coatings present slightly lower roughness than the corresponding substrate. ► Coatings with smoother substrates possess better adhesion than those with rougher substrates. ► Coatings on substrates with lower roughness provide higher antioxidant protection than those provided by coatings with rougher substrate.The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100°C in air for 50 cycles, each cycle consisting of 1h heating in the tube furnace followed by 15min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate.

Keywords: Surface roughness; Real surface area; Adhesion; Oxidation behavior; NiCoCrAlY coating; Magnetron sputtering

Superhydrophobic sol–gel nanocomposite coatings with enhanced hardness by R.V. Lakshmi; T. Bharathidasan; Bharathibai J. Basu (pp. 10421-10426).

► Hard superhydrophobic sol–gel composite coatings were fabricated using a sol of Methyltriethoxysilane and colloidal silica. ► They had a highly porous structure with nano size voids and micron size bumps. ► They exhibited very good hardness and adhesion strength with the substrate. ► Superhydrophobicity in these coatings is a combined effect of surface roughness and low surface energy due to siloxane bond network formation.Sol–gel superhydrophobic coatings with improved hardness were prepared by embedding fumed silica nanoparticles in a partially condensed hybrid sol of methyltriethoxysilane (MTEOS) and colloidal silica. Fumed silica particles of size 25–30nm were incorporated in the sol and the mixture was spray-coated on glass substrate. Water contact angle (WCA) of the composite coating increased with increase in silica content of the sol mixture. The concentration of silica in the sol mixture was optimized to obtain robust superhydrophobic coatings with a WCA of 162.5° and a pencil hardness of 5H. The wetting state of water droplet on the sol–gel composite coatings was analysed with both Wenzel and Cassie-Baxter models.

Keywords: Superhydrophobic; Sol–gel; Colloidal silica; Hardness; Roughness

Investigation on femtosecond laser irradiation energy in inducing hydrophobic polymer surfaces by Z.K. Wang; H.Y. Zheng; Y.C. Lam (pp. 10427-10433).

► Ultrashort femtosecond laser pulses can induce hydrophobic properties on PMMA surfaces. ► The wettability modification depends on the laser energy deposition. ► A simple equation deduced from the laser parameters can express the energy deposition. ► Water contact angle exceeds 120° with a maximum of around 125° at the energy deposition range 600–900J/cm².This study investigates the use of ultrashort femtosecond laser pulses to induce hydrophobic properties on PMMA surfaces. The modification of surface wetting property exhibits a strong dependence on the amount of energy deposited on the PMMA surface. A simple equation has been deduced from the laser parameters to express the energy deposition. It was revealed that water contact angle (WCA) of more than 120°, with a maximum of around 125°, could be achieved when the total energy deposited per unit area on the PMMA surface ranged from 600J/cm² to 900J/cm² at an energy deposition rate of around 50J/cm²/s. Beyond this range, WCA reduced with increasing amount of energy deposition. Furthermore, with higher energy deposition rate or higher laser fluence, total energy required to induce hydrophobic surfaces was reduced. Under different energy deposition, the quantity of polar groups or non-polar groups induced was responsible for the changes in WCA and thus the different surface hydrophobicity.

Keywords: Wettability; PMMA; Femtosecond laser irradiation; Surface modification

Sputter deposition of high transparent TiO2−_xN_x/TiO₂/ZnO layers on glass for development of photocatalytic self-cleaning application by B. Abdollahi Nejand; S. Sanjabi; V. Ahmadi (pp. 10434-10442).

► In this study, TiO2−_xN_x/TiO₂/ZnO multilayer thin film was deposited on ZnO (80nm thickness)/soda–lime glass substrate by a dc reactive magnetron sputtering. ► The results showed that by nitrogen doping of a fraction (∼1/5) of TiO₂ film thickness, the optical transmittance of TiO2−_xN_x/TiO₂ film was improved than TiO₂ thin film. ► The optical transmittance of the film on glass was not destroyed by this doping due to considering doping of only fraction of TiO₂ coating thickness. ► Besides, the films showed also good photocatalytic and hydrophilicity activity in visible light. So, the low absorption edge of TiO₂ in visible light range was improved by nitrogen doping.In this study, TiO2−_xN_x/TiO₂ double layers thin film was deposited on ZnO (80nm thickness)/soda–lime glass substrate by a dc reactive magnetron sputtering. The TiO₂ film was deposited under different total gas pressures of 1Pa, 2Pa, and 4Pa with constant oxygen flow rate of 0.8sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2sccm in constant total gas pressure of 4Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600°C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet–visible light (UV–vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (∼1/5) of TiO₂ film thickness, the optical transmittance of TiO2−_xN_x/TiO₂ film was compared with TiO₂ thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light.

Keywords: N-doped TiO; ₂; film; Optical transmittance; Visible light hydrophilicity; Photochemical; Sputtering

A histogram-based segmentation method for characterization of self-assembled hexagonal lattices by Mohammad J. Abdollahifard; Karim Faez; Mohammadreza Pourfard; Mojtaba Abdollahi (pp. 10443-10450).

► A new robust method to localize the domains of nano-porous alumina images is introduced. ► A three step robust preprocessing technique is employed to convert the original image into a binary one. ► A new distinguishing criterion, orientation, is employed, to segment the image into its domains, which makes the segmentation part of our algorithm significantly robust against ordering tolerance parameters. ► A new concept of angle-histogram is proposed in this paper. ► Angle-histogram analysis enables us to segment the image into domains in an unsupervised way.Lattice characterization techniques are often used to quantify the effects of different anodization conditions on nano-porous anodized aluminum oxides. In this work, we develop a comprehensive hexagonal lattice characterization method to evaluate the amount of ordering of the lattice and localize the domains of the image and report their characteristics. A robust preprocessing is proposed to find pores’ centroids. Different domains of SEM images usually have different orientations. Pores orientation distribution is analyzed using angle-histogram. The valleys of angle-histogram are employed as thresholds to separate different dominant orientations. We show that using orientation as a distinguishing feature of different domains, significantly improves the robustness of the algorithm against tolerance parameters. Some new parameters are introduced to exactly characterize each of the domains and the whole lattice.

Keywords: Nanostructures; Quantitative grain analysis; Anodic alumina oxide characterization; Image processing

Modulation of residual stress in diamond like carbon films with incorporation of nanocrystalline gold by R. Paul; S.R. Bhattacharyya; R. Bhar; A.K. Pal (pp. 10451-10458).

► Nanocrystalline gold doped diamond like carbon films were synthesized. ► Residual stress in the films was estimated through a nondestructive way using optical absorption band tail broadening. ► Stress was found to dependent on relative amount of sp²/sp³ hybridized carbon atoms in the films. ► Films became stress relieved upon gold incorporation.Residual stress modulation in the diamond-like carbon coatings with incorporation of gold nanoparticles was studied critically. The films were deposited on glass and Si (100) substrates by using capacitatively coupled plasma chemical vapor deposition. Stresses in the films were determined from the broadening of the optical absorption tail and were found to decrease from 2.3GPa to 0.48GPa with increasing gold content (2–7at.% Au) in the DLC matrix. Gold incorporation also made the films harder than the corresponding DLC coatings. Modulation of stress with nanocrystalline gold content in the DLC matrix was related to the relative amount of sp²/sp³ content in the DLC films.

Keywords: Diamond-like carbon; Nanocrystalline gold; Stress

Surface and interface properties of carbon fiber composites under cyclical aging by Xinying Lv; Rongguo Wang; Wenbo Liu; Long Jiang (pp. 10459-10464).

Display Omitted► Subject carbon fiber–reinforced BMI composites to combination cycling aging. ► Determine the flexural and inter-laminar shear strength of composite at various aging intervals. ► Characterize the composite at various aging intervals accordingly. ► Analyze the effects of cycling aging on surface and interface properties of carbon fiber–BMI composites.Carbon fiber–reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have been characterized by FTIR, SEM/EDXA, XRD, and moisture-uptake determination. The results indicated that combination accelerated aging had great effects on the mechanical properties of the composite, the network structure of the BMI matrix, and the moisture uptake by the composite. After a third cycle of accelerated aging, moisture reached the center layer of the composite and as a result led to an obvious decrease in ILSS due to deterioration of the carbon fiber–BMI interface. Sufficient moisture absorption on the composite surface made the network structure of the BMI matrix more open, which facilitated stress relaxation and the creation of micro-cracks, with a consequent obvious decrease in flexural strength. With increasing number of combined-action accelerated aging cycles, ever more moisture was absorbed during each hygrothermal process due to the plasticizing effect of water, and micro-cracks propagated as a result of internal stresses caused by the hygrothermal process, the thermal-oxidative process, and the freezing process of each cycle. XRD analysis indicated that moisture penetrated through the amorphous region of the BMI matrix.

Keywords: Composites; Accelerated aging; Mechanical properties; Structure–property relations; Carbon fiber; Bis-maleimide resin

STM study of successive Ge growth on “V”-stripe patterned Si (001) surfaces at different growth temperatures by B. Sanduijav; D.G. Matei; G. Springholz (pp. 10465-10470).

Display Omitted► Ge growth on stripe-patterned Si leads to significant side wall roughening. ► Onset of 3D island formation at about 4.5–5 monolayers. ► Nucleation sites of Ge islands strongly depends on the growth temperature. ► Low growth temperature: Islands formed on top of the ridges. ► High growth temperature: Islands are formed at the bottom of grooves.1Present address: University of Bielefeld, D-33501 Bielefeld, Germany.The self-assembly process of Ge islands on patterned Si (001) substrates is investigated using scanning tunneling microscopy. The substrate patterns consist of one-dimensional stripes with “V”-shaped geometry and sidewalls inclined by an angle of 9° to the (001) surface. Onto these stripes, Ge is deposited in a step-wise manner at different temperatures from 520°C to 650°C. At low temperature, the Ge first grows nearly conformally over the patterned surface but at about 3 monolayers a strong surface roughening due to reconstruction of the surface ridges as well as side wall ripple formation occurs. At 600°C, a similar roughening takes place, but Ge accumulates within the grooves such that at a critical thickness of 4.5 monolayers, 3D islands are formed at the bottom of the grooves. This accumulation process is enhanced at 650°C growth, so that the island formation starts about 1 monolayers earlier. At 600 and 650°C, all islands are all aligned at the bottom of the stripes, whereas at 550°C Ge island form preferentially on top of ridges. The experimental observations are explained by the strong temperature dependence of Ge diffusion over the patterned surface.

Keywords: Silicon; Germanium; Quantum dots; Scanning tunneling microscopy; Molecular beam epitaxy; Self-assembly

Diameter-dependent thermal-oxidative stability of single-walled carbon nanotubes synthesized by a floating catalytic chemical vapor deposition method by Jie Ma; Fei Yu; Zhiwen Yuan; Junhong Chen (pp. 10471-10476).

Display Omitted► The present study reports the continuous synthesis of SWCNTs controllably from ∼1nm to ∼5nm. ► Different-diameter SWCNTs present many special properties without any complicated functionalization. ► The thermal-oxidation rate of SWCNTs varies inversely with the tube diameter.In this paper, purified single-walled carbon naotubes (SWCNTs) with three different diameters were synthesized using a floating catalytic chemical vapor deposition method with ethanol as carbon feedstock, ferrocene as catalyst, and thiophene as growth promoter. The thermal-oxidative stability of different-diameter SWCNTs was studied by using thermal analysis (TG, DTA), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. The results indicate that small diameter SWCNTs (∼1nm) are less stable and burn at lower temperature (610°C), however, the larger diameter SWCNTs (∼5nm) survive after burning at higher temperature (685°C), the oxidation rate varies inversely with the tube diameter of SWCNTs, which may be concluded that the higher oxidation-resistant temperature of larger diameter SWCNTs can be attributed to the lower curvature-induced strain by rolling the planar graphene sheet for the larger diameter, so small tubes will become thermodynamically unstable.

Keywords: Diameter-dependent; Thermal stability; Single-walled carbon nanotubes

Behavior of Ru surfaces after ozonated water treatment by Dongwan Seo; Chanhyoung Park; Juneui Jung; Mihyun Yoon; Dongwook Lee; Chang Yeol Kim; Sangwoo Lim (pp. 10477-10482).

► Study on the Ru surfaces after ozonated deionized water treatment. ► Ru surface roughening with a longer DIO₃ cleaning. ► No significant changes in crystalline structures or chemical states of the Ru surfaces. ► No similarities with the structures or states of ruthenium oxide. ► Observation of adsorption of H₂O molecules on the Ru surface.In order for the development of cleaning technology of extreme ultra violet lithography photomask, the behavior of Ru surfaces after treatment with ozonated deionized water (DIO₃) solution was studied using Ru and ruthenium oxide particles and 2nm-thick Ru capping layers. No significant changes in crystalline structures or chemical states of the Ru surfaces, nor any similarities with the structures or states of ruthenium oxide, were observed after DIO₃ treatment. Oxidation of ruthenium to form RuO₂ or RuO₃ was not observed. Adsorption of H₂O molecules on the Ru layer increased the surface roughness, but the desorption of H₂O molecules recovered it. Local chemisorption of H₂O molecules on the Ru surface may be the reason why rougher Ru surfaces were observed after DIO₃ cleaning.

Keywords: EUV; Photomask; Surface; Cleaning; Oxidation

Synthesis of carbon supported palladium nanoparticles catalyst using a facile homogeneous precipitation-reduction reaction method for formic acid electrooxidation by Juan Ma; Yigang Ji; Hanjun Sun; Yu Chen; Yawen Tang; Tianhong Lu; Junwei Zheng (pp. 10483-10488).

► A facile homogeneous precipitation-reduction reaction is used to prepare Pd/C catalyst. ► [PdCl₄]²⁻ species can slowly transformed into the insoluble PdO·H₂O precipitation. ► A ultrafine Pd/C catalyst is synthesized by PdO·H₂O→Pd⁰ in situ reduction reaction path. ► The Pd/C catalyst possesses excellent catalytic performance for formic acid oxidation.A highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst is synthesized by a facile homogeneous precipitation-reduction reaction method. Under the appropriate pH conditions, [PdCl₄]²⁻ species in PdCl₂ solution are slowly transformed into the insoluble palladium oxide hydrate (PdO·H₂O) precipitation by heat treatment due to a slow hydrolysis reaction, which results in the generation of carbon supported PdO·H₂O nanoparticles (PdO·H₂O/C) sample with the high dispersion and small particle size. Consequently, a highly dispersed and ultrafine Pd/C catalyst can be synthesized by PdO·H₂O→Pd⁰ in situ reduction reaction path in the presence of NaBH₄. As a result, the resulting Pd/C catalyst possesses a significantly electrocatalytic performance for formic acid electrooxidation, which is attributed to the uniformly sized and highly dispersed nanostructure.

Keywords: Direct formic acid fuel cell; Homogeneous precipitation; Palladium catalyst; Formic acid electrooxidation; Electrocatalytic activity

Multiform structures with silicon nanopillars by cesium chloride self-assembly and dry etching by Yuan-xun Liao; Jing Liu; Bo Wang; Fu-ting Yi (pp. 10489-10493).

Display Omitted► Nanopillars homogeneously cover uneven surface by dry etch with CsCl nanoislands. ► Wettability and roughness of substrate influence CsCl mask formation. ► Formation within 1min and process flow within 30min are possible. ► 2D patterns are realized by using photoresist as lift-off or intermediate layer. ► Two rounds of 2D process enable 3D patterns of nanopillars.We develop a novel method to fabricate multiform structures of Si nanopillars (diameters>40nm, aspect ratio>10, coverage ratio>35%) by dry etch with self-assembled cesium chloride (CsCl) nanoislands as mask. The pillars can cover structures of lateral size 1μm and unpolished Si wafer, enabling uneven surface to be textured by nanopillars without complex process or expensive polishing. Planar micro-patterns and tridimensional localization of nanopillars have been easily realized, useful for integrating nanopillars to devices. By figuring out substrate influences, fast formation of CsCl islands within 1min has been achieved for the first time, making CsCl process flow to be possibly controlled within 30min. Based on the deliquescence of salt, CsCl self-assembly is simple, widely tunable and compatible, which endows the approaches great practical potential.

Keywords: Silicon nanopillar; Cesium chloride self-assembly; Dry etching

Growth of branched rutile TiO₂ nanorod arrays on F-doped tin oxide substrate by Hong Zhu; Jie Tao; Tao Wang; Jie Deng (pp. 10494-10498).

.Display Omitted► Branched TiO2 nanorod(TiO2-NB) arrays were hydrothermally grown on FTO substrate. ► The TiO2-NB film presented superior photocatalytic activity than P25 particulate film. ► Direct electrical pathway and enhanced light-harvesting efficiency were key factors for the superior photocatalytic activity of the TiO2-NB film.Branched rutile TiO₂ nanorod arrays were directly synthesized on the F-doped tin oxide (FTO) substrate through a two-step hydrothermal treatment by a seeding method with TiO₂-nanorods as seeds. The samples were characterized respectively by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Results showed that TiO₂ nanorods with nanobranches (TiO₂-NB) grew vertically on the FTO substrate. XRD and HRTEM results confirmed that the TiO₂-NB arrays were single-crystalline rutile. The optical properties of the samples were studied with a UV–vis spectrometer. The photocatalytic activity of the TiO₂-NB film is better than that of P25 particulate film. Direct electrical pathway and improved light-harvesting efficiency were crucial for the superior photocatalytic activity of the TiO₂-NB arrays.

Keywords: Rutile TiO; ₂; Nanorod arrays; Nanobranch; Hydrothermal; Photocatalytic activity

Studies on the structural and electrical properties of F-doped SnO₂ film prepared by APCVD by Jingkai Yang; Wenchang Liu; Lizhong Dong; Yuanxun Li; Chuan Li; Hongli Zhao (pp. 10499-10502).

► SnO was present in SnO₂ film. ► Large polyhedron-like grains were distributed over small round grains. ► When heated for 262s, the oxygen content in the surface increased to 83.38%. ► After heated, The resistivity increased, carrier concentration decreased. ► μ is limited by ionized impurity scattering rather than grain boundary scattering.Fluorine-doped tin oxide films (SnO₂:F, FTO) were deposited by atmosphere pressure chemical vapor deposition (APCVD) on Na–Ca–Si glass coated with a diffusion barrier layer of SiO_xC_y. The effects of post-heating time at 700°C on the structural and electrical properties of SnO₂:F films were investigated. The results showed that SnO₂:F films were polycrystalline with tetragonal SnO₂ structure, SnO phase was present in SnO₂ film, and abnormal grain growth was observed. The element distribution in the film depth was measured with X-ray photoelectron spectroscopy (XPS) and revealed that when the heating time increased from 202s to 262s, the oxygen content in the surface increased from 78.63% to 83.38%. The resistivity increased from 3.13×10⁻⁴ for as-deposited films to 4.73×10⁻⁴Ωcm when post-heated for 262s. Hall mobility is limited by the ionized impurity scattering rather than the grain boundary scattering.

Keywords: Thin films; Vapor deposition; Photoelectron spectroscopy; Crystal structure; Electrical properties

Comparison of reactivity on step and terrace sites of Pd (332) surface for the dissociative adsorption of hydrogen: A quantum chemical molecular dynamics study by Farouq Ahmed; Ryo Nagumo; Ryuji Miura; Suzuki Ai; Hideyuki Tsuboi; Nozomu Hatakeyama; Akira Endou; Hiromitsu Takaba; Momoji Kubo; Akira Miyamoto (pp. 10503-10513).

Display Omitted► The exact nature of the active sites hence the mechanism by which they act, are still largely a matter of speculation. ► We have presented QCMD calculations for the interaction of H₂ on different step and terrace sites of the Pd (332) surface. ► Saturated step sites can dissociate H₂ moderately and that a monovacancy surface is suitable for significant dissociation. ► However in terrace site dissociation of H₂ takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed H atom. ► We identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage.The notion of “active sites” is fundamental to heterogeneous catalysis. However, the exact nature of the active sites, and hence the mechanism by which they act, are still largely a matter of speculation. In this study, we have presented a systematic quantum chemical molecular dynamics (QCMD) calculations for the interaction of hydrogen on different step and terrace sites of the Pd (332) surface. Finally the dissociative adsorption of hydrogen on step and terrace as well as the influence of surface hydrogen vacancy for the dissociative adsorption of hydrogen has been investigated through QCMD. This is a state-of-the-art method for calculating the interaction of atoms and molecules with metal surfaces. It is found that fully hydrogen covered (saturated) step sites can dissociate hydrogen moderately and that a monovacancy surface is suitable for significant dissociative adsorption of hydrogen. However in terrace site of the surface we have found that dissociation of hydrogen takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed hydrogen atoms. Furthermore, from the molecular dynamics and electronic structure calculations, we identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage and directional dependence of atomic hydrogen diffusion on stepped palladium surface.

Keywords: Dissociation; Adsorption; Surface defects; Quantum chemical molecular dynamics method

A new approach to immobilize poly(vinyl alcohol) on poly(dimethylsiloxane) resulting in low protein adsorption by Leandro B. Carneiro; Jacqueline Ferreira; Marcos J.L. Santos; Johny P. Monteiro; Emerson M. Girotto (pp. 10514-10519).

► Room temperature immobilization of PVA on plasma oxidized PDMS surface. ► Long-term hydrophilic, neutral, and non-fouling surface. ► Fast procedure to obtain a high-performance PDMS surface for application in microfluidic systems.The hydrophobic characteristics of PDMS and non-specific protein adsorption are major drawbacks for its application in biosensing. Here we have combined surface oxidation by plasma and chemical binding of polyvinyl alcohol (PVA) to obtain long-term stability of hydrophilic PDMS surfaces. Mercaptopropyltrimethoxisilane and aminopropyltrimethoxisilane were used as adhesives between the plasma-oxidized PDMS surface and the PVA, immobilized at room temperature. This approach has allowed for fast, uniform, and very stable modification of the PDMS surface, which maintained a hydrophilic character for as long as 30 days. In addition, the modified hydrophilic surface presented minimized protein adsorption when compared to pristine PDMS. The results obtained in this work are important contributions to the growing field of integrated microfluidic biosensors.

Keywords: Polydimethylsiloxane; PDMS; PVA; Protein adsorption; Microfluidics; Biosensors

Surface chemical study on the covalent attachment of hydroxypropyltrimethyl ammonium chloride chitosan to titanium surfaces by Xiaofen Xu; Ling Wang; Shengrong Guo; Lei Lei; Tingting Tang (pp. 10520-10528).

► Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) with a degree of substitution of 18% was synthesized. ► HACC was bonded to the surface of titanium foil by a three-step process. ► XPS and FT-IR were used for the surface chemical analysis, showing that HACC was successfully bonded to the surface of titanium foil. ► The HACC-modified titanium foil might have promising application in orthopaedics and other related fields.An anti-microbial and bioactive coating could not only reduce the probability of infection related to titanium implants but also support the growth of surrounding osteogenic cells. Our previous study has showed that hydroxypropyltrimethyl ammonium chloride chitosan (HACC) with a DS (degrees of substitution) of 18% had improved solubility and significantly higher antibacterial activities against three bacteria which were usually associated with infections in orthopaedics. In the current study, HACC with a DS of 18% coating was bonded to titanium surface by a three-step process. The titanium surface after each individual reaction step was analyzed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection (ATR) of Fourier-transformed infrared (FT-IR) spectroscopy. The XPS results demonstrated that there were great changes in the atomic ratios of C/Ti, O/Ti, and N/Ti after each reaction step. The XPS high resolution and corresponding devolution spectra of carbon, oxygen, nitrogen, and titanium were also in good coordination with the anticipated reaction steps. Additionally, the absorption bands around 3365cm⁻¹ (–OH vibration), 1664cm⁻¹ (Amide I), 1165cm⁻¹ ( ν_as, C–O–C bridge), and the broad absorption bands between 958cm⁻¹ and 1155cm⁻¹ (skeletal vibrations involving the C–O stretching of saccharide structure of HACC) verified that HACC was successfully attached to titanium surface.

Keywords: HACC; Surface modification; Anti-microbial coatings; XPS; FT-IR/ATR

2-Mercaptobenzothiazole doped chitosan/11-alkanethiolate acid composite coating: Dual function for copper protection by Qi Bao; Dun Zhang; Yi Wan (pp. 10529-10534).

► A new composite coating with anticorrosion and antibacterial properties has been fabricated with a facile method. ► High protective efficiency was achieved with much less inhibitors. ► The prepared composite coating can provide protection in both aerated and hydrogen sulphide-containing sodium chloride solution. ► Even the dissolved chitosan macromolecule is still bactericidal active against sulphate reducing bacteria.Chitosan (CS) hydrogel loaded with the well-known corrosion inhibitor 2-mercaptobenzothiazole (MBT) has been introduced into a composite coating to improve copper protection. This composite coating, which has both anticorrosion and antibacterial properties, was fabricated onto the surface of copper by combining a simple self-assembled monolayer technique with a sol–gel method. The anti-corrosion ability of the coating in 3.5wt.% NaCl solution was investigated by electrochemical methods including potentiodynamic polarization and electrochemical impedance spectroscopy. The protection efficiency of the coating is 97.70%, calculated on the basis of the corrosion current density. The stability and integrity of the composite coating were evaluated by field emission scanning electron microscopy (FESEM) and energy dispersive spectrometry (EDS). The FESEM and EDS results suggest that the composite coating endows the copper substrate with antibacterial properties, as untreated bare copper underwent microbiologically influenced corrosion in the presence of sulphate reducing bacteria (SRB). This antibacterial feature was further confirmed by the SRB culture method. In a 3.5% NaCl solution and highly corrosive SRB culture media, the as-prepared CS based composite coating gave corrosion protection by exhibiting better barrier effects against the attack of aggressive environments.

Keywords: Copper; 2-mercaptobenzothiazole; Corrosion; Microbiologically influenced corrosion

Synthesis and photoelectric characterization of semiconductor CdSe microrod array by a simple electrochemical synthesis method by Lecheng Tian; Juan Ding; Wei Zhang; Haibin Yang; Wuyou Fu; Xiaoming Zhou; Wenyan Zhao; Lina Zhang; Xiaoyu Fan (pp. 10535-10538).

► The CdSe microrod array was prepared via electrodeposition chemistry method. ► We have done an in-depth exploration on the synthesis conditions of the CdSe microrod array. ► The photoelectrochemical properties of the CdSe microrod array have been described. ► The simple synthesis is useful for the large-scale production of other II–VI semiconductors.It is reported here that the microrod array of CdSe on indium doped tin oxide coated conducting glass (ITO) substrate has been developed by a simple electrochemical synthesis method. The electrodeposition of CdSe was also investigated by cyclic voltammetric technique. The sample was characterized by XRD, EDX, FESEM and UV–vis spectroscopic. The X-ray diffraction investigation demonstrates that the CdSe microrod is a uniform hexagonal CdSe crystal. EDX shows that the high purity CdSe is obtained. Field emission scanning electron microscope (FESEM) results show that the microrods’ length, diameter, and direction of growth are nearly uniform and perpendicular to the ITO substrate. UV–vis absorption spectrum study shows the presence of direct transition with the band gap energy 2.13eV. Photoelectrochemical solar cells are constructed using CdSe microrod array as the photocathode in polysulphide electrolyte and their power output characteristics are studied.

Keywords: Electrodeposition; CdSe; Microrod; Array; Photo-response

Facile fabrication of Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructure on the surface of Zn coated with poly ( N-methyl pyrrole) by M.R. Mahmoudian; W.J. Basirun; Y. Alias; M. Ebadi (pp. 10539-10544).

► In this work we report the electrodeposition of flowerlike Zn/Zn₅(OH)₈Cl₂·H₂O nanostructures. ► We have proved the ability of PMPy to create a mold for the growth of flower-like nanostructure. ► The trapping of Cl⁻ and OH⁻ within pores can be considered as the reason for the formation of flowerlike nanostructure.Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructures was electrodeposited on the coated Zn with poly ( N-methyl pyrrole) in 0.1M Zn (NO₃)₂ and 0.1M KCl solution. The morphology and the structure of the Zn/Zn₅(OH)₈Cl₂·H₂O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728cm⁻¹ related to Zn₅(OH)₈Cl₂·H₂O. The FESEM results indicated that Zn/Zn₅(OH)₈Cl₂·H₂O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1M KCl as supporting electrolyte was Zn₅(OH)₈Cl₂·H₂O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructure. The trapping of Cl⁻ and OH⁻ within pores can be considered as the reason for the formation of flowerlike Zn/Zn₅(OH)₈Cl₂·H₂O nanostructures in 0.1M KCl.

Keywords: Poly (; N; -methyl pyrrole); Zn/Zn; ₅; (OH); ₈; Cl; ₂; ·H; ₂; O flower-like; Electrodeposition

Optical and electrical properties of thermally oxidized bismuth thin films by S. Condurache-Bota; N. Tigau; A.P. Rambu; G.G. Rusu; G.I. Rusu (pp. 10545-10550).

► Thermally oxidized bismuth thin films have polycrystalline and multiphase structure. ► The optical properties of bismuth trioxide thin films are sensitive to substrate temperature. ► The electrical measurements I= I( U) for all investigated films show that Ohm's law is obeyed.Bismuth trioxide (Bi₂O₃) thin films were prepared by dry thermal oxidation of metallic bismuth films deposited by vacuum evaporation. The oxidation process of Bi films consists of a heating from the room temperature to an oxidation temperature ( T_o=673K), with a temperature rate of 8K/min; an annealing for 1h at oxidation temperature and, finally, a cooling to room temperature. The optical transmission and reflection spectra of the films were studied in spectral domains ranged between 300nm and 1700nm, for the transmission coefficient, and between 380nm and 1050nm for the reflection coefficient, respectively. The thin-film surface structures of the metal/oxide/metal type were used for the study of the static current–voltage ( I– U) characteristics. The temperature of the substrate during bismuth deposition strongly influences both the optical and the electrical properties of the oxidized films. For lower values of intensity of electric field ( ξ<5×10⁴V/cm), I– U characteristics are ohmic.

Keywords: Bismuth trioxide thin films; Thermal oxidation; Optical properties; Electrical properties

Characterization of ZnO–SnO₂ thin film composites prepared by pulsed laser deposition by S.K. Sinha; T. Rakshit; S.K. Ray; I. Manna (pp. 10551-10556).

► ZnO–SnO₂ composite oxide films with various concentrations of ZnO (1–50wt%) have been synthesized by pulsed laser deposition. ► Addition of ZnO (above 10wt%) converts the composite films from crystalline to amorphous. ► The film with 1wt% ZnO content shows much better optical transparency (∼90%) compared to others. ► The combined TCO property of the composite films improved (marginally) as compared to the pure ones (ZnO or SnO₂).Thin films of ZnO–SnO₂ composites have been deposited on Si(100) and glass substrates at 500°C by pulsed laser ablation using different composite targets with ZnO amount varying between 1 and 50wt%. The effect of increasing ZnO-content on electrical, optical and structural properties of the ZnO–SnO₂ films has been investigated. X-ray diffraction analysis indicates that the as-deposited ZnO–SnO₂ films can be both crystalline (for ZnO<1wt%) and amorphous (for ZnO≥10wt%) in nature. Atomic force microscopy studies of the as-prepared composite films indicate that the surfaces are fairly smooth with rms roughness varying between 3.07 and 2.04nm. The average optical transmittance of the as-deposited films in the visible range (400–800nm), decreases from 90% to 72% for increasing ZnO concentration in the film. The band gap energy ( E_g) seems to depend on the amount of ZnO addition, with the maximum obtained at 1wt% ZnO. Assuming that the interband electron transition is direct, the optical band gap has been found to be in the range 3.24–3.69eV for as-deposited composite films. The lowest electrical resistivity of 7.6×10⁻³Ωcm has been achieved with the 25wt% ZnO composite film deposited at 500°C. The photoluminescence spectrum of the composite films shows a decrease in PL intensity with increasing ZnO concentration.

Keywords: Pulsed laser ablation; Photoluminescence; Composite; Zinc oxide; Band gap

Structural, magnetic and electronic structure studies of Mn doped TiO₂ thin films by Shalendra Kumar; S. Gautam; G.W. Kim; Faheem Ahmed; M.S. Anwar; K.H. Chae; H.K. Choi; H. Chung; B.H. Koo (pp. 10557-10561).

► We have synthesized single phase Mn doped TiO₂ thin films using PLD technique. ► XRD results indicate that films exhibit single phase nature with rutile structure and exclude the secondary phase. ► Field cooled magnetization and magnetic hysteresis loop studies infer that Mn doped TiO₂ films show room temperature ferromagnetism. ► XMCD measurements at Mn L_3,2 edge show that Mn²⁺ ions contribute to the ferromagnetism. ► NEXAFS spectra measured at Mn and Ti L_3,2 edge show that Mn exist in +2 valence state, whereas, Ti is in +4 state in Mn doped TiO₂ films.We report structural, magnetic and electronic structure study of Mn doped TiO₂ thin films grown using pulsed laser deposition method. The films were characterized using X-ray diffraction (XRD), dc magnetization, X-ray magnetic circular dichroism (XMCD) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. XRD results indicate that films exhibit single phase nature with rutile structure and exclude the secondary phase related to Mn metal cluster or any oxide phase of Mn. Magnetization studies reveal that both the films (3% and 5% Mn doped TiO₂) exhibit room temperature ferromagnetism and saturation magnetization increases with increase in concentration of Mn doping. The spectral features of XMCD at Mn L_3,2 edge show that Mn²⁺ ions contribute to the ferromagnetism. NEXAFS spectra measured at O K edge show a strong hybridization between Mn, Ti 3d and O 2p orbitals. NEXAFS spectra measured at Mn and Ti L_3,2 edge show that Mn exist in +2 valence state, whereas, Ti is in +4 state in Mn doped TiO₂ films.

Keywords: TiO; ₂; XRD; Magnetization; NEXAFS; DMS; XMCD

A chemical kinetic model for chemical vapor deposition of carbon nanotubes by K. Raji; Shijo Thomas; C.B. Sobhan (pp. 10562-10570).

Display Omitted► We studied the dependence of the deposition parameters on the controllable parameters for CNTs during CVD process. ► The deposition temperature and the deposition pressure show a decreasing trend with an increase of furnace temperature upto 1000K. ► The deposition temperature decreases with reaction time. The deposition pressure is found to remain constant at the initial stage, and then decrease as time progresses. ► All deposition parameters show a decreasing trend with increase of volumetric flow rate. ► An experimental study was also conducted and the results were found to agree well with the theoretical predictions obtained.Carbon nanotubes (CNTs) are classified among the most promising novel materials due to their exceptional physical properties. Still, optimal fabrication of carbon nanotubes involves a number of challenges. Whatever be the fabrication method, a process optimization can be evolved only on the basis of a good theoretical model to predict the parametric influences on the final product. The work reported here investigates the dependence of the deposition parameters on the controllable parameters for carbon nanotube growth during Chemical vapor deposition (CVD), through a chemical kinetic model. The theoretical model consisted of the design equations and the energy balance equations, based on the reaction kinetics, for the plug flow and the batch reactor, which simulate the CVD system. The numerical simulation code was developed in-house in a g++ environment. The results predicted the growth conditions for CNT: the deposition temperature, pressure and number of atoms, which were found to be influenced substantially by the initial controllable parameters namely the temperature, volumetric flow rate of the carbon precursor, and the reaction time. An experimental study was also conducted on a CVD system developed in the laboratory, to benchmark the computational results. The experimental results were found to agree well with the theoretical predictions obtained from the model.

Keywords: Carbon nanotubes; Chemical vapor deposition; Chemical kinetic model

Study of nickel silicide formation on Si(110) substrate by Xiao Guo; Hao Yu; Yu-Long Jiang; Guo-Ping Ru; David Wei Zhang; Bing-Zong Li (pp. 10571-10575).

► A higher annealing temperature is required for NiSi formation on Si(110) substrate. ► Larger Ni₂Si or NiSi grains form on Si(110) substrate. ► Characteristics of NiSi/n-Si(110) Schottky contacts are inferior to that of NiSi/n-Si(100) Schottky contacts.Nickel silicide formation on Si(110) and Si(100) substrate was investigated in this paper. It is confirmed that nickel monosilicide (NiSi) starts to form after 450°C annealing for Si(100) substrate, but a higher annealing temperature is required for NiSi formation on Si(110) substrate, which is demonstrated by X-ray diffraction (XRD) and Raman scattering spectroscopy. The higher formation temperature of NiSi is attributed to the larger Ni₂Si grain size formed on Si(110) substrate. Ni silicided Schottky contacts on both Si(100) and Si(110) substrates were also fabricated for electrical characteristics evaluation. It clearly reveals that the rectifying characteristics of NiSi/n-Si(110) Schottky contacts is inferior to that of NiSi/n-Si(100) Schottky contacts, which is attributed to a lower Schottky barrier height and a rougher contact interface. The formation kinetics for nickel silicide on Si(110) substrate is also discussed in this paper.

Keywords: PACS; 73.30.+y, 68.60.Dv, 85.40.LsNickel silicide; Si(1; 1; 0) substrate; Rapid thermal annealing; Schottky contacts

Perylene-containing polysiloxane: An effective candidate for corrosion protection of iron surface by Yan Liang; Dengxu Wang; Yue Wu; Qingling Lai; Lei Xue; Shengyu Feng (pp. 10576-10580).

The SEM images of the surface of bare iron sheet and the surface of iron sheet which was modified by perylene-containing polysiloxane after being corroded in 0.5M H₂SO₄ solution for 2h.Display Omitted► Perylene-containing polysiloxane (PCP) was successfully synthesized. ► The self-assembly films can be formed on the iron surface by PCP. ► The inhibition efficiency proves PCP is a good corrosion protection material.A new modified polysiloxane, perylene-containing polysiloxane (PCP), was successfully synthesized by amine-terminated polysiloxane (ATP) and 3,4,9,10-perylene tetracarboxylic dianhydride. The synthesized compound was characterized by Fourier transform infrared spectroscopy (FT-IR) and¹H nuclear magnetic resonance (¹H NMR). The thermal analysis of the PCP indicates that the modified polysiloxane has outstanding thermal stability. The PCP also possesses good fluorescence property. Due to the appearance of lone-pair electrons and π bond in PCP, it could be self-assembled on iron surface and thus used in the corrosion protection area. The PCP films were characterized by EIS (electrochemical impedance spectroscopy) and SEM (scanning electron microscopy). These results indicate that the films modified by PCP could protect the iron from corrosion efficiently.

Keywords: Corrosion protection; Perylene derivatives; Polysiloxanes; Self-assembly film; Synthesis

Coating of Cr–V ledeburitic steel with CrN containing a small addition of Ag by Peter Jurči; Ivo Dlouhý (pp. 10581-10589).

► Effect of CrN and CrAgN coating on performance of ledeburitic PM steel analysed. ► Improved adhesion of CrAgN coating comparing to the CrN coating found. ► Friction coefficient lowered by 70% at 400 and 500°C for CrAgN coating. ► Only a slight effect of coating on flexural strength of the substrate observed.Samples made from Vanadis 6 PM ledeburitic tool steel were surface machined, ground, and mirror polished. They were heat treated and coated with CrN with and without Ag addition by reactive magnetron sputtering. The CrN film grew in a typically columnar manner. A small addition of 3% Ag did not lead to alterations in the growth mechanism. The hardness of the CrN coating was 16.79±1.49GPa compared to 15.97±1.44GPa for the coating with Ag addition. The Ag addition in the CrN improved adhesion of the coating, which can be attributed to the capability of CrAgN coating to accommodate higher deformation energy before failure. The CrAgN coating exhibited superior tribological properties at intermediate temperatures. Compared to pure CrN the friction coefficient is lowered to 70–75% when measured at 400 and 500°C, respectively. This is reflected in a reduction in the volume wear, which was found to be three times lower for the coating containing Ag. Flexural strength decreased slightly for the CrN- or CrAgN-coated material compared to uncoated steel. However, as the decrease in flexural strength is very weak there is practically no risk of significant embrittlement of the investigated material due to the CrN coating with or without Ag addition.

Keywords: Magnetron sputtering; Cr–N coating; Ag; Ledeburitic steel; Scratch test; Flexural strength

Characterization of oxide coatings formed on tantalum by plasma electrolytic oxidation in 12-tungstosilicic acid by M. Petković; S. Stojadinović; R. Vasilić; Lj. Zeković (pp. 10590-10594).

► Oxide coatings are formed on tantalum by PEO process in 12-tungstosilicic acid. ► PEO process is divided into three stages according to change of voltage–time curve. ► Oxide coating morphology is strongly dependent of PEO time. ► Oxide coating is partly crystallized and mainly composed of WO₃, Ta₂O₅ and SiO₂. ► Outer layer of the coating is silicate tungsten bronze.Oxide coatings were formed on tantalum by plasma electrolytic oxidation (PEO) process in 12-tungstosilicic acid. The PEO process can be divided into three stages with respect to change of the voltage–time response. The contribution of electron current density in total current density during anodization results in the transformation of the slope of voltage–time curve. The surface morphology, chemical and phase composition of oxide coatings were investigated by AFM, SEM-EDX, XRD and Raman spectroscopy. Oxide coating morphology is strongly dependent of PEO time. The elemental components of PEO coatings are Ta, O, Si and W. The oxide coatings are partly crystallized and mainly composed of WO₃, Ta₂O₅ and SiO₂. Raman spectroscopy showed that the outer layer of oxide coatings formed during the PEO process is silicate tungsten bronze.

Keywords: Tantalum; Plasma electrolytic oxidation (PEO); 12-Tungstosilicic acid; Silicate tungsten bronze

Optimization of the synthesis parameters of high surface area ceria nanopowder prepared by surfactant assisted precipitation method by S.A. Hassanzadeh-Tabrizi (pp. 10595-10600).

► RSM has been used to optimize the critical parameters responsible for higher surface area of ceria nanopowder. ► The optimum conditions were a pH value of 9.4, CTAB/metal molar ratio of 0.5 and calcination temperature of 266°C. ► Under these optimal conditions maximum surface area of 158m²/g was achieved.Response surface methodology (RSM) has been used to optimize the critical parameters responsible for higher surface area of ceria nanopowder prepared by surfactant assisted precipitation method. A three-level central composite design (CCD) was used to optimize pH, CTAB/metal molar ratio and calcination temperature. A quadratic model between response and the independent parameters was developed and the response surface model was tested with analysis of variance (ANOVA). The optimum operating conditions determined were a pH value of 9.4, CTAB/metal molar ratio of 0.5 and calcination temperature of 266°C. Under these optimal conditions maximum surface area of 158m²/g has been achieved.

Keywords: Surface area; Response surface methodology; Nanopowder; Precipitation method

Nanostructured core–shell Ni deposition on SiC particles by alkaline electroless coating by M. Uysal; R. Karslioğlu; A. Alp; H. Akbulut (pp. 10601-10606).

► Thin core shell-structure of Ni on the SiC surfaces was assessed beneficial as reinforcement for possible metal matrix composite manufacturing. ► The grain size of Ni on the surface of SiC particles was obtained between 100 and 300nm depending on hypophosphate and particle content in the electrolyte. ► The effect of processing parameters of the Ni deposition on the surfaces of SiC powders in the core–shell structures, two series of experiments were carried out at different reducer contents and powder concentrations.In this study, core–shell nanostructured nickel formation on silicon carbide (SiC) ceramic powders was achieved through the electroless deposition method using alkaline solutions. To produce a nano core–shell Ni deposition on the SiC surfaces, process parameters such as pH values, the type of reducer material, deposition temperature, stirring rate and activation procedure among others were determined. Full coverage of core–shell nickel structures on SiC surfaces was achieved with a grain size of between 100 and 300nm, which was approximately the same deposition thickness on the SiC surfaces. The surface morphology of the coated SiC particles showed a homogenous distribution of nanostructured nickel grains characterized by scanning electron microscopy and X-ray diffraction techniques. The nanostructures of the crystalline Ni coatings were observed to be attractive for achieving both good bonding and dense structure. The thin core shell-structure of Ni on the SiC surfaces was assessed as a beneficial reinforcement for possible metal matrix composite manufacturing.

Keywords: Electroless Ni coating; Core–shell structure; SiC powder

Structural and spectroscopic studies of thin film of silver nanoparticles by M.A. Majeed Khan; Sushil Kumar; Maqusood Ahamed; Salman A. Alrokayan; M.S. Alsalhi; Mansour Alhoshan; A.S. Aldwayyan (pp. 10607-10612).

► Silver nanoparticles and its thin film have scientific and technological importance. ► Samples have been prepared by simple and viable wet chemical solution method. ► Synthesized samples exhibit excellent structural and optical properties. ► Investigated properties may be utilized in design and fabrication of optical devices.We report the deposition of thin film of silver (Ag) nanoparticles by wet chemical method. The as-synthesized Ag nanoparticles have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray energy dispersive spectroscopy (EDS), field emission transmission electron microscopy (FETEM) and high-resolution TEM (HRTEM), UV–vis spectroscopy and thermogravimetric-differential thermal analysis (TG-DTA) respectively. FESEM image indicates that the silver film prepared on the quartz substrate is smooth and dense. XRD pattern reveals the face-centered cubic (fcc) structure of silver nanoparticles. EDS spectrum indicates that samples are nearly stoichiometric. From TEM analysis, it is found that the size of high purity Ag nanoparticles is ranging from 10 to 20nm with slight agglomeration. Absorption in UV–vis region by these nanoparticles is characterized by the features reported in the literature, namely, a possible Plasmon peak at ∼403nm. Optical absorbance spectra analysis reveals that the Ag film has an indirect band structure with bandgap energy 3.88eV. TGA/DTA studies revealed that a considerable weight loss occurs between 175 and 275°C; and the reaction is exothermic.

Keywords: Thin film; Chemical synthesis silver nanoparticles; Scanning and transmission electron microscopy; Optical propertiesPACS; 61.46.−Df; 42.65−K; 81.15−Z

Multiscale modeling of nanoindentation in copper thin films via the concurrent coupling of the meshless Hermite–Cloud method with molecular dynamics by T.Y. Ng; Venkataraman Pandurangan; Hua Li (pp. 10613-10620).

► 2D nanoindentation in copper film investigated using new multiscale model. ► Load versus displacement graph shows only slight variation with MD model. ► Model ensures first-order compatibility and reduces computational time by one order.This paper investigates the 2D nanoindentation of a copper thin film using a concurrent multiscale method. The method uses molecular dynamics (MD) simulation in the atomistic region, the strong-form meshless Hermite–Cloud method in the continuum region and a handshaking algorithm to concurrently couple them. A fully atomistic simulation is also carried out to validate the multiscale method. The results, namely the load versus indentation depth graph obtained from the multiscale method shows only slight quantitative variation from that of the full atomistic model. More importantly, the graphs from both simulations show a similar trend thus validating the 2D multiscale method. The displacement profile without discontinuities further supports the efficiency of the multiscale method in ensuring smooth exchange of information between the atomistic and continuum domains. The material properties extracted from the simulation include the force/unit length values obtained by dividing the maximum load on the indenter by its contact perimeter, instead of the hardness value obtained in 3D simulations. By restricting the atomic scale detail to the critical regions beneath the indenter, the multiscale method effectively saves computational resources to more than one order (close to 13 times less for this problem), thus making it feasible to simulate problems of larger dimensions that are not amenable to complete atomistic simulations.

Keywords: Nanoindentation; Thin films; Multiscale modeling; Concurrent coupling; Meshless Hermite–Cloud method; Molecular dynamics simulation

Preparation of activated carbon from Enteromorpha prolifera and its use on cationic red X-GRL removal by Yanhui Li; Qiuju Du; Tonghao Liu; Yan Qi; Pan Zhang; Zonghua Wang; Yanzhi Xia (pp. 10621-10627).

The surface of Enteromorpha prolifera, employed as the raw material for the preparation of activated carbon, is very smooth and there are no obvious porous structures on it (Fig. a). After activation, the surface of activated carbon becomes rough (Fig. b) and lots of homogeneous particles and pores appear.Display Omitted► Detailed activation procedures to prepare activated carbon. ► Activated carbon with the high surface area of 1722m²/g. ► Excellent dye adsorption capacity (263.16mg/g) of activated carbon. ► Spontaneous and endothermic adsorption process. ► Langmuir isotherm indicates a monolayer adsorption behavior. Enteromorpha prolifera was pyrolyzed to prepare activated carbon using chemical activation by zinc chloride. The effect of activation parameters such as activation temperature, weight ratio ( Enteromorpha prolifera to ZnCl₂), and activation time was investigated. The BET results showed that the surface area and pore volume of activated carbons were achieved as high as 1722m²/g and 1.11cm³/g, respectively, in the optimal activation conditions. Batch adsorption studies were carried out to study the adsorption properties of cationic red X-GRL onto activated carbon by varying the parameters like initial solution pH, contact time, and temperature. The kinetic studies showed that the adsorption data followed a pseudo second-order model. The isotherm analysis indicated that the adsorption data could be represented by the Langmuir isotherm model. The Langmuir monolayer adsorption capacity of cationic red X-GRL was estimated as 263.16mg/g at pH 6.0.

Keywords: Activated carbon; Cationic red X-GRL; Adsorption; Isotherm; Kinetic; Thermodynamics

Deposition behavior of mixed binary metallic powders in cold spraying process by X.L. Zhou; S.J. Mou; X.K. Wu; J.S. Zhang (pp. 10628-10633).

► A Zn/Al pseudo-alloy coating was prepared by cold spray. ► Microstructures of the coating were characterized. ► Multicomposite particle impact was simulated using the ANSYS/LS-DYNA software. ► The bonding of particles and the formation of coatings are discussed. ► The research tries to supply a guide in the preparation of metal composite coatings.In the present study, Zn/Al composite coating was selected for the typical case to study the deposition behavior and the deformation of binary mixing particles in cold spraying process by means of an experiment and numerical simulation. The experimental results demonstrated that the coating had a dense microstructure, and that Zn and Al were uniformly distributed in the coating. Al particles deformed more severely than Zn particles, and extensively deformed Al particles had a local jet-metallic mixing area. The steel substrate underwent a small amount of deformation when impacted by Zn particles, whereas the substrate did not deform when impacted by Al particles. XRD results show that the Zn/Al composite coating did not form a new phase, and only resulted in the mechanical mixing of Zn and Al, producing a pseudo-alloy coating. In addition, a binary Zn/Al multiparticle impact was first simulated using the finite element analysis software ANSYS/LS-DYNA. The effective plastic strain contour, which enabled the description of the particle deposit procedure, was demonstrated. The plastic deformation evolution of Zn and Al particles in the composite coating was analyzed individually, and the curves of effective plastic strain versus time of typical monitored elements at the edge of the Zn and Al particles were plotted. The simulations showed good concordance with the experimental results.

Keywords: Cold spraying; Mixed binary particles; Deposition behavior; Coating formation

Synthesis and performance of core–shell structured ZnO/In₂O₃ composites in situ growth by Yun-long Zhao; Hong-xia Lu; Xiu-jun Yu; Bing-bing Fan; De-liang Chen; Li-wei Zhang; Hai-long Wang; Dao-yuan Yang; Hong-liang Xu; Rui Zhang (pp. 10634-10638).

► In₂O₃/ZnO composites were successfully synthesized via situ growth method. ► HMTA played an important role in the morphology and agglomeration of composites. ► The possible formation mechanism was also proposed based on the experimental results. ► The addition of In₂O₃ had a great effect on PL spectrum.Core–shell structured ZnO/In₂O₃ composites were successfully synthesized via situ growth method. Phase structure, morphology, microstructure and property of the products were investigated by X-ray diffraction (XRD), TG-DTA, field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), transmission electron microscope (TEM) and photoluminescence (PL). Results show that the core–shell structures consist of spindle-like ZnO with about 800nm in length and 200nm in diameter, and In₂O₃ particles with a diameter of 50nm coated on the surface of ZnO uniformly. HMTA plays an important role in the formation of core–shell structures and the addition of In₂O₃ has a great effect on PL spectrum. Possible mechanism for the formation of core–shell structures is also proposed in this paper.

Keywords: Composite materials; Crystal growth; Core–shell structures; ZnO/In; ₂; O; ₃

Efficient visible-light-induced photocatalytic degradation of MO on the Cr–nanocrystalline titania–S by Masood Hamadanian; Ali Sadeghi Sarabi; Ali Mihammadi Mehra; Vahid Jabbari (pp. 10639-10644).

Mechanism of TiO₂ photocatalysis: hv1: pure TiO₂; hv2: metal-doped TiO₂ and hv3: nonmetal-doped TiO₂.Display Omitted► Synthesis of Cr–TiO₂–S nanoparticles as a novel and efficient visible-light-induced photocatalysts. ► Structural, chemical and morphological characteristics of prepared samples. ► The promoting effects of Cr,S-modification on the photocatalytic activity of pure TiO₂ was observed and discussed. ► The prepared Cr–TiO₂–S exhibited much higher activity than the undoped TiO₂. ► Maximum of photocatalytic degradation reach till 93% by Cr(5)–TiO₂–S(5).In order to improve visible light photocatalytic activities of the nanometer TiO₂, a novel and efficient Cr,S-codoped TiO₂ (Cr–TiO₂–S) photocatalyst was prepared by precipitation-doping method. The crystalline structure, morphology, particle size, and chemical structure of Cr–TiO₂–S were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) techniques, respectively. Results indicate that the doping of Cr and S, cause absorption edge shifts to the visible light region ( λ>420nm) compare to the pure TiO₂, reduces average size of the TiO₂ crystallites, enhances desired lattice distortion of Ti, promotes separation of photo-induced electron and hole pair, and thus improves pollutant decomposition under visible light irradiation. The photocatalytic activities of Cr–TiO₂–S nanoparticles were evaluated using the photodegradation of methyl orange (MO) as probe reaction under the irradiation of UV and visible light and it was observed that the Cr–TiO₂–S photocatalyst shows higher visible photocatalytic activity than the pure TiO₂. The optimal Cr–TiO₂–S concentration to obtain the highest photocatalytic activity was 5mol% for both of Cr and S.

Keywords: Cr–TiO; ₂; –S nanoparticle; Visible light; Photocatalyst; MO decomposition

The mechanism of oxide whisker growth and hot corrosion of hot-dipped Al–Si coated 430 stainless steels in air–NaCl_(g) atmosphere by Hsiao-Hung Liu; Wei-Jen Cheng; Chaur-Jeng Wang (pp. 10645-10652).

► The hypothetical growth mechanism for Al₂O₃ and Fe₂O₃ whiskers has been proposed. ► The NaCl-induced hot corrosion of aluminide steel has been described in detail. ► NaCl acted as a catalyst to increase oxidation rate of the oxides in one direction. ► Grain boundary of scale provides a rapid diffusion path for oxide whiskers to grow. ► Temperature and concentration of NaCl dominate the morphology of oxide whiskers.The mechanisms of oxide whisker growth and hot corrosion of 430 stainless steel (430SS) and aluminide 430 stainless steel hot-dipped in a Al–10wt.%Si molten bath (430HDAS) were studied at 750 and 850°C in air mixed with 500 and 990vppm NaCl_(g). The results showed that the loose Cr₂O₃ scale which formed on the 430SS could not prevent the corrosion of 430SS in a 500vppm NaCl_(g) atmosphere, resulting in the formation of Fe₂O₃ scale. Fe₂O₃ whiskers grew at the grain boundary of the Fe₂O₃ scale. However, no Fe₂O₃ whiskers formed on the Fe₂O₃ scale while 430SS was exposed in a 900vppm NaCl_(g) atmosphere. During the initial high-temperature corrosion of 430HDAS in a 500vppm NaCl_(g) atmosphere, a dense Al₂O₃ scale formed on the surface of the specimens. Also, Al₂O₃ whiskers grew on the Al₂O₃ scale. As exposure time increased, cyclic chlorination/oxidation degraded the protective aluminide layer and caused the formation of Fe₂O₃ scale and Fe₂O₃ whiskers. The morphology of Fe₂O₃ whiskers formed at 750°C is more slender than those formed at 850°C. The formation and growth of both Fe₂O₃ and Al₂O₃ whiskers may be attributed to the chloridation of both the steel substrate and aluminide layer, accelerating the diffusion rate of metallic ions in the oxide scales.

Keywords: Oxide whisker; Hot corrosion; Aluminide 430 stainless steel; NaCl; _(g); atmosphere; Cycle chlorination/oxidation

Effect of surface ethoxy groups on photoactivity of TiO₂ nanocrystals by Lihong Tian; Kejian Deng; Liqun Ye; Lin Zan (pp. 10653-10658).

The TiO₂ nanocrystals modified by ethoxy groups had plenty of surface negative charges, which selectively absorbed the positive –N(Et)₂ group of RhB and resulted in N-dealkylation process under visible-light irradiation.Display Omitted► High surface charge of ethoxy groups modified TiO₂ nanocrystals promoted the adsorption of RhB on catalysts. ► Positive –N(Et)₂ group of Rhodamine B absorbed selectively on the catalyst surface. ► RhB underwent the N-dealkylation process on ethoxide groups modified nanocrystals.TiO₂ nanocrystals modified by ethoxy groups were prepared by a facile nonhydrolytic solvothermal method and characterized by XRD, TEM, TG-DTA and XPS, which showed an enhanced visible-light photocatalytic activity on the degradation of Rhodamine B compared with TiO₂ modified by benzyloxy groups and the “naked” TiO₂. The adsorption and degradation pathway of Rhodamine B on TiO₂ modified by ethoxy groups were also investigated. The zeta-potential ( ζ) results showed that the TiO₂ modified by ethoxy groups had high negative surface charge, which incited the positive –N(Et)₂ group of RhB absorbing on the TiO₂ surface and preferably led the N-dealkylation pathway under visible light irradiation.

Keywords: TiO; ₂; nanocrystal; Ethoxy group; Solvothermal synthesis; Photocatalytic activity

Phase transfer synthesis of N,N′(1,2-phenylene) bis-hippuricamide tethered metal based functionalized nanoparticles: A study on some novel microbial targeting peptide-mimic nanoparticles by N. Raman; S. Sudharsan (pp. 10659-10666).

A new versatile peptide ligand and its four metal based functionalized nanoparticles have been synthesized via modified Brust–Schiffrin approach. The remarkable DNA binding affinity and their excellent bioactive properties against microbial strains suggest a potential application of nanoscience towards the development of novel peptide based biomarkers.Display Omitted► Synthesis of metal based functionalized nanoparticles via modified Brust–Schiffrin approach. ► DNA interfacial dealings explored the excellent DNA damaging property of these nanoparticles. ► Biological studies clearly depict the potential value of peptide in these types of nanoparticles. ► The functionalized nanoparticle of cobalt is the most active microbial marker among the others.This paper presents the novel synthesis of peptide, N,N′(1,2-phenylene) bis-hippuricamide tethered metal [Cu(II), Zn(II), Ni(II) and Co(II)] based functionalized nanoparticles via modified Brust–Schiffrin methodology. The growth, organic composition and morphology of these functionalized nanoparticles have been evaluated by UV–Vis, FT–IR spectroscopy and scanning electron microscopy. They are structurally and thermally characterized by X-ray diffraction and thermogravimetric analysis. Moreover, the interfacial dealings of these functionalized nanoparticles with Calf-thymus DNA and pUC19 DNA reveal that the functionalized nanoparticles of cobalt is an effective DNA damaging agent under physiological conditions. This has been supported by its efficient antimicrobial character against few fungal and bacterial strains, thereby steering its way towards biomedical applications as a metal based nanocarrier.

Keywords: Functionalized nanoparticles; DNA; Peptide; Antimicrobial; Metal-based nanocarriers

Performance improvement of Sb₂Te₃ phase change material by Al doping by Cheng Peng; Liangcai Wu; Zhitang Song; Feng Rao; Min Zhu; Xuelai Li; Bo Liu; Limin Cheng; Songlin Feng; Pingxiong Yang; Junhao Chu (pp. 10667-10670).

► Al atoms are introduced in Sb₂Te₃ phase change material in order to improve the thermal stability. ► The data retention temperature at 10 years is up to 110°C, much better than the Ge₂Sb₂Te₅ material. ► The additional Al–Sb and Al–Te bonds within Sb₂Te₃ lead to better thermal stability. ► Phase-change memory cell based on Al_0.69Sb₂Te₃ can be triggered by a nanosecond magnitude pulse between amorphous and crystalline states.Al doped Sb₂Te₃ material was proposed to improve the performance of phase-change memory. Crystallization temperature, activation energy, and electrical resistance of the Al doped Sb₂Te₃ films increase markedly with the increasing of Al concentration. The additional Al–Sb and Al–Te bonds enhance the amorphous thermal stability of the material. Al_0.69Sb₂Te₃ material has a better data retention (10 years at 110°C) than that of Ge₂Sb₂Te₅ material (10 years at 87°C). With a 100ns width voltage pulse, SET and RESET voltages of 1.3 and 3.3V are achieved for the Al_0.69Sb₂Te₃ based device.

Keywords: Phase transformation; Thin films; Sb; ₂; Te; ₃; XPS; Thermal properties

Photoluminescence of Si-based nanotips fabricated by anodic aluminum oxide template by Yangjuan Li; Kai Huang; Hongkai Lai; Cheng Li; Songyan Chen; Junyong Kang (pp. 10671-10673).

► Large-area, high-density and uniform Si-based nanotips by ECL method. ► Si-based nanotips on Si and GeSi/Si supperlattice substrates. ► Photoluminescent peak centered at 585nm with a FWHM of 24nm. ► No evident peak energy shift when the measurement temperature increases.Large-area, high-density silicon-based nanotips were fabricated using electrochemical lithography. The morphology and optical properties of the samples were characterized by atomic force microscopy and photoluminescence. The distribution and size of the silicon-based nanotips were uniform. Two photoluminescence peaks were observed at 585 and 620nm. The peak centered at 585nm exhibited a narrow full-width at half maximum. No evident peak energy shift was observed when the measurement temperature was increased from 10K to room temperature, which suggested that the photoluminescence should be attributed to the interface states and/or defects in the silicon-based nanotips.

Keywords: Anodic aluminum oxide template; Si-based nanotips; Morphology; Optical properties

Elongation rate measurements of nanofilms by microbump method induced by laser pulse by Aihuan Dun; Jingsong Wei; Fuxi Gan (pp. 10674-10678).

Display Omitted► A new method aims to measure elongation rate of thin films with nano-level thickness. ► The method made use of a simple chemical reaction as follows:AgOx⟶160oCAg+x2O2. ► The parameters of the microbumps could be controlled by adjusting laser energy. ► Residual stress, Young's modulus, and Poisson's ratio, could be studied in next work.A laser pulse-induced microbump method that aims to measure the elongation rate of nanofilms is proposed. The sample structure is designed as “substrate/active layer/nanofilm” and the laser pulse is used as energy source to heat the active layer and to create microbump. These cause the nanofilm to expand and elongate. The surface area and length change of nanofilm is calculated by measuring the deflections and diameters of the microbumps, as well as to obtain the elongation rate of the nanofilms. A series of microbumps with different deflections are obtained. The deflections are measured precisely by atomic force microscopy (AFM) by taking AgO_x and ZnS–SiO₂ as the active layer and nanofilm, respectively, and by controlling pulse laser parameters. The line elongation rate and plane elongation rate of ZnS–SiO₂ nanofilm are measured at thickness of only 10nm. Results show that both the two elongation rates linearly increases with laser power from 3.2 to 5.2mW. Plane elongation rate is a little higher than the line elongation rate at the same laser power. The rupture at 5.4mW laser power corresponds to fracture strength of the film. The maximum line elongation rate and plane elongation rate are 13.241% and 19.766%, respectively. This method applies a reproducible and efficient method for its applications in the near future.

Keywords: PACS; 68.35.Rh; 68.55.−a; 78.66.Jg; 79.20.DsElongation rate, Nanofilm, Microbump, Pulse laser

Synthesis and photocatalytic property of ZnSe flowerlike hierarchical structure by Yan Zhang; Chenguo Hu; Bin Feng; Xue Wang; Buyong Wan (pp. 10679-10685).

Display Omitted► Spherical flowerlike hierarchical structure of ZnSe(en)_0.5 is obtained via a solvothermal route. ► NH₃·H₂O–ethylenediamine (en)–N₂H₄·H₂O as solvent. ► The ZnSe(en)_0.5 can be converted into ZnSe by annealing with morphology preserved. ► The ZnSe hierarchical structure shows excellent catalytic activity for the degradation of methyl orange under the irradiation of the simulated sunlight.Spherical flowerlike hierarchical structure of ZnSe(en)_0.5 was synthesized via a solvothermal route in the NH₃·H₂O–ethylenediamine (en)–N₂H₄·H₂O system at 180°C for 24h. The hierarchical structure is assembled from lots of regular nanosheets. The ZnSe(en)_0.5 was further converted into pure hexagonal ZnSe by annealing in a flowing nitrogen gas at 500°C for 1h with morphology preserved. The formation mechanism of ZnSe was discussed. The UV–visible absorption spectrum and PL spectrum of the ZnSe spherical flowerlike hierarchical structure were measured. In addition, photocatalytic activity of the ZnSe flowerlike structure for the degradation of methyl orange under the irradiation of the simulated sunlight was investigated. The excellent catalytic activity for the degradation of methyl orange was found and the possible mechanism of the photocatalytic activity is also proposed.

Keywords: Hierarchical structure; Photocatalytic activity; Methyl orange

Aminealkylthiol and dithiol self-assembly as adhesion promoter between copper substrate and epoxy resin by J. Denayer; J. Delhalle; Z. Mekhalif (pp. 10686-10691).

► Amine terminated SAMs as promoter of adhesion in PCB industry. ► Successful linkage between amine SAMs and epoxy function. ► Improve adhesiveness between copper and epoxy polymer thanks to the SAMs.To improve adhesion between copper and epoxy resin in printed circuit board, a roughness treatment of copper has been widely used. Nevertheless, new adhesion promoters have to be developed to face the miniaturization and sophistication of the electronic device. Self-assembled monolayers have met increasing interest in this field by using them as coupling agent between copper and the epoxy resin.This paper presents the deposition of an epoxy resin on copper modified by amine alkylthiol and dithiol monolayers and highlights the benefit brought by the monolayer in terms of adhesion.The chemical linkage between the amine SAMs and the epoxy function has been proved by the deposition on a short epoxy fragment, the 2-(4-fluorophenoxy-methyl)oxirane. The deposition of an epoxy resin mixed with amine curing agent has then been successfully achieved on amine terminated SAMs. The resulting polymer is homogeneous and well adherent on their surface, while the adhesion is lower on bare copper and not existing on methyl terminated SAMs. The formation of chemical bond Cu–S and N-epoxy is thus essential to increase the adhesion strength between copper and the polymer.

Keywords: Self-assembled monolayers; Aminoalkanethiol; Epoxy resin; Copper

Microstructure and tribological properties of TiAg intermetallic compound coating by Chun Guo; Jianmin Chen; Jiansong Zhou; Jierong Zhao; Linqian Wang; Youjun Yu; Huidi Zhou (pp. 10692-10698).

► TiAg intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding using Ag powder as the precursor. ► Microstructre and tribological properties of the prepared TiAg intermetallic compound coating was systematically analyzed. ► The prepared TiAg intermetallic compound coating has excellent wear resistance.TiAg intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding using Ag powder as the precursor. It has been found that the prepared coating mainly comprised TiAg and Ti phases. The high resolution transmission electron microscopy results further conform the existence of TiAg intermetallic compound in the prepared coating. The magnified high resolution transmission electron microscopy images shown that the laser cladding coating contains TiAg nanocrystalline with the size of about 4nm. Tribological properties of the prepared TiAg intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiAg intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiAg intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate increased as the normal load increased.

Keywords: Titanium-sliver; Intermetallics; Friction and wear; Laser processing

Influences of the iron ion (Fe³⁺)-doping on structural and optical properties of nanocrystalline TiO₂ thin films prepared by sol–gel spin coating by J. Ben Naceur; R. Mechiakh; F. Bousbih; R. Chtourou (pp. 10699-10703).

► Elaboration and characterization of structural and optical properties. ► Sol–gel. ► Nano materials, nano systems, thin films, surfaces and interfaces, applications.Titanium dioxide (TiO₂) thin films doping of various iron ion (Fe³⁺) concentrations were deposited on silicon (Si) (100) and quartz substrates by sol–gel Spin Coating technique followed by a thermal treatment at 600°C. The structure, surface morphology and optical properties, as a function of the doping, have been studied by X-ray diffractometer (XRD), Raman, ultraviolet-visible (UV–vis) and Spectroscopic Ellipsometry (SE). XRD and Raman analyzes of our thin films show that the crystalline phase of TiO₂ thin films comprised only the anatase TiO₂, but the crystallinity decreased when the Fe³⁺ content increased from 0% to 20%. During the Fe³⁺ addition to 20%, the phase of TiO₂ thin film still maintained the amorphous state. The grain size calculated from XRD patterns varies from 29.3 to 22.6nm. The complex index and the optical band gap ( E_g) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreased with an increasing Fe³⁺ content.

Keywords: TiO; ₂; Thin films; Fe; ³⁺; -doped; Anatase; Sol–gel; Spin coating

Ion beam sputter deposited W/Si multilayers: Influence of re-sputtering on the interface structure and structure modification at ultra short periods by S.K. Rai; Arijeet Das; A.K. Srivastava; G.S. Lodha; Rajnish Dhawan (pp. 10704-10709).

► W/Si multilayers of periods ranging from 1.7nm to 9.6nm have been examined for changes in structure with period thickness. ► Loss of Si due to re-sputtering during W deposition has been estimated. ► Minimum thickness of continuous W layer has been estimated. ► Minimum period thickness possible to deposit has been estimated. ► Cause of interface asymmetry has been found out.X-ray multilayer mirrors of period ranging from 9.6 to 1.7nm, deposited using ion beam sputtering, have been examined using grazing incidence X-ray reflectivity (GIXRR) and grazing incidence X-ray diffraction. Detailed analysis of GIXRR data revealed that significant amount of re-sputtering of Si layer takes place while W deposition is underway. Re-sputtering is mainly due to bombardment of high-energy neutrals getting reflected from the W target. Due to re-sputtering interface of the multilayer becomes asymmetric. This puts a major hindrance in avoiding the intermixing and achieving sharp interfaces at shorter periods. Maximum thickness of Si which gets lost due to re-sputtering during deposition is ∼0.8nm. The shortest period multilayer estimated, that could be deposited without intermixing, was 2.7nm. These results are of significance for developing low period W/Si multilayers.

Keywords: PACS; 65.35.Ct; 68.37.Lp; 68.65.Ac; 61.05.cf; 41.50.+hMultilayer; X-ray reflectivity; X-ray diffraction; X-ray optics

Density functional theory calculations of surface properties and H₂ adsorption on the Cu₂O (111) surface by Min Li; Jun-ying Zhang; Yue Zhang; Guo-feng Zhang; Tian-min Wang (pp. 10710-10714).

► H₂ molecule is only very weakly bound to the Cu₂O (111)–Cu_CUS surface. ► H₂ on Cu_CUS site parallel to O-terminated Cu₂O (111) surface and H₂ molecule adsorption on Cu₂ site parallel to Cu-terminated Cu₂O (111) surface are the most favored. ► Cu_CUS 3d has moved to a lower energy compared to that before H₂ adsorption. ► The sharp band of Cu_CUS 4s is delocalized due to adsorbed H₂.First-principles calculation on the basis of the density functional theory (DFT) and generalized gradient approximation have been applied to study the adsorption of H₂ on the stoichiometric O-terminated Cu₂O (111), Cu₂O (111)–Cu_CUS and Cu-terminated Cu₂O (111) surfaces. The optimal adsorption position and orientation of H₂ on the stoichiometric O-terminated Cu₂O (111) surface and Cu-terminated Cu₂O (111) surface were determined and electronic structural changes upon adsorption were investigated by calculating the Local Density of States (LDOS) of the Cu_CUS 3d and Cu_CUS 4s of stoichiometric O-terminated Cu₂O (111) surface. These results showed that H₂ molecule adsorption on Cu_CUS site parallel to stoichiometric O-terminated Cu₂O (111) surface and H₂ molecule adsorption on Cu₂ site parallel to Cu-terminated Cu₂O (111) surface were the most favored, respectively. The presence of surface copper vacancy has a little influence on the structures when H₂ molecule adsorbs on Cu_CSA, O_CUS and O_CSA atoms and the H₂ molecule is only very weakly bound to the Cu₂O (111)–Cu_CUS surface. From the analysis of stoichiometric O-terminated Cu₂O (111) Local Density of States, it is observed that Cu_CUS 3d orbital has moved to a lower energy and the sharp band of Cu_CUS 4s is delocalized when compared to that before H₂ molecule adsorption, and overlapped substantially with bands due to adsorbed H₂ molecule. The Mulliken charges of H₂ adsorption on Cu_CUS site showed that H₂ molecule obtained electron from Cu_CUS which was consistent with the calculated electronic structural changes upon H₂ adsorption.

Keywords: Density functional theory; Adsorption; Cu; ₂; O (1; 1; 1)

Study of effect annealing temperature on the structure, morphology and photocatalytic activity of Si doped TiO₂ thin films deposited by electron beam evaporation by Zhongdan Lu; Xiaohong Jiang; Bing Zhou; Xiaodong Wu; Lude Lu (pp. 10715-10720).

► Si-TiO₂ target has been simply prepared and the corresponding film was deposited on quartz glass substrates by electron beam evaporation. ► It can be demonstrated the annealing temperature had significant effect on the structure, phase transition temperature and surface morphology of Si-TiO₂ thin films. ► The Si-TiO₂ films exhibit better photocatalytic efficiency owing to the reduction of the photo-generated electron and holes recombination rate under illumination.Transparent Si-doped TiO₂ thin films (Si-TiO₂) were deposited on quartz glasses using electron beam evaporation (EBE) and annealed at different temperature in an air atmosphere. The structure and morphology of these films were analyzed by X-ray diffraction (XRD), Raman microscopy (Raman), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Meanwhile the photocatalytic activity of the films has also been evaluated on the basis of the degradation degree of rhodamine B in aqueous solution. Our experimental results suggest that the annealing temperature impact a strong effect on the structure, morphology and photocatalytic activity of Si-TiO₂ thin films. Furthermore the enhanced thermal stability of Si-TiO₂ films enabled them to elevate the phase transformation temperature of TiO₂ from anatase to rutile and enhanced the photocatalytic efficiency.

Keywords: Si doped TiO; ₂; thin films; Electron beam evaporation; Annealing; Photocatalytic activity

Effect of MgO buffer layer thickness on the electrical properties of MgZnO thin film transistors fabricated by plasma assisted molecular beam epitaxy by H.Q. Huang; F.J. Liu; J. Sun; J.W. Zhao; Z.F. Hu; Z.J. Li; X.Q. Zhang; Y.S. Wang (pp. 10721-10724).

► MgZnO films with different thicknesses of MgO buffer layer were grown by MBE. ► MgZnO TFTs with different thicknesses of MgO buffer layer were fabricated. ► The crystal quality of MgZnO films was enhanced with 4nm MgO buffer layer. ► MgZnO TFT with 4nm MgO buffer layer showed the best performance.We report the fabrication and electrical characteristics of thin film transistors based on MgZnO thin films with different thicknesses of MgO buffer layer. The MgZnO thin films with MgO buffer layers were grown on SiO₂/p-Si substrates by plasma assisted molecular beam epitaxy. The effects of the buffer layer thickness on the structural properties of MgZnO films are investigated by X-ray diffraction, and the results show that the crystal quality of the MgZnO film is enhanced with 4nm MgO buffer layer. The MgZnO TFT with 4nm MgO buffer layer exhibits an n-type enhancement mode characteristics with a field effect mobility of 1.85cm²/Vs, a threshold voltage of 27.6V and an on/off ratio of above 10⁶.

Keywords: MgZnO; MgO buffer layer; Thin film transistor; Electrical property; MBE

Fabrication of three-dimensionally ordered macroporous Ta₂O₅ films through aqueous organic gel process by Xin Wuhong; Zhao Jiupeng; Ding Yanbo; Li Yao (pp. 10725-10728).

► DOM Ta₂O₅ was first prepared by aqueous organic gel progress using PS templates. ► This method is free of special atmosphere and reagents, simple and cost-effective. ► Spin-coating method can be used to minimize the capping precursor. ► The final material is nice and free of capping layer when spin-coating is used. ► Composition and crystallinity of the product are studied.Ta₂O₅ thin films have been prepared in the forms of three-dimensionally ordered macroporous (3-DOM) materials through aqueous organic gel process guided by polystyrene (PS) colloidal templates. The structure of the films was strongly affected by the infiltration process. This suggests that the infiltration process which aims at introducing desired materials into the interstitial spaces between the PS templates is of critical importance. Dip-drawing method was adopted for infiltration in this article. However, excess precursor worked as a capping agent for films prepared from the precursor of high concentration. Spin-coating method can efficiently remove the excess precursor by high speed rotating, which makes it a promising process for the infiltration of Ta-citric precursor with concentration higher than 0.5mol/L. X-ray diffraction (XRD) pattern showed that the products can crystallize at 600°C and had a pure orthorhombic phase. The chemical composition of the product was also studied by X-ray photoelectron spectroscopy (XPS).

Keywords: Three-dimensionally ordered macroporous (3-DOM); Colloidal crystals; Aqueous organic gel process; Porous materials; X-ray diffraction

A facile process to prepare copper oxide thin films as solar selective absorbers by Xiudi Xiao; Lei Miao; Gang Xu; Limei Lu; Zhanmin Su; Ning Wang; Sakae Tanemura (pp. 10729-10736).

► CuO_x coating prepared by chemical conversion method is an important solar selective absorber. ► Reaction temperature, time and concentration of NaOH are important factors to influence structure and optical properties of thin films. ► The porous belt-like structure can greatly enhance absorbance, while the composition, thickness and roughness of thin films can greatly influence emissivity.Copper oxide thin films as solar selective absorbers were conveniently prepared by one-step chemical conversion method. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis–NIR spectra and Fourier transform infrared (FTIR) spectra were employed to characterize the composition, structure and optical properties of thin films. The results indicated that the composition, structure and optical properties of thin films were greatly influenced by reaction temperature, time and concentration of NaOH. When reaction temperature was fixed at 40°C, the as-prepared films consist of pure cubic Cu₂O. The surface morphology of thin films was changed from square-like structure (reaction time≤25min) to porous belt-like structure (reaction time≥30min) with the elongation of reaction time. While for thin films prepared at 60°C and 80°C, single Cu₂O was observed after 5min reaction. When reaction time is longer than 5min, CuO appears and the content of CuO is increasing with the elongation of reaction time. With the increase of reaction temperature, the belt-like structure was easily formed for 60°C/10min and 80°C/5min. Decreasing concentration of NaOH also could result in the formation of CuO and porous belt-like structure. Simultaneously, the film thickness is increasing with the increase of reaction time, temperature and concentration. Films containing CuO with belt-like structure exhibited high absorptance (>0.9), and the emissivity of films increased with elongation of reaction time. Combination of the composition, structure and optical properties, it can be deduced that the porous belt-like structure like as a light trap can greatly enhance absorbance ( α), while the composition, thickness and roughness of thin films can greatly influence the emissivity ( ɛ). The highest photo-thermal conversion efficiency was up to 0.86 ( α/ ɛ=0.94/0.08) for thin films prepared at 80°C/5min, which proved that the CuO_x thin films can be served as high performance solar selective absorbers.

Keywords: Copper oxide; Solar selective absorber; Absorbance; Emissivity

Structural characterization of Ni and Ni/Ti ohmic contact on n-type 4H–SiC by M. Siad; M. Abdesselam; N. Souami; A.C. Chami (pp. 10737-10742).

► Structural characterization of Ni layer and Ni/Ti bilayer contacts on n-type 4H–SiC. ► Study of Ni-silicides and the redistribution of carbon, after annealing at 950°C, in the Ni/SiC and the Ni/Ti/SiC contacts. ► Rutherford Backscattering Spectrometry (RBS) at E_α=3.2MeV. ► Nuclear reaction analysis (NRA) at E_d=1MeV. ► Scanning electron microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) techniques.In this study, we report on the structural characterization of Ni layer and Ni/Ti bilayer contacts on n-type 4H–SiC. The resulting Ni-silicides and the redistribution of carbon, after annealing at 950°C, in the Ni/SiC and the Ni/Ti/SiC contacts are particularly studied by Rutherford Backscattering Spectrometry (RBS) at E_α=3.2MeV, nuclear reaction analysis (NRA) at E_d=1MeV, scanning electron microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) techniques.

Keywords: SiC; Ohmic contact; Nickel; Titanium; RBS; NRA; SEM/EDS

Pinning–depinning behavior in the wetting of (0001) α-Al₂O₃ single crystal by molten Mg by Laixin Shi; Ping Shen; Dan Zhang; Qichuan Jiang (pp. 10743-10747).

► The evaporation-coupled wetting was studied using an improved sessile drop method. ► Three characteristic wetting stages were identified. ► A distinct pinning–depinning behavior was observed. ► Underlying mechanisms were proposed from the viewpoints of energetics and geometries.Wetting of (0001) α-Al₂O₃ single crystal by molten Mg was studied by an improved sessile drop method in a purified flowing Ar atmosphere. A distinct pinning–depinning behavior was observed during the evaporation-coupled wetting process. The underlying mechanism for this behavior was expatiated from the viewpoints of energetics and geometries at the triple junction.

Keywords: Wetting; Magnesium; Pinning–depinning; Modeling

X-ray absorption and emission spectroscopic investigation of Mn doped ZnO films by J. Jin; G.S. Chang; Y.X. Zhou; X.Y. Zhang; D.W. Boukhvalov; E.Z. Kurmaev; A. Moewes (pp. 10748-10751).

► We employed soft X-ray spectra to investigate the electronic structure of (Zn,Mn)O.► Band gap narrowing of (Zn,Mn)O is due to Mn doping and sp– d exchange interactions.► High-energy Mn 3 d subband can be explained as a result of ferromagnetism in (Zn,Mn)O. ► Ferromagnetism in (Zn,Mn)O is carrier-induced and not due to the secondary phases.The electronic structure of (Zn,Mn)O films with different Mn concentrations has been investigated by element-selective soft X-ray absorption and emission spectroscopy. The band gap narrowing of (Zn,Mn)O with increase of Mn concentration (<20% Mn) is attributed to the Mn doping and sp– d exchange interactions. According to analysis of the O Kα and resonant Mn L_2,3 X-ray emission spectra, the splitting of Mn 3 d subbands is related to Mn-derived states. It indicates that ferromagnetic coupling in (Zn,Mn)O can be taken into account to be carrier-induced. The presence of antiferromagnetism in the heavier Mn-doped films can be explained in terms of the existence of MnO secondary phases.

Keywords: (Zn,Mn)O; sp; –; d; exchange interactions; X-ray spectroscopy

Synthesis of boron nitride coatings on quartz fibers: Thickness control and mechanism research by Yu Zheng; Shubin Wang (pp. 10752-10757).

► Boron nitride coatings were synthesized on quartz fibers by dip-coating. ► The relationship between coating thicknesses and dip times was obtained. ► Micro cavity bodies, forming in heat-treatment, could help the synthesis process.Boron nitride (BN) coatings were successfully synthesized on quartz fibers by dip-coating in boric acid and urea solutions at 700°C. The SEM micrographs indicated that the quartz fibers were fully covered by coatings with smooth surface. The XRD, FT-IR, XPS spectra and HR-TEM results showed that the composition of the coatings which combined closely with the quartz fibers was polycrystalline h-BN. By changing the dip circles, the coating thickness was well controlled. The thicknesses of samples dipped less than six circles increased linearly with dipping-circles; and the increment of coating thickness would slow down when the fibers were dipped 10 circles. After being dipped for 10 circles, the thickness was about 300nm. The coating thickness was also established by calculation and the calculated results were consistent with the results measured by micrograph.

Keywords: Boron nitride; Fiber coatings; Dip-coating

Decorating graphene sheets with Pt nanoparticles using sodium citrate as reductant by Yong Qian; Chunyan Wang; Zhang-Gao Le (pp. 10758-10762).

► We demonstrated that sodium citrate could convert GO to GNS for the first time, which was commonly used as an environmentally friendly reducing and stabilizing reagent for Pt nanoparticles preparation. ► A uniform distribution of Pt nanoparticles on the surface of GNS and Pt/GNS hybrid materials can be easily obtained in simple reducing reaction by use of sodium citrate. ► Pt/GNS exhibits high electrochemical activity.In this paper, we proposed a novel and green approach for the synthesis of graphene nanosheets (GNS) and Pt nanoparticles–graphene nanosheets (Pt/GNS) hybrid materials, employing graphene oxide (GO) as precursor and sodium citrate as environmentally friendly reducing and stabilizing agent. The microstructures of GO and Pt/GNS were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and electrochemical measurements. The results confirmed that the uniform size distribution of Pt nanoparticles on the surface of GNS without agglomerates could be easily obtained via using sodium citrate as reductant, moreover the Pt/GNS hybrids exhibited high electrochemical activity.

Keywords: Graphene sheets; Sodium citrate; Hybrid materials

Synthesis of nanorods and mixed shaped copper ferrite and their applications as liquefied petroleum gas sensor by Satyendra Singh; B.C. Yadav; Rajiv Prakash; Bharat Bajaj; Jae Rock lee (pp. 10763-10770).

► Mixed shaped (nanocubes/nanospheres) and nanorods of copper ferrite were synthesized by co-precipitation method. ► The influence of surface morphology on the LPG sensing properties of copper ferrite was investigated. ► The role of PEG in the synthesis for obtaining uniform sphericals/nanocubes like surface morphology has been demonstrated. ► Mixed shaped copper ferrite shows an improved sensing performance in comparison with that of the CuFe₂O₄ nanorods. ► The maximum sensor response obtained with mixed shaped CuFe₂O₄ to LPG is 57.Present paper reports the preparation and characterization of nanorods and mixed shaped (nanospheres/nanocubes) copper ferrite for liquefied petroleum gas (LPG) sensing at room temperature. The structural, surface morphological, optical, electrical as well as LPG sensing properties of the copper ferrite were investigated. Single phase spinel structure of the CuFe₂O₄ was confirmed by XRD data. The minimum crystallite size of copper ferrite was found 25nm. The stoichiometry was confirmed by elemental analysis and it revealed the presence of oxygen, iron and copper elements with 21.91, 12.39 and 65.70 atomic weight percentages in copper ferrite nanorods. The band gap of copper ferrite was 3.09 and 2.81eV, respectively for nanospheres/nanocubes and nanorods. The sensing films were made by using screen printing technology and investigated with the exposure of LPG. Our results show that the mixed shaped CuFe₂O₄ had an improved sensing performance over that of the CuFe₂O₄ nanorods, of which a possible sensing mechanism related to a surface reaction process was discussed. Sensor based on mixed shaped copper ferrite is 92% reproducible after one month. The role of PEG in the synthesis for obtaining nanospheres/nanocubes has also been demonstrated.

Keywords: LPG sensor; CuFe; ₂; O; ₄; Surface morphology; Poly-ethylene glycol (PEG)

Synthesis and characterization of Parylene C/nanosilica composite film by Xin Chai; Jingquan Liu; Qing He; Guangbin Peng; Chunsheng Yang (pp. 10771-10774).

► We prepare Parylene C composite film doped with modified nanosilica particles. ► The nanosilica particles in the film have uniform diameters and distribution. ► The composite exhibits excellent thermal stability and mechanical properties. ► The degradation temperature is about 100°C higher than Parylene C film. ► The elastic limit is increased by 10N.A smooth, semitransparent and homogeneous Parylene C/nanosilica composite film was prepared by chemical vapor deposition (CVD). The film was deposited onto the Si substrate coated with a modified nanosilica layer. The nanosilica modified by silane coupling agent have uniform diameters and distribution in the film. The diameter can be roughly estimated in the range of 80–150nm. The thermal stability of the composite film containing modified silica nanoparticles is better than that of the pure and doped film with commercial nanoparticles, which is ascribed to the strong chemical bonding between the modified nanosilica and Parylene monomers. σ_e and σ_s, as elastic limit and yield stress, are about 21.2MPa and 23.4MPa of the pure film, compared with 32.1MPa and 33.4MPa of the composite film due to the nanosize effect and intensive interface adhesion of silica nanoparticles as reinforcement.

Keywords: Modification; Parylene C/nanosilica; Nanocomposites

Room temperature weak ferromagnetism and magnetoconductance in functional CuO film by S. Das; S. Majumdar; S. Giri (pp. 10775-10779).

► Properties of sol–gel derived CuO films are strongly influenced by the substrates, on which films are deposited. ► The ferromagnetic and semiconducting properties are clearly demonstrated at room temperature. ► A large magnetoconductance is observed at room temperature. ► Large magnetoconductance and convincing ferromagnetism in granular CuO film are promising for spintronic applications. ►The granular CuO films are deposited on n-Si (100) and sapphire substrates using sol–gel route. Small microstrain leads to ∼5 times larger grain sizes (200–300nm) and ∼2.5 times larger film thickness (∼0.57μm) for sapphire than n-Si substrate, which are confirmed by X-ray diffraction and Atomic Force Microscopy. A diode-like current–voltage characteristics are observed for film deposited on n-Si substrate, which is absent for sapphire substrate. Typical manifestation of ferromagnetic character is observed for CuO films, which are strongly influenced by the substrates. Magnetic anisotropy is larger for sapphire substrate than n-Si substrate. At room temperature considerably large magnetoconductance ∼21% and soft ferromagnetic character of CuO film on n-Si substrate are attractive for functional applications.

Keywords: CuO film; Sol–gel technique; Ferromagnetism; Semiconductor; Spintronics

Biocompatible polymeric implants for controlled drug delivery produced by MAPLE by Irina Alexandra Paun; Antoniu Moldovan; Catalin Romeo Luculescu; Maria Dinescu (pp. 10780-10788).

► Implants consisting of indomethacin coated with polymeric films were produced by MAPLE. ► The implants were tested in vitro in conditions close to those encountered inside the body. ► The implants containing PEG:PLGA films exhibit enhanced biocompatibility. ► The implants containing PEG:PLGA films offer prolonged release rates of the drug. ► The drug release is controlled by a diffusion mediated mechanism (Higuchi's model).Implants consisting of drug cores coated with polymeric films were developed for delivering drugs in a controlled manner. The polymeric films were produced using matrix assisted pulsed laser evaporation (MAPLE) and consist of poly(lactide-co-glycolide) (PLGA), used individually as well as blended with polyethylene glycol (PEG). Indomethacin (INC) was used as model drug. The implants were tested in vitro (i.e. in conditions similar with those encountered inside the body), for predicting their behavior after implantation at the site of action. To this end, they were immersed in physiological media (i.e. phosphate buffered saline PBS pH 7.4 and blood). At various intervals of PBS immersion (and respectively in blood), the polymeric films coating the drug cores were studied in terms of morphology, chemistry, wettability and blood compatibility. PEG:PLGA film exhibited superior properties as compared to PLGA film, the corresponding implant being thus more suitable for internal use in the human body. In addition, the implant containing PEG:PLGA film provided an efficient and sustained release of the drug. The kinetics of the drug release was consistent with a diffusion mediated mechanism (as revealed by fitting the data with Higuchi's model); the drug was gradually released through the pores formed during PBS immersion. In contrast, the implant containing PLGA film showed poor drug delivery rates and mechanical failure. In this case, fitting the data with Hixson–Crowell model indicated a release mechanism dominated by polymer erosion.

Keywords: MAPLE; Thin films; Polymers; Biocompatibility; Drug delivery

Photoluminescence and photoelectrochemical properties of nanocrystalline ZnO thin films synthesized by spray pyrolysis technique by N.L. Tarwal; V.V. Shinde; A.S. Kamble; P.R. Jadhav; D.S. Patil; V.B. Patil; P.S. Patil (pp. 10789-10794).

► Synthesis of nanocrystalline ZnO thin films onto glass and ITO coated glass substrates by SPT. ► The substrate temperature dependent properties of ZnO thin films were investigated. ► The sample deposited at 450°C shows the better photoelectrochemical performance.A simple and inexpensive spray pyrolysis technique (SPT) was employed for the synthesis of nanocrystalline zinc oxide (ZnO) thin films onto soda lime glass and tin doped indium oxide (ITO) coated glass substrates at different substrate temperatures ranging from 300°C to 500°C. The synthesized films were polycrystalline, with a (002) preferential growth along c-axis. SEM micrographs revealed the uniform distribution of spherical grains of about 80–90nm size. The films were transparent with average visible transmittance of 85% having band gap energy 3.25eV. All the samples exhibit room temperature photoluminescence (PL). A strong ultraviolet (UV) emission at 398nm with weak green emission centered at 520nm confirmed the less defect density in the samples. Moreover, the samples are photoelectrochemically active and exhibit the highest photocurrent of 60μA, a photovoltage of 280mV and 0.23 fill factor (FF) for the Zn₄₅₀ films in 0.5M Na₂SO₄ electrolyte, when illuminated under UV light.

Keywords: Zinc oxide thin films; X-ray diffraction; Optical properties; Photoluminescence

Polysulfobetaine films prepared by electrografting technique for reduction of biofouling on electroconductive surfaces by Marek Stach; Zuzana Kroneková; Peter Kasák; Jozef Kollár; Martin Pentrák; Matej Mičušík; Dušan Chorvát Jr.; Tim S. Nunney; Igor Lacík (pp. 10795-10801).

► Poly(2-(dimethylamino)ethyl methacrylate) is covalently attached to the electroconductive substrate by electrografting polymerization. ► Electrografted film can be effectively modified to the corresponding sulfobetaine structure. ► Electrografted film was thoroughly characterized by various complementary techniques in terms of surface chemistry and topography. ► Non-biofouling properties were confirmed for electrografted film after modification to zwitterionic character.The sulfobetaine films were prepared on stainless steel and golden surfaces. In the first step, the poly(2-(dimethylamino)ethyl methacrylate) film was created by employing the electrografting polymerization technique. In the second step, this film was modified to polysulfobetaine, i.e. the polymer film bearing the zwitterionic groups. The presence of the electrografted film and its modification were determined by contact angle measurements, infrared spectroscopy in reflectance mode and X-ray photoelectron spectroscopy. The prepared films were homogeneous with the thickness from about 5 to 26nm as determined by X-ray photoelectron spectroscopy. The atomic force microscopy measurements showed the increase of surface roughness upon the surface coating. In vitro tests using adherent RAT-2 fibroblast cells and fluorescently labelled bovine serum albumin proteins showed that prepared polysulfobetaine films can be used in applications requiring the resistance against cell attachment and biofouling.

Keywords: Electrografting; Zwitterions; XPS; ATR-FTIR; CLSM; Contact angle; Biofouling; 2-(Dimethylamino)ethyl methacrylate; Sulfobetaine

Preparation and characterization of silicon oil based ferrofluid by H.J. Chen; Y.M. Wang; J.M. Qu; R.Y. Hong; H.Z. Li (pp. 10802-10807).

► Silicon oil based ferrofluid was prepared using silicon oil surfactant EtO-PDMS as modifier. ► The optimal amount of TEOS and EtO-PDMS was obtained. ► Silicon oil based ferrofluid had high magnetism and good stability.Stable silicon oil based ferrofluid was prepared in the present investigation. Silicon oil surfactant ethoxy terminated polydimethylsiloxane was used to modify the Fe₃O₄ nanoparticles. The Fe₃O₄ nanoparticles were firstly coated with a SiO₂ layer by the hydrolysis of tetraethoxysilane. Then using the active hydroxyl groups on the surface of the SiO₂, silicon oil surfactant was covalently grafted onto the Fe₃O₄ nanoparticles surface. The ethoxy terminated polydimethylsiloxane has similar molecular chain structure and good compatibility with that of the carrier liquid, thus ensuring stable dispersion of modified Fe₃O₄ in the carrier silicon oil. The interaction between Fe₃O₄ and the modifier was characterized by IR and XPS. The crystal structure and the magnetic properties of the Fe₃O₄ nanoparticles were determined by XRD and VSM, respectively. The size and morphology of the particles were observed using TEM. The properties of the silicon oil based ferrofluid were characterized by Gouy magnetic balance. The results indicated that the ferrofluid had high magnetism and good stability. The rheological properties and thermostability of the ferrofluid were also investigated.

Keywords: Ferrofluid; Magnetic fluid; Nanoparticle; Silicon oil; Rheology

The electrochemical preparation and microwave absorption properties of magnetic carbon fibers coated with Fe₃O₄ films by Xianguang Meng; Yizao Wan; Qunying Li; Jing Wang; Honglin Luo (pp. 10808-10814).

► Uniform and compact Fe₃O₄ films are fabricated on carbon fibers by electrodeposition. ► Composition and morphology of products are influenced by fiber surface pretreatment. ► Microwave property of magnetic fibers varies greatly with preparation temperature. ► Overlarge permittivity adversely affects microwave property of magnetic fibers. ► Magnetic fibers prepared at 75°C exhibit good microwave absorption property.Electrodeposition was employed to fabricate magnetite (Fe₃O₄) coated carbon fibers (MCCFs). Temperature and fiber surface pretreatment had a significant influence on the composition and morphology of Fe₃O₄ films. Uniform and compact Fe₃O₄ films were fabricated at 75°C on both nitric acid treated and untreated carbon fibers, while the films prepared at 60°C were continuous and rough. Microwave measurements of MCCF/paraffin composites (50wt.% of MCCFs, pretreated carbon fibers as deposition substrates) were carried out in the 2–18GHz frequency range. MCCFs prepared at 60°C obtained a much higher loss factor than that prepared at 75°C. However, the calculation results of reflection loss were very abnormal that MCCFs prepared at 60°C almost had no absorption property. While MCCFs prepared at 75°C exhibited a good absorption property and obtained −10dB and −20dB refection loss in wide matching thickness ranges (1.0–6.0mm and 1.7–6.0mm range, respectively). A secondary attenuation peak could also be observed when the thickness of MCCF/paraffin composite exceeded 4.0mm. The minimum reflection loss was lower.

Keywords: Carbon fibers; Fe; ₃; O; ₄; films; Electrodeposition; Surface treatment; Microwave absorption

Structure–property and composition–property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation by A. Tóth; M. Veres; K. Kereszturi; M. Mohai; I. Bertóti; J. Szépvölgyi (pp. 10815-10820).

► Inverse relationship for lightness vs. I_D/ I_G and for chroma vs. I_D/ I_G. ► Direct relationship for Θ_w vs. I_D/ I_G. ► Inverse relationship for γ_tot vs. I_D/ I_G and γ_disp vs. I_D/ I_G. ► Inverse relationship for electrical resistance vs. surface C-content. ► Inverse relationship for electrical resistance vs. π→ π* satellite of C 1s.The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and I_D/ I_G ratio and between chroma and I_D/ I_G ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp² carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the I_D/ I_G ratio and inverse correlations between surface energy and I_D/ I_G ratio and between dispersive component of surface energy and I_D/ I_G ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp² carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the π→ π* shake-up satellite of the C 1s peak.

Keywords: Poly(ethylene terephthalate); Plasma-based ion implantation; Colorimetry; Wettability; Electrical resistance

Organo-silane coated substrates for DNA purification by L. Pasquardini; L. Lunelli; C. Potrich; L. Marocchi; S. Fiorilli; D. Vozzi; L. Vanzetti; P. Gasparini; M. Anderle; C. Pederzolli (pp. 10821-10827).

► Thermally grown silicon oxide, silicon oxide by PECVD and Pyrex were silanized. ► DNA capture and elution by AEEA- or APTES-treated surfaces were evaluated. ► AEEA-surface releases more DNA than APTES. ► APTES-treated PECVD or Pyrex is the best for DNA purification. ► Possible use to purify DNA from blood or short DNA fragments from longer ones.The use of blood as DNA source to be employed in genetic analysis requires a purification process in order to remove proteins, lipids and any other contaminants, such as hemoglobin, which inhibit PCR. On the other hand, the increasing demand of miniaturized and automated biological tests able to reduce time and cost of analysis, requires the development and the characterization of materials aimed to perform the DNA purification processes in micro-devices. In this work we studied the interaction of DNA molecules with modified silicon based substrates, positively charged after deposition of a (3-aminopropyl)triethoxysilane (APTES) or 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEEA) interfacial layer. The evaluation of the DNA adsorption and elution capacity of different substrates (thermally grown silicon oxide, silicon oxide obtained by plasma enhanced chemical vapour deposition, and Pyrex^®) was studied taking into account the nature of the substrate and the effect of DNA length (in the 208–50,000 base pairs range). Main findings are that DNA elution capacity depends both on the utilized substrate and on the choice of the silanizing agent. Higher DNA recovery was obtained from AEEA-modified substrates, but the eluted DNA had different electrophoretic properties from native DNA. DNA with the same electrophoretic behaviour as genomic DNA was instead recovered from APTES-treated surfaces. Furthermore, the length of DNA present in the starting material strongly modulates the elution efficiency, longer DNA being released in a lesser amount, suggesting that opportunely modified surfaces could be used as systems for differential DNA separation.

Keywords: DNA extraction; Electrostatic interaction; Organo-silane molecules

Improvement in the properties of plasma-sprayed metallic, alloy and ceramic coatings using dry-ice blasting by Shujuan Dong; Bo Song; Bernard Hansz; Hanlin Liao; Christian Coddet (pp. 10828-10833).

► Dry-ice blasting was introduced into atmospheric plasma spraying for improving properties of coatings. ► A denser steel or CoNiCrAlY alloy coating with a lower content of oxide was achieved with the dry-ice blasting. ► The adhesive strength of Al₂O₃ coating plasma-sprayed with dry-ice blasting was nearly increased by 30%. ► Dry-ice blasting was found to potentially clean organic substances adsorbed on the substrates besides a cooling effect during APS.Dry-ice blasting, as an environmental-friendly method, was introduced into atmospheric plasma spraying for improving properties of metallic, alloy and ceramic coatings. The deposited coatings were then compared with coatings plasma-sprayed using conventional air cooling in terms of microstructure, temperature, oxidation, porosity, residual stress and adhesion. It was found that a denser steel or CoNiCrAlY alloy coating with a lower content of oxide can be achieved with the application of dry-ice blasting during the plasma spraying. In addition, the adhesive strength of Al₂O₃ coating deposited with dry-ice blasting exceeded 60MPa, which was nearly increased by 30% compared with that of the coating deposited with conventional air cooling. The improvement in properties of plasma-sprayed metallic, alloy and ceramic coatings caused by dry-ice blasting was attributed to the decrease of annulus-ringed disk like splats, the better cooling efficiency of dry-ice pellets and even the mechanical effect of dry-ice impact.

Keywords: Atmospheric plasma spraying; Dry-ice blasting; Steel coating; CoNiCrAlY coating; Al; ₂; O; ₃; coating

AgSbSe₂ and AgSb(S,Se)₂ thin films for photovoltaic applications by J.G. Garza; S. Shaji; A.C. Rodriguez; T.K. Das Roy; B. Krishnan (pp. 10834-10838).

► Silver antimony selenide (AgSbSe₂) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb₂S₃), silver selenide (Ag₂Se), selenium (Se) and silver (Ag). ► Polycrystalline AgSbSe₂ or AgSb(S,Se)₂ thin films were formed depending on selenium content in the precursor films. ► A photovoltaic structure: glass/ITO/CdS/AgSbSe₂/Al was formed and obtained V_oc=435mV and J_sc=0.08mA/cm² under illumination.Silver antimony selenide (AgSbSe₂) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb₂S₃), silver selenide (Ag₂Se), selenium (Se) and silver (Ag). Sb₂S₃ thin film was prepared from a chemical bath containing SbCl₃ and Na₂S₂O₃, Ag₂Se from a solution containing AgNO₃ and Na₂SeSO₃ and Se thin films from an acidified solution of Na₂SeSO₃, at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350°C in vacuum (10⁻³Torr) for 1h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe₂ or AgSb(S,Se)₂ depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV–visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe₂/Al was formed, in which CdS was deposited by chemical bath deposition. J– V characteristics of this structure showed V_oc=435mV and J_sc=0.08mA/cm² under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe₂ as an absorber material by a non-toxic selenization process is achieved.

Keywords: Silver antimony selenide; AgSb(S,Se); ₂; Thin films; Chemical bath deposition

Influence of FeSO₄ concentration on thermal emissivity of coatings formed on titanium alloy by micro-arc oxidation by Hui Tang; Tiezhu Xin; Qiu Sun; Chuangui Yi; Zhaohua Jiang; Fuping Wang (pp. 10839-10844).

► Ceramic coatings with high emission were fabricated on Ti6Al4V alloy by microarc oxidation (MAO). ► The influence of FeSO₄ concentration on the spectral emission was studied. ► The bonding strength thermal shock resistance of the coatings were influenced by FeSO₄ concentration. ► Coatings possessed high emission and good bonding strength, thermal shock resistance.Ceramic coatings with high emission were fabricated on Ti6Al4V alloy by microarc oxidation (MAO) with additive FeSO₄ into the electrolyte. The microstructure, chemical composition and chemical state of the coatings were determined by SEM, XRD, EDS and XPS, respectively. The bonding strength between the coating and substrate was studied by tensile strength test, together with the thermal shock resistance of the coating. The results showed that Fe content in the coating layer significantly affect its thermal emissivity. The relative content of Fe in the coatings surface increased at first and then decreased with increasing the concentration of FeSO₄ in electrolytes, so does the emissivity of the coatings. The bonding strength became weaker with increasing the concentration of FeSO₄. In addition, the coating remains stable over 40 cycles of thermal shocking. The coating formed at 3g/L FeSO₄ demonstrates the highest an average spectral emissivity value around of 0.87, and bonding strength higher than 33MPa.

Keywords: Microarc oxidation; Titanium alloy; FeSO; ₄; High emissivity; Bonding strength; Thermal shock resistance

Effects of electric field annealing on the interface diffusion of Cu/Ta/Si stacks by L. Wang; Z.H. Cao; K. Hu; Q.W. She; X.K. Meng (pp. 10845-10849).

► The atom diffusion is accelerated by the electric field. ► The acceleration is enhanced with an increment of annealing temperature. ► It is resulted from the increase of the mobility of vacancies and atoms.In the present paper, the effects of electric field annealing on interface diffusion of Cu/Ta/Si stacks were studied by means of XRD, XPS and TEM. The barrier property of Ta films was evaluated based on the diffusion of Cu atoms. It was found that the external electric field accelerates the diffusion of Cu atoms through Cu/Ta/Si interfaces during annealing. With the increment of annealing temperature, the effect of the electric field upon the atomic diffusion becomes more significant. The mechanism of accelerated interface diffusion is suggested and the failure of Ta barrier layer is discussed based on the mobility of vacancies and Cu atoms inside Cu/Ta/Si stacks caused by the electric field.

Keywords: Electric field; Annealing; Interface diffusion; Cu/Ta/Si stacks

Synthesis and field emission properties of GaN nanowires by Enling Li; Zhen Cui; Yuanbin Dai; Danna Zhao; Tao Zhao (pp. 10850-10854).

► Ni as catalyst, high-quality GaN nanowires films were synthesized by chemical vapor deposition (CVD). ► The open electric field of the sample1 was 9.1V/μm. ► The field emission properties of GaN nanowires films are related to the roughness and density of the nanowires in the film.Gallium nitride (GaN) nanowires grown on nickel-coated n-type Si (100) substrates have been synthesized using chemical vapor deposition (CVD), and the field emission properties of GaN nanowires have been studied. The results show that (1) the grown GaN nanowires, which have diameters in the range of 50–100nm and lengths of several micrometers, are uniformly distributed on Si substrates. The characteristics of the grown GaN nanowires have been investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and through these investigations it was found that the GaN nanowires are of a good crystalline quality (2) When the emission current density is 100μA/cm², the necessary electric field is an open electric field of around 9.1V/μm (at room temperature). The field enhancement factor is ∼730. The field emission properties of GaN nanowires films are related both to the surface roughness and the density of the nanowires in the film.

Keywords: GaN nanowire; Chemical vapor deposition (CVD); Field emission; Open electric field

The effect of deposition temperature on the surface coverage and morphology of iron-phosphate coatings on low carbon steel by J.P. Popić; B.V. Jegdić; J.B. Bajat; Đ. Veljović; S.I. Stevanović; V.B. Mišković-Stanković (pp. 10855-10862).

► The influence of temperature and concentration of NaNO₂ in iron-phosphating bath was investigated. ► The increase in temperature of the NaNO₂-free bath up to 70°C caused increase in surface coverage. ► The addition of NaNO₂ increased surface coverage at temperatures lower than 50°C. ► The increase of NaNO₂ concentration decreased phosphate crystals size, favouring phosphate nucleation with better crystals packing. ► Phosphate crystals had laminated and needle-like structures.The influence of deposition temperature and concentration of NaNO₂ in the phosphating bath on the surface morphology and coverage of iron-phosphate coatings on low carbon steel was investigated. The phosphate coatings were chemically deposited on steel from phosphate bath at different temperatures (30–70°C) and with the addition of different amounts of accelerator, NaNO₂ (0.1, 0.5 and 1.0gdm⁻³). The morphology of phosphate coatings was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The composition of iron-phosphate coatings was determined using energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Surface coverage was evaluated by the voltammetric anodic dissolution (VAD) technique.It was shown that the increase in temperature of the NaNO₂-free phosphating bath up to 70°C caused an increase in surface coverage. The addition of NaNO₂ in the phosphating bath significantly increased the surface coverage of phosphate coatings deposited at temperatures lower than 50°C. The phosphate crystals were of laminated and needle-like structures for deposits obtained at temperatures lower than 50°C, while at higher temperatures needle-like structure was transformed to laminated structure. The increase in NaNO₂ concentration in the phosphating bath from 0.1 to 1.0gdm⁻³ did not significantly increase the surface coverage, but decreased the crystals size, consequently favouring the phosphate nucleation and better packing of the crystals.

Keywords: Low carbon steel; Iron-phosphate coatings; Surface coverage; VAD; AFM; SEM

Application of factor analysis to XPS valence band of superparamagnetic iron oxide nanoparticles by L. Minati; V. Micheli; B. Rossi; C. Migliaresi; L. Dalbosco; G. Bao; S. Hou; G. Speranza (pp. 10863-10868).

. Superparamagnetic iron oxide nanoparticles were characterized by Raman and X-ray photoelectron spectroscopy to quantify the amount of maghemite and magnetite in the nanoparticles.Display Omitted► Magnetic iron oxide nanoparticles. ► Spectroscopic analysis of the nanoparticles.► Presence of magnetite e maghemite phases.► Quantification of the phases by analysis of the XPS valence band.X-Ray photoelectron spectra of nano-sized superparamagnetic iron oxide nanoparticles were examined with the aim to discriminate the different degree of iron oxidation. Careful analysis of the valence band regions reveals the presence of both Fe₃O₄ and Fe₂O₃. The application of factor analysis enabled us to extract the relative molar concentrations of these oxides in the nanoparticles. This is of particular interest in improving the magnetic properties of iron oxide nanoparticles whose superparamagnetic character can be optimized to obtain better contrast in images from nuclear magnetic resonance. As a result, the factor analysis allows tuning the nanoparticle synthesis conditions in order to obtain the optimal magnetic properties for imaging. Results obtained by the XPS valence band analysis were compared to the transmission electron microscopy, X-ray diffraction and Raman measurements.

Keywords: Magnetic iron oxide; Nanocrystals; Raman spectroscopy; X-ray photoelectron spectroscopy; Factor analysis

Effect of RF power and sputtering pressure on the structural and optical properties of TiO₂ thin films prepared by RF magnetron sputtering by Prabitha B. Nair; V.B. Justinvictor; Georgi P. Daniel; K. Joy; V. Ramakrishnan; P.V. Thomas (pp. 10869-10875).

► Preparation of nanocrystalline TiO₂ thin films from a ceramic target by RF magnetron sputtering. ► The use of micro Raman spectroscopic analysis for the unambiguous presence of anatase and rutile phases in amorphous-like TiO₂ films. ► Analysis of optical parameters of nanocrystalline films using the concept of quantum confinement effect. ► Study of PL spectra of pure TiO₂ thin films and the effect of sputtering parameters on the PL spectra.TiO₂ thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544–0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions.

Keywords: RF magnetron sputtering; TiO; ₂; thin films; Optical properties; Quantum size effect; Photoluminescence

Role of laser-induced plasma in ultradeep drilling of materials by nanosecond laser pulses by Nadezhda M. Bulgakova; Anton B. Evtushenko; Yuri G. Shukhov; Sergey I. Kudryashov; Alexander V. Bulgakov (pp. 10876-10882).

► We show that laser-induced plasma plume is responsible for ultradeep laser drilling. ► Much of the laser energy absorbed by plasma can be reradiated back toward the target. ► A model of thermal laser ablation under plasma reradiation conditions is developed. ► Plasma radiative heating considerably deepens the molten layer on the target. ► The proposed mechanism of ultradeep drilling is verified by experiments and modeling.Radiative effects of the laser-induced ablative plasma on the heating and ablation dynamics of materials irradiated by nanosecond laser pulses are studied by the example of graphite ablation. On the basis of combined thermal and gas dynamic modeling, the laser-induced plasma plume is shown to be a controlling factor responsible for ultradeep laser drilling due to plasma radiation, both bremsstrahlung and recombinative. We demonstrate that plasma radiative heating of the target considerably deepens the molten layer, thus explaining the observed crater depths.

Keywords: Pulsed laser ablation; Phase explosion; Ultradeep laser drilling; Laser-induced plasma; Plasma radiation; Graphite

Synthesis of Au–CeO₂/SiO₂ catalyst via adsorbed-layer reactor technique combined with alcohol-thermal treatment by Xin Jiang; Hui Deng (pp. 10883-10887).

Display Omitted► A new method was introduced to synthesize Au–CeO₂/SiO₂ catalyst. ► CeO₂ size and its surface microstructure were easily and simultaneously controlled. ► Au played an increasingly important role with reaction temperature increasing. ► The effect of CeO₂ size could be unified into that of oxygen species’ content.Au–CeO₂/SiO₂ was prepared via adsorbed-layer reactor technique combined with alcohol-thermal treatment. The catalytic performance in complete oxidation of benzene was investigated. TEM, Raman characterization showed that Au particles grew up obviously during alcohol-thermal process, while CeO₂ particles maintained 4nm in diameter. The content of oxygen vacancies and adsorbed oxygen species on catalysts surface increased apparently. Alcohol-thermally treated Au–CeO₂/SiO₂ and CeO₂/SiO₂ showed similar change in catalytic performance, and were much superior to calcined CeO₂/SiO₂. Of alcohol-thermally treated and calcined CeO₂/SiO₂, initial temperatures of the reaction were 80°C and 150°C, respectively. The benzene conversions reached 85% and 40% at 300°C.

Keywords: Benzene oxidation; Conversion platform; Adsorbed oxygen species; Low-temperature activity

The XPS and XAES spectra of Na_0.88Mn_0.56PS₃ by L. Silipigni; L. Schirò; L. Monsù Scolaro; G. De Luca; G. Salvato (pp. 10888-10892).

► Effects of long Na intercalation times on the Na2_xMn1−_xPS₃ electronic properties. ► XPS and XAES spectra on the Na2_xMn1−_xPS₃ as a function of intercalation time. ► No charge transfer between Na and MnPS₃ even with long intercalation times. ► No change in the bond between Na and MnPS₃ as a function of intercalation time. ► Na_0.88Mn_0.56PS₃ good candidate for further intercalation.Na_0.88Mn_0.56PS₃compounds have been synthesized by starting from MnPS₃ polycrystalline powders by means of a two-step cation-exchange process at a higher intercalation time than the one used for producing the literature reported Na_0.62Mn_0.69PS₃ compounds. The obtained samples have been characterized by X-ray photoelectron spectroscopy (XPS). The resulting spectra of the so-synthesized compounds have been compared with those observed in Na_0.62Mn_0.69PS₃ in our previous paper and similar electronic properties have been noted. In particular by XPS it has been shown that greater sodium content affects neither the core-level binding energies of the host matrix elements nor the type of link between Na⁺ and (Mn1−_xPS₃)⁻.

Keywords: PACS; 33.60.FyLayered intercalation materials; Sodium intercalated compounds; XPS spectra; XAES spectra

Fabrication of highly ordered CuInSe₂ films with hollow nanocones for anti-reflection by Jinrong Xiao; Ling Xu; Lei Geng; Liang Tong; Fei Yang; Jun Xu; Weining Su; Dong Liu; Yao Yu; Zhongyuan Ma; Kunji Chen (pp. 10893-10897).

Reflection for ordered hollow nanocone array has the larger suppression value than nancone-patterned films, which proves that this new surface pattern of hollow nancones has better anti-reflection effect.Display Omitted► Highly ordered CuInSe2 films with hollow nanocones are fabricated. ► Surface patterns of nanocones array and hollow nanocones array are obtained. ► Both of these textured array show anti-reflection properties. ► Hollow nanocones array has larger reflection suppression effect than nancones without hollow. ► The deeper the hollow, the more the reflection is reduced.Highly ordered CuInSe₂ films with hollow nanocones were fabricated by electron beam evaporation and nanospheres lithograph. From the AFM analyses, polystyrene nanospheres with diameter of 220nm are assembled regularly on glass substrates. After reaction ion etching under different powers and residues removal, different and new surface morphologies of substrates have been obtained, such as smooth nanocones and hollow nanocones. The diffuse reflection spectra demonstrate that films on the substrates with periodic nanopatterned structure have less reflection over wavelengths ranged from 200nm to 2500nm due to light trapping. Especially, reflection for hollow nanocone arrays has the larger suppression value than nanocone-patterned films, which proves that surface pattern of hollow nanocones has better anti-reflection effect. Furthermore, while hollow depth increases from 6nm to 9nm, its optical antireflective effect becomes remarkable. These results could yield new options for solar-cell design with higher energy conversion efficiency.

Keywords: Anti-reflection; CuInSe; ₂; Nanolithograph; Hollow

Synthesis of Mn-doped ZnS architectures in ternary solution and their optical properties by Xinjuan Wang; Qinglin Zhang; Bingsuo Zou; Aihua Lei; Pinyun Ren (pp. 10898-10902).

Sea urchin-like Mn-doped ZnS structures were synthesized via a one-pot solvothermal route in a ternary solution.Display Omitted► Mn-doped ZnS sea urchin-like architectures were synthesized via a one-pot solvothermal route in a ternary solution. ► The sea urchin-like architectures were composed of nanorods, possessing a wurtzite structures and the preferred growth orientation of nanorods was the [002] direction. ► The possible formation mechanism was discussed. The optical properties of the products were analyzed by PL spectra.Mn-doped ZnS sea urchin-like architectures were fabricated by a one-pot solvothermal route in a ternary solution made of ethylenediamine, ethanolamine and distilled water. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was demonstrated that the as-prepared sea urchin-like architectures with diameter of 0.5–1.5μm were composed of nanorods, possessing a wurtzite structures. The preferred growth orientation of nanorods was found to be the [002] direction. The PL spectra of the Mn-doped ZnS sea urchin-like architectures show a strong orange emission at 587nm, indicating the successful doping of Mn²⁺ ions into ZnS host. Ethanolamine played the role of oriented-assembly agent in the formation of sea urchin-like architectures. A possible growth mechanism was proposed to explain the formation of sea urchin-like architectures.

Keywords: Semiconductors; Nanostructure; ZnS; Solvothermal; Photoluminescence

Morphology, magnetic, magnetoresistance and optical properties of Co–Ni–Mo alloys thin films by S.I. Tanase; D. Pinzaru Tanase; M. Dobromir; V. Georgescu (pp. 10903-10909).

► Co–Ni–Mo thin films were prepared by electrodeposition onto Al substrate. ► The applied current density significantly influenced the film composition and their magnetic properties. ► The coercivity varied in the range 16.5–29kA/m depending on the molybdenum content ( c_Mo) in the films. ► We report the first observation of magnetoresistance as high as 8% in Co–Ni–Mo thin films.We present in this paper several results concerning the preparation by means of electrolysis and characterization of Co–Ni–Mo thin films. Co–Ni–Mo thin films with different molybdenum content in the range 0–25at% Mo were prepared from a complex solution containing ions of Co, Ni and Mo, using galvanostatic control, on aluminum substrates. The effects of applied current density on the morphology, magnetic, magnetoresistance, and optical properties of the electrodeposited Co–Ni–Mo films were investigated. The applied current density significantly influenced the film composition and their magnetic properties. The increase of molybdenum content in Co–Ni films (up to 25at% Mo) enhances the resistivity, but it reduces the magnetoresistance effect. We report the first observation of magnetoresistance as high as 8% in Co–Ni–Mo thin films.

Keywords: Co–Ni alloy; Thin films; Magnetic properties; Magnetoresistance

Rapid fabrication of superhydrophobic surfaces on copper substrates by electrochemical machining by Jinlong Song; Wenji Xu; Yao Lu; Xujuan Fan (pp. 10910-10916).

► A new method was developed to fabricate the superhydrophobic copper surface. ► This method does not require strong acid and alkali, but the neutral NaCl electrolyte. ► This method has a very higher efficiency than other methods. ► It just needs 3s to get the roughness required by the superhydrophobicity.Hierarchical micrometer-nanometer-scale binary rough structures were fabricated on copper substrates by electrochemical machining in a neutral NaCl electrolyte. The rough structures are composed of the micrometer scale potato-like structures and the nanometer scale cube-like structures. After modified by the fluoroalkylsilane, the copper surfaces reached superhydrophobicity with a water contact angle of 164.3° and a water tilting angle less than 9°. This method has a high processing efficiency which can take just 3s to fabricate the roughness required by the superhydrophobic surface. The effect of the processing time on wettability of the copper surfaces was investigated in this paper. The possible mechanism of the formation of the hierarchical roughness was also proposed, and the wettability of the copper surfaces was discussed on the basis of the Cassie–Baxter theory.

Keywords: Superhydrophobic surface; Rapid; Electrochemical; Copper

An easy-to-fabricate improved microinstrument for systematically investigating adhesion between MEMS sidewalls by N. Ansari; W.R. Ashurst (pp. 10917-10925).

► This paper reports on a MEMS device that can be used to study sidewall stiction. ► Details on the design, fabrication, modeling and testing of the device are reported. ► The device is easy to fabricate and overcomes some of the limitations of other devices. ► The apparent adhesion energy of OTS SAM coated sidewalls is approximately 38μJ/m².Since many potential MEMS devices may involve contact between sidewalls, studying stiction between sidewalls can be critical to the commercial success of MEMS. However, to date, only a few microinstruments dedicated to investigate sidewall stiction have been reported and even they posses several limitations. Therefore, in this paper, we report on an improved microinstrument to study sidewall stiction, which not only addresses some of the limitations of other microinstruments but is also easy to fabricate. The design, fabrication and modeling of the microinstrument are described in the paper. The paper also reports the apparent work of adhesion of octadecyltrichloro-silane (OTS) coated sidewall surfaces as well as sidewall surfaces with only native oxide on them.

Keywords: PACS; 68.35.Np; 82.45.Mp; 85.85.+jMEMS; Stiction; Sidewall; Adhesion energy; Octadecyltrichloro-silane

Bio-functionalization of electro-synthesized polypyrrole surface by heme enzyme using a mixture of Nafion and glutaraldehyde as synergetic immobilization matrix: Conformational characterization and electrocatalytic studies by Mohammed ElKaoutit; Ignacio Naranjo-Rodriguez; Manuel Domínguez; José Luis Hidalgo-Hidalgo-de-Cisneros (pp. 10926-10935).

Display Omitted► Use of glutaraldehyde entails inevitable phenomena of inter-crosslinking of immobilized proteins. ► We propose synergic matrix to enhance the conformational stability of HRP crosslinked on the surface of PPy. ► UV–vis, FT-IR and AFM were used to characterize the immobilized enzyme. ► The results validate the hypothesis of a possible introduction of HRP in Nafion ionic cluster sites.Use of a mixture of Nafion and glutaraldehyde as new immobilization matrix was described. The percentage of Nafion was optimized to prevent denaturation of horseradish peroxidase enzyme after its crosslinkage with glutaraldehyde on electro-synthesized polypyrrole surface. Topographic study by Atomic Force Microscopy (AFM) shows that the enzyme seems to have been introduced inside the ionic cluster of Nafion. The characterization of the resulting bio-interfaces by UV–vis and FT-IR shows that the intra-crosslinkage phenomena caused by the use of glutaraldehyde can be eliminated by the optimization of the concentration of Nafion additive. The secondary structure contents of native and immobilized enzyme were analyzed by a Gaussian curve fitting of the respective FT-IR spectra in the amide I region. Immobilized enzyme presented notable increasing percentages of globular and short helical structure compared with native enzyme. This indicates that immobilized enzyme was folded which is in accordance with AFM studies and supports the enzyme entrance inside ionic clutter of Nafion.Thanks to synergic effects of the polypyrrole conducting polymer and the perfluorosulfonic acid polymer Nafion, HRP enzyme was immobilized in its “native” state, the resulting biosensor was able to sense peroxide without any chemical mediator and can be categorized as third generation.

Keywords: Polypyrrole–glutaraldehyde–Nafion; Conformational changes; Horseradish peroxidase; Direct bioelectrocatalysis; Bio-interface characterization

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Applied Surface Science (v.257, #24)

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Applied Surface Science (v.257, #24)