Applied Surface Science (v.292, #C)

P2IMS depth profile analysis of high temperature boron oxynitride dielectric films by N. Badi; S. Vijayaraghavan; A. Benqaoula; A. Tempez; C. Tauziède; P. Chapon (1-4).
Existing silicon oxynitride (SiON) dielectric can only provide a very near term solution for the metal oxide semiconductor technology. The emerging high-k dielectric materials have a limited thermal stability and are prone to electrical behavior degradation which is associated with unwanted chemical reactions with silicon (Si). We investigated here applicability of amorphous boron oxynitride (BON) thin films as an emerging dielectric for high temperature capacitors. BON samples of thickness varying from 200 nm down to 10 nm were deposited in a high vacuum reactor using ion source assisted physical vapor deposition (PVD) technique. Plasma profiling ion mass spectrometry (P2IMS) was utilized to specifically determine the interface quality and best capacitor performance as a function of growth temperatures of a graded sample with alternate layers of deposited titanium (Ti) and BON layers on Si. P2IMS depth profiling of these layers were also performed to evaluate the stability of the dielectric layers and their efficacy against B dopant diffusion simulating processes occurring in activated polySi-based devices. For this purpose, BON layers were deposited on boron-isotope 10 (B10) implanted Si substrates and subsequently annealed at high temperatures up to 1050 °C for about 10 s. Results comparing inter-diffusion of B10 intensities at the interfaces of BON–Si and SiON–Si samples suggest suitability of BON as barrier layers against boron diffusion at high temperature. Stable Ti/BON/Ti capacitor behavior was achieved at optimum growth temperature of 600 °C of the BON dielectric layer. Capacitance change with frequency (10 kHz to 2 MHz) and temperature up to 400 °C is about 1% and 10%, respectively.
Keywords: BON/metal interface; High temperature dielectric; Boron diffusion; Plasma profiling ion mass spectrometry;

Adsorption behaviors of thiophene, benzene, and cyclohexene on FAU zeolites: Comparison of CeY obtained by liquid-, and solid-state ion exchange by Yucai Qin; Zhousheng Mo; Wenguang Yu; Shiwei Dong; Linhai Duan; Xionghou Gao; Lijuan Song (5-15).
Cerium containing Y zeolites were prepared by liquid- (L-CeY) and solid- (S-CeY) state ion exchange from NaY and HY, respectively. The structural and textural properties were characterized by XRD and N2 adsorption, and acidity properties were characterized by NH3 temperature-programmed desorption (NH3-TPD) and in situ FTIR spectrum of chemisorbed pyridine (in situ Py-FTIR). Furthermore, the single component adsorption and multi-component competitive adsorption behavior of thiophene, benzene and cyclohexene on those zeolites have also been studied by using vapor adsorption isotherms, solution adsorption breakthrough curves, thermogravimetry and derivative thermogravimetry (TG/DTG), frequency response (FR) and in situ FTIR techniques. The results indicate that the primary adsorption mode of benzene is simply micropore filling process, but the nature of effect of aromatics on selective adsorption of thiophene is competitive adsorption. The strong chemical adsorptions and protonization reactions of thiophene and cyclohexene occur upon the Brönsted acid sites of the HY and L-CeY zeolites, and the preferable acid catalytic protonization reactions of olefins hinder the further adsorption of sulfur compounds.
Keywords: CeY zeolites; Competitive adsorption; Protonization reaction; Oligomerization;

Two diamond-like carbon (DLC) coatings are prepared on stainless steel 304 by cathodic arc plasma deposition technology at different substrate bias voltages and arc currents (−200 V/80 A, labeled DLC-1, and −100 V/60 A, labeled DLC-2). Cavitation tests are performed by using a rotating-disk test rig to explore the cavitation erosion resistance of the DLC coating. The mass losses, surface morphologies, chemical compositions and the phase constituents of the specimens after cavitation tests are examined by using digital balance, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The results indicate that the DLC-2 coatings can elongate the incubation period of stainless steel, leading to an excellent cavitation erosion resistance as compared to the untreated stainless steel specimens. After duration of 100 h cavitation test, serious damaged surfaces and plenty of scratches can be observed on the surfaces of the stainless steel specimens, while only a few grooves and tiny pits are observed on the DLC-2 coatings. It is concluded that, decreasing micro defects and increasing adhesion can reduce the delamination of DLC coating, and the erosion continues in the stainless steel substrate after DLC coating failure, and the eroded surface of the substrate is subjected to the combined action from cavitation erosion and slurry erosion.
Keywords: Cathodic arc deposition; Diamond-like carbon; Cavitation erosion resistance; Pits;

Inline RF sputtered TAZO films for applications in hydrogenated amorphous silicon thin film solar cells by Shui-Yang Lien; Chia-Hsun Hsu; Chia-Hung Chang; Hsin-Yu Wu; In-Cha Hsieh; Da-Yung Wang (27-33).
In this paper, we aim to evaluate feasibility of replacing tin oxide (SnO2) films by in-line sputtered (titanium, aluminum)-doped zinc oxide (TAZO) as a front electrode of hydrogenated amorphous silicon (a-Si:H) thin film solar cells. The HCl wet-etching process and the device performances are investigated and optimized. The results show that the textured TAZO can have a lower sheet resistance of 7 Ω/square and a higher haze of 22% compared to commercial Asahi-U SnO2 films. The a-Si:H solar cells with a TAZO front contact is found to have a low fill factor due to a poor TAZO/p-a-Si:H interface. However, the interface problem can be significantly improved by inserting a microcrystalline p-layer silicon thin-film. In addition, the reproducibility of the wet-etching process is investigated. The fluctuation in the haze of the etched TAZO films can be obviously reduced when a multi-step wet-etching process is used. Moreover, the light soaking test is performed on the TAZO films. Only slight degradation in film properties indicates high stability with respect to time. These results encourage potential adoption of cost-effective in-line sputtered TAZO films as an alternative for the front contact of a-Si:H thin film solar cells.
Keywords: Hydrogenated amorphous silicon; Thin film solar cell; In-line sputtered; TAZO;

Well-controlled wet etching of ZnO films using hydrogen peroxide solution by Yuchao Wang; Tianzhun Wu; Mingming Chen; Longxing Su; Quanlin Zhang; Lifang Yuan; Yuan Zhu; Zikang Tang (34-38).
We propose hydrogen peroxide (H2O2) solution as a novel and promising etchant for ZnO thin film with well-controlled etching performances and enhanced ultraviolet (UV) luminescence, which is also facile, inexpensive and environmentally friendly. We have analyzed its etching mechanism and surface modification effect for ZnO. Using this etchant, fine patterns have been transferred to the ZnO single-crystal films with good fidelity. The etching performances have been comprehensively investigated using Raman spectroscopy, scanning electronic microscopy (SEM), atom force microscopy (AFM), surface profiler and photoluminescence (PL) spectrometer. The results have shown that ZnO films after the long-time etching exhibited linear etching rate, smooth profile and increased UV emission, which enables H2O2 solution as an excellent wet etchant for various ZnO-based optoelectronic devices.
Keywords: Zinc oxide; Wet etching; Hydrogen peroxide; Ultraviolet luminescence;

Growth of linear Ni-filled carbon nanotubes by local arc discharge in liquid ethanol by Takuya Sagara; Satoshi Kurumi; Kaoru Suzuki (39-43).
The cylindrical geometry of carbon nanotubes (CNTs) allows them to be filled with metal catalysts; the resulting metal-filled CNTs possess different properties depending on the filler metal. Here we report the synthesis of Ni-filled CNTs in which Ni is situated linearly and homogeneously by local arc discharge in liquid ethanol. The structural characteristics of synthesized Ni-filled CNTs were determined by transmission electron microscopy (TEM), and the relationship between pyrolysis conditions and the length and diameter of Ni-filled CNTs was examined. The encapsulated Ni was identified by a TEM-equipped energy-dispersive X-ray spectroscope and found to have a single-crystal fcc structure by nano-beam diffraction. The features of linear Ni-filled CNT are expected to be applicable to probes for magnetic force microscopy.
Keywords: Carbon nanotube; Arc discharge; Ni-filled CNT; Magnetic force microscopy;

A simple method has been developed to fabricate superhydrophobic surfaces with fractal structures with epoxy resin microspheres (ERMs). The ERMs is produced by phase separation in an epoxy-amine curing system with a silica sol (SS) dispersant. The transparent epoxy solution becomes cloudy and turns into epoxy suspension (ES) in this process. The fractal structure (two tier structure) generated by synthetic epoxy resin microspheres (ERMs) and deposited nanoincrutations on the surfaces of these ERMs, which have been observed by scanning electron microscope (SEM). The curing time of ES is an important condition to obtain films with good comprehensive performances. Superhydrophobic films can be prepared by adding extra SS into ES with a curing time longer than 5 h. The optimal curing time is 10 h to fabricate a film with good mechanical stability and high superhydrophobicity. In addition, a surface with anti-wetting property of impacting microdroplets can be fabricated by prolonging the curing time of ES to 24 h. The gradually decreased hydrophilic groups resulted from a longer curing time enable the surface to have smaller surface adhesions to water droplets, which is the main reason to keep its superhydrophobicity under impacting conditions. The coated surface is highly hydrophobic and the impacting water droplets are bounced off from the surface.
Keywords: Epoxy resin microspheres (ERMs); Silica sol; Curing time; Two-tier structures; Fractal structures; Superhydrophobicity; Microdroplets rebound;

A solvothermal method was used to synthesize Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles. CZTS/CZTSe bilayer films have been fabricated via a layer-by-layer blade coating process on the fluorine dope tin oxide (FTO) substrates. We converted conventional dye-sensitized solar cells (DSSCs) into double junction photoelectrochemical solar cells with the replacement of the Pt-coated counter electrode with the as-prepared films as composite photocathodes. Compared with conventional DSSCs, the cells show an increased short circuit current and power conversion efficiency.
Keywords: Cu2ZnSnS4; Cu2ZnSnSe4; Photocathode; Solvothermal; Photoelectrochemical solar cells; Dye-sensitized solar cells;

CO2 capture using zeolite 13X prepared from bentonite by Chao Chen; Dong-Wha Park; Wha-Seung Ahn (63-67).
Zeolite 13X was prepared using bentonite as the raw material by alkaline fusion followed by a hydrothermal treatment without adding any extra silica or alumina sources. The prepared zeolite 13X was characterized by X-ray powder diffraction, N2-adsorption–desorption measurements, and scanning electron microscopy. The CO2 capture performance of the prepared zeolite 13X was examined under both static and flow conditions. The prepared zeolite 13X showed a high BET surface area of 688 m2/g with a high micropore volume (0.30 cm3/g), and exhibited high CO2 capture capacity (211 mg/g) and selectivity to N2 (CO2/N2  = 37) at 25 °C and 1 bar. In addition, the material showed fast adsorption kinetics, and stable CO2 adsorption–desorption recycling performance at both 25 and 200 °C.
Keywords: Bentonite; Alkali fusion; Zeolite 13X synthesis; CO2 capture; Adsorption;

Transparent and superhydrophobic films with different adhesion were obtained using trimethylethoxysilane (TMES) as a co-precursor by dip-coating. Silica sol was prepared by keeping the molar ratio of tetraethylorthosilicate (TEOS), ethanol (EtOH), ammonium hydroxide (25%) constant at 1:85.7:8.6, respectively. Along with the increase in molar ratio of TMES/TEOS, the tilt angles of prepared films increased from 2 to 90°. According to the humidity test, the surface roughness is more important in humidity resistance property compared to the chemical compositions; and the films with higher surface roughness showed better humidity resistance. All the films exhibited higher transmittance than the bare substrate in visible light, and better visual transparency was obtained on the films with higher molar ratio of TMES/TEOS.
Keywords: Superhydrophobic; Humidity resistance; Adhesion; Transmittance;

Surface/interface analysis and optical properties of RF sputter-deposited nanocrystalline titanium nitride thin films by N. White; A.L. Campbell; J.T. Grant; R. Pachter; K. Eyink; R. Jakubiak; G. Martinez; C.V. Ramana (74-85).
Titanium nitride (TiN x ) thin films were grown by radio-frequency (RF) magnetron sputter deposition by varying the nitrogen content in the reactive gas mixture over a wide range. The effect of nitrogen gas flow rate on the surface and interface morphology, chemical composition and optical properties of TiN thin films was studied employing atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Analysis of the optical properties probed with SE has shown that films deposited at low (0–5 sccm) nitrogen flow rates have the highest absorption at energies <2 eV. It was also shown that Lorentz oscillators with energy positions lower than 2 eV can be distinguished from the Drude oscillator function during parameter fitting. AFM imaging analysis indicates that the roughness decreases and plateaus at approximately 1.5 nm with the introduction of a small N2 flow rate, remaining consistent thereafter. SEM cross-sectional imaging analysis indicates the dense, columnar structure for the films grown at lower nitrogen flow rates. XPS analysis of atomic composition and the chemical states indicate that the atomic composition remained nearly constant while the chemical states varied significantly among the samples as a function of N2 flow rate. XPS analyses confirm the presence of TiN x , TiO2 and TiO x N y . These process–property relationships derived could be useful for defining and expanding the range of optical and electronic applications of titanium nitrides and (oxy)nitrides.
Keywords: Titanium nitride; Thin films; XPS; Ellipsometry; Optical properties;

Fabrication and photoelectrochemical properties of ordered Si nanohole arrays by Jiuyu Ji; Heqiu Zhang; Yu Qiu; Lina Wang; Yan Wang; Lizhong Hu (86-92).
Large-area highly ordered silicon nanohole (SiNH) arrays on Si substrate have been fabricated by the combination of nanosphere lithography and metal assisted electroless etching. The diameter, length of nanoholes, and the center-to-center distance of adjacent nanoholes, can be accurately controlled by nanosphere lithography and metal assisted electroless etching conditions. The sub-wavelength structure of SiNH arrays had excellent antireflection property with a low reflectance of 3.5% within the wavelength range of 300–1000 nm. Compared to the planar Si, the SiNH samples exhibited a higher photoelectrochemical hydrogen generation performance. The improved performance was attributed to SiNH arrays providing an effective light-trapping and a higher semiconductor/electrolyte interface areas which reduce the overpotential required for photoelectrochemical hydrogen reaction. Furthermore, decorating the SiNH arrays with platinum nanoparticles (PtNPs) yielded a significantly high photovoltage of 0.12 V. The photoconversion efficiency of Pt-decorated SiNH (Pt/SiNH) arrays was 22% under the illumination of 100 mW/cm2, higher than that of SiNH arrays (15.5%) and the planar Si (8.1%).
Keywords: Silicon nanohole arrays; Electroless etching; Antireflection; Photoelectrochemistry; Solar water splitting;

Mg-rich primer as a new type protective coating provides cathodic protection for Al alloy. In this paper, a kind of phosphatizing surface treatment on Mg particles was studied in order to improve the protective performance of Mg-rich primer. After treated with phosphoric acid, a protective magnesium phosphate layer was formed on the surface of Mg particles, which had no negative influence on the cathodic protection of the Mg-rich primer for Al alloy. The coating resistance of the treated Mg-rich primer was bigger than that of untreated primer, meanwhile the coating capacitance of the treated Mg-rich primer was smaller than that of untreated primer, suggesting that the barrier effect of the primer was improved and the lifetime was extended. The magnesium phosphate layer could reduce the consumption rate of Mg particles. Meanwhile, the phosphate radicals transported to Al alloy substrate to form a product layer composed of magnesium phosphate and aluminum phosphate on the substrate surface, which decreased the corrosion rate of Al alloy and improved the protective performance of the primer.
Keywords: Aluminum alloy; Phosphatizing; Mg particle; Cathodic protection;

Effect of light illumination and temperature on P3HT films, n-type Si, and ITO by Louis Scudiero; Yang Shen; Mool C. Gupta (100-106).
The secondary electron (SE) cutoff energy region spectra are recorded before (dark), during (light) and after laser exposure (dark) for P3HT, Si, and ITO. An SE cutoff energy shift is observed when the bare n-type doped Si substrate is exposed to 532 nm light. This is attributed to the presence of a thin native oxide layer (∼1.5 nm) on Si. No energy shift is detected on the Ar sputtered clean Si. Also, no shift was observed for ITO. When exposed to light, a net SE energy cutoff shift was measured for P3HT deposited on both Si and ITO substrates at room temperature. However, no significant valence band maximum (VBM) energy shifts were measured for P3HT that was spun cast on both substrates under dark and light illumination. Furthermore, light effect was investigated at three different temperatures; 25, 70, and 160 ̊C and it is found that for P3HT, the magnitude of the SE cutoff energy change is not only substrate dependent but also depends on temperature.
Keywords: Ultraviolet photoelectron spectroscopy; Lasers; Secondary electron (SE) energy cutoff; Valence band maximum; Temperature; P3HT; Si; ITO;

Adhesion forces in AFM of redox responsive polymer grafts: Effects of tip hydrophilicity by Xueling Feng; Bernard D. Kieviet; Jing Song; Peter M. Schön; G. Julius Vancso (107-110).
The adherence between silicon nitride AFM tips and redox-active poly(ferrocenylsilanes) (PFS) grafts on gold was investigated by electrochemical AFM force spectroscopy. Before the adhesion measurements silicon nitride AFM probes were cleaned with organic solvents (acetone and ethanol) or piranha solution. Interestingly, these different AFM tip cleaning procedures drastically affected the observed adhesion forces. Water contact angle measurements on the corresponding AFM probe chips showed that piranha treatment resulted in a significant increase of AFM probe chip surface hydrophilicity compared to the organic solvent treatment. Obviously this hydrophilicity change caused drastic, even opposite changes in the tip-PFS adhesive force measurement upon electrode potential change to reversibly oxidize and reduce the PFS grafts. Our findings are of pivotal importance for AFM tip adhesion measurements utilizing standard silicon nitride AFM tips. Probe hydrophilicity must be carefully taken into consideration and controlled.
Keywords: AFM force spectroscopy; Adhesion probing; Poly(ferrocenylsilane) (PFS); Silicon nitride probe; Electrochemistry;

Dye-sensitized solar cells based on nanoparticle-decorated ZnO/SnO2 core/shell nanoneedle arrays by Yang Zhou; Chao Xia; Xiaoyan Hu; Wei Huang; A.A. Aref; Bixiao Wang; Zhengjing Liu; Yongming Sun; Wei Zhou; Yiwen Tang (111-116).
Novel ZnO/SnO2 core–shell nanoneedle arrays were developed with a two-step synthesis strategy. The strategy combines two processes: a hydrothermal synthesis of a ZnO nanoneedle array and a coating of a SnO2 layer on the surface of the ZnO nanoneedle. The addition of F to the hydrothermal reaction solution played an important role in the formation of the ZnO nanoneedle array. The ZnO/SnO2 core–shell structure was successfully achieved after depositing a thin SnO2 layer on the ZnO nanoneedle by dip-coating. Dye-sensitized solar cells (DSSCs) based on ZnO/SnO2 core–shell nanoneedle arrays were assembled, and a high conversion efficiency (η) of around 4.71% was obtained at 0.9 suns. This can be attributed to the advantages of the core–shell structure. On the one hand, it affords a larger surface area for a more dye loading and light harvesting, which result in enhancing the photocurrent of the DSSC. On the other hand, the core/shell structure passivates nanoneedle surface defects for suppressing the recombination, which leads to the increase of the open-circuit voltage. Accordingly, the enhanced photocurrent and open-circuit voltage have led to a prominent increase in the photovoltaic efficiency of around 4.71%, which is much higher than that of an ordinary ZnO nanoneedle array-based DSSC.
Keywords: ZnO/SnO2 Core–shell nanoneedle; F; High conversion efficiency; A larger surface area;

Surface structure and reaction property of CuCl2-PdCl2 bimetallic catalyst in methanol oxycarbonylation: A DFT approach by Qingsen Meng; Shengping Wang; Yongli Shen; Bing Yan; Yuanxin Wu; Xinbin Ma (117-127).
Surface structure of CuCl2-PdCl2 bimetallic catalyst (Wacker-type catalyst) was built employing density functional theory (DFT) calculations, and the reaction mechanism of methanol oxycarbonylation over the CuCl2-PdCl2 surfaces was also investigated. On the CuCl2-PdCl2 surface, the active site for methanol oxidation was confirmed as Cu-Cl-Cu (Pd). Comparing with pure CuCl2 surface, the introduction of Pd atom causes the electron repopulation on the surface and lowers the energy barrier for methanol oxidation, but the number of the active site decreases with the increasing of Pd doping volume. Agreed with previous experimental results, the Pd site is most favorable for the CO insertion, indicated by the lowest activation barrier for the formation of COOCH3 on Pd atom. The lowest energy barrier for the formation of DMC appears when COOCH3 species adsorbed on Pd atom and methoxyl adsorbed on Cu atoms, which is 0.42 eV. Finally, the reconstruction of the unsaturated surface is a spontaneous and exothermic process. Comparing with other surfaces, the rate-limiting step, methanol oxidation, on CuCl2-PdCl2 surface with Pd/Cu = 1:17 has the lowest energy barrier, which is agreed with the experimental observation that PdCl2-CuCl2 catalyst with Pd/Cu = 1:20 has the favorable activity. The adsorbed methoxyl will further lower the activation barrier of methanol oxidation, which is agreed with experimental observation that the Wacker-type catalysts have an induction period in the methanol oxidative carbonylation system.
Keywords: Mechanism; Dimethyl carbonate; Methanol; PdCl2-CuCl2; Density functional theory;

Controlling formation of gold nanoparticles generated in situ at a polymeric surface by Christopher J. Clukay; Christopher N. Grabill; Michelle A. Hettinger; Aniruddha Dutta; Daniel J. Freppon; Anthony Robledo; Helge Heinrich; Aniket Bhattacharya; Stephen M. Kuebler (128-136).
This work shows that in situ reduction of metal ions bound at a polymer surface can form nanoparticles within the polymer matrix as well as at the interface, and the size and distribution of nanoparticles between the interface and subsurface depends upon the choice of reagents and reaction conditions. Tetrachloroaurate ions were bound to cross-linked SU-8 films that were functionalized using a variety of multi-functional amines, then reduced using one of several reagents. Reduction using sodium borohydride or sodium citrate generates bands of interspersed gold nanoparticles as much as 40 nm deep within the polymer, indicating that both the Au ions and the reducing agent can penetrate the surface enabling formation of nanoparticles within the polymer matrix. Nanoparticle formation can be confined nearer to the polymer interface by reducing with hydroquinone, or by processing the polymer film in aqueous media using high molecular-weight multifunctional amines that confine the gold ions at the interface.
Keywords: Gold nanoparticle; Polymer surface; SU-8; Plasmonics; Catalysis;

Study of calixarenes thin films as chemical sensors for the detection of explosives by P. Montmeat; F. Veignal; C. Methivier; C.M. Pradier; L. Hairault (137-141).
Calix(n)arenes (n  = 4, 6, 8) are used as sensitive coatings for Quartz Crystal Microbalance (QCM)-based chemical sensors, and specially for the detection of dinitrotoluene as a model explosive molecule. Calix(n)arenes complex organic architectures were deposited by spray on gold-coated wafer surfaces, and DNT detection tests were performed by measuring both frequency changes and IR spectra during exposure to DNT vapours. The adsorption of DNT on calixarenes surface is proved by Polarisation Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) experiments, which brings a chemical characterisation of the sensing surfaces. Kinetics of interaction of DNT with the surface was measured by QCM. When deposited onto QCM, calixarenes showed an excellent sensitivity to DNT vapours; no significant effect of the size of the cage was observed.The main drawback is the poor reversibility of these sensors, possibly due to a too strong interaction of dinitrotoluene inside the cage of the calixarenes, or to a loss of the ternary structure of these molecules, which in turn induces a loss of interaction strength with host molecules.
Keywords: QCM sensors; Detection of explosives; Calixarenes; PM-IRRAS;

An environmentally friendly approach for contaminants removal using supercritical CO2 for remanufacturing industry by Wei-wei Liu; Bin Zhang; Yan-zeng Li; Yan-ming He; Hong-chao Zhang (142-148).
The cleaning technology plays an important role in product quality during the remanufacturing processing. Remanufacturing cleaning is among the most demanding steps and is a particularly essential process in remanufacturing. In the meantime, remanufacturing cleaning is often the main source of pollution in the remanufacturing process. During the past decades, supercritical fluids due to their unique properties gained an increasingly attention in many cleaning industries. The supercritical carbon dioxide as a novel cleaning technology for remanufacturing cleaning process is discussed, which can realize cleaning and drying at the same time, promoting a greener solution for remanufacturing industry. In this paper, we reported the experimental results of the effect of some operating parameters. The CO2 at different operating pressures, temperatures and residence time was made to continuously flowing over this. The decontamination rate and amount were monitored and compared. The obtained results show that the optimum parameters were operating temperature and pressure of 60 °C and 20 MPa respectively, to have the highest decontamination rate value at the investigated experimental conditions. In additon, the success of supercritical CO2 cleaning effectively promotes the research for next-generation cleaning methods for remanufacturing industry.
Keywords: Supercritical carbon dioxide; Cleaning; Remanufacturing; Oil and grease;

Lead dodecanoate coatings for the protection of lead and lead–tin alloy artifacts: Two examples by Michel De Keersmaecker; Kim Verbeken; Annemie Adriaens (149-160).
In order to understand the corrosive and morphological characteristics of lead dodecanoate protective coatings on real samples, three pipe organ samples were studied using optical microscopy (OM), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The corrosion products and elemental composition of the top layer of the different pipe organ samples were investigated. The results indicate that the three pipe organ samples are made of an alloy composed mainly of lead and tin. After immersion and the deposition of the protective coating, only lead and no tin is detected, which indicates the formation of a thick coating containing lead dodecanoate complexes.
Keywords: Pipe organ; Conservation; Sodium dodecanoate; Corrosion inhibition; XRD; SEM–EDS;

Enhanced hydrogen production by water splitting using Cu-doped TiO2 film with preferred (0 0 1) orientation by Chong Wang; Qianqian Hu; Jiquan Huang; Chen Zhu; Zhonghua Deng; Hongling Shi; Lan Wu; Zhuguang Liu; Yongge Cao (161-164).
Cu-doped TiO2 film with preferred (0 0 1) orientation was deposited by RF magnetron sputtering. Experimental results show that the preferred orientation of the film can be greatly influenced by the sputtering of copper target during the deposition. With the introduction of copper, minor rutile phase appears and the main exposed anatase facets of the film change from (1 0 1) to (0 0 1) facets. The H2 production rate of Cu-doped TiO2 film is about 810 μmol g−1  h−1, which is far higher than that of undoped TiO2 film and even about 67 times higher than that of P25 powder.
Keywords: Cu-doped TiO2 film; Preferred (0 0 1) orientation; RF magnetron sputtering; Photocatalytic water splitting; Hydrogen production;

Surface passivation of aluminum alloy 6061 with gaseous trichlorosilane: A surface investigation by Rickielle Ngongang; Eric Marceau; Xavier Carrier; Claire-Marie Pradier; Christophe Methivier; Jean-Luc Blanc; Martine Carre (165-173).
A molecular-scale investigation of the interaction at room temperature between gaseous trichlorosilane (HSiCl3), used as a passivating agent, and surfaces of aluminum alloy AA6061 in a polished or hydroxylated state is conducted. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) provide information on the topography and morphology of AA6061 before and after hydroxylation and surface passivation, while surface chemistry has been investigated by Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) and X-ray photoelectron spectroscopy (XPS). Oxidation and hydroxylation of the polished alloy surface in boiling water strongly modifies the roughness of the surface, with formation of platelets and needles of oxyhydroxide AlOOH. PM-IRRAS and XPS reveal that, upon adsorption, HSiCl3 dissociates and mainly forms HSiOH n (OAl)3−n , HSi(OSi) n (OAl)3−n and condensed HSiO x species, by reaction with ―OH groups from the AlOOH surface phase. The amount of deposited Si-containing species is larger on the rough surface of the hydroxylated alloy and this deposit is accompanied by a decrease of the amount of free ―OH groups evidenced by PM-IRRAS. These results can find applications in the field of functionalization of aluminum alloys. It is suggested that a homogeneous oxidation of the alloy surface prior to exposure to gaseous HSiCl3 may enhance the adsorption of the passivating agent.
Keywords: Aluminum alloy 6061; Passivation; Hydroxylation; AFM; PM-IRRAS; XPS;

Facile additive-free synthesis of iron oxide nanoparticles for efficient adsorptive removal of Congo red and Cr(VI) by Tao Hao; Chao Yang; Xuehui Rao; Jide Wang; Chunge Niu; Xintai Su (174-180).
The iron oxide nanoparticles had been successfully synthesized via an additive-free hydrolysis process at 75 °C for 12 h. The product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption–desorption. The results of XRD and N2 adsorption–desorption demonstrated that the as-prepared product was mainly α-Fe2O3 with a large surface area of 164.1 m2  g−1. The TEM images illustrated that the as-prepared product was found to consist of a mixture of irregular spherical nanoparticles (a diameter of ∼50 nm) and nanowhiskers (a diameter of ∼50 nm and uneven length). The as-prepared product was used to investigate its promising applications in water treatment. Due to its small size and large surface area, the maximum adsorption capacities of Congo red and Cr(VI) have been determined using the Langmuir equation and found to reach up to 253.8 and 17.0 mg g−1, respectively. The facile synthesis method and the superior adsorption performance derived from the iron oxide nanoparticles display the potential applications for the removal of Congo red and Cr(VI) from aqueous solution.
Keywords: Iron oxide nanoparticles; Water treatment; Adsorption; Congo red; Cr(VI);

According to anisotropic and inhomogeneous structure of fiber-reinforced ceramic matrix composites (FRCMC), it is difficult to control the surface quality with the traditional method used in metal material. The present paper studies the influence of diamond wheel grinding process on surface micro-topography and properties of SiO2/SiO2 composite. The research is based on some new discovery that the material enhanced fiber orientations play a key role in micro-topography of FRCMC grinding surface. Through a series of experiments, we investigate the relationship between grinding process and the quality of composites surface. We also analyze characteristics of the material surface topography height, wave distribution and surface support properties in details. This paper employs the orthogonal design to optimize grinding process parameters and also successfully models a critical condition to modify the surface characteristics. The results show that speed of grinding wheel has the greatest influence on height and surface support properties, the next is grain mesh size and depth of cut. The grain mesh size is the key factor for surface micro-topography modification. Compared to the surface with woven texture, the modified surface has better symmetrical characteristic. The research obtained will be an important technical support on improving the processing quality of FRCMC.
Keywords: Glass fibers; Composite; Grinding; Surface micro-topography; Orthogonal experiment;

The corrosion of high strength maraging steel after varied immersion times in concentrated solution, 2.0 M, of sulfuric acid has been investigated. The work was also extended to study the effect of 5-(3-aminophenyl)-tetrazole (APTA) on the inhibition of the steel corrosion. The study has been carried out using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscope (SEM) along with energy dispersive X-ray analyzer (EDX) investigations. EIS spectra showed that the corrosion and polarization resistances decrease with increasing the immersion time of the steel before measurement and increase in the presence of APTA and the increase of its concentration. Polarization data agreed with the EIS measurements and indicated that the increase of immersion time increases the corrosion of steel by increasing its corrosion current and corrosion rate and lowering its polarization resistance. On the other hand, the addition of APTA and the increase of its concentration minimized the corrosion of steel through decreasing the corrosion current and corrosion rate and increasing the polarization resistance at all exposure test periods. SEM and EDX investigations confirmed that the inhibition of the maraging steel in the 2.0 M H2SO4 solutions is achieved via the adsorption of the APTA molecules onto the steel protecting its surface from being dissolved easily.
Keywords: 5-(3-Aminophenyl)-tetrazole; Electrochemical impedance spectroscopy; High strength maraging steel; Scanning electron microscopy; Sulfuric acid;

Ni-based superalloy represents a significant metal portion of the aircraft critical structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels and excellent service performance, surface integrity is one of the most relevant parameter used for evaluating the quality of finish machined surfaces. In the study of surface integrity, the formation white layer is a very important research topic. The formation of white layer on the Ni-based superalloy machined surface will reduce the machined parts service performance and fatigue life. This paper was conducted to determine the effects of cutting speed on white layer formation in high speed machining of FGH95 Ni-based superalloy. Optical microscope, scanning electron microscope and X-ray diffraction were employed to analyze the elements and microstructures of white layer and bulk materials. The statistical analysis for grain numbers was executed to study the influence of cutting speed on the grain refinement in the machined surface. The investigation results showed that white layer exhibits significantly different microstructures with the bulk materials. It shows densification, no obvious structural features characteristic. The microstructure and phase of Ni-based solid solution changed during cutting process. The increase of cutting speed causes the increase of white layer thickness when the cutting speed is less than 2000 m/min. However, white layer thickness reduces with the cutting speed further increase. The higher the cutting speed, the more serious grains refinement in machined surface. 2-D FEM for machining FGH95 were carried out to simulate the cutting process and obtained the cutting temperature field, cutting strain field and strain rate field. The impact mechanisms of cutting temperature, cutting strain and strain rates on white layer formation were analyzed. At last, deformation-phase transformation coupling mechanism was proposed to illustrate the white layer formation mechanism in high speed machining of PM superalloy.
Keywords: White layer; FGH95; High speed machining; FEM;

Effect of sandblasting intensity on microstructures and properties of pure titanium micro-arc oxidation coatings in an optimized composite technique by Hong-Yuan Wang; Rui-Fu Zhu; Yu-Peng Lu; Gui-Yong Xiao; Kun He; Y.F. Yuan; Xiao-Ni Ma; Ying Li (204-212).
Sandblasting is one of the most effective methods to modify a metal surface and improve its properties for application. Micro-arc oxidation (MAO) could produce a ceramic coating on a dental implant, facilitating cellular differentiation and osseocomposite on it. This study aims to deposit bioceramic Ca- and P-containing coatings on sandblasted commercially pure titanium by an optimum composite technique to improve the bioactive performance. The effect of sandblasting intensity on microstructures and properties of the implant coatings is examined, and the modified surfaces are characterized in terms of their topography, phase, chemical composition, mechanical properties and hydroxyapatite (HA)-inducing ability. The results show that a moderate sandblasting micromachines the substrate in favorable combination of rough and residual stresses; its MAO coating deposits nano-hydroxyapatite after immersion in simulated body fluid (SBF) for 5 days exhibiting better bioactivity. The further improvement of the implant surface performance is attributed to an optimized composite technique.
Keywords: Sandblasting; Microstructure; Property; Micro-arc oxidation; Coating; Pure titanium;

Oxygen-deficient indium tin oxide thin films annealed by atmospheric pressure plasma jets with/without air-quenching by Wei-Yang Liao; Haoming Chang; Yao-Jhen Yang; Cheng-Che Hsu; I-Chun Cheng; Jian-Zhang Chen (213-218).
This paper reports the experimental results of oxygen-deficient ITO thin films annealed by atmospheric pressure plasma jets (APPJs) with and without air-quenching. The as-deposited oxygen-deficient ITO thin films are dark in color and gradually become transparent after N2 APPJ treatment. Quartz tubes with and without side holes are installed downstream of the APPJ to control the introduction of air into the plasma jets. Air-quenching reduces the plasma jet temperature from 580 to 385 °C but enhances the reactivity and renders faster conversion of dark ITO to transparent ITO despite the lower plasma jet temperature. With air-quenching, the transmittance (λ  = 550 nm) of a 100-nm-thick ITO thin film on glass substrate reaches 87% after 90 s of APPJ treatment, compared to 7.2% in the case of the as-deposited ITO thin film. The resistivity decreases dramatically from 1.81 × 10−2 to 8.58 × 10−4  Ω cm after 15 s of APPJ treatment with air-quenching owing to crystallization and oxidation processes that reduce the defect density in the material. Subsequently, the resistivity increases slightly to 1.71 × 10−3  Ω cm after 90 s of APPJ treatment with air-quenching because of the reaction of oxygen and ITO that reduces the oxygen vacancies. Our results demonstrate that APPJ treatment can be used as a rapid thermal annealing process for ITO thin films.
Keywords: ITO; Atmospheric pressure plasma jet; Rapid thermal annealing;

Nb-doped zinc oxide (NZO) transparent conductive thin films with highly (0 0 2)-preferred orientation were deposited on glass substrates by pulsed laser deposition method in oxygen ambience under different oxygen pressures. The as-deposited films were characterized by X-ray diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), electrical and optical characterization techniques. It was found that a desirable amount of oxygen can reduce the related defect scattering and enhance the carrier mobility. The resistivity and average optical transmittance of the NZO thin films are of 10−4  Ω cm and over 88%, respectively. The lowest electrical resistivity of the film is found to be about 4.37 × 10−4  Ω cm. In addition, the influence of oxygen pressure on optical properties in NZO thin films was systematically studied as well.
Keywords: NZO; Pulsed laser deposition; Oxygen pressure; TCO;

In order to improve the tribological properties of beryllium bronze substrate, Ti/Cu diffusion coatings were prepared by deposition and thermo-diffusing process. The substrates were firstly deposited with Ti film by magnetron sputtering. And post diffusion process was conducted at 810 °C for 4 h and then aged at 450 °C for 1 h under hydrogen plasma atmosphere in cathodic cage plasma treatment (CCPT) system. The as-obtained coating was characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness tests, and pin-on-disk tribometer. The results show that the coating consists of Cu4Ti, Cu3Ti2, and Cu (Ti) solid solution. The hardness of the coating has reached about 528 HV0.01, which is much higher than that of the substrate. The coefficient of friction decreased from 0.65 for the uncoated substrate to about 0.3 for the coated one. And the wear rate of coated samples decreased nearly 97% compared with the uncoated one, so the coated specimen has a much better wear resistance. The analysis of worn surface indicated that the coated beryllium bronze exhibited predominant oxidation wear behavior, whereas the uncoated one shown adhesive wear behavior.
Keywords: C17200 Cu–Be alloy; Intermetallic coatings; Tribological properties;

Preparation and characterization of CuInSe2 electrodeposited thin films annealed in vacuum by S. Hamrouni; Manea S. AlKhalifah; M.F. Boujmil; K. Ben Saad (231-236).
The effect of the annealing temperature on the CuInSe2 (CIS) electrodeposed films on FTO substrates has been investigated. Followed by different annealing, in vacuum and for different temperatures, X-ray diffraction has proved that the CuInSe2 films have chalcopyrite structure oriented along the (1 1 2) direction with good crystallinity at 400 °C.From the evolution of the full width at half maximum (FWHM) of the (1 1 2) peak, we have estimated the grain size versus the annealing temperature. The results show that the grain size increases from 0.45 to 0.75 μm with the annealing temperature. The morphological, optical and electrical properties of the CIS films have been investigated respectively, by the scanning electron microscopy (SEM), UV–vis spectroscopy and IV characteristics. The band gaps of the CIS films also shows an evolution when the temperature is varied. In fact the band gap decreases from 1.24 eV at 250 °C to 0.98 eV at 450 °C. The electrical characterization of the junction Al/CIS/FTO shows an interesting Schottky rectifying behavior.
Keywords: Electrodeposition; CuInSe2; CIS; Chalcopyrite; Schottky junction;

Self-assembly of carbon nanoclusters on dielectric boron nitride by Xiaoqing Tian; Yadong Wei; Scott A. Edwards; Yunjin Yu; Xingmin Cai; Jian-bin Xu (237-246).
Nucleation and growth of C nanoclusters on a dielectric boron nitride (BN) substrate is investigated by first-principles calculations. Monatomic C quantum wires, chemically bonded by one terminal atom to the BN substrate, are found to be stable during the initial growth stage when the number of atoms is less than 10. Monatomic C rings, physically adsorbed on the substrate dominate the second growth stage. The critical number of atoms for quantum rings is 22. Hexagonal honeycomb structures dominate the third growth stage. No critical size is found for hexagonal honeycomb nanoclusters, in contrast to the growth of C clusters on metal surfaces. The stability of hexagonal honeycomb nanoclusters increases with cluster size, and a graphene layer has the highest stability. The presence of C5 ring units has a negative impact on a cluster's stability and also acts as the source of a magnetic moment due to the unpaired 2p electron. 3D-like C cluster structures are not stable on a BN substrate.
Keywords: Carbon nanoclusters; Graphene; Nucleation and growth; First-principles calculation; Stability;

Regular self-microstructuring on CR39 using high UV laser dose by P. Parvin; M. Refahizadeh; S.Z. Mortazavi; K. Silakhori; A. Mahdiloo; P. Aghaii (247-255).
The UV laser induced replicas in the form of self-lining microstructures are created by high dose (with high fluence) ArF laser irradiation on CR39. Microstructures as the self-induced contours, in the form of concentric circles, appear when the laser fluence is well above the ablation threshold. It leads to the regular periodic parallel lines, i.e. circles with large radii having spatial separation 100–200 nm and line width 300–600 nm, where the number of shots increases to achieve higher UV doses. The surface wettability is also investigated after laser texturing to exhibit that a notable hydrophilicity takes place at high doses.
Keywords: Laser induced periodic surface structure (LIPSS); CR39; Self-lining microstructures; ArF excimoer laser; Hydrophilicity;

Preparation, characterization, and photocatalytic activity of porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts by Fan Yang; Baozhu Tian; Jinlong Zhang; Tianqing Xiong; Tingting Wang (256-261).
Porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts were synthesized by a multistep route, including a dealloying method to prepare porous Ag, a transformation from Ag to AgBr and AgBrI, and a photo-reduction process to form Ag nanoparticles on the surface of AgBr and AgBrI. It was found that the porous structure kept unchanged during Ag was transferred into AgBr, AgBrI, AgBr@Ag, and AgBrI@Ag. Both porous AgBr@Ag and porous AgBrI@Ag showed much higher visible-light photocatalytic activity than cubic AgBr@Ag for the degradation of methyl orange, which is because the interconnected pore channels not only provide more reactive sites but also favor the transportation of photo-generated electrons and holes. For AgBrI@Ag, AgBrI solid solution formed at the interface of AgBr and AgI, and the phase junction can effectively separate the photo-generated electrons and holes, favorable to the improvement of photocatalytic activity. The optimal I content for obtaining the highest activity is ∼10 at.%.
Keywords: Porous AgBrI@Ag; Surface plasmon resonance; Dealloying method; Photocatalytic degradation; Methyl orange;

Interface state-related linear and nonlinear optical properties of nanocrystalline Si/SiO2 multilayers by Pei Zhang; Xiaowei Zhang; Peng Lu; Jun Xu; Xin Xu; Wei Li; Kunji Chen (262-266).
Nanocrystalline Si (nc-Si)/SiO2 multilayers with dot size of 2.5 nm were prepared and their microstructures were characterized by cross-sectional transmission electron microscopy and Raman spectroscopy. A broad photoluminescence band centered at 870 nm was observed which can be ascribed to the recombination of photo-excited carriers via luminescence centers at the interfacial region of nc-Si/SiO2. Meanwhile, the nonlinear optical response of the multilayers under excitation of two laser pulse durations had been investigated through Z-scan technique, the pumping lasers were picosecond (λ  = 1.06 μm, t p  = 25 ps) and femtosecond (λ  = 800 nm, t p  = 50 fs) lasers, respectively. Under picosecond laser pumping, the saturation absorption was observed while the reverse saturation absorption happened under the femtosecond excitation. The model based on the interface state-assisted process was proposed to explain the observed optical nonlinearities.
Keywords: Luminescence; Nonlinear optical properties; Multilayers; Nanocrystalline Si;

Further damage induced by water in micro-indentations in phosphate laser glass by Jiaxin Yu; Qingyun Jian; Weifeng Yuan; Bin Gu; Fang Ji; Wen Huang (267-277).
Using a microhardness tester, artificial flaws were made by micro-indentation in N31 Nd-doped phosphate laser glass. Indentation fracture toughness, K IC, was estimated as 0.45–0.53 MPa m1/2 from these indentations. The glasses with indentations were then immersed in ultrapure water to investigate further water-induced damage of these indentations. Stress-enhanced hydrolysis leads to the propagations of radial crack, lateral cracks and microcracks in the subsurface. These crack propagations therefore cause deformation in subsurface to form annular reflections regions around the indentations and further material collapse within imprints. After the residual stresses are exhausted, the leaching plays a more dominated role in glass corrosion in the further immersion. After immersion, the material structure slackens around micro-indentation, which decreases the contact stiffness and results in a lower nano-hardness. For the surface far away from flaws, water immersion presents a weak effect on the near-surface mechanical since the matrix leaching in phosphate glass restricts the formation of hydration layer. During first 20 min immersion, due to higher chemical activity and lower fracture toughness, the radial cracks show a faster propagation in phosphate glass compared with that in K9 silicate glass. For further immersion, crack healing occurs in silicate glass but not in phosphate glass. Analysis shows that the formation of hydration layer on crack walls plays an important role in crack healing in glasses.
Keywords: Phosphate glass; Corrosion; Crack; Nanoindentation;

Fabrication of α-Fe2O3@graphene nanostructures for enhanced gas-sensing property to ethanol by Shiming Liang; Junwu Zhu; Chao Wang; Songtao Yu; Huiping Bi; Xiaoheng Liu; Xin Wang (278-284).
A simple and straightforward strategy was developed for anchoring α-Fe2O3 nanoparticles on graphene as gas sensor material. The XRD and TEM results indicate that graphene sheets are decorated with α-Fe2O3 nanoparticles with various diameters and shapes. To demonstrate the potential applications, we have fabricated gas sensors using the as-synthesized α-Fe2O3@graphene and investigated sensor activity for ethanol detection. The results show that an appropriate content of graphene dopant could effectively enhance the gas-sensing properties of α-Fe2O3 operated at different temperatures. Especially, the α-Fe2O3@graphene (contained 2 wt% of graphene) sensor exhibits better sensor performances in comparison with pure α-Fe2O3 counterpart, indicating the potential applications as sensor material toward ethanol detection.
Keywords: α-Fe2O3; Graphene; Gas sensor;

Cost-efficient and flexible fabrication of rectangular-shaped microlens arrays with controllable aspect ratio and spherical morphology by Yang Hu; Qing Yang; Feng Chen; Hao Bian; Zefang Deng; Guangqing Du; Jinhai Si; Feng Yun; Xun Hou (285-290).
This paper presents a cost-efficient and flexible approach to the development of controllable-shape concave and convex microlens arrays by using femtosecond laser wet etch and replication techniques. Periodic concave rectangular-shaped microlens arrays with different length–width ratios were achieved by firstly introducing periodic microcraters on silica glass using an 800 nm femtosecond laser, and subsequently enlarging the craters into microlens with smooth curved surfaces in hydrofluoric (HF) acid solution. The concave microlens can serve as molds of replication to obtain convex microlenses on polymers. Over 10,000 rectangular-shaped concave and convex microlens with controllable aspect ratio, high fill factor and spherical morphology can be fabricated in 5 h. A simulation result and a projection experiment result verify the optical performance of these rectangular-shaped spherical microlens arrays (MLAs).
Keywords: Microlens arrays; Rectangular-shaped; Controllable aspect ratio; Spherical morphology;

Cupric oxide nanowires assembled by nanoparticles in situ with enhancing electrocatalytic oxidation of ascorbic acid by Chuanxi Wang; Jie Liu; Xing Huang; Huanhuan Wang; Youdan Zheng; Li Lin; Siyu Wang; Song Chen; Yong Jin (291-296).
CuO nanowires are facilely fabricated on the surface of AgCuZn alloy in situ by direct oxidation and partial reduction procedures, which shows an improved electrocatalytic activity toward ascorbic acid oxidation. The morphology shows the nanowires are assembled by CuO nanoparticles and we consider the process that the unordered spheres convert to ordered wires is due to the reduction of [1 1 0] and [ 1 ¯ 1 1 ] crystal planes in CuO. Moreover, the prepared modified electrode displays a high sensitivity of 1660 μA cm−2  mM−1, wide linear range from 0.1 μM to 3.1 mM and a low detection limit of 0.095 μmol (signal/noise = 3). Further, the sensor is also tested for anti-interferences and real samples determination, exhibiting distinguished selectivity, accuracy, and recovery. Such excellent properties are owing to the special structure of the synthesized CuO that would provide more specific surface area and enhanced activity compared with common nanowires. Hence, this work of fabricating CuO nanowires assembled by CuO nanoparticles with high performance might supply a way for facile obtain more electrochemical sensor in this structure.
Keywords: Ascorbic acid; Electrochemical sensor; CuO; Nanowires; Nanoparticles; Assemble in situ;

A low cost and effective working electrode with one dimensional ZnO nanorod grown on the porous TiO2 film is used to improve the power conversion efficiency of dye sensitized solar cells. The one dimensional ZnO nanorod is introduced into the porous TiO2 film by a simple and facile hydrothermal route, and the obtained composite film is characterized using the field-emission scan electron microscopy, X-ray diffractometer and photoluminescence spectroscopy. The photocurrent–voltage curves of fabricated dye sensitized solar cells are measured by a solar cell measurement system. Compared with the bare porous TiO2 film based dye sensitized solar cell, it is found that the power conversion efficiency of dye sensitized solar cell with ZnO nanorod decorated TiO2 porous film was improved by more than triple. It is mainly believed that the improved power conversion efficiency of dye sensitized solar cell is ascribed to the increased dye adsorption amount and formation of energy barrier between ZnO nanorod and porous TiO2 film.
Keywords: Dye sensitized solar cells; ZnO nanorod decorated porous TiO2 film; Dye adsorption amount; Energy barrier layer; Power conversion efficiency;

A green and low-cost adsorbent with both magnetic property and high adsorption capacity was prepared on the basis of nickel magnetic core with silica shell. The surface of the prepared Ni@SiO2 composite was not modified. The influence of different functional groups and different charged of the dyes on the adsorption process on the non functionalized Ni@SiO2 have been studied. The results indicated that synthesized adsorbent exhibited higher adsorption capacity for dyes with negative charge/hydroxyl groups as compared to dyes with positive charge/without hydroxyl groups due to the hydrogen bonding interaction and electrostatic interaction between the adsorbent and dyes. Adsorption kinetics and isotherms experiments were carried out and the results indicated that the adsorption process was fitted by pseudo second order kinetics and Freundlich model. The binding of these dyes with magnetic adsorbent surface mainly involves physical adsorption according to D–R model. Furthermore, the adsorption process is spontaneous and endothermic as studied from adsorption thermodynamics. The value of ΔH° and mean free energy further confirmed that physical adsorption is the major adsorption process. After regeneration, the adsorbent still shows high adsorption capacity even for 4 cycles of desorption–adsorption.
Keywords: Adsorption; Magnetic adsorbent; Ni; SiO2; Hydrogen bonding; Organic dyes;

So far clays have always been considered, both experimentally and theoretically, as ideally flat and under arbitrary orientations. The goal here is to shed light on the different cases of possible contact between portions of clay, which will be subject to peculiar conditions of temperature and pressure. To this end, molecular dynamics study has been performed to investigate the evolution of nonparallel hydrated Wyoming-type Na-montmorillonite. In the present work, we study two clay structures containing two then three nonparallel portions. The contact manners between each other are considered as point and/or edge. We show that under the effect of environmental constraints, the dihedral angle of the horizontal and inclined portions tend to shrink; at the same time, the clay layers of inclined portions have a tendency to rotate. Due to this rotation, the contact of point can be considered as the evolution of the contact of edge. With the presence of water, the layers of inclined clay portions turn in different ways. The temperature effect is negligible, but the pressure plays an important role on the behaviour of clay layers.
Keywords: Clay pieces; Pressure; Temperature; Molecular dynamics;

Amorphous silicon oxycarbide (SiOC) and silicon oxynitrocarbide (SiONC) ceramic films coated aluminum nitride (AlN) were prepared by using preceramic-polysilazane (PSZ) with dip-coating method, followed by pyrolysis at 700 °C in different (air, Ar, N2 and NH3) atmospheres to converted PSZ into SiOCair and SiONC ( Ar, N 2 and NH 3 ) ceramic. The existence of amorphous SiOCair and SiONC ( Ar, N 2 and NH 3 ) ceramic films on AlN surface was characterized by FTIR, XRD and XPS. The interfacial adhesion between silicone rubber and AlN was significantly improved after the introduction of amorphous SiOCair and SiONC ( Ar, N 2 and NH 3 ) ceramic films on AlN surface. It can be observed from AFM that the pyrolysis of PSZ at different atmosphere strongly affected to films morphology on AlN surface as SiOCair and SiONC NH 3 ceramic films were more flat and smooth than SiONC N 2 and SiONCAr ceramic films. Besides, the enhancement of the thermal conductivity of silicone rubber composites was found to be related to the decrease in the surface roughness of SiOCair and SiONC ( Ar, N 2 and NH 3 ) ceramic films on AlN surface. This present work provided an alternative surface modification of thermally conductive fillers to improve the thermal conductivity of silicon rubber composites by coating with amorphous SiOCair and SiONC ( Ar, N 2 and NH 3 ) ceramic films.
Keywords: Surface modification; Aluminum nitride; Thermal conductivity; Polysilazane; Silicon oxynitrocarbide; Silicone rubber;

Adsorption and dissociation of H2S on Mo(1 0 0) surface by first-principles study by Haijun Luo; Jianqiu Cai; Xiangming Tao; Mingqiu Tan (328-335).
Density-functional theory calculations had been used to investigate the adsorption and dissociation of H2S on Mo(1 0 0) surface. Adsorption mechanisms of H2S, HS, S and H on the Mo(1 0 0) surface were analyzed. H2S was found to be adsorbed at bridge, hollow and top sites with adsorption energies of −1.25, −1.03 and −0.92 eV, respectively. HS was strongly chemically absorbed at hollow, bridge and top sites with adsorption energies of −4.51, −4.08 and −3.45 eV, respectively, and sulfur and hydrogen preferred to be absorbed at hollow and bridge sites, respectively. In addition, potential energy profiles of H2S dissociation on Mo(1 0 0) had been constructed by a climbing image nudged elastic band method. Four possible dissociation pathways of the first H2S dehydrogenation were examined with reaction barriers of 0.28, 0.37, 0.075, and 0.21 eV, respectively, while the energy barrier to break the S―H bond of HS with or without hydrogen co-adsorption was almost the same low. This work showed that the decomposition of H2S on the molybdenum surface was kinetically and thermodynamically facile. Local densities of electronic states were further used to characterize the interaction between H2S and substrate.
Keywords: Mo(1 0 0)/H2S surface; Surface reaction; Climbing image nudged elastic band;

Keywords: Co–Cr–Mo alloy; S-phase; GiC coating and duplex surface;

High resolution soft x-ray photoemission spectroscopy (SXPS) have been used to study the high temperature thermal stability of ultra-thin atomic layer deposited (ALD) HfO2 layers (∼1 nm) on sulphur passivated and hydrofluoric acid (HF) treated germanium surfaces. The interfacial oxides which are detected for both surface preparations following HfO2 deposition can be effectively removed by annealing upto 700 °C without any evidence of chemical interaction at the HfO2/Ge interface. The estimated valence and conduction band offsets for the HfO2/Ge abrupt interface indicated that effective barriers exist to inhibit carrier injection.
Keywords: ALD HfO2; Germanium; Core level photoemission; Post deposition; Annealing;

The influence of a polydopamine (PDA) adhesive layer on the friction and wear resistance of polytetrafluoroethylene (PTFE) thin films coated on stainless steel was investigated. The friction and wear tests were carried out using a ball on flat configuration under a normal load of 50 g, sliding speed of 2.5 mm/s, and stroke length of 15 mm. It is found that the PDA/PTFE film is able to withstand approximately 500 times more rubbing cycles than the PTFE film alone. X-ray photoelectron spectroscopy (XPS) results show that a tenacious layer of PTFE remains adhered to the PDA layer, which enables the durability of the PDA/PTFE film. Because of the relatively low thickness of the film, PDA/PTFE shows great potential for use in applications where durable, thin films are desirable.
Keywords: Polytetrafluoroethylene; Polydopamine; Thin film; Wear; Durability; Adhesion;

Preparation and characterization of direct Z-scheme photocatalyst Bi2O3/NaNbO3 and its reaction mechanism by Shifu Chen; Yingfei Hu; Lei Ji; Xiaoliang Jiang; Xianliang Fu (357-366).
In this paper, highly active Bi2O3/NaNbO3 photocatalyst was prepared by a facile ball milling method using NaNbO3 and Bi2O3 as precursors. The photocatalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), X-ray photoelectron spectra (XPS), and Brunauer–Emmett–Teller (BET) surface areas. The photocatalytic activity was evaluated by photocatalytic oxidation of rhodamine B (RhB). The results showed that the photodegradation rate of RhB for Bi2O3(5.0 wt%)/NaNbO3 photocatalyst is 6.3 times that of pure NaNbO3. The optimum percentage of doped Bi2O3 is 5.0 wt%. And the composite photocatalyst exhibits good stability. Based on the results of characterization by determining reactive species, terephthalic acid photoluminescence probing technique (TA-PL), and electron spin resonance (ESR) technology, it is proposed that the Bi2O3/NaNbO3 has the characteristic of direct Z-scheme type photocatalyst. The mechanism of increased photocatalytic activity was also discussed.
Keywords: Photocatalyst; Bi2O3/NaNbO3; Z-scheme; Activity; Reaction mechanism;

Controlling the porosity of collagen, gelatin and elastin biomaterials by ultrashort laser pulses by A. Daskalova; Chandra S.R. Nathala; I. Bliznakova; E. Stoyanova; A. Zhelyazkova; T. Ganz; S. Lueftenegger; W. Husinsky (367-377).
We report on the structural investigation of self-organized micropores generated in thin gelatin, collagen, and collagen–elastin films after single and multishot irradiation with pulse durations ranging from 30100 fs at 800 nm. We systematically studied the effect of laser parameters: laser energy, number of pulses, and pulse duration on the development of the micropores. This work showed that applying laser pulses at different rates significantly modified the thin film surface. The results clearly revealed that femtosecond laser treatment of thin films of biomaterials: gelatin, collagen and collagen–elastin, results in creation of micro/nanopores with different size of cavity formations. Experimentally, it is demonstrated that it is possible to influence the dimensions of the pore sizes, ranging from 100 nm to 2 μm by tuning the laser parameters. We are currently further exploring the possibility of structuring these biomaterials by applying a time delay between separate pulses. First results from cell culture experiments on laser created surface foam of collagenelastin were successfully obtained, showing the potential of the method to cultivate cells on superficial porous substrates and the preferable selectivity of the cells to proliferate on the laser modified parts of the biopolymer substrate.
Keywords: Biomaterials; Femtosecond laser irradiation; Surface modification; Tissue engineering; Cell growth;

In this study, a new chelerythrine nanomaterial targeted drug delivery system (Fe3O4/MWNTs-CHE) was designed with chelerythrine (CHE) as model of antitumor drug and magnetic multiwalled carbon nanotubes (Fe3O4/MWNTs) nanocomposites as drug carrier. The process and formulation variables of Fe3O4/MWNTs-CHE were optimized using response surface methodology (RSM) with a three-level, three-factor Box–Behnken design (BBD). Mathematical equations and response surface plots were used to relate the dependent and independent variables. The experimental results were fitted into second-order response surface model. When Fe3O4/MWNTs:CHE ratio was 20.6:1, CHE concentration was 172.0 μg/mL, temperature was 34.5 °C, the drug loading content and entrapment efficiency were 3.04 ± 0.17% and 63.68 ± 2.36%, respectively. The optimized Fe3O4/MWNTs-CHE nanoparticles were characterized by scanning electron microscopy (SEM), Zeta potential, in vitro drug release and MTT assays. The in vitro CHE drug release behavior from Fe3O4/MWNTs-CHE displayed a biphasic drug release pattern and followed Korsmeyer–Peppas model with Fickian diffusion mechanism for drug release. The results from MTT assays suggested that the Fe3O4/MWNTs-CHE could effectively inhibit the proliferation of human hepatoma cells (HepG2), which displayed time or concentration-dependent manner. All these preliminary studies were expected to provide a theoretical basis and offer new methods for preparation efficient magnetic targeted drug delivery systems.
Keywords: Magnetic carbon nanotubes; Response surface methodology; Drug delivery; Optimization; Chelerythrine;

In situ monitoring of GaN substrate surface in ICP containing energetic electrons by Xiaojiang Huang; Ying Guo; Jing Zhang; Yoshitaka Nakano; Hideo Sugai; Keiji Nakamura (387-389).
In this paper we describe a new method for in situ monitoring damage density of GaN substrate surface in inductively coupled plasmas (ICP) containing energetic electrons. Energetic electrons are produced by sheath acceleration of secondary electrons at a negatively biased electrode. A current of a Langmuir probe located in such plasma is used to examine behavior of the energetic electrons. When the plasma contains the high energy electrons, a sample of n-type GaN film exposed to the plasma is observed to emit significant optical fluorescence in the wavelength range of 370–390 nm corresponding to band gap energy of the GaN. The fluorescence intensity of the GaN film increases with the incident electron energy higher than a critical value of ∼5.8 keV. By the XPS results suggested the NBE intensity probably reflects the accumulation degree of the plasma and DC bias induced damage. These results suggest the cathode luminescence technique will be usable to detect a damage density of GaN substrate surface even in plasma conditions.
Keywords: In situ; GaN film; Damage; ICP; Target voltage;

Improvement of corrosion resistance and antibacterial effect of NiTi orthopedic materials by chitosan and gold nanoparticles by Rasha A. Ahmed; Sahar A. Fadl-allah; Nader El-Bagoury; Sanaa M.F. Gad El-Rab (390-399).
Biocomposite consists of gold nanoparticles (AuNPs) and a natural polymer as Chitosan (CS) was electrodeposited over NiTi alloy to improve biocompatibility, biostability, surface corrosion resistance and antibacterial effect for orthopedic implantation. The forming process and surface morphology of this biocomposite coats over NiTi alloy were studied. The results showed that the nm-scale gold particles were embedded in the composite forming compact, thick and smooth coat. Elemental analysis revealed significant less Ni ion release from the coated NiTi alloy compared with the uncoated one by 20 fold. Furthermore, the electrochemical corrosion measurements indicated that AuNPs/CS composite coat was effective for improving corrosion resistance in different immersion times and at all pH values, which suggests that the coated NiTi alloys have potential for orthopedic applications. Additionally, the efficiencies of the biocomposite coats for inhibiting bacterial growth indicate high antibacterial effect.
Keywords: AuNPs; Chitosan; NiTi; Electrochemical impedance; SEM; Antibacterial effect;

FePtAg-C nanogranular film for ultrahigh density magnetic recording media by Wen-Wu Zhong; Rong Hu; Li Zhang; Shuang-Xi Xue; Yan-Ping Liu; Wei-Ping Chen (400-404).
A FePtAg-C nanogranular film was studied for ultrahigh density perpendicular recording media with the density of 1 Tbits/in2 or even higher because of the strong anisotropy at FePt L10-phase. In experiments, a Fe47Pt42Ag11-C45% (6.6 nm) film was deposited on a silicon substrate with a MgO (12 nm) interlayer at 500 °C. The perpendicular coercivity of the film is 34 kOe, with a unit squareness. Bright-field TEM images show that the FePtAg-C nanogranular film has small and uniform grains of 6.8 ± 1.6 nm. More work of high-resolution TEM imaging shows excellent L10-ordering for this film, consistent with the texture measurement by XRD. The measurement of remnant coercivity proves that it has an energy barrier of 310  k B T at room temperature, meaning excellent thermal stability. As a result, FePtAg-C nanogranular film is a qualified candidate for high-density magnetic recording media.
Keywords: FePt nanogranular film; Hard magnetic thin film; Magnetic recording media;

Effect of surface modification and UVA photoactivation on antibacterial bioactivity of zinc oxide powder by Ling Chuo Ann; Shahrom Mahmud; Siti Khadijah Mohd Bakhori; Amna Sirelkhatim; Dasmawati Mohamad; Habsah Hasan; Azman Seeni; Rosliza Abdul Rahman (405-412).
The effects of surface modification of zinc oxide (ZnO) powder and UVA illumination on the powder towards Escherichia coli and Staphylococcus aureus were investigated. FESEM-EDS results showed that oxygen annealing increased the O:Zn ratio on the surface of ZnO-rod and ZnO-plate samples. Surface conductances of ZnO-rod and ZnO-plate pellets were reduced from 1.05 nS to 0.15 nS and 1.34 nS to 0.23 nS, respectively. Meanwhile, UVA illumination on the surface of the ZnO-rod and ZnO-plate samples was found to improve surface conductance to 7.08 nS and 6.51 nS, respectively, due to the release of charge carrier. Photoluminescence results revealed that oxygen annealing halved the UV emission intensity and green emission intensity, presumably caused by oxygen absorption in the ZnO lattice. The antibacterial results showed that oxygen-treated ZnO exhibited slightly higher growth inhibition on E. coli and S. aureus compared with unannealed ZnO. UVA illumination on ZnO causes the greatest inhibition toward E. coli and S. aureus. Under the UVA excitation, the inhibition of E. coli increased by 18% (ZnO-rod) and 13% (ZnO-plate) while the inhibition of S. aureus increased by 22% (ZnO-rod) and 21% (ZnO-plate). Release of reactive oxygen species were proposed in antibacterial mechanisms, which were aided by surface modification and UVA photoactivation. The reactive oxygen species disrupted the DNA and protein synthesis of the bacterial cell, causing bacteriostatic effects toward E. coli and S. aureus.
Keywords: Annealing; UVA; Antibacterial; Conductance; Reactive oxygen species.;

RIR MAPLE procedure for deposition of carbon rich Si/C/H films by Vladislav Dřínek; Tomáš Strašák; Filip Novotný; Radek Fajgar; Zdeněk Bastl (413-419).
We applied the resonant infrared matrix assisted pulsed laser evaporation (RIR MAPLE) technique to demonstrate a new approach to a controlled deposition of carbon rich amorphous Si/C/H film. In absence of radicals and accelerated species commonly generated in PECVD and sputtering setups, the RIR MAPLE method does not decompose precursor molecules. Moreover, unlike the standard MAPLE procedure, in which solvent molecules absorb laser energy from excimer or near infrared lasers, we applied the pulsed TEA CO2 laser to excite the dendrimer precursor molecules in a frozen target. In this manner we achieved just cross-linking of the starting precursor on substrates and the deposition of carbon rich Si/C/H film. The film was analyzed by Fourier Transformed Infrared (FTIR), UV/VIS, Raman and X-ray Photoelectron (XPS) spectroscopy and Atomic Force Microscopy (AFM) technique. According to analyses the film retained the precursor elemental composition free of graphitic (sp2) clusters. In course of reaction only the peripheral allyl groups containing C=C bonds were opened to achieve cross-linking. Whereas annealing to 300 °C was necessary for the elimination of =C–H1, 2 bonds in the films prepared at 200 °C, those bonds vanished completely for the films prepared at substrate temperature 255 °C. The film posseses a smooth surface with root mean square (RMS) parameter up to 10 nm within scanned distance 2.5 μm.
Keywords: MAPLE; Dendrimer; SiC; DLC; Cross-linking;

The present study depicts a one-pot strategy to fabricate silver-polyaniline hybrid nanocomposites with superior and tunable electrical properties, supported by structural characterizations and detail analysis of their temperature dependent current density (J)–voltage (V) characteristics. TEM micrographs clearly reveal that the nanocomposites synthesized by this one-pot strategy contain higher dispersion of sliver nanoparticle within the polyaniline matrix with respect to that obtained from the embedment of externally pre-synthesized silver nanoparticles. The results obtained from the analysis of JV characteristics indicate the prevalence of trapped charge-limited conduction mechanism in doped polyaniline and its nanocomposites. For the nanocomposites obtained from one-pot strategy, a transition of charge transport mechanism from deep exponential trap limited to shallow traps limited conduction has been occurred due to higher dispersion of silver nanoparticles within the polyaniline matrix. Such distinct variation of charge conduction is absent in the nanocomposites obtained from the embedment of externally pre-synthesized silver nanoparticles. A direct evaluation of carrier mobility as a function of electric field and temperature illustrates that the incorporation of only ∼13 to 18 wt% of silver nanoparticles within the polyaniline matrix enhances the carrier mobility in a large extent by reducing the concentration of traps within the polymer matrix. The calculated mobility is consistent with the Poole–Frenkel form for the electrical field up to a certain temperature range. The nonlinear low temperature dependency of mobility of all the nanostructured samples has been explained by Mott variable range hopping conduction mechanisms. Qualitative estimation of various disorder parameters such as optimal hopping distance, localization lengths etc., would help us to outspread the strategies for the fabrication of new organic semiconducting nano-structured devices.
Keywords: Silver polyaniline nanocomposites; Space charge limited conduction; Electric field and temperature dependent mobility;

Mechanical and anticorrosion properties of nanosilica-filled epoxy-resin composite coatings by M. Conradi; A. Kocijan; D. Kek-Merl; M. Zorko; I. Verpoest (432-437).
Homogeneous, 50-μm-thick, epoxy coatings and composite epoxy coatings containing 2 wt% of 130-nm silica particles were successfully synthetized on austenitic stainless steel of the type AISI 316L. The surface morphology and mechanical properties of these coatings were compared and characterized using a profilometer, defining the average surface roughness and the Vickers hardness, respectively. The effects of incorporating the silica particles on the surface characteristics and the corrosion resistance of the epoxy-coated steel were additionally investigated with contact-angle measurements as well as by potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5 wt% NaCl solution. The silica particles were found to significantly improve the microstructure of the coating matrix, which was reflected in an increased hardness, increased surface roughness and induced hydrophobicity. Finally, the silica/epoxy coating was proven to serve as a successful barrier in a chloride-ion-rich environment with an enhanced anticorrosive performance, which was confirmed by the reduced corrosion rate and the increased coating resistance due to zigzagging of the diffusion path available to the ionic species.
Keywords: Nanosilica; Epoxy; Coating; Hardness; Corrosion resistance;

Magnetic ion-imprinted and –SH functionalized polymer for selective removal of Pb(II) from aqueous samples by Bin Guo; Fang Deng; Yu Zhao; Xubiao Luo; Shenglian Luo; Chaktong Au (438-446).
A magnetic ion-imprinted polymer (Fe3O4@SiO2-IIP) functionalized with –SH groups for the selective removal of Pb(II) ions from aqueous samples was synthesized by surface imprinting technique combined with a sol–gel process using 3-mercaptopropyl trimethoxysilane as monomer, tetraethyl orthosilicate as cross-linking agent, and Pb(II) ion as template. The Fe3O4@SiO2-IIP was characterized by infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometry. Fe3O4@SiO2-IIP showed higher capacity and selectivity than that of Fe3O4@SiO2-NIP. The effects of initial concentration of Pb(II) and pH of medium on adsorption capacity of Fe3O4@SiO2-IIP were studied. The experimental data fits well with the Langmuir adsorption isotherm. The maximum Pb(II)-sorption capacity calculated from Langmuir isotherm is 32.58 mg/g and 16.50 mg/g for Fe3O4@SiO2-IIP and Fe3O4@SiO2-NIP, respectively. Kinetics studies show that the adsorption process obeys a pseudo-second-order kinetic model with high correlation coefficient (R 2  = 0.9982). The separation factor of Fe3O4@SiO2-IIP for Pb(II)/Cu(II), Pb(II)/Zn(II), and Pb(II)/Co(II) are 50.54, 52.14, and 37.39, respectively. The adsorption thermodynamic parameters ΔG, ΔH and ΔS were −4.98 kJ/mol, 3.27 kJ/mol and 28.84 J/mol/K, respectively. In addition, the spent Fe3O4@SiO2-IIP can be refreshed by simple washing with aqueous HCl solution, and there is no significant decrease in adsorption capacity after a test of up to five cycles, demonstrating that the Fe3O4@SiO2-IIP is stable and reusable.
Keywords: Surface imprinting technique; Magnetic ion-imprinted polymer; Pb(II); Selectivity;

We report a novel multi-functional magnesium oxide (MgO) immobilized chitosan (CS) composite was prepared by chemical precipitation method. The CS–MgO composite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and zeta potential. The composite was applied as a novel adsorbent for removal of methyl orange model dye and the effect of adsorbent dosage, pH and contact time were studied. The adsorption kinetics followed a pseudo second order reaction. The adsorbent efficiency was unaltered even after five cycles of reuse. In addition, the composite exhibited a superior antibacterial efficacy of 93% within 24 h against Escherichia coli as measured by colony forming units. Based on the data of present investigation the composite being a biocompatible, eco-friendly and low-cost adsorbent with antibacterial activity could find potential applications in variety of fields and in particular environmental applications.
Keywords: Chitosan; MgO; Composite; Adsorbent; Antibacterial agent;

The effects of vacuum pressure and gas adsorption on field emission current of α-Fe2O3 nanoflakes were studied. It was found that field emission current of α-Fe2O3 nanoflakes decreased with increasing pressure. The field emission current decreased when N2 or O2 was introduced into chamber, while no obvious change was observed for H2 gas. An in-situ thermal treatment was carried out to eradicate the effect of absorbed gas. After the in-situ thermal treatment, the field emission current density was largely enhanced from 60 to 500 μA/cm2 under applied electrical field of 10 MV/m and the turn on field (E turn-on) decreased from 7.6 to 5.2 MV/m. The lowered turn-on field was attributed to the decrease of surface work function induced by surface gas desorption and reduction of α-Fe2O3 nanoflakes. Moreover, the improvement of field emission performance can be retained in high vacuum condition, which indicates the in-situ thermal treatment is an efficient method to improve field emission properties of α-Fe2O3 nanoflakes.
Keywords: α-Fe2O3; Field emission; Gas adsorption; Thermal treatment; Work function.;

Preparation and characterization of Ni–P/Ni3.1B composite alloy coatings by Yurong Wang; Jiawei He; Wenchang Wang; Jianhua Shi; Naotoshi Mitsuzaki; Zhidong Chen (462-468).
The preparation of Ni–P/Ni3.1B composite alloy coating on the surface of copper was achieved by co-deposition of Ni3.1B nanoparticles with Ni–P coating during electroless plating. Ni–P–B alloy coating was obtained by heat-treating the as-plated Ni–P/Ni3.1B composite coating. The effect of the concentration of sodium alginate, borax, thiourea, Ni3.1B, temperature, and pH value on the deposition rate and B content were investigated and determined to be: 30 g L−1, 10 g L−1, 2 mg L−1, 20 mg L−1, 70 °C and 9.0 , respectively. Sodium alginate and thiourea were played as surfactant for coating Ni3.1B nanoparticles and stabilizer for the plating bath, respectively. Ni–P/Ni3.1B composite coating had good performance such as corrosion resistance and solderability.
Keywords: Ni-based alloys; Ni–P–B alloys; Composite coatings; Ni–B nanoparticles;

Effect of acidification conditions on the properties of carbon nanotube fibers by Kun Wang; Min Li; Ya-Nan Liu; Yizhuo Gu; Qingwen Li; Zuoguang Zhang (469-474).
Carbon nanotube (CNT) fibers prepared by dry-spun method were functionalized by mixture of nitric and sulfuric acids. The effects of acidification conditions on the electrical conductivity and tensile properties of CNT fibers were investigated. A strong, high conductive CNT fiber was obtained under the optimal mixture ratio and processing time, with a electrical conductivity and tensile strength up to 3.2 × 104  S/m and 1103 MPa, respectively. It showed that the acids densified the surface of the CNT fiber and introduced functional groups onto the tubes, both of which contributed to the conductivity improvement of the CNT fiber. The infrared spectroscopy, Raman and fracture analysis indicated that acidification process resulted in two competitive effects on the tensile properties of CNT fibers, one was the positive contribution by the enhancement of interactions between CNTs through the densification and functional groups, and the other was the negative effect due to the structural destruction of the tubes.
Keywords: Carbon nanotube fiber; Acidification; Electrical conductivity; Tensile property;

We have studied the electronic structure and magnetic properties of oxygen vacancy on anatase TiO2 (0 0 1) surface using density functional theory (DFT) calculations. We find that the oxygen vacancy on the surface may be responsible for the unexpected ferromagnetism in anatase TiO2 films without doping. The formation energies of surface vacancies are calculated. Results of our first-principles GGA +  U calculations show that the oxygen vacancy at the ridge has the lowest formation energy. The spins induced by the local oxygen vacancy form a stable ferromagnetic state, and the anion vacancy can result in a magnetic moment of 1.63  μ B. The localized state of spin polarization will be formed in the band gap. The magnetic moment which is produced by the oxygen vacancy mainly comes from the d orbitals of two low-charge-state Ti ions converted from Ti4+ ions adjacent to the surface oxygen vacancy. We calculate the magnetic coupling between the two oxygen vacancies at the ridge in different distances. Although the spin dimerization will be formed along with the decrease of Ti–Ti distance, the results also show that the two oxygen vacancies on anatase TiO2 (0 0 1) surface are mainly coupled ferromagnetically. In addition, the other kind of oxygen vacancy at the valley can also induce the ferromagnetism on the surface. The experimentally observed d 0-ferromagnetism behavior in TiO2 system is in good agreement with our calculated results.
Keywords: Anatase TiO2; Surface; Oxygen vacancy; Magnetism; First principles;

Preparation and antibacterial property of silver decorated carbon microspheres by Sha Li; Xiaoliang Yan; Zhi Yang; Yongzhen Yang; Xuguang Liu; Jing Zou (480-487).
Carbon microspheres (CMSs) were prepared by glucose hydrothermal method. The effects of glucose concentration and reaction time on the size and morphology of CMSs were studied. CMSs with surface area of 642.5 m2/g and pore size of 0.8 nm were exploited to design hybrid material of CMSs with Ag decoration by radio frequency plasma (RF plasma). A series of investigations using X-ray diffraction, UV–vis spectrometry, Fourier transform infrared spectrometry, X-ray photoelectron spectrometry, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy was carried out to characterize the Ag decorated CMSs. RF plasma was employed to reduce Ag+ ions to metallic nano-particles with the particle size of 10–20 nm and form a clean metal-support (Ag-CMSs) interface. The mechanism for the structure formation of Ag decorated CMSs was discussed. Plasma produced Ag/CMSs showed antibacterial property and proved suitable for potential biological and environmental applications.
Keywords: Carbon microspheres; Ag; RF plasma; Antibacterial property;

Fluorine interaction with defects on graphite surface by a first-principles study by Song Wang; Ke Xuezhi; Wei Zhang; Wenbin Gong; Ping Huai; Wenqing Zhang; Zhiyuan Zhu (488-493).
The interaction between fluorine atom and graphite surface has been investigated in the framework of density functional theory. Due to the consideration of molten salt reactor system, only carbon adatoms and vacancies are chemical reactive for fluorine atoms. Fluorine adsorption on carbon adatom will enhance the mobility of carbon adatom. Carbon adatom can also be removed easily from graphite surface in form of CF2 molecule, explaining the formation mechanism of CF2 molecule in previous experiment. For the interaction between fluorine and vacancy, we find that fluorine atoms which adsorb at vacancy can hardly escape. Both pristine surface and vacancy are impossible for fluorine to penetrate due to the high penetration barrier. We believe our result is helpful to understand the compatibility between graphite and fluorine molten salt in molten salt reactor system.
Keywords: Graphite; Diffusion; Reaction; First principles; Molten salt reactor; Fluorine;

Density functional theory study on direct catalytic decomposition of ammonia on Pd (1 1 1) surface by Zhao Jiang; Qi Pan; Mengmeng Li; Ting Yan; Tao Fang (494-499).
The adsorption and step dehydrogenation mechanism of NH3 on Pd (1 1 1) have been studied using density functional theory (DFT) together with periodic slab models. According to the optimized structural and energetic properties, it was found that NH3 and N2 prefer to adsorb on the top site, whereas NH, N, H prefer to adsorb on the fcc site and NH2 prefers on the bri site. In addition, this work identified the optimum configurations for the stable co-adsorption configurations of NH x  + H, and N + N. Finally, three transition states were found for analyzing the mechanism of dehydrogenation of NH3, and the N recombination reaction was also considered. The results show that NH is the most abundant intermediate on Pd (1 1 1) surface and the dehydrogenation of NH3 is the rate-determining step in the overall reaction. The distinct differences over Pd (1 1 1) and Pd (1 0 0) surface imply that ammonia decomposition over Pd-based catalyst is a structure-sensitive reaction.
Keywords: Density functional theory; Pd (1 1 1) surface; Ammonia; Transition State; Decomposition;

Effect of nanograin size on nanoformed NiTi alloys by Cheng-Da Wu; Te-Hua Fang; Cyun-Yuan Chen; Cheng-I Weng (500-505).
The nanoforming process of single-crystal (SC) and nanocrystalline (NC) NiTi alloys is studied and compared using molecular dynamics simulations based on the many-body tight-binding potential. The effect of the grain size (GS) is evaluated in terms of atomic trajectories, slip vectors, potential energy, loading force, and elastic recovery. The simulation results show that for the SC NiTi alloy, the deformation proceeds through a series of nucleations and emissions of dislocations along the {1 1 0} close-packed plane, extending to the interior. The SC NiTi alloy has better filling ability than that of the NC NiTi alloys due to its lack of grain boundaries (GBs). The filling ability of the NC workpieces slightly increases with decreasing GS. For the NC NiTi alloys, dislocations nucleate and are emitted along the {1 1 0} close-packed plane in grains from the GBs. Emitted dislocations easily terminate at GBs. There is no clear relationship between elastic recovery and GS.
Keywords: Nanoforming; NiTi; Nanocrystallization; Grain boundary; Molecular dynamics;

Three-dimensional modeling of chloroprene rubber surface topography upon composition by Kristina Žukienė; Virginija Jankauskaitė; Stase Petraitienė (506-513).
In this study the effect of polymer blend composition on the surface roughness has been investigated and simulated. Three-dimensional modeling of chloroprene rubber film surface upon piperylene-styrene copolymer content was conducted. The efficiency of various surface roughness modeling methods, including Monte Carlo, surface growth and proposed method, named as parabolas, were compared. The required parameters for modeling were obtained from atomic force microscopy topographical images of polymer films surface. It was shown that experimental and modeled surfaces have the same correlation function. The quantitative comparison of function parameters was made. It was determined that novel parabolas method is suitable for three-dimensional polymer blends surface roughness description.
Keywords: Polymer blend; Surface roughness; Monte Carlo simulation; Surface growth simulation; Parabolas simulation;

Photoelectrochemical behavior of TiO2 nanorod arrays decorated with CuInS2 quantum dots by Zhuoyin Peng; Yueli Liu; Yinghan Zhao; Keqiang Chen; Valery Kovalev; Wen Chen (514-519).
One-dimensional single crystalline TiO2 nanorod arrays with different lengths were prepared by controlling the hydrothermal cycles, which were successfully sensitized with CuInS2 quantum dots by assembly linking cycles, and their optical absorption properties and photoelectrochemical properties were investigated. 6 μm-TiO2 nanorod electrodes with the CuInS2 quantum dots sensitization of three linking cycles had the best photoelectrochemical properties and short-circuit current density, such as the short-circuit current density are 27.3 times higher than that of pure 6 μm-TiO2 nanorod electrodes. The reason may be attributed to the suitable internal surface area of TiO2 nanorod, with the increasing of the adsorption content of CuInS2 quantum dots to generate much more photo-induce electrons. Moreover, it will also enhance the interface connection between TiO2 nanorod and FTO conducting substrate, which favors to reduce the recombination of photo-induced electron–hole pairs.
Keywords: TiO2 nanorod arrays; Hydrothermal process; CuInS2 quantum dots; Assembly linking method; Photoelectrochemical behavior;

In this article, ZnO nanogranules were synthesised rapidly by the thorough solid state mixing of nitrate precursor with citric acid followed by aging and calcination at two different temperatures of 400 °C and 600 °C. Here, citric acid played a superior role in the development of porous ZnO nanostructures. The ZnO nanogranules obtained in this way were characterised by different techniques. X-ray diffraction patterns indicated a hexagonal wurtzite structure of ZnO with high crystallinity and nanocrystalline size. Scanning and transmission electron microscopy images indicated the uniformly well separated hexagonal morphology of the ZnO nanoparticles, with granular shape. BET surface area-porosity analysis confirmed the presence of a mesoporous network in both samples, with high surface area and a monomodal pore size distribution. Room temperature Photoluminescence spectra of the samples exhibited characteristic blue and green emission bands in accordance with the calcination temperature. The photocatalytic performance of the ZnO nanogranules was studied using methylene blue degradation and found that the ZnO prepared at 400 °C exhibited higher photocatalytic activity due to its high surface area and more oxygen vacancies. High concentrations of several hazardous dye pollutants were effectively degraded, when the solution was passed over 50 mg of ZnO nanogranules under UV-light illumination.
Keywords: Solid state synthesis; Citric acid; ZnO nanogranules; Optical properties; Photodegradation; Industrial dyes;

Evaluation of subsurface damage in GaN substrate induced by mechanical polishing with diamond abrasives by Hideo Aida; Hidetoshi Takeda; Seong-Woo Kim; Natsuko Aota; Koji Koyama; Tsutomu Yamazaki; Toshiro Doi (531-536).
The relationship between the depth of the subsurface damage (SSD) and the size of the diamond abrasive used for mechanical polishing (MP) of GaN substrates was investigated in detail. GaN is categorized as a hard, brittle material, and material removal in MP proceeds principally to the fracture of GaN crystals. Atomic force microscopy and cathodoluminescence imaging revealed that the mechanical processing generated surface scratches and SSD. The SSD depth reduced as the diamond abrasive size reduced. A comparison of the relationship between the SSD depth and the diamond abrasive size used in the MP of GaN with the same relationship for typical brittle materials such as glass substrates suggests that the MP of GaN substrates proceeds via the same mechanism as glass.
Keywords: GaN substrate; Mechanical polishing; Chemical mechanical polishing; Subsurface damage; Cathodoluminescence; Brittle materials;

This work studied dodecylamine-protected silver nanoparticles modified by a small amount of dodecanethiol as the co-protective agent. Contents of the dodecanethiol and the protective agent capping on the surface of silver nanoparticles were analyzed using the method of oxygen flask combustion and a thermogravimetric analysis instrument. Results of electrical property determination and transmission electron microscopy indicate that certain amount of capping dodecanethiol can slow down the spontaneous sintering process of silver nanoparticles. When capping DDT content of silver nanoparticles is 1.70 wt%, 10 wt% suspensions are stable under −18 °C and can be stored stably at room temperature as long as 120 days. Furthermore, the silver nanoparticle concentration could be increased to 20 wt% with a stable storage time of 60 days at room temperature. Finally, stable polymer-free conductive inks with the silver nanoparticle concentration of 20 wt% were produced to fabricate patterns by ink-jet printing. The resistivity of the PI-supported patterns having been annealed at 130 °C for 10 min is 7.2 μΩ cm.
Keywords: Ag nanoparticles; Conductive inks; Inkjet printing; Sintering; Stability;

ZnO nanorods inserted graphene sheets with improved supercapacitive performance by Z. Qin; Z.J. Li; G.Q. Yun; K. Shi; K. Li; B.C. Yang (544-550).
In this paper, we demonstrate a facile one-pot approach for the synthesis of reduced graphene oxide-ZnO (Gr–ZnO) hybrids. Structural analysis revealed a homogeneous distribution of ZnO nanorods are inserted in graphene nanosheets, formed a sandwiched architecture. The Gr–ZnO material demonstrates superior electrochemical performance with high specific capacitance (140 F g−1 even at the scan rate of 500 mV s−1) and long–term cycle stability (94% capacitance retention over 2000 cycles). The improved supercapacitance property of these materials could be ascribed to the increased the specific surface of graphene sheets by ZnO nanorods inserted. These results demonstrate the potential of the Gr–ZnO hybrid nanocomposites as an electrode in high-performance supercapacitors.
Keywords: Zinc oxide nanorods; Graphene nanosheets; Electrochemical performance;

Room temperature NO2-sensing properties of WO3 nanoparticles/porous silicon by Wenjun Yan; Ming Hu; Peng Zeng; Shuangyun Ma; Mingda Li (551-555).
WO3 nanoparticles were synthesized by sol–gel method with tungsten hexachloride (WCl6) as precursor and deposited onto porous silicon and alumina substrates by dip-coating. The morphology and crystal structure of samples were investigated by means of field emission scanning electron microscope and X-ray diffractometer. It is the experimental results demonstrated by gas sensing tests that WO3 nanoparticles combining with the substrate of porous silicon presented an improved NO2-sensing property at room temperature. Compared to WO3 deposited on alumina working above 100 °C, the WO3 nanoparticles/porous silicon exhibited higher properties upon exposure to sub-ppm concentrations of NO2 gas at room temperature. Additionally, the NO2-sensing performance of WO3 nanoparticles/porous silicon was enhanced markedly, in comparison to pure porous silicon. The mechanism of WO3/porous silicon composite structure on the NO2 sensing was explained in detail.
Keywords: WO3; Porous silicon; Gas sensor; NO2; Room temperature;

Bulk nanocrystalline has been produced in the surface of a tempered reduced activation ferrite/martensite (RAFM) steel by means of surface mechanical attrition treatment (SMAT), the grain size decreases gradually from the strain-free matrix to the treated surface with the increase of deformation strains. Both XRD and SEM results indicate the dissolving or refinement of carbides during SMAT. The nanocrystalline has excellent thermal stability when annealing at 823 K; the average grain sizes calculated from statistical analysis of the TEM images after annealing for 5 min, 30 min, 120 min and 240 min are 67.6 nm, 87.1 nm, 93.8 nm and 109.6 nm, respectively. Because of the large volume fraction of grain boundaries (GBs) and enhanced diffusion rates in the nanocrystalline (NC) steels, fast grain growth and small precipitated carbides are observed after annealing for 5 min at 823 K, while the existence of numerous second-phase particles hinders grain growth after annealing for longer times.
Keywords: Bulk nanocrystalline; Surface mechanical attrition treatment; Residual stress; Thermal stability;

Scalable superhydrophobic coatings based on fluorinated diatomaceous earth: Abrasion resistance versus particle geometry by Georgios Polizos; Kyle Winter; Michael J. Lance; Harry M. Meyer; Beth L. Armstrong; Daniel A. Schaeffer; John T. Simpson; Scott R. Hunter; Panos G. Datskos (563-569).
Bio-inspired superhydrophobic surfaces were fabricated based on fossilized silica fresh water diatomaceous earth (DE) particles. These nanostructured silicified diatom frustules of cylindrical and circular structures were fluorinated to impart them with superhydrophobic properties. Substrates coated with superhydrophobic DE structures of varying size and shape were found to have water contact angles of approximately 170° and sliding angles of approximately 3°. The substrates were subjected to significant abrasion forces using a standard surface abrader. The ability to retain their superhydrophobic properties was observed to depend on the geometry and average size of the DE particles. The wettability of the abraded coatings was determined by their surface topology, and a transition from a non-wetted state to a partially wetted state was observed to occur and was dependent on the surface roughness. The proposed coatings are scalable, cost-effective, and can be applied on a variety of surfaces on critical infrastructures requiring protection from water saturation, ice formation and water based corrosion.
Keywords: Diatomaceous earth; Superhydrophobic; Coatings; Scalable; Abrasion resistance;

The photo-catalytic activities of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO4 3−, HPO4 2−) microparticles by Fan Zhang; Yuanji Shi; Zongshan Zhao; Weijie Song; Yang Cheng (570-575).
For the good performance of apatite-based materials in the removal of dyes and their environment-friendly advantage, five kinds of apatite microparticles of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO4 3−, HPO4 2−) were synthesized by a simple precipitation method and their photo-catalytic properties were invested. Better performance in the decolorization of methyl orange (MO) under the assistance of H2O2 than that of TiO2 were obtained for all the MPs. The photo-catalytic activity was mainly affected by surface area, energy band, impurity, crystallinity and crystal structure. The DFT calculation results demonstrated that the 2p of O and 3p of P in PO4 3− played the main role in the photo-catalytic process. This work would be helpful to design and synthesize low cost apatite materials with good photo-catalytic performance.
Keywords: Apatite; Photo-catalyst; Degradation; Mechanism; Calculation;

Preparation of titanium peroxide and its selective adsorption property on cationic dyes by Xiao-guang Zhao; Ji-guo Huang; Bo Wang; Qiang Bi; Li-li Dong; Xing-juan Liu (576-582).
Titanium peroxide powder was prepared with the reaction of titanium sulfate and H2O2 and showed good selective adsorption property on cationic dyes. The obtained material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric and differential scanning calorimetry (TG-DSC). The selective adsorption property was confirmed and evaluated by adsorption experiments of methyl orange (MO), phenol and three kinds of cationic dyes including methylene blue (MB), malachite green (MG) and neutral red (NR). The adsorption was very fast and adsorption equilibrium was reached in a very short time for all three cationic dyes. The adsorption kinetics of MB, MG and NR were studied then. It was found that the adsorption data fitted perfectly with the pseudo-second-order kinetics and the saturated adsorption capacities for MB, MG and NR were 224.37, 251.38 and 327.61 mg/g at 25 °C, respectively. The characterization and adsorption results indicated the controlling mechanism of adsorption processes could be electrostatic adsorption.
Keywords: Titanium peroxide; Adsorption; Cationic dyes; Kinetics;

Development of an oxidation resistant glass–ceramic composite coating on Ti–47Al–2Cr–2Nb alloy by Wenbo Li; Shenglong Zhu; Minghui Chen; Cheng Wang; Fuhui Wang (583-590).
Three glass–ceramic composite coatings were prepared on Ti–47Al–2Cr–2Nb alloy by air spraying technique and subsequent firing. The aim of this work is to study the reactions between glass matrix and inclusions and their effects on the oxidation resistance of the glass–ceramic composite coating. The powders of alumina, quartz, or both were added into the aqueous solution of potassium silicate (ASPS) to form slurries used as the starting materials for the composite coatings. The coating formed from an ASPS-alumina slurry was porous, because the reaction between alumina and potassium silicate glass resulted in the formation of leucite (KAlSi2O6), consuming substantive glass phase and hindering the densification of the composite coating. Cracks were observed in the coating prepared from an ASPS-quartz slurry due to the larger volume shrinkage of the coating than that of the alloy. In contrast, an intact and dense SiO2–Al2O3-glass coating was successfully prepared from an ASPS-alumina–silica slurry. The oxidation behavior of the SiO2–Al2O3-glass composite coating on Ti–47Al–2Cr–2Nb alloy was studied at 900 °C. The SiO2–Al2O3-glass composite coating acted as an oxygen diffusion barrier, and prevented the inward diffusion of the oxygen from the air to the coating/alloy interface, therefore, decreasing the oxidation rate of the Ti–47Al–2Cr–2Nb alloy significantly.
Keywords: Oxidation; Glass–ceramic; Coating; Ti–47Al–2Cr–2Nb alloy;

Superhydrophobic and oleophobic rough copolymer surfaces containing micro- and nano-hierarchical ball-like islands having diameters between 100 nm and 7 μm were formed using styrene-perfluoromethacrylate random copolymers which were dip-coated on glass slides from THF and MEK mixture containing methanol as nonsolvent. These copolymers were synthesized in a CO2-expanded monomer medium at 250 bar pressure and 80 °C. The sizes of the micro-islands can be controlled by varying the copolymer composition; and the degree of phase separation by adjusting the solvent/non-solvent ratio. Flat and lotus-like hierarchical surfaces of the copolymers were characterized using contact angle measurements and SEM. The increase in the perfluoromethacrylate content of the flat copolymers resulted in a decrease of the total surface free energy of the flat copolymer surfaces from 18.3 down to 14.2 mJ/m2. The increase in the methanol non-solvent fraction resulted in decrease of the micro-island diameter from 7 μm down to 100 nm and the water contact angle increased from 117° up to 160° and hexadecane from 65° up to 90°.
Keywords: Superhydrophobic; Oleophobic; Hierarchical; Perfluoroacrylate; Phase separation;

The successful synthesis of catalyst free zinc oxide (ZnO) Nanowall networks with honeycomb like structure by Pulsed Laser Deposition (PLD) is demonstrated in this paper. The synthesis was conducted directly on Silicon (Si) (1 0 0) and Glass–ITO substrates without the intermediate of metal catalyst, template or chemical etching. Kinetic of growth and effects of gas pressure and substrate temperature were studied by depositing ZnO films on P type Si (1 0 0) substrates with different deposition parameters. The optimized growth parameters were found as: 10 mTorr oxygen pressure, 600 °C substrate temperature, and deposition duration equal or higher than 10 min. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Photoluminescence (PL) measurements were used to investigate structural, microstructural and optical properties of ZnO Nanowall networks produced. They exhibit a non-uniform size high quality honeycomb structure with low deep level defects.
Keywords: ZnO; Two dimensional nanostructure; Textured thin-layer; Honeycomb like structure; Nanowalls; c-Axis oriented;

SO4 2−-doped Zn/Ce/TiO2 nano-materials (Zn/Ce/SO4 2−/TiO2) were prepared by a sol–gel method. The structures of Zn/Ce/SO4 2−/TiO2 nano-materials were characterized by Transmission electron microscope (TEM), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron (PL) spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Gram-negative Escherichia coli (ATCC25922) and Gram-positive Staphylococcus aureus (ATCC6538) as model organisms, antibacterial activities of nano-materials were tested using inhibition zone method and shaking flask method under visible light irradiation and in the dark. The results show that the materials crystal structure and elemental composition are changed after SO4 2− doped. Zn/Ce/SO4 2−/TiO2 exhibit predominant antibacterial activity in the dark and visible light irradiation. The action mechanism of Zn/Ce/SO4 2−/TiO2 is discussed.
Keywords: Antibacterial activity; SO4 2−; Zn and Ce co-doped; TiO2;

Enhanced luminescence of quantum dot/dielectric layer/metal colloid multilayer thin films by Bo-Tau Liu; Tai-Hsiang Liao; Shiojenn Tseng; Mei-Hua Lee (615-619).
In this study, we reported the effect of the dielectric constants of the medium between quantum dots (QDs) and metal nanoparticles on the plasmon-enhanced fluorescence. The evaluation was conducted on (CdSe/ZnS)–(TiO2/SiO2)–(Au colloid) three-layer hybrid films prepared by the layer-by-layer coating. The CdSe/ZnS layer and the Au-nanoparticle layer were separated by a dielectric layer fabricated from tetraethyl orthosilicate and tetrabutyl orthotitanate. The dielectric constant of the dielectric layer was adjusted by varying the ratio of tetraethyl orthosilicate to tetrabutyl orthotitanate. We found that the optimal excitation wavelength for CdSe/ZnS QDs came with the localized surface plasmon resonance wavelength of Au colloids and could be controllable by virtue of adjusting the dielectric constant of the dielectric layer. Experimental results showed that both the optimal distance and the PL enhancement reduced with the increase of the dielectric constant. The decrease of the enhancement factor may arise from the increase of the rate of the resonant energy transfer from photo-excited CdSe/ZnS QDs to Au colloids.
Keywords: CdSe/ZnS; Quantum dot; Au colloid; Photoluminescence; Localized surface plasmon resonance;

Ni–Al composite coatings with different contents of Al microparticles were prepared from a conventional Watt bath. The influences of Al particle loadings in the bath on the surface morphology, composition, texture, grain size, microstrain, residual stress and anti-corrosion of the Ni–Al composite coating were investigated. The friction coefficients of the coatings at 200 °C were also evaluated by a pin-on-disctribometer. The results showed that the surface morphology of the coatings changed from pyramid + colonied structure to colonied structure with increasing Al particle loadings. The (2 0 0) preferred orientation for pure Ni coating evolved to random orientation with increasing Al particle loadings. The grain size obtained the minimum value of 72.28 nm at Al particle loading of 100 g/L and the microstrain of the coating increased with increasing the Al particle loadings. The incorporation of Al particles decreased the residual stress of the electro-deposited coating and all the coatings deposited at different Al particle loadings possessed low residual stress. As the Al particle loading increased, the anti-corrosion of the Ni–Al coatings increased owing to the combined effect of increasing Al content in the coatings and the texture evolution from (2 0 0) plane to (1 1 1) plane. The wear result suggested that the increasing Al particle content did not improve the wear performance of the Ni–Al composite coatings.
Keywords: Ni–Al coating; Electrodeposition; Texture; Residual stress;

Adherence of human mesenchymal stem cells on Ti and TiO2 nano-columnar surfaces fabricated by glancing angle sputter deposition by Yahya Motemani; Christina Greulich; Chinmay Khare; Michael Lopian; Pio John S. Buenconsejo; Thomas A. Schildhauer; Alfred Ludwig; Manfred Köller (626-631).
The interaction of human mesenchymal stem cells (hMSCs) with Ti and TiO2 nano-columnar surfaces fabricated using glancing angle sputter deposition was investigated. The adherence and proliferation of hMSCs on different nano-columnar surfaces, including vertical columns, slanted columns and chevrons, were examined with calcein-acetoxymethyl ester fluorescence staining and scanning electron microscopy. For comparison, adherence of hMSCs on compact, dense films was also studied. After 24 h and 7 days, adherent and viable cells were observed on both, Ti nano-columns as well as dense Ti films, which confirms the biocompatibility of these nanostructures. Very small pseudopodia with width of approximately 20–35 nm and length varying from 20 to 200 nm were observed between the nano-columns, independent of the type of the nano-columnar morphology. Large inter-column spacing and effectively increased surface area make these nanostructures promising candidates for bio-functionalization or drug loading on the surface of Ti-based implants.
Keywords: Human mesenchymal stem cells; Cell adhesion; Nanostructure; Titanium; Glancing angle sputter deposition;

We successfully prepared one-dimensional (Ba, La)SnO3 (BLSO)–ZnO heterostructures for gas sensing applications, by sputter deposition of BLSO ultra-thin films onto ZnO nanowire templates. The BLSO shell layer exhibits polycrystalline morphology; electron microscope images revealed that BLSO particles were homogeneously distributed over the surface of the ZnO underlayer, and the diameters of the BLSO particles ranged from 8 to 18 nm. The photoluminescence spectrum of the BLSO–ZnO heterostructure exhibited a UV emission band, together with a distinct visible-light emission band. The presence of many depleted ultra-thin BLSO particles, and the occurrence of electron depletion at the BLSO–ZnO interface, might affect the observed resistance responses to test gases.
Keywords: Characterization; Sputtering; Morphology; Oxides; Electrical response;

Thinning of reverse osmosis membranes by ionic liquids by Hong Meng; Beibei Gong; Tao Geng; Chunxi Li (638-644).
In this study, ionic liquids (ILs) were used to thin out the dense layer and, in turn, tune the surface properties and separation performance of commercial aromatic polyamide reverse osmosis membranes. It was observed that the structure of the ILs and dipping time had a strong impact on the dense layer thickness and morphology. This can be understood in terms of the dissolubility and interaction force between ILs and the organic membrane surface, such as hydrogen bonding and ππ interactions. Among the ILs synthesized, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) showed the most promising thinning effects. It was observed that the thickness of the dense layer on the surface decreased from 127 to 67 nm after dipping treatment with [BMIM]Cl for 24 h. The water flux was enhanced by 20% at the expense of a slight decline of salt rejection. AFM, contact angle and zeta potential analyses suggest that the surface hydrophilicity and electronegativity increased, while the roughness decreased, which improved the anti-fouling properties.
Keywords: Ionic liquids; Reverse osmosis membranes; Thinning;

The low reaction temperature for synthesis of carbon nanotubes (CNTs) with high quality was investigated by Ni/MgO catalytic decomposition of CH4 using a home-designed micro-fluidized bed reactor. It was found that the low and mild temperature at 500 ∼ 550 °C would bring the dynamic equilibrium between the rate of CH4 decomposition and the rate of carbon diffusion over Ni catalyst for continuous precipitation of CNTs in the micro-fluidized bed condition. The CNTs synthesized at the corresponding conditions exhibited high quality with relatively small and mean outer diameter, less defect, and high purity.
Keywords: Carbon nanotubes; Temperature; Dynamic equilibrium; Chemical vapor deposition; Micro fluidized bed;

Influence of silanes on the wettability of anodized titanium by S.C. Vanithakumari; R.P. George; U. Kamachi Mudali (650-657).
A facile method was adapted to make superhydrophobic (SHP) titanium in which a synergistic combination of surface roughness and surface chemistry was utilized. In the first step, titanium was mechanically polished and pickled followed by anodization. The next step was to dip coat the samples with silane solution and then were cured at 110 °C. Influence of different synthesis parameters such as silane concentration, number of dip coating and curing temperature on water contact angle (WCA) was studied and conditions were optimized to achieve a WCA of 150°. The wetting properties of the samples were elucidated using contact angle meter and the water just rolled off the modified titanium surface with a slight tilting. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the morphology and surface roughness of the silane coated titanium samples. Grazing incidence X-ray diffraction (GIXRD), energy dispersive spectroscopy (EDS), attenuated total reflection-infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemical composition of the coatings which confirmed the presence of silicon along with titanium and oxygen. Immersion studies in sea water and nitric acid medium for 15 days indicated the stability of the coatings with minimal variations in contact angle.
Keywords: Surface modification; Superhydrophobicity; Water contact angle; Anodization; Silane; Titania;

The micro-arc oxidation (MAO) has increasingly gained attention as a novel and unique technique for depositing thick, dense, and ultra-hard ceramic coatings on aluminum and its alloys substrates. For the MAO technology, discharge parameter, especially the cathodic current, has an important effect on the characteristics of ceramic coatings. But the effects of the ratio of anodic and cathodic currents on properties of the ceramic coatings on Al alloys are rarely studied. This work investigates the effects of the ratio of anodic and cathodic currents under the constant current density on morphology, phase composition, microstructure, and properties of ceramic coatings on 6061 Al alloys. It is found that the ceramic coatings surface roughness Ra is decreasing, and the hardness of ceramic coatings is increasing with the decrease of the ratio. The ceramic coatings are mainly composed of a large amount of α-Al2O3 and γ-Al2O3. The content of α-Al2O3 in the ceramic coatings increases with the decrease of the ratio.
Keywords: Micro-arc oxidation; Al alloys; Cathodic current; Anodic current; Ceramic coatings;

The electrical and morphological properties of magnesium oxide (MgO)/alumina (Al2O3) bilayered thin films prepared by electron beam evaporation at oblique incidence are reported. The MgO thin films are deposited when the incline angle is 55° on various Al2O3 thin films incline angles. A columnar grain with a roofing-tile-shaped surface is observed in these MgO/Al2O3 thin films. X-ray pole figures and θ-2θ scan, ω-scan are used to characterize in-plane and out-of-plane textures. The relationships between ω-FWHM, capacitor, leakage current, and the inclined angles are studied. The morphology is investigated by using scanning electron microscope (SEM). So the oblique angle deposition method is an effective way to control the microstructure of thin films.
Keywords: Oblique angle deposition; Magnesium oxide/alumina; X-ray; SEM;

Removal of hexavalent chromium from aqueous solution by granular and powdered Peganum Harmala by Rasoul Khosravi; Mehdi Fazlzadehdavil; Behnam Barikbin; Ali Akbar Taghizadeh (670-677).
In this paper, batch removal of hexavalent chromium from aqueous solutions by granular and powdered seeds of Peganum Harmala was investigated. The Peganum Harmala seeds were collected and after beating slowly, separating and cleaning the Harmala seeds done using a sieve. Batch adsorption studies were performed in 100 ml Erlenmeyer flasks inside an incubator container. The main process parameters considered were pH, initial Cr(VI) concentration for PPH and GPH, adsorbent dose, and contact time. Cr(VI) was measured at a wavelength of 540 nm using a UV–vis T80+ spectrophotometer. The adsorption data were fitted well by Freundlich isotherm. The result shows that the maximum removal of Cr(VI) was observed at pH 1.5 for both adsorbents. Also, by increase adsorption dose, adsorption capacity of Cr(VI) decreased but the chromium adsorption rate increased. The mount of adsorbed Cr(VI) onto both adsorbents increased with an increase in the contact time but by increases initial concentration of Cr(VI), the mount of adsorbed Cr(VI) onto both adsorbents decreased. The results indicate that the powdered Peganum Harmala can be effective adsorbent than the granular Peganum Harmala for the removal of Cr(VI) from aqueous solution.
Keywords: Adsorption; Isotherm; Peganum Harmala; Wastewater treatment;

Femtosecond laser fabrication of sub-diffraction nanoripples on wet Al surface in multi-filamentation regime: High optical harmonics effects? by A.A. Ionin; S.I. Kudryashov; S.V. Makarov; A.A. Rudenko; P.N. Saltuganov; L.V. Seleznev; D.V. Sinitsyn; E.S. Sunchugasheva (678-681).
Relief ripples with sub-diffraction periods (≈λ las/3, λ las/4) were produced on a aluminum surface immersed in water and irradiated in a multi-filamentation regime by focused 744 nm femtosecond laser pulses with highly supercritical, multi-GW peak powers. For the VUV (8.5 eV) surface plasmon resonance on the wet aluminum surface, such small-scale surface nanogratings can be produced by high – second and third – optical harmonics, coming to the surface from the optical filaments in the water layer. Then, the sub-diffraction surface ripples may appear through interference of their transverse electric fields with the longitudinal electric fields of their counterparts, scattered on the surface roughness and appeared as the corresponding high-energy, high-wavenumber surface polaritons.
Keywords: Wet aluminum; Sub-diffraction surface nanoripples; Femtosecond laser pulses; Supercritical peak powers for self-focusing; Multi-filamentation in water; High optical harmonics;

Preparation and electrochemical properties of core-shell carbon coated Mn–Sn complex metal oxide as anode materials for lithium-ion batteries by Ruixue Zhang; Guoqing Fang; Weiwei Liu; Bingbo Xia; Hongdan Sun; Junwei Zheng; Decheng Li (682-687).
In this study, we synthesized a carbon coated Mn–Sn metal oxide composite with core-shell structure (MTO@C) via a simple glucose hydrothermal reaction and subsequent carbonization approach. When the MTO@C composite was applied as an anode material for lithium-ion batteries, it maintained a reversible capacity of 409 mA h g−1 after 200 cycles at a current density of 100 mA g−1. The uniformed and continuous carbon layer formed on the MTO nanoparticles, effectively buffered the volumetric change of the active material and increased electronic conductivity, which thus prolonged the cycling performance of the MTO@C electrode.
Keywords: Mn–Sn metal oxide; Carbon coating; MnSnO3; Core-shell;

Structure and properties of TiAlLaN films deposited at various bias voltages by Hao Du; Ji Xiong; Haibo Zhao; Yuemei Wu; Weicai Wan; Linlin Wang (688-694).
The TiAlLaN films were deposited on YG8 and silicon (1 1 1) substrates by a hybrid PVD coater which is combined with medium frequency reactive magnetron sputtering and ion-plating evaporation. The effects of lanthanum addition and bias voltages on the composition, crystal morphology, microstructure, mechanical properties, and oxidation resistance of the TiAlLaN films were investigated systematically. With lanthanum addition in the TiAlN film, the crystal morphology changed from columnar to equiaxial, and the grain refinement accompanied by the increase of hardness and elastic modulus was found. The indentation adhesion test showed that the adhesion strength was deteriorated by adding lanthanum in the deposited film; however, the scratch adhesion test expressed a better morphology of the scratch track line for the TiAlLaN film. With the substrate bias increasing, the elements concentration of films were alternated, and the equiaxial crystals were turned to columnar crystals. The oxidation resistance of the deposited films increased with the increase of bias voltage. The adhesion qualities, which are affected by the increasing hardness and elastic modulus, were worse for the TiAlLaN films under higher bias voltages. The TiAlLaN film under the bias of −10 V showed the highest H/E ratio.
Keywords: TiAlLaN film; Bias voltage; Properties; Oxidation resistance;

A facile approach of preparing well-dispersed silver nanoparticles (Ag NPs) which fabricated on surface of porous silicon (PSi) generating Ag NPs/PSi chip and the catalyses towards reduction of nitro aromatics are described in detail in this work. Aqueous silver ions are reduced readily by the surface Si―H x (x  =1, 2 or 3) species of PSi within dozens of seconds at room temperature. The resulted Ag NPs are demonstrated by scanning and transmission electron microscopes, ultraviolet-visible spectrum and X-ray powder diffraction. A proposed mechanism of forming Ag NPs on PSi chip is discussed in light of the observed phenomena and the analyses of infrared and energy dispersive X-ray spectra. The stably porous architecture of PSi and the well-dispersed Ag NPs on PSi surface guarantee the highly catalytic activities of the Ag NPs/PSi chip. The progresses of reducing nitro aromatics catalyzed by the Ag NPs/PSi chip in the presence of sodium borohydride are traced by ultraviolet-visible measurements to estimate the catalytic performance of the Ag NPs/PSi chip.
Keywords: Porous silicon; Silver nanoparticles; Catalysis; Reduction; Nitro group;

Effects of rare earth Nd and (Ag, Ni and In) ions codoping on the structural, electrical, optical, ferroelectric and magnetic properties of the BiFeO3 (BFO) thin films prepared on FTO/glass substrates by using a sol–gel method were investigated. From X-ray diffraction and Raman scattering analyses, distorted rhombohedral perovskite structures were observed for all the films. The X-ray photoelectron spectroscopy analysis was carried out to investigate the chemical states and lattice deficiencies of the films. Both charge states 3+ and 2+ of Fe ions are simultaneously present in all the films but 2+ state appears to be dominant. The leakage mechanisms of the films were systematically investigated by two kinds of bulk-limited conductions (space-charge-limited conduction and Poole–Frenkel emission) and two kinds of interface-limited conductions (Schottky emission and Fowler–Nordheim tunneling). The optical measurement showed that all the films have a conspicuous absorption in the blue and green light region with the band gap values around 2.7 eV. The present work reveals that the non-magnetically active Ag and In ions are more helpful than the magnetically active Ni ion in enhancing the macroscopic magnetization of BFO by the introduction of a local ferromagnetic coupling rather than an antiferromagnetic one.
Keywords: BiFeO3; Multiferroics, Leakage current, Optical properties;

Cd(II) removal from aqueous solution by adsorption on α-ketoglutaric acid-modified magnetic chitosan by Guide Yang; Lin Tang; Xiaoxia Lei; Guangming Zeng; Ye Cai; Xue Wei; Yaoyu Zhou; Sisi Li; Yan Fang; Yi Zhang (710-716).
The present study developed an α-ketoglutaric acid-modified magnetic chitosan (α-KA-Fe3O4/CS) for highly efficient adsorption of Cd(II) from aqueous solution. Several techniques, including transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and vibrating sample magnetometer (VSM), were applied to characterize the adsorbent. Batch tests were conducted to investigate the Cd(II) adsorption performance of α-KA-Fe3O4/CS. The maximum adsorption efficiency of Cd(II) appeared at pH 6.0 with the value of 93%. The adsorption amount was large and even reached 201.2 mg/g with the initial Cd(II) concentration of 1000 mg/L. The adsorption equilibrium was reached within 30 min and commendably described by pseudo-second-order model, and Langmuir model fitted the adsorption isotherm better. Furthermore, thermodynamic parameters, free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of Cd(II) adsorption were also calculated and showed that the overall adsorption process was endothermic and spontaneous in nature because of positive ΔH values and negative ΔG values, respectively. Moreover, the Cd(II)-loaded α-KA-Fe3O4/CS could be regenerated by 0.02 mol/L NaOH solution, and the cadmium removal capacity could still be kept around 89% in the sixth cycle. All the results indicated that α-KA-Fe3O4/CS was a promising adsorbent in environment pollution cleanup.
Keywords: Chitosan; α-Ketoglutaric acid; Cd(II); Adsorption; Magnetic separation;

Growth of gold overlayers on a clean and oxidized tungsten tip has been studied by Field Emission Microscopy. Gold was deposited by conventional vacuum evaporation (VE) and by pulsed laser deposition (PLD) method using a Nd:YAG laser. The effect of the applied deposition method on gold growth was examined and the influence of high-kinetic energy particles produced by PLD in vacuum on the morphology and size of prepared gold nanostructures is discussed. PLD of gold on oxidized tungsten tip resulted in a significant reduction of the oxide layer. Presence of He (∼5 mbar) during PLD decreased the kinetic energy of the species arriving at the substrate and resulted in gold growth similar to that we observed for conventional VE.
Keywords: Nanoparticles; Nucleation and growth; Pulsed laser deposition; Work function; Field emission microscopy;

Characterization of fully functional spray-on antibody thin films by Jhon Figueroa; Sonia Magaña; Daniel V. Lim; Rudy Schlaf (726-734).
The authors recently demonstrated that fully functional Escherichia coli O157:H7 antibody thin films can be prepared using a simple pneumatic nebulizer on glass surface [1]. This paper focuses on the investigation of the morphology and physical properties of these films with the aim to better understand their performance. A series of E. coli O157:H7 antibody spray-on thin films were investigated by ellipsometry, X-ray photoelectron spectroscopy (XPS), immunoassays, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), fluorescence microscopy, atomic force microscope (AFM) and contact angle analysis. These data were compared to measurements on films prepared with the biotin–avidin covalent bonding scheme. The investigation showed that films created by a 2 min pneumatic spray deposition time can capture antigens similar as the avidin–biotin wet-chemical method. The results also suggests that an influential factor for the comparable capture cell ability between sprayed and covalent films is an increased antibody surface coverage for the sprayed films (non-equilibrium technique), which compensates for the lack of its antibody orientation. There was no significant antibody denaturation detected on any of the sprayed films. Both techniques led to the formation of cluster-aggregates, a factor that seems unavoidable due to the natural tendency of protein to cluster. The avidin–biotin bridge films generally had a higher roughness, which manifested itself in a higher wettability compared to the sprayed films.
Keywords: Pneumatic spray; Surface morphology; Antibody immobilization; Physical adsorption;

Highly efficient adsorption of chlorophenols onto chemically modified chitosan by Liang-Chun Zhou; Xiang-Guang Meng; Jing-Wei Fu; Yu-Chong Yang; Peng Yang; Chun Mi (735-741).
A novel chemically modified chitosan CS-SA-CD with phenol and β-cyclodextrin groups was prepared. The adsorptions of phenol, 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP) on the functional chitosan from aqueous solution were investigated. CS-SA-CD exhibited excellent adsorption ability for chlorophenols especially for DCP and TCP. The maximum adsorption capacities of phenol, 2-CP, 4-CP, DCP and TCP on CS-SA-CD were 59.74, 70.52, 96.43, 315.46 and 375.94 mg/g, respectively. The scanning electron microscope and Brunauer–Emmett–Teller analyses revealed that the introduction of phenol group changed the surface morphology and surface properties of chitosan. The modified chitosan CS-SA-CD possesses larger surface areas (4.72 m2/g), pore volume (7.29 × 10−3  mL/g) and average pore diameter (59.99 Å) as compared to those of chitosan 3.27 m2/g, 2.00 × 10−3  mL/g and 15.95 Å, respectively. The enhanced adsorption of chlorophenols was also attributed to the interaction of hydrogen bond between Cl atom and ―OH group. The adsorption of chlorophenols on CS-SA-CD followed the pseudo-second-order kinetic model. Adsorbent could be regenerated easily and the regenerated CS-SA-CD remained 80–91% adsorption efficiency.
Keywords: Chitosan; β-Cyclodextrin; Adsorption; Chlorophenols; Wastewater;

The energetics of formation and hydration of functionalized silica nanoparticles were studied using a combination of first-principles calculations based on density functional theory with van der Waals dispersion correction and molecular dynamics. The energetics and effects of group density were evaluated in both; hydrophilic (ethylene-glycol) and hydrophobic (sulfonic) organosilane functional groups, and the optimum group density were obtained in vacuum and aqueous environment. The functional group bounded in a geminal silanol site was found to be more stable than silanol one, by ∼1.30 and ∼1.32 eV for hydrophilic and hydrophobic groups, respectively. In vacuum, an optimum graft density of 4.2 and 4.5 groups/nm2 was obtained for hydrophobic and hydrophilic coverage, based on molecular dynamics calculations. Interestingly, a double well energy profile is obtained when functionalized nanoparticles are placed within aqueous media, and those minima for hydrophilic groups appear at lower coverage compared to hydrophobic one. The double energy minima is explained by the H2O molecules arrangement as function of the group density on nanoparticles surface. At low coverage, H2O molecules surround the groups while at high coverage, the functional groups shield the molecules to penetrate within the groups and the size effect of the functional group studied here was found to be negligible on the stability.
Keywords: Silica; Nanoparticle; Functionalization; DFT; van der Waals; Molecular dynamics;

Adhesion, friction, and wear are the three key problems in moving parts of nano/microelectromechanical system devices. Self-assembly technique has become an important route to solve these problems for its construction of lubricants in micro/nano scales. The present work fabricated a composite dual-layer film of polydopamine/gold nanoparticles on silicon. The morphologies, structures, and chemical constitute of the synthesized nanoparticles and the self-assembled films were confirmed by ultraviolet absorption spectrum, transmission electron microscopy, and atomic force microscopy. To evaluate their micro adhesion forces and macro tribological behaviors of the films, atomic force microscopy and UMT-2M tribometer were employed. The worn surface morphologies of the films and the counterpart steel balls were observed by scanning electron microscopy. The results show that the film has favorable friction reduction and wear resistance ability, which is expected to be applied in nano/microelectromechanical systems.
Keywords: Self-assembly; Polydopamine; Gold nanoparticles; Adhesive force; Tribological properties;

The behavior of active bactericidal and antifungal coating under visible light irradiation by Gang Xiao; Xiaodong Zhang; Yan Zhao; Haijia Su; Tianwei Tan (756-763).
In the present paper, the novel active bactericidal and antifungal coatings (ABAC) have been prepared through the immobilization of Fe-doped TiO2 (anatase) with chitosan. The characterization of ABAC using optical microscope imaging, SEM, AFM and FTIR shows that the Fe doped TiO2 is embedded into the chitosan coating with favorable dispersion through the hydrogen bonds interaction between chitosan molecules and TiO2. The contact angle measurement demonstrated the hydrophilicity of ABAC (θ  = 34.5 ± 4.1°). The bactericidal activity of ABAC has been evaluated by inactivating three different test strains: Escherichia coli, Candida albicans and Aspergillus niger which illustrates the apparently higher bactericidal ability than chitosan, Fe-TiO2 and chitosan/TiO2 (pure) under visible light irradiation and its bactericidal activity is lasting for at least 24 h. ABAC showed rapid and efficient antibacterial ability for the three tested strains and its antibacterial ratio in 2 h for E. coli, C. albicans and A. niger was 99.9%, 97.0% and 95.0%, respectively. The prepared chitosan/TiO2 composite emulsion shows favorable storage stability and can be stored up to 1 year without losing its bactericidal activity. ABAC is a low-cost and eco-friendly antibacterial coating products and promising for domestic, medical and industrial applications.
Keywords: Chitosan; TiO2; Visible light irradiation; Bactericidal; Coating;

Modified composite microspheres of hydroxyapatite and poly(lactide-co-glycolide) as an injectable scaffold by Xixue Hu; Hong Shen; Fei Yang; Xinjie Liang; Shenguo Wang; Decheng Wu (764-772).
The compound of hydroxyapatite-poly(lactide-co-glycolide) (HA-PLGA) was prepared by ionic bond between HA and PLGA. HA-PLGA was more stable than the simple physical blend of hydroxyapatite and poly(lactide-co-glycolide) (HA/PLGA). The surface of HA-PLGA microsphere fabricated by an emulsion–solvent evaporation method was rougher than that of HA/PLGA microspheres. Moreover, surface HA content of HA-PLGA microspheres was more than that of HA/PLGA microspheres. In vitro mouse OCT-1 osteoblast-like cell culture results showed that the HA-PLGA microspheres clearly promoted osteoblast attachment, proliferation and alkaline phosphatase activity. It was considered that surface rich HA component and rough surface of HA-PLGA microsphere enhanced cell growth and differentiation. The good cell affinity of the HA-PLGA microspheres indicated that they could be used as an injectable scaffold for bone tissue engineering.
Keywords: Hydroxyapatite; Poly(lactide-co-glycolide); Composite microspheres; Injectable scaffold; Tissue engineering;

Magnetic and electrical properties of TiO2:Nb thin films by Chang-Feng Yu; Shih-Jye Sun; Jian-Ming Chen (773-776).
This study investigated the electrical and especially the magnetic properties of Niobium (Nb) doped TiO2 (TiO2:Nb) thin films. Experiments evidently present that both minimum of ferromagnetism and resistivity exist in a same Nb doping ratio (3.0%). The XPS experiments revealed that Nb doping simultaneously increases and compensates for oxygen vacancies. The proposed model explains magnetic and electrical properties by analyzing oxygen vacancies induced by vacuum annealing or by Nb doping.
Keywords: TiO2:Nb; Rapid thermal annealing; Ferromagnetism; Coulomb repulsion;

Investigation of static and dynamic wetting transitions of UV responsive tunable wetting surfaces by Reeta Pant; Subhash Singha; Aritra Bandyopadhyay; Krishnacharya Khare (777-781).
Ultraviolet (UV) radiation responsive surfaces, with tunable wetting properties, are fabricated by spin casting polystyrene/titania nanocomposite dispersion in tetrahydrofuran on silicon substrates. The prepared samples are found hydrophilic due to the presence of the water miscible solvent. Upon annealing, as the solvent evaporates, samples become superhydrophobic due to presence of hydrophobic polystyrene and formation of nano and micro scale surface roughness due to titania nanoparticles. Effect of different annealing temperatures and time on resulting wettability is investigated. Photocatalytic property of titania is exploited to make transition from superhydrophobic to hydrophilic state upon UV exposure. Subsequently, upon annealing again at elevated temperatures for sufficient time, the UV exposed hydrophilic samples recover their superhydrophobicity showing transition from hydrophilic to superhydrophobic state. Detailed static and dynamic study of these reversible transitions, between superhydrophobic and hydrophilic states, due to UV exposure and annealing is presented in this article.
Keywords: Tunable wetting; Surface modification; Superhydrophobic; Titania; Photo-responsive;

Texturation and superhydrophobicity of polyethylene terephthalate thanks to plasma technology by Jeanne Tarrade; Thierry Darmanin; Elisabeth Taffin de Givenchy; Frédéric Guittard; Dominique Debarnot; Fabienne Poncin-Epaillard (782-789).
Anti-bioadhesive surfaces were designed from polyethylene terephthalate (PET) by three steps plasma-treatment. First, the nano-pattern is created by oxygen plasma-treatment with controlled dimensions. Then, the plasma-treated polymeric surface was hydrophobized with a tetrafluorocarbon plasma, allowing to obtain a water contact angle of 145 ± 4°. However, the SEM pictures give evidence to show the degradation of the structuration caused by the CF4-plasma and consequently, the superhydrophobicity was not reached. Thus, a plasma-polypyrrole layer was deposited before the plasma-fluorination, which has a protective role against the degradation generated by fluorinated species, preserving the structuration and improving the fluorination rate. Therefore, the obtained surfaces are superhydrophobic with water contact angle of 157 ± 2° and a hysteresis of 65 ± 3°. The ability of these surfaces to reduce bioadhesion will be performed in further work.
Keywords: Superhydrophobicity; Texturation; Nanofiber; Plasma polymerization; Plasma fluorination; Plasma oxidation;

Architecting boron nanostructure on the diamond particle surface by H. Bai; D. Dai; J.H. Yu; K. Nishimura; S. Sasaoka; N. Jiang (790-794).
The present study provides an efficient approach for nano-functionalization of diamond powders. Boron nanostructure can be grown on diamond particle entire surface by a simple heat-treatment process. After treatment, various boron nanoforms were grown on the diamond particle surface at different processing temperature. High-density boron nanowires (BNWs) grow on the diamond particle entire surface at 1333 K, while nanopillars cover diamond powders when the heat treatment process is performed at 1393 K. The influence of the pretreatment temperature on the microstructure and thermal conductivity of Cu/diamond composites were investigated. Cu/diamond composites with high thermal conductivity of 670 W (m K)−1 was obtained, which was achieved by the formation of large number of nanowires and nanopillars on the diamond particle surface.
Keywords: Diamond powders; Surface functionalization; Boron nanostructure; Thermal conductivity;

An investigation on the effect of surface morphology and crystalline texture on corrosion behavior, structural and magnetic properties of electrodeposited nanocrystalline nickel films by F. Nasirpouri; M.R. Sanaeian; A.S. Samardak; E.V. Sukovatitsina; A.V. Ognev; L.A. Chebotkevich; M.-G. Hosseini; M. Abdolmaleki (795-805).
In this work, nanocrystalline nickel films with different surface morphologies were electrodeposited from Watts bath using direct (DC), pulsed (PC), and pulsed reverse (PRC) current techniques. The effect of electrodeposition conditions on the evolution of microstructure, cathodic efficiency, crystallographic micro-texture, micro-hardness, magnetic and corrosion properties of nickel films were investigated. Ni films electrodeposited by PC method revealed the highest cathodic efficiency due to minimum amount of hydrogen evolution. All films electrodeposited by PC and PRC methods making the films nanocrystalline (NC) exhibited greater hardness values and smaller crystallite size compared to those deposited by DC method. A preferential crystallographic orientation or texture was found in Ni films depending upon the electrodeposition pulse shape, as the microstructure is polycrystalline in the DC electrodeposited films, while exhibits 〈1 1 1〉 and 〈1 0 0〉 crystallographic growth directions for PC and PRC methods, respectively. Magnetic properties of the nanocrystalline Ni films indicate the existence of strong magnetocrystalline anisotropy depending on the microstructure of the films. Corrosion evaluation results showed that the PC electrodeposited NC-Ni films are more corrosion resistive in 2 mol/l NaOH solution, compared to those electrodeposited by PRC and DC methods. In contrast, in 0.5 mol/l H2SO4 solution, corrosion resistance of the films is in descending order from PC to PRC and DC.
Keywords: Nanocrystalline nickel; Electrodeposition; Surface morphology; Magnetic anisotropy; Corrosion behavior;

Effect of silane treatment on microstructure of sisal fibers by Feng Zhou; Guangxu Cheng; Bo Jiang (806-812).
Sisal fibers were modified using silane coupling agents to determine the mechanism of the chemical reaction between the fiber and silane. A combination of scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), and TG/mass spectrometry (TG/MS) were used to investigate the effects of chemical treatment on sisal fibers systemically. The results showed that a layer of film was formed on the fiber surface by silane adsorption. The layer consisted of siloxane and polysiloxane. FTIR spectroscopy indicated that chemical bonds were formed between the silane coupling agent and the fiber. It was further verified by TG-DSC and TG/MS analysis that the decomposition properties of the sisal fibers were changed by the formation of chemical bonds between the silane and the sisal fiber surface.
Keywords: Sisal fibers; Silane treatment; Infrared spectra; Differential scanning calorimetry; Mass spectrometry;

Core/shell CdS/ZnS nanoparticles: Molecular modelling and characterization by photocatalytic decomposition of Methylene Blue by Petr Praus; Ladislav Svoboda; Jonáš Tokarský; Alice Hospodková; Volker Klemm (813-822).
Core/shell CdS/ZnS nanoparticles were modelled in the Material Studio environment and synthesized by one-pot procedure. The core CdS radius size and thickness of the ZnS shell composed of 1–3 ZnS monolayers were predicted from the molecular models. From UV–vis absorption spectra of the CdS/ZnS colloid dispersions transition energies of CdS and ZnS nanostructures were calculated. They indicated penetration of electrons and holes from the CdS core into the ZnS shell and relaxation strain in the ZnS shell structure. The transitions energies were used for calculation of the CdS core radius by the Schrödinger equation. Both the relaxation strain in ZnS shells and the size of the CdS core radius were predicted by the molecular modelling.The ZnS shell thickness and a degree of the CdS core coverage were characterized by the photocatalytic decomposition of Methylene Blue (MB) using CdS/ZnS nanoparticles as photocatalysts. The observed kinetic constants of the MB photodecomposition (k obs) were evaluated and a relationship between k obs and the ZnS shell thickness was derived. Regression results revealed that 86% of the CdS core surface was covered with ZnS and the average thickness of ZnS shell was about 12% higher than that predicted by molecular modelling.
Keywords: Core/shell nanoparticles; CdS/ZnS; Molecular modelling; Electron tunnelling; Photocatalysis;

Enhanced thermoelectric properties of mixed zinc antimonide thin films via phase optimization by Zhuang-hao Zheng; Ping Fan; Peng-juan Liu; Jing-ting Luo; Xing-min Cai; Guang-xing Liang; Dong-ping Zhang; Fan Ye; Ying-zhen Li; Qing-yun Lin (823-827).
A series of Zn-Sb thin films were deposited by direct current (DC) magnetron co-sputtering through fixing the sputtering power of Zn target while varying the sputtering power of Sb target. The deposited thin films were annealed at 673 K under Ar atmosphere for 1 h. X-ray diffraction (XRD) results show that the prepared thin film gradually transforms from β phase Zn4Sb3 to ZnSb phase with increasing Sb sputtering power. It is found that the thermoelectric properties of the prepared Zn-Sb thin films are related to the phase transformation. Firstly, the carrier concentration decreases while the Hall mobility increases with increasing Sb sputtering power until 20 W, and then with further increasing Sb sputtering power, the carrier concentration increases while Hall mobility decreases. The thin films prepared by the Sb sputtering power of 20 W shows a mixed phase of ZnSb and Zn4Sb3 and its Seebeck coefficient has a higher value than the samples with single β-Zn4Sb3 or ZnSb phase. Through optimizing the ratio of β-Zn4Sb3 to ZnSb phase in the mixed Zn-Sb thin film, an enhanced power factor of 1.91 × 10−3  W/m K2 can be obtained with a high Seebeck coefficient of 360 μV K−1 and a low resistivity of 6.79 × 10−5  Ω m at 573 K. X-ray photoelectron spectroscopy (XPS) was used to investigate the binding energy of Zn and Sb in the thin film with a power factor of 1.91 × 10−3  W/m K2 and it is suggested that the weak bonding of the thin film could be one of the reasons resulting in enhanced thermoelectric performance.
Keywords: Thermoelectric thin film; Zinc antimonide; Thermoelectric properties;

Effects of a carbon nanotube-collagen coating on a titanium surface on osteoblast growth by Jung Eun Park; Il-Song Park; Madhav Prasad Neupane; Tae-Sung Bae; Min-Ho Lee (828-836).
This study was performed to evaluate the effect of collagen-multi-walled carbon nanotubes (MWCNTs) composite coating deposited on titanium on osteoblast growth. Titanium samples coated with only collagen and MWCNTs were used as controls. Pure titanium was coated with collagen-MWCNTs composite coating with 5, 10 and 20 μg cm−2 MWCNTs by dip coating method. Scanning probe microscopy, field emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy were used to ascertain the root mean squared roughness, structural and morphological features and, the interaction between the collagen and the MWCNTs, respectively. The biocompatibility of the collagen-MWCNTs composite coated Ti was assessed by MTT and ALP activity assays after culturing the cells for 2 and 5 days. The study reveals that root mean squared surface roughness of collagen-MWCNTs composite coated titanium is relatively higher than those of collagen and MWCNTs coated Ti. There is a strong interaction between the MWCNTs and the collagen, which is supported by the inferences made in FE-SEM and TEM studies and further confirmed by FT-IR spectra. Among all the specimens tested, cell proliferation is relatively higher on collagen-MWCNTs composite coated Ti specimen incorporated with 20 μg cm−2 of MWCNTs (p  < 0.05) after 5 days of cell culture. Cell proliferation studies confirm the existence of a strong dependence of the extent of cell proliferation on the amount of MWCNTs incorporated in the composite; the higher the amount of MWCNTs, the greater the extent of cell proliferation. The higher surface roughness of collagen-MWCNTs composite coated Ti specimens is considered responsible for the relatively higher extent of cell proliferation. The MWCNTs incorporated in the composite could have also contributed to the cell viability and growth.
Keywords: Carbon nanotube; Collagen; Titanium; Osteoblast; Bioactivity;

ZnO thin films, prepared by ultrasonic spray onto glass substrate, crystallize in the wurtzite structure. The XRD pattern shows preferential orientation along the [0 0 2] direction. The films deposited at 350 °C consist of 60 nm crystallites with an average thickness of ∼150 nm and SEM images show rough surface areas. The gap increases with increasing the temperature of the substrate and a value of 3.25 eV is obtained for films deposited at 350 °C. ZnO is nominally non-stochiometric and exhibits n-type conduction because of the native defects such as oxygen vacancies (V O) and/or interstitial zinc atom (Zni) which act as donor shallows. The conductivity is thermally activated and obeys to an exponential type law with activation energy of 57 meV and an electron mobility of 7 cm2  V−1  s−1. The capacitance-voltage (C−2  V) measurement in acid electrolyte (pH ∼ 3) shows a linear behavior with a positive slope, characteristic of n-type conduction. A flat band potential of −0.70 V SCE and a donors density of 5.30 × 1016  cm−3 are determined. The Nyquist plot exhibits two semicircles attributed to a capacitive behavior with a low density of surface states within the gap region. The centre is localized below the real axis with a depletion angle of 16° ascribed to a constant phase element (CPE) due to the roughness of the film. The energy band diagram assesses the potentiality of ZnO films for the photo-electrochemical conversion. As application, 94% of chromate (3.8 × 10−4  M) is reduced after 6 h under sunlight (AM 1) with a quantum yield of 0.06% and the oxidation follows a first order kinetic.
Keywords: ZnO thin film; Ultrasonic spray; Photo-electrochemical; Chromate; Sunlight;

Drug release from porous silicon for stable neural interface by Tao Sun; Wei Mong Tsang; Woo-Tae Park (843-851).
70 μm-thick porous Si (PSi) layer with the pore size of 11.1 ± 7.6 nm was formed on an 8-in. Si wafer via an anodization process for the microfabrication of a microelectrode to record neural signals. To reduce host tissue responses to the microelectrode and achieve a stable neural interface, water-soluble dexamethesone (Dex) was loaded into the PSi via incubation with the drug solution overnight. After the drug loading process, the pore size of PSi reduced to 4.7 ± 2.6 nm on the basis of scanning electron microscopic (SEM) images, while its wettability was remarkably enhanced. Fluorescence images demonstrated that Dex was loaded into the porous structure of the PSi. Degradation rate of the PSi was investigated by incubation in distilled water for 21 days. Moreover, the drug release profile of the Dex-loaded PSi was a combination of an initial burst release and subsequent sustained release. To evaluate cellular responses to the drug release from the PSi, primary astrocytes were seeded on the surface of samples. After 2 days of culture, the Dex-loaded PSi could not only moderately prevent astrocyte adhesion in comparison with Si, but also more effectively suppress the activation of primary astrocytes than unloaded PSi due to the drug release. Therefore, it might be an effective method to reduce host tissue responses and stabilize the quality of the recorded neural signal by means of loading drugs into the PSi component of the microelectrode.
Keywords: Neural interface; Drug release; Porous silicon; Dexamethasone; Primary astrocyte;

Chemical structures and electrical properties of atomic layer deposited HfO2 thin films grown at an extremely low temperature (≤100 °C) using O3 as an oxygen source by Jeong Hwan Kim; Tae Joo Park; Seong Keun Kim; Deok-Yong Cho; Hyung-Suk Jung; Sang Young Lee; Cheol Seong Hwang (852-856).
The properties of atomic layer deposited (ALD) HfO2 films grown at low temperatures (≤100 °C) were examined for potential applications in flexible display and bioelectronics. A saturated ALD growth behavior was observed even at an extremely low temperature (30 °C) due to the strong oxidizing potential of O3. However, HfO2 films grown at low temperatures showed a low film density and high impurity concentration, because the thermal energy during film growth was insufficient to remove ligands completely from Hf ions in precursor molecule. This resulted in low dielectric constant and high leakage current density of the films. Nevertheless, HfO2 film grown at 100 °C using O3 gas with a high concentration (390 g/Nm3) showed a tolerable impurity concentration with the dielectric constant of ∼16 and breakdown field of ∼4 MV/cm, which are approximately two-thirds of those of HfO2 film grown at 250 °C.
Keywords: Atomic layer deposition; HfO2; Ozone concentration; Low temperature process;

An investigation of water contact angles (CAs), contact angle hysteresis (CAH) was carried out for 1-year to 4-year old needles (Pinus sylvestris) collected in urban (Gdansk) and rural (Karsin) locations using an original measuring technique based on the geometry of the drop on a vertical filament. Concentrations of air pollutants (SO2, NO x , C6H6, and suspended particular matter – SPM) currently considered to be most important in causing direct damage to vegetation were simultaneously monitored. A set of the surface wettability parameters: the apparent surface free energy γ SV, adhesive film tension Π, work of adhesion W A, and spreading W S, were determined from CAH data using the approach developed by Chibowski (2003) to quantify the surface energetics of the needle substrata affected by aging and pollution impacts. This formalism relates the total apparent surface free energy of the solid γ SV with only three measurable quantities: the surface tension of the probe liquid γ LV and its advancing θ A and receding θ R contact angle hysteresis. Since CAH depends on the outermost wax layer surface roughness and spatial physicochemical heterogeneity of a solid surface, CA data were corrected using surface architecture profiles registered with confocal scanning laser microscopy. It was found that the roughness parameter r is significantly negatively correlated (R  = −0.74) with the needle age (collected at Karsin). The needle surface aging process resulted in its surface hydrophilization (CA↓ and CAH↓ with γ SV↑ and W A↑). A temporal evolution of the needles wettability was traced with the data point distribution in the 2D space of CAH plotted versus W S. The wettability parameters were closely correlated to pollutant concentrations as evidenced from Spearman's rank correlation procedure (R  = 0.63–0.91; p  < 0.05). The aim of the study was to validate the established CA methodology to create a new non-invasive, low-cost technique suitable for monitoring of structural changes at interfaces of biological systems.
Keywords: Pinus sylvestris L. needle; Air pollution; Surface wettability; Contact angle hysteresis; Surface energetics; Microroughness quantification;

In order to shed some light on DNA preservation over time in skeletal remains from a physicochemical viewpoint, adsorption and desorption of DNA on a well characterized synthetic apatite mimicking bone and dentin biominerals were studied. Batch adsorption experiments have been carried out to determine the effect of contact time (kinetics), DNA concentration (isotherms) and environmentally relevant factors such as temperature, ionic strength and pH on the adsorption behavior. The analogy of the nanocrystalline carbonated apatite used in this work with biological apatite was first demonstrated by XRD, FTIR, and chemical analyses. Then, DNA adsorption kinetics was fitted with the pseudo-first order, pseudo-second order, Elovich, Ritchie and double exponential models. The best results were achieved with the Elovich kinetic model. The adsorption isotherms of partially sheared calf thymus DNA conformed satisfactorily to Temkin's equation which is often used to describe heterogeneous adsorption behavior involving polyelectrolytes. For the first time, the irreversibility of DNA adsorption toward dilution and significant phosphate-promoted DNA desorption were evidenced, suggesting that a concomitant ion exchange process between phosphate anionic groups of DNA backbone and labile non-apatitic hydrogenphosphate ions potentially released from the hydrated layer of apatite crystals. This work should prove helpful for a better understanding of diagenetic processes related to DNA preservation in calcified tissues.
Keywords: Nanocrystalline apatite; Hydroxyapatite; Ancient DNA; Polyelectrolyte adsorption; Temkin isotherm; Elovich;

Hexagonal boron nitride (h-BN) coatings with different thickness were prepared on quartz fibers to improve mechanical properties of quartz fiber reinforced Si―O―C―N composite. Scanning electron microscopy (SEM), push-out test and single edge notched beam (SENB) in three point bending test were employed to study morphology, interface shear strength and fracture toughness of the composite. The results showed that h-BN coatings changed the crack growth direction and weaken the interface shear strength efficiently. When the h-BN coating was 308.2 nm, the interface shear strength was about 5.2 MPa, which was about one-quarter of that of the sample without h-BN coatings. After the heating process for obtaining composite, the h-BN nanometer-sized grains would grow up to micron-sized hexagonal grains. Different thickness h-BN coatings had different structure. When the coatings were relatively thin, the hexagonal grains were single layer structure, and when the coatings were thicker, the hexagonal grains were multiple layer structure. This multiple layer interface phase would consume more power of cracks, thus interface shear strength of the composite decreased steadily with the increasing of h-BN coatings thickness. When the coating thickness was 238.8 nm, K IC reaches the peak value 3.8 MPa m1/2, which was more than two times of that of composites without h-BN coatings.
Keywords: Ceramic-matrix composites; h-BN coatings; Interfacial strength; Fracture toughness;

The effects of oxidant (H2O) feeding time and growth temperature on the C- and N-related impurities and Si diffusion behavior in the atomic-layer-deposition (ALD) of La2O3 films were examined using in situ X-ray photoelectron spectroscopy analysis. Longer H2O pulse time assisted in a complete ligand exchange reaction during ALD, which suppressed the accumulation in the film of residual C- and N-related byproducts/impurities with low bonding energy that originated from incompletely reacted ligands and carboxyl compound intermediate phases. In addition, this phenomenon slightly increased the growth rate of the La2O3 film even under the nominal growth-saturated ALD conditions because the concentration of residual C- and N-related byproducts/impurities, which disturb the formation of the active sites, was reduced. The band gap energy of the films increased slightly with H2O feeding time due to the reduction of C impurities. The residual C- and N-related byproducts/impurities and carboxyl compound intermediate phases in the La2O3 films were effectively reduced by increased growth temperature. However, increased growth temperature enhanced the Si out-diffusion from the substrate into the films and decreased the film growth rate because the surface functional groups for sequential film growth during ALD were reduced. The enhanced Si out-diffusion increased the band gap of the film and the valence band off-set with respect to the Si substrate.
Keywords: ALD; La2O3; Impurity; Si diffusion; In situ XPS;

Highly-ordered TiO2 nanotube arrays were synthesized electrochemically. Effect of irradiation on deposition of CdS in fabricating co-axial heterogeneous structure via chemical deposition was investigated. The field emission measurements revealed that irradiation with higher energy will help to achieve not only more CdS, but also neater and more intimate heterostructure through exerting influences on ion migration into the tubes and attachment of ions onto the tube walls. The XRD measurements revealed that the deposited nanotubes are composed of anatase TiO2, metallic Ti, and CdS. The optical characterization revealed that the photoabsorption and absorption activity are correlated with the energy of irradiation. The photoelectrochemical measurements revealed that the photocurrent density are also correlated with the energy of the irradiation. The stability of the obtained structures was governed by the contact between CdS and TiO2 as well as the amount of CdS.
Keywords: TiO2 nanotube arrays; Chemical deposition; Irradiation; CdS; Performances;

Ag/Pd core-shell nanoparticles by a successive method: Pulsed laser ablation of Ag in water and reduction reaction of PdCl2 by N. Mottaghi; M. Ranjbar; H. Farrokhpour; M. Khoshouei; A. Khoshouei; P. Kameli; H. Salamati; M. Tabrizchi; M. Jalilian-Nosrati (892-897).
In this study Ag/Pd nanoparticles (NPs) have been fabricated by a successive method; first, colloids of Ag nanoparticles (NPs) have been prepared in water by pulsed laser ablation in liquid (PLAL) method. Then PdCl2 solution (up to 0.2 g/l) were added to the as-prepared or aged colloidal Ag NPs. Characterizations were done using UV–vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmissions electron microscopy (TEM) techniques. Spectroscopy data showed that surface plasmon resonance (SPR) peaks of as-prepared Ag NPs at about λ  = 400 nm were completely extinguished after addition of PdCl2 solution while this effect was not observed when aged Ag NPs are used. XRD and XPS results revealed that by addition of the PdCl2 solution into the as-prepared Ag NPs, metallic palladium, and silver chloride composition products are generated. TEM images revealed that as a result of this reaction, single and core-shell nanoparticles are obtained and their average sizes are 2.4 nm (Ag) and 3.2 nm (Ag/Pd). The calculated d-spacing values form XRD data with observations on high magnification TEM images were able to explain the chemical nature of different parts of Ag/Pd NPs.
Keywords: Ag/Pd; Bimetallic nanoparticles; Laser ablation; Reduction reaction; XRD; XPS; TEM.;

Lipolytic biocatalyst based on recyclable magnetite-polysiloxane nanoparticles by Anamaria Durdureanu-Angheluta; Maurusa-Elena Ignat; Stelian Sergiu Maier; Lucia Pricop; Adina Coroaba; Adrian Fifere; Mariana Pinteala; Anca Chiriac (898-905).
This work presents a novel hydrophobic magnetizable nanosupport able to load and valorize the lipase derived from Candida cylindracea (CCL). Nude magnetite nanoparticles (MP) were coated by covalent binding with an ester-polysiloxane (PS). The chemical composition, dimensions, morphology and magnetic properties of the resulted core–shell nanoparticles (MP-PS-CCL) are analyzed. The amount of immobilized lipase increase when loaded from aqueous solutions of up to 12.8 mg/mL CCL, when a lipolytic activity of 74.76 U/g is achieved. For higher concentrations of the loading solution, the activity of immobilized lipase decreases, probably due to the enzyme steric hindrance.MP-PS-CCL exhibits a good lipolytic activity against 4-nitrophenyl laurate (4-NPL), which allows the kinetic study of lipolysis reaction by measuring the amount of released 4-nitrophenol (4-NP), when working at room temperature, in TRIS buffer (pH 8.2). Even after three months of storage, the product is able to sustain up to 4 reusing cycles.
Keywords: Magnetite nanoparticles; Polysiloxane ester; Lipase immobilization; Lipolytic activity;

Epitaxial GaN thin films are grown on conventional sapphire (0 0 0 1) substrates using pulsed laser deposition in five different sets. The evolution of crystallization and surface morphology of the as-deposited films is studied to evaluate the influence of growth conditions such as: substrate heating, background N2 pressure, target-substrate distance, laser energy density, and substrate location, which were systematically varied. Upon the optimization of process conditions, E2-h Raman peak red-shifts toward the unstrained 567.6 cm−1 location are observed, accompanied with an increase in texture coefficient of (0 0 0 2) orientation, a decrease in average surface roughness to values less than 3 nm, and threading dislocations density in the order of ∼3 × 109  cm−2. This study accounts for the physics behind the careful tuning of PLD parameters as an approach to optimize the structural quality of GaN grown films on conventional sapphire substrates. The results could be a reference for further growth complications in PLD.
Keywords: Pulsed laser deposition; Gallium nitride thin film; Dislocations density; LED;

In this work, the etching characteristics of the zinc tin oxide (ZTO) thin films were investigated as a function of the BCl3/Ar gas mixture ratio in the inductively coupled plasma system. As the BCl3 content in Ar plasma increased, the etch rate of ZTO and indium tin oxide (ITO) thin films, and the selectivity of ITO over ZTO increased reaching the maximum of 54.2 nm/min, 126.2 nm/min, and 2.33 in the BCl3/Ar (6:14 sccm) gas mixing ratio, respectively. The chemical mechanism and byproduct of the etching process were determined by XPS analysis. It was confirmed that the etching process affects the surface of the active layers. Clearly, the damage caused by the etching process can affect the surface roughness of the active layers.
Keywords: ITO; ZTO; BCl3; Inductively coupled plasma; XPS;

The structure and hydrogen storage behavior of Pd-decorated nitrogen-doped graphene are investigated using the first principals based on density functional theory (DFT) calculations. Among the three types of defective structures, it is found that Pd-decorated graphene with pyridinic and pyrrolic N-doped defects are more stable and exhibit hydrogen uptake ability up to three H2 per Pd atom. A single H2 or two H2 are molecularly chemisorbed on the Pd atom, where the stretched H―H bond is relaxed but not dissociated. The binding mechanism of H2 molecule is attributed to hybridization of the 4d orbitals of Pd with the σ orbitals of H2 (so-called Kubas interaction). Out of two adsorbed H2, the first and second H2 are still chemisorbed molecularly, the nature of bonding is very weak physisorption for the third adsorbed H2. Double-side Pd-decorated graphene with pyridinic and pyrrolic N defects can theoretically reach a gravimetric capacity of 1.99 wt.% hydrogen, which is very close to the recent experimental finding.
Keywords: Hydrogen storage; N-doped graphene; Density functional theory;

Polysilazane (PSZ) and its polymer-derived amorphous silicon oxycarbide (SiOC) ceramic were coated on aluminum nitride (AlN) by using a dip-coating method to allow moisture-crosslinking of PSZ on AlN, followed by heat treatment at 700 °C in air to convert PSZ into SiOC on AlN. The results from FTIR, XPS and SEM indicated that the surface of AlN was successfully coated by PSZ and SiOC film. It was found that the introduction of PSZ and SiOC film help improve in the interfacial adhesion between the modified AlN (PSZ/AlN and SiOC/AlN) and silicone rubber lead to the increase in the thermal conductivity of the composites since the thermal boundary resistance at the filler–matrix interface was decreased. However, the introduction of SiOC as an intermediate layer between AlN and silicone rubber could help increase the thermal energy transport at the filler–matrix interface rather than using PSZ. This result was due to the decrease in the surface roughness and thickness of SiOC film after heat treatment at 700 °C in air. Thus, in the present work, a SiOC ceramic coating could provide a new surface modification for the improvement of the interfacial adhesion between the thermally conductive filler and the matrix in which can enhance the thermal conductivity of the composites.
Keywords: Surface modification; Aluminum nitride; Thermal conductivity; Polysilazane; Silicon oxycarbide; Silicone rubber;

TiO2 (B) nanosheets mediate phase selective synthesis of TiO2 nanostructured photocatalyst by Yuxi Wang; Changhua Wang; Xintong Zhang; Panpan Sun; Lina Kong; Yongan Wei; Han Zheng; Yichun Liu (937-943).
We developed a general soft chemical route that used a TiO2 (B) nanosheet as a precursor to synthesize TiO2 nanostructures of desired phase. Photocatalytic activity tests demonstrated the brookite/anatase mixture had the highest activity in degrading acetaldehyde under UV irradiation.Phase selective synthesis is particularly valuable in revealing performance of photocatalyst existing as several polymorphic phases. In this work, we develop a general soft chemical route that used a TiO2 (B) nanosheet as a precursor to synthesize TiO2 nanostructures of desired phase. Benefiting from the structural similarity and ultrathin thickness feature, TiO2 (B) nanosheet precursor can readily transform to pure phase of anatase, rutile and brookite as well as mixed phase of brookite/anatase. A possible dissolution-recrystallization mechanism is proposed for the phase transition of TiO2 (B) nanosheets to other phases. Photocatalytic activity tests demonstrated that the brookite/anatase mixture had the highest activity in degrading acetaldehyde under UV light irradiation, due to the synergistic effect of high crystallinity, large surface area and mixed phase structure.
Keywords: TiO2 (B); Brookite; Phase selective; Photocatalysis;

Microstructure and antibacterial properties of Cu-doped TiO2 coating on titanium by micro-arc oxidation by Xiaohong Yao; Xiangyu Zhang; Haibo Wu; Linhai Tian; Yong Ma; Bin Tang (944-947).
Infection associated with titanium implants remains the most common serious complication after surgery. In this work, Cu-doped antibacterial TiO2 coating was synthesized by micro-arc oxidation of titanium in an electrolyte bearing Cu nanoparticles. Surface morphology and structure of the coating were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that Cu nanoparticles were not only distributed on the surface and inside the pores but also embedded in the coating. Cu mainly exists in the Cu2+ state in the TiO2 coating. The Cu-doped coating exhibited excellent antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).
Keywords: Micro-arc oxidation; Titanium; Cu nanoparticles; Antibacterial activities;

Synthesis of dumbbell-like Bi2WO6@CaWO4 composite photocatalyst and application in water treatment by Zhijie Zhang; Wenzhong Wang; Dong Jiang; Jiayue Xu (948-953).
Dumbbell-like Bi2WO6@CaWO4 composite photocatalyst was successfully synthesized via hydrothermal method in one step, in which the Bi2WO6 nanoplates assembled on the surface of the CaWO4 microspheres. The growth mechanism of such a special micro-nano structure was investigated. This structure holds the advantages of both a microstructure and a nanostructure, which can not only ensure the sufficient contact between the Bi2WO6 photocatalyst and the organic molecules, but also favor the sediment of the catalyst particles. Photocatalytic degradation of rhodamine B (RhB), demonstrated that the Bi2WO6@CaWO4 composite reserved the high photo-activity of Bi2WO6. Besides RhB, the Bi2WO6@CaWO4 composite could also degrade other model pollutants such as methyl orange (MO) and phenol effectively. Moreover, the composite photocatalyst could settle naturally in 15 min, which is beneficial for its separation and recycling.
Keywords: Bi2WO6@CaWO4; Composite photocatalyst; RhB; Micro-nano structure;

C60 layer growth on the Co/Si(1 1 1) 7 × 7 surface by D.A. Olyanich; T.V. Utas; V.G. Kotlyar; A.V. Zotov; A.A. Saranin; L.N. Romashev; N.I. Solin; V.V. Ustinov (954-957).
The system of C60 layer on Si(1 1 1) 7 × 7 –Co surface has a negligible lattice mismatch and with the designed two-step procedure which allows formation of the highly ordered Si(1 1 1) 7 × 7 –Co surface with domain size of ∼100 nm, one could expect to achieve a perfect epitaxial growth of C60 molecular layer. However, using scanning tunneling microscopy observations we have found that regular C60 arrays grown on such a promising surface typically do not exceed the size of ∼10 nm. It has been recognized that the main reason for lacking the long-range ordering in the C60 layer is occurrence of several adsorption sites within the 7 × 7  unit cell.
Keywords: Atom–solid interactions; Silicon; Fullerene; Self-assembly; Scanning tunneling microscopy;

Molecular dynamics simulations are used to study the interactions between polyethylene and single-walled carbon nanotubes. The effect of initial angle of polyethylene chain and nanotube axis is investigated. To study the influence of nanotube geometry on the interfacial properties of polyethylene/nanotube system, a range of nanotubes with different radii are considered. Besides, the influences of temperature and polyethylene chain length on the final conformation of polyethylene chain adsorbed on the nanotube surface are studied. It is shown that the polymer chain structures adsorbed on the armchair and zigzag single-walled carbon nanotubes are almost similar. Finally, systems containing a nanotube placed at the center of multiple polyethylene chains are studied. Long parallel patterns are observed in the final morphologies of multiple chains placed beside the single-walled carbon nanotube.
Keywords: Molecular dynamics simulation; Polyethylene; Single-walled carbon nanotube; Interaction; Adsorption;

LaF3 nanoparticles surface-capped by tributyl phosphate (denoted as TBP–LaF3) were prepared by in situ surface modification route. The size, morphology and phase structure of as-prepared TBP–LaF3 nanoparticles were analyzed by means of X-ray diffraction and transmission electron microscopy. The thermal stability of as-synthesized TBP–LaF3 nanoparticles was evaluated based on thermogravimetric analysis, and their tribological properties as additive in liquid paraffin were evaluated with a four-ball friction and wear tester. Moreover, the morphology of worn steel surfaces was analyzed with a scanning electron microscope, and the composition and chemical state of typical elements on worn steel surfaces were examined with an X-ray photoelectron spectroscope. Results show that as-synthesized TBP–LaF3 nanoparticles possess good thermal stability and excellent anti-wear and load-carrying capacities as well as good friction-reducing ability. This is because, on the one hand, TBP as the surface-modifier is able to improve the dispersibility of LaF3 nanoparticles in liquid paraffin and allows good adsorption of LaF3 nanoparticles on sliding steel surfaces. On the other hand, active P element of TBP can form tribochemical reaction film on sliding steel surfaces. As a result, the boundary lubricating film consisting of adsorbed LaF3 nanoparticles and tribochemical reaction film results in greatly improved friction-reducing and anti-wear abilities as well as load-carrying capacity of the lubricant base stock and gives rise to significantly reduced friction and wear of the steel–steel sliding pair.
Keywords: Surface-capped LaF3 nanoparticles; Lubricant additive; Preparation; Tribological properties;

Preparation and visible light-induced photo-catalytic activity of H-PVA/TiO2 composite loaded on glass via sol–gel method by Yuanqing Song; Jianling Zhang; Haigang Yang; Shoubin Xu; Long Jiang; Yi Dan (978-985).
Sol–gel method was used to prepare polyvinyl alcohol/titanium dioxide (PVA/TiO2) composite films on glass slide, then the heat-treated polyvinyl alcohol/titanium dioxide (H-PVA/TiO2) composite loaded on glass and used as photo-catalyst was prepared by calcinating the precursor. Scanning electron microscopy (SEM), X-ray diffractionscopy (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RAM) and fluorescence emission spectroscopy (FL) were used to characterize H-PVA/TiO2 composites. The visible light-induced photo-catalytic activities of the obtained composites prepared by different heat-treated temperature and different composition were examined through investigating the decolouration of rhodamine B (RhB) solution under visible light irradiation in the presence of the composites by means of UV–vis measurement. The results show that under the visible light irradiation, the H-PVA/TiO2 composite can make rhodamine B be degraded more efficiently than the PVA/TiO2 composite does, and the visible light photo-catalytic activity obviously depends on the heat-treated temperature and the composite composition. The 180 °C of heat-treated temperature and the 16.7 mass% of polymer content are beneficial for enhancing the efficiency of H-PVA/TiO2 of degrading RhB.
Keywords: Sol–gel method; Polymer/TiO2 composite photo-catalysis; Visible light-induced photo-catalytic activity; Rhodamine B;

Observation of chemical separation of In3Sb1Te2 thin film during phase transition by Y.M. Lee; J. Baik; H.-J. Shin; Y.S. Kim; S.G. Yoon; M.-C. Jung; Y.B. Qi (986-989).
We investigated the chemical states of In3Sb1Te2 (IST) thin film using high-resolution X-ray photoelectron spectroscopy (HRXPS) with the synchrotron radiation during in-situ annealing in ultra-high vacuum. To obtain the oxygen-free amorphous IST (a-IST), we performed the mild Ne+ ion sputtering. And also we confirmed the relative a-IST stoichiometry to be 54%:17%:29% based on HRXPS data. At the first and second phase transition temperatures of 350 and 400 °C, we observed the dramatic changes of chemical states from a-IST to InSb and the mixture of crystalline-IST and InTe, respectively. There was a depletion of Sb atoms on the surface after annealing at 750 °C. We assume that Sb atom is a key for the phase transition in IST. However, chemical state of the Sb in IST is unstable during the phase transition and it will be caused with the non-reversible process by this structural instability.
Keywords: In3Sb1Te2; Chemical state; X-ray photoelectron spectroscopy; Phase-change random access memory;

Comparative study of the impact and sliding behavior of water droplets on two different hydrophobic silane coatings by Akira Nakajima; Takumi Miyamoto; Munetoshi Sakai; Toshihiro Isobe; Sachiko Matsushita (990-996).
Smooth hydrophobic silane coatings were prepared on a Si substrate using ODS (CH3(CH2)17Si(OCH3)3) and FAS17 (CF3(CF2)7(CH2)2Si(OCH3)3). Results obtained using ellipsometry and Kelvin force microscopy suggest that ODS molecules in the coating are tilting or inflected, whereas those of FAS17 are more normal to the substrate. Impact and sliding behaviors of water droplets on the respective surfaces were investigated using a 15 μL water droplet by varying the droplet release height. Droplets on ODS slid down faster than on FAS17 when released from 0 mm height (i.e. traditional dynamic hydrophobicity measurement). The order was reversed when providing the impact velocity. Comparison of energy dissipation during the impact process revealed that the droplet on ODS, because of its large deformation, loses more energy than that on FAS17. These results demonstrate that the order of droplet removal performance depends on the presence or absence of some initial velocity.
Keywords: Hydrophobic; Silane; Impact; Sliding; Dynamic;

Nanostructured plasma etched, magnetron sputtered nanolaminar Cr2AlC MAX phase thin films by Rolf Grieseler; Bernd Hähnlein; Mike Stubenrauch; Thomas Kups; Marcus Wilke; Marcus Hopfeld; Jörg Pezoldt; Peter Schaaf (997-1001).
The knowledge of the mechanical properties of new materials determines essentially their usability and functionality when used in micro- and nanostructures. MAX phases are new and highly interesting materials due to their unique combination of materials properties. In this article a new method for producing the Cr2AlC MAX phase is presented. Thin film elemental multilayer deposition and subsequent rapid thermal annealing forms the MAX phase within seconds. Additionally, free standing microstructures (beams and cantilevers) based on this MAX phase films are prepared by plasma etching. The mechanical properties of these MAX phase microstructures are investigated.
Keywords: MAX phase; Cr2AlC; Multilayer; Rapid thermal annealing; MEMS; Mechanical properties;

Absorption efficiencies and near-electric field enhancement factors of Au- and Ag-Fe3O4 dimers have been calculated with the discrete dipole approximation (DDA) and electrostatics approximation (EA). The influences of metal nanoparticle size, incident wavelength and incident polarization angle on the enhancement factor are systematically investigated. It is found that the electric field enhancement effect on magnetite cube is positive above the surface plasmon resonance (SPR) wavelength in the longitudinal mode (LM), while being negative in nonresonant region in the transverse mode (TM). The maximum enhancement factors derived from SPR may be achieved in the LM. Most importantly, when we accurately evaluate the enhancement factors of the dimers, the presence of the magnetite nanocube must be taken into account because the cube significantly alters the amplitude distribution of the enhanced electric field of the metal nanosphere especially in SPR region. This study helps to understand and design the plasmonic nanostructures for the applications with strong photon–particle interactions.
Keywords: Discrete dipole approximation; Electric field enhancement factor; Surface plasmon resonance; Nanostructure;

Titanium-functionalized silica-pillared clays synthesized through post synthetic route was utilized as adsorbers for the removal of Cr(VI) ions from aqueous solutions under different temperatures and initial concentrations. The starting mesostructured silica-pillared clay is assembled by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using cationic surfactant as gallery template, and subsequently, the formed interlayered pore walls were decorated with nano-sized TiO2 particle through organic titanium functionalization process. The kind of structural transformation has been confirmed by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared (FT-IR) analysis, UV–vis diffuse reflectance spectroscopy (DRS), elemental analysis (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Such results indicate that most of the grafted titanium species was combined with Si–OH on the surface of gallery pores. By changing the concentration of organic titanium source during synthesis, the porous structure system is effected. Under suitable conditions, these materials exhibit high adsorption capacity and efficiency. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). The adsorption isotherms of Cr(VI) on titanium-functionalized silica-pillared clay were best fitted by Redlich–Peterson models. Detail results of thermodynamics and kinetics are also presented.
Keywords: Titanium-functionalized; Silica-pillared clay; Adsorption; Heavy metals removal;

A novel adsorbent of hydroxyapatite–gelatin (HAP–GEL) nanocomposite was developed for nitrobenzene removal from aqueous solution. The adsorbent was characterized and its performance in nitrobenzene removal was evaluated. The effects of contact time, adsorbent dosage, temperature, pH, ionic strength, humic acid, and the presence of solvent on nitrobenzene adsorption, as well as the thermodynamic parameters for adsorption equilibrium were also investigated. Results showed that HAP–GEL nanocomposite possessed good adsorption ability to nitrobenzene. The adsorption process was fast, and it reached a steady state after only 1 min. Nitrobenzene removal was increased with an increasing amount of adsorbent dosage but decreased as the temperature and pH increased. Meanwhile the amount of nitrobenzene adsorbed decreased with an increase of ionic strength from 0.01 to 1.0 mol/L and humic acid from 10 to 50 mg/L. The adsorption isotherm studies showed that both Langmuir and Freundlich models could fit the experimental data well, and the maximum adsorption capacity was estimated to be 42.373 mg/g. The thermodynamic parameters suggested that the adsorption of nitrobenzene on HAP–GEL nanocomposite was physisorption, spontaneous and exothermic in nature. Findings of this study demonstrated the potential utility of the HAP–GEL nanocomposite as an effective adsorbent for nitrobenzene removal from aqueous solution.
Keywords: Nitrobenzene; Adsorption; Hydroxyapatite–gelatin nanocomposite; Isotherm; Biocompatible adsorbent;

Micro-arc oxidization of a novel Mg–1Ca alloy in three alkaline KF electrolytes: Corrosion resistance and cytotoxicity by Z.J. Jia; M. Li; Q. Liu; X.C. Xu; Y. Cheng; Y.F. Zheng; T.F. Xi; S.C. Wei (1030-1039).
The newly-developed biodegradable Mg–1Ca (wt%) alloy was micro-arc oxidized in KF-silicate-, KF-phosphate-, and KF-silicate-phosphate electrolytes, respectively. The correspondent ceramic-like coatings, Si-, P-, and SiP coatings, with different porous microstructures were successfully fabricated. Large deep irregular micropores (diameter up to 2.5 μm) plus a few large cracks were observed for Si coating. In contrast, P coating had much smaller (diameter ∼0.6 μm) and more uniform shallow micropores, with invisible cracks. Interestingly, zooming in, we observed squama-like nanostructures (several tens of nanometers) growing around the micropores of P coating. SiP coating had pores comparable to those for Si coating in diameter but smaller in depth, along with a few inconspicuous microcracks. Our study found that electrolyte affected microstructure other than composition of MAO coatings, which subsequently resulted in different corrosion resistance and biocompatibility of Mg–1Ca alloy.A newly-developed Mg–1Ca (wt%) alloy was treated by micro-arc oxidization (MAO) in KF-silicate- (Si coating), KF-phosphate- (P coating) and KF-silicate-phosphate (SiP coating) electrolytes. The microstructure, composition and corrosion resistance of the resultant MAO coatings were investigated using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffractometry (XRD). Electrochemical analysis and immersion test in Hanks’ solution and MTT assay for in-vitro toxicity against MG63 cells were subsequently carried out. Results showed that all the three MAO coatings contributed to the improvement of corrosion resistance and cytocompatibility of substrate; however, P coating outperformed the two others due to its specific microstructure and composition.
Keywords: Mg–1Ca alloy; Micro-arc oxidation (MAO); Electrolyte; Corrosion resistance; Cytotoxicity;

Covalently assembly of low molecular weight poly(ethyleneimine) was introduced to glass surfaces via glutaraldehyde crosslinking, with focus on its application on protein immobilization or bacteria attachment. Characterizations of Fourier transform infrared spectroscopy and ellipsometry measurement revealed a stepwise growth of poly(ethyleneimine) films by layer-by-layer deposition. After fluorescein isothiocyanate labelling, photoluminescence spectroscopy measurement indicated that the amount of surface accessible amine groups had been gradually enhanced with increasing poly(ethyleneimine) layers deposition. As compared with traditional aminosilanized surfaces, the surface density of amine groups was enhanced by ∼11 times after five layers grafting, which resulted in ∼9-time increasing of surface density of immobilized bovine serum albumin. Finally, these as-prepared PEI multi-films with excellent biocompatibility were adopted as culture substrates to improve Escherichia coli adherence, which showed that their surface density had been increased by ∼251 times.
Keywords: Poly(ethyleneimine); Covalently assembly; Protein immobilization; Bacteria adherence;

New approach of long-term modification of Topas® to acquire surface hydrophilicity for chromosome spreading by O. Mednova; D. Kwasny; N. Rozlosnik; W.E. Svendsen; K. Almdal (1045-1051).
A modified and improved photografting procedure of Topas® surface hydrophilization is investigated in order to obtain stable modification of the polymer for long term storage. The achieved hydrophilicity and monitoring of the wettability during one month of storage are presented as well as a description of the optimal cleaning procedure and storage conditions to maintain the modified surface. Three minutes of oxygen plasma activation followed by 4 min of acrylic acid UV-photografting at 50 °C leads to the most stable hydrophilicity that was characterized by an initial water contact angle of 53.5° ± 1.2°. Storage of the modified material in cold water at 4 °C and refraining from ultrasonic cleaning limit water contact angle increase to 5° over 30 days. In comparison with pristine hydrophobic Topas, the proposed treatment improves chromosome spreading ability significantly.
Keywords: Cyclic olefin copolymers; Surface modification; hydrophilicity; Surface aging; Chromosome spreading;

In this paper, in situ monitoring of excimer laser irradiation processing is examined for application to the production of thin films of transparent conductive oxides (TCOs) such as tin-doped indium oxide (ITO). Numerical simulations reveal that differences in the thin film state, for example, in the dopant levels, could greatly affect the proper laser fluence, suggesting the importance of in situ monitoring of the excimer laser processing. The thermal emission signals of ITO thin films under irradiation by a pulsed ultraviolet laser were successfully detected in situ with a near-infrared sensor on a nanosecond timescale. Non-monotonic decay of the thermal radiation from the ITO thin films was observed under XeCl laser irradiation above a certain fluence. At this fluence, the surface morphology of the ITO thin films observed by atomic force microscopy changed to a microstructure reflecting melting and solidification. This correspondence between the thermal radiation and morphology suggests that the observed non-monotonic decay was caused by recalescence upon solidification and that the in situ monitoring technique can be used to detect such phase changes.
Keywords: Excimer laser irradiation; Indium–tin-oxide; Thin film; Near-infrared sensor; In situ measurement; Photo-induced chemical solution deposition;

Mechanochemical approach to get layered double hydroxides: Mechanism explore on crystallite growth by Mei-Gui Zeng; Xiao-Lei Huo; Su-Qing Liu; Shu-Ping Li; Xiao-Dong Li (1059-1066).
In this paper, the mechanochemical approach, which includes solid state reactions and hydrothermal treatment, has been proposed to synthesize magnesium–aluminum–layered double hydroxides (Mg–Al–LDHs). Specially, the reaction process of solid state reactions has been explored, and it presents that crystallite growth is the rate-controlling process. The hydrothermal treatment is performed after solid state reactions, on one hand, the crystallinity and monodispersity of final LDHs particles can be improved, on the other hand, such treatment can tailor the particle size efficiently. Furthermore, the relationship between particle size and hydrothermal conditions (time and temperature) has been systematically investigated, which indicates that the particle size and monodispersity can be effectively controlled. The crystallite growth along ab plane and c-axis has been emphatically discussed, and the results show that under relatively low temperatures such as 100 °C, the gradual growth along c-axis has been found in the range of 48 h, and high temperatures will hider its growth on the contrary. Crystal growth along ab plane could be accelerated by higher hydrothermal temperature and longer treatment time. Our studies also show that during the hydrothermal treatment, such events as aggregation, disaggregation and particle growth, occur in series or in parallel with time. At last, the Mg–Al–CO3–LDHs samples (synthesized at 100 °C for 24, 36 and 48 h) which were acid activated by HCOOH were used to adsorb fluoride ions present in aqueous solution.
Keywords: Reactions in solid state; Layered double hydroxides; Hydrothermal treatment;

A novel magnetic chitosan nanoparticle (MCNP) with a BET surface area of 108.32 m2/g was prepared using a time and energy saving method at mild condition. MCNP exhibits an excellent ability to adsorb humic acid (HA) from aqueous solution in a wide range of initial HA concentration. The rate of HA adsorption is rapid with more than 50% of HA can be adsorbed in initial 10 min, and the equilibrium state can be reached in 60 min. The adsorption kinetics data fits well to the pseudo-second-order model, and the adsorption process is transport-limited at low initial HA concentration and attachment-limited at high initial HA concentration. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model, indicating that the adsorption of HA onto MCNP is a monolayer adsorption. Based on the Langmuir isotherm model, the maximum adsorption capacity of HA is 32.6 mg/g at 25 °C. Thermodynamic parameters presents that the adsorption of HA onto MCNP is spontaneous and endothermic in nature. The mechanism for the adsorption of HA onto MCNP involves electrostatic interaction and hydrogen bonding. Regeneration studies indicate that MCNP can be recyclable for a long term. All the experimental results suggest that MCNP is a promising adsorbent for treating water that is contaminated with humic acid.
Keywords: Magnetic chitosan; Nanoparticle; Humic acid; Adsorption;

Preparation of carbon-supported Bi/Ti composites and its catalytic activity under solar irradiation by Peng Wang; Yanlin Wu; Jin Shi; Dan Liu; Wenbo Dong (1077-1082).
Carbon-supported photocatalysts of Bi/Ti oxides (Bi/Ti-C) were synthesized by a facile sol–gel process. Carbon was mounted as support substrate by controlling calcination temperature. The as-prepared materials were characterized through X-ray diffraction, and the N2 adsorption–desorption isotherm and surface texture of Bi/Ti-C at 673 K were observed by scanning electron microscopy and transmission electron microscopy. Characterization results revealed that BiOCl was the major phase of the catalytic composites, and that Bi/Ti-673 K was endowed with the porous structure of the coated C. The photocatalytic degradation activity of these samples to Rhodamine B was determined through ultraviolet-visible spectrophotometry. The composite prepared at 673 K demonstrated the highest photocatalytic efficiency. The addition of C avoided the need to modify the surface area of the crystals. In addition, the photocatalytic activities of the Bi/Ti composites were significantly improved by the compounded microstructure.
Keywords: Solar irradiation; Bi/Ti-C; Photocatalyst; Rhodamine B (RhB);