Applied Surface Science (v.359, #C)

TiS2 transformation into S-doped and N-doped TiO2 with visible-light catalytic activity by Yu-Chen Lin; Tzu-En Chien; Po-Chih Lai; Yu-Hsien Chiang; Kun-Lin Li; Jong-Liang Lin (1-6).
S-doped rutile TiO2 with high visible-light photocatalytic activity.S-doped rutile has been prepared for the first time by hydrothermal reaction of TiS2 in hydrochloric acid at a low temperature (180 °C), with the S atoms in three states of Ti―S―Ti, Ti―S―O and SO4. TiS2 in nitric acid can also be transformed into TiO2, but with mixed phases of anatase and rutile, containing nitrogen atoms at interstitial sites in the form of Ti―O―N or Ti―N―O. The S―TiO2 catalyst shows a better visible-light reactivity toward adsorbed methylene blue (MB) photodegradation and hydroxylation of terephthalic acid with respect to the N―TiO2. The possible reasons leading to the high photoactivity of the S―TiO2 are discussed in terms of the incorporated sulfur states.
Keywords: S-doped TiO2; N-doped TiO2; TiS2; Methylene blue; Visible-light; Photocatalysis;

Optical functional surfaces are key components of nearly every optical device and they have become a special focus in both academia and industry. The no contact, one step, direct, and maskless laser surface texturing technique is one of the most encouraging approaches for realizing the surface functions. We use a high power and high repetition rate ultrafast laser system to produce micro–nano structures on metal surfaces. We demonstrate that metal surface micro–nano structures and correspondingly their optical responses can be facilely tailored by simple controlling the ultrafast laser processing parameters. Nano particles of tens to hundreds nm, sub-micro particles of 0.5–1 μm, fine-micro particles of 1–10 μm, micro particles of 10–50 μm, and coarse-micro particles larger than 50 μm have been fabricated on Cu surfaces. And surface reflection of copper surfaces has been tuned from 10% to 90% in spectra level and from UV to MIR in spectrum range, with unique optical properties like visible selective reflection, linear changing reflection, band reflection, and broadband absorption being achieved. The formation processes of those particle structures as well as the underlying mechanisms for their optical responses are discussed.
Keywords: Metal; Optical properties; Micro–nano structure; Particle; Ultrafast laser processing;

A DFT study of phenol adsorption on a low doping Mn–Ce composite oxide model by Oriana D́Alessandro; Delfina García Pintos; Alfredo Juan; Beatriz Irigoyen; Jorge Sambeth (14-20).
Density functional theory calculations (DFT + U) were performed on a low doping Mn–Ce composite oxide prepared from experimental data, including X-ray diffraction (XRD) and temperature-programmed reduction (TPR). We considered a 12.5% Mn-doped CeO2 solid solution with fluorite-type structure, where Mn replaces Ce4+ leading to an oxygen-deficient bulk structure. Then, we modeled the adsorption of phenol on the bare Ce0.875Mn0.125O1.9375(1 1 1) surface. We also studied the effect of water adsorption and dissociation on phenol adsorption on this surface, and compared the predictions of DFT + U calculations with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements. The experimental results allowed us to both build a realistic model of the low doping Mn–Ce composite oxide and support the prediction that phenol is adsorbed as a phenoxy group with a tilt angle of about 70° with respect to the surface.
Keywords: Phenol adsorption; DRIFTS; Phenoxy; DFT; CeO2;

Anti-fouling properties of Fab’ fragments immobilized on silane-based adlayers by Victor Crivianu-Gaita; Alexander Romaschin; Michael Thompson (21-29).
Biosensors require surfaces that are highly specific towards the target analyte and that are minimally fouling. However, surface tuning to minimize fouling is a difficult task. The last decade has seen an increase in the use of immobilized antigen-binding antibody fragments (Fab’) in biosensors. One Fab’ linker compound S-(11-trichlorosilyl-undecanyl)-benzothiosulfonate (TUBTS) and three spacers were used to create the silane-based adlayers. The ultra-high frequency electromagnetic piezoelectric acoustic sensor (EMPAS) was used to gauge the fouling properties of the various surfaces using bovine serum albumin (BSA), goat IgG, and mouse serum. X-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM) were employed to characterize the surfaces. It was discovered that immobilized oriented Fab’ fragments reduced the fouling levels of surfaces up to 80% compared to the surfaces without fragments. An explanation for this phenomenon is that the antibody fragments increase the hydration of the surfaces and aid in the formation of an anti-fouling water barrier. The anti-fouling effect of the Fab’ fragments is at its maximum when there is an even distribution of fragments across the surfaces. Finally, using Fab’-covered surfaces, a cancer biomarker was detected from serum, showing the applicability of this work to the field of biodetection.Biosensors require surfaces that are highly specific towards the target analyte and that are minimally fouling. However, surface tuning to minimize fouling is a difficult task. The last decade has seen an increase in the use of immobilized antigen-binding antibody fragments (Fab’) in biosensors. One Fab’ linker compound S-(11-trichlorosilyl-undecanyl)-benzothiosulfonate (TUBTS) and three spacers were used to create the silane-based adlayers. The ultra-high frequency electromagnetic piezoelectric acoustic sensor (EMPAS) was used to gauge the fouling properties of the various surfaces using bovine serum albumin (BSA), goat IgG, and mouse serum. X-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM) were employed to characterize the surfaces. It was discovered that immobilized oriented Fab’ fragments reduced the fouling levels of surfaces up to 80% compared to the surfaces without fragments. An explanation for this phenomenon is that the antibody fragments increase the hydration of the surfaces and aid in the formation of an anti-fouling water barrier. The anti-fouling effect of the Fab’ fragments is at its maximum when there is an even distribution of fragments across the surfaces. Finally, using Fab’-covered surfaces, a cancer biomarker was detected from serum, showing the applicability of this work to the field of biodetection.
Keywords: Anti-fouling; Fab’ fragments; Adlayers; Acoustic wave sensor; Serum;

Polycrystalline vanadium thin films of 50, 75, and 100 nm thickness were deposited by magnetron sputtering of a vanadium metal target of 2 inch diameter with 99.9% purity on native oxide covered Si substrates. One set of the fabricated samples were kept in moisture free environment and the other set was exposed to ambient air at room temperature for a long period of time that resulted in formation of native oxide prior to testing. The crystal structure and phase purity of the vanadium and the oxidized vanadium thin films were characterized by X-ray diffraction (XRD). The XRD results yield a preferential (1 1 0), and (2 0 0) orientation of the polycrystalline V films and (0 0 4) vanadium oxide (V3O7). The vanadium films thickness were verified using field emission scanning electron microscopy and the films surface morphologies were inspected using atomic force microscopy (AFM). AFM images reveal surface roughness was observed to increase with increasing film thickness and also subsequent to oxidation at room temperature. The nanomechanical properties were measured by nanoindentation to evaluate the modulus and hardness of the vanadium and the oxidized vanadium thin films. The elastic modulus of the vanadium and the oxidized vanadium films was estimated as 150 GPa at 30% film thickness and the elastic modulus of the bulk vanadium target is estimated as 135 GPa. The measured hardness of the vanadium films at 30% film thickness varies between 9 and 14 GPa for the 100 and 50 nm films, respectively, exhibiting size effects, where the hardness increases as the film thickness decreases. The hardness of the oxidized films depicted less variation and is reported as ∼10 GPa at 30% film thickness for the three oxides. The scanning electron microscopy (SEM) imaging depicted a gradual progression of pile up as the film thickness increased from 75 to 100 nm. It is noticed that as the film thickness increases the films experience softening effect due to grain coarsening and the hardness values depict the hardness of the Si substrate at deep indents.
Keywords: Vanadium thin films; RF magnetron sputtering; FE-SEM; XRD; AFM; Nanoindentation; Hardness;

Influences of CuO phase on electrical and optical performance of Cu2O films prepared by middle frequency magnetron sputtering by Li Guo; Ming Zhao; Da-Ming Zhuang; MingJie Cao; Liangqi Ouyang; Xiaolong Li; Rujun Sun; Zedong Gao (36-40).
In the work, Cu2O films were prepared by middle frequency (mf) magnetron sputtering and subsequent anneals. CuO phase has been detected in a few Cu2O samples and its influences have been examined. The results show that the CuO phase can lead to a decrease of Hall mobility and change the surface morphology of the Cu2O films. The highest hall mobility of 43 cm2  V−1  s−1 with the optical band gaps of about 2.5 eV has been achieved in the Cu2O films where CuO is absent, which demonstrates the potential to fabricate high field-effected mobility Cu2O-based devices through this method.
Keywords: p-Type; Cu2O; Thin film transistor;

Nanostructured Ta x C interlayer synthesized via double glow plasma surface alloying process for diamond deposition on cemented carbide by Wolong Rong; Hongjun Hei; Qiang Zhong; Yanyan Shen; Xiaoping Liu; Xin Wang; Bing Zhou; Zhiyong He; Shengwang Yu (41-47).
The aim in this work was to improve the adhesion of diamond coating with pre-deposition of a Ta x C interlayer on cemented carbide (WC–Co) substrate by double glow plasma surface alloying technique. The following deposition of diamond coating on the interlayer was performed in a microwave plasma chemical vapor deposition (MPCVD) reactor. Ta x C interlayer with an inner diffusion layer and an outer deposition layer was composed of Ta2C and TaC nanocrystalline, and it exhibited a special compact surface morphology formed of flower-shaped pits. As the gradual element distributions existed in the diffusion layer, the interlayer displayed a superior adherence to the substrate with significantly enhanced surface microhardness to the original substrate. After CVD process, the preferred orientation of TaC changed from (2 2 2) to (2 0 0) plane, and a uniform and tense diamond coating with adhesion referred to class HF 2 at least (Verein Deutscher Ingenieure 3198 norm) was obtained on the interlayered substrate. It indicated that the diffusion of Co was effectively inhibited by the formation of Ta x C diffusion–deposition interlayer. The Ta x C interlayer is most likely to improve the performance of diamond coatings used in cutting tools.
Keywords: Nanostructured Ta x C interlayer; Double glow plasma surface alloying; CVD diamond coating; Cemented carbide substrate; Adhesion;

Surface complexation modeling calculation of Pb(II) adsorption onto the calcined diatomite by Shu-Cui Ma; Ji-Lin Zhang; De-Hui Sun; Gui-Xia Liu (48-54).
Apparent surface complexation modeling calculation of Pb(II) on diatomite at low pH values was studied using PEST and PHREEQC programs for the first time.Removal of noxious heavy metal ions (e.g. Pb(II)) by surface adsorption of minerals (e.g. diatomite) is an important means in the environmental aqueous pollution control. Thus, it is very essential to understand the surface adsorptive behavior and mechanism. In this work, the Pb(II) apparent surface complexation reaction equilibrium constants on the calcined diatomite and distributions of Pb(II) surface species were investigated through modeling calculations of Pb(II) based on diffuse double layer model (DLM) with three amphoteric sites. Batch experiments were used to study the adsorption of Pb(II) onto the calcined diatomite as a function of pH (3.0–7.0) and different ionic strengths (0.05 and 0.1 mol L−1 NaCl) under ambient atmosphere. Adsorption of Pb(II) can be well described by Freundlich isotherm models. The apparent surface complexation equilibrium constants (log  K) were obtained by fitting the batch experimental data using the PEST 13.0 together with PHREEQC 3.1.2 codes and there is good agreement between measured and predicted data. Distribution of Pb(II) surface species on the diatomite calculated by PHREEQC 3.1.2 program indicates that the impurity cations (e.g. Al3+, Fe3+, etc.) in the diatomite play a leading role in the Pb(II) adsorption and dominant formation of complexes and additional electrostatic interaction are the main adsorption mechanism of Pb(II) on the diatomite under weak acidic conditions.
Keywords: Diatomite; Pb(II); Adsorption; PEST; PHREEQC;

We calculated the geometrical and electronic structures of graphene with different vacancy densities and configurations. Vacancy was varied in graphene from mono- to tri-vacancy and configured to zigzag and armchair lattice directions. While di-vacancy in graphene led to a gap in the electronic structure, mono- and tri-vacancies shifted the Fermi level below the valence band maximum irrespective of vacancy configurations. Under the same density of vacancies, di-vacancy to zigzag direction had lower formation energy than defects along armchair direction. Meanwhile, tri-vacancy to zigzag lattice direction led to higher formation energy than defects to armchair direction.
Keywords: Graphene; Vacancy; Density; Configuration; Band Structure;

Surface structure and electronic structure of ultra thin NiO flms grown on Ag(0 0 1) substrate have been investigated in detail by means of low energy electron diffraction and photoemission spectroscopic studies under systematic modifications of surface Ni to O stoichiometry. Mild Ar+ bombardments (300 eV) were applied to the oxide films to produce predominant surface oxygen vacancies. These vacancy defects, which are mostly localized to the near surface region of the film, produce ‘defect states’ within the forbidden energy gap which pin the Fermi level (E F) away from valence band maxima. Angle-dependent X-ray photoemission spectroscopic studies have been undertaken to characterize the core level as well as the valence band electronic structures of the film which confirm the existence of metallic nickel clusters at the sputtered surface. The depletion of oxygen at the NiO surface produced by annealing in ultra high vacuum at sufficient temperature and its enhanced effect on the monolayer NiO film have been elucidated.
Keywords: Oxide ultrathin film; Oxygen vacancy defect; Angle resolved photoemission spectroscopy; X-ray photoemission spectroscopy; Low energy electron diffraction;

By performing in situ growth studies during pulsed laser deposition, we observed a strong reduction of the surface diffusion coefficients for slightly non-stoichiometric SrTiO3. Both, stoichiometric and non-stoichiometric thin films exhibit 2D layer by layer growth. However, in the non-stoichiometric case the 2D island coalescence is significantly delayed, which goes along with a shift of the reflection high electron energy diffraction (RHEED) minimum. We could explain this shift of the RHEED minimum by developing a model for the step density evolution taking into account finite surface diffusion.
Keywords: Pulsed laser deposition; 2D sub-monolayer growth; Non-stoichiometry of SrTiO3; Surface diffusion; Combined AFM/RHEED;

Fractal and probability analysis of creep crack growth behavior in 2.25Cr–1.6W steel incorporating residual stresses by Mengjia Xu; Jijin Xu; Hao Lu; Jieshi Chen; Junmei Chen; Xiao Wei (73-81).
In order to clarify creep crack growth behavior in 2.25Cr–1.6W steel incorporating residual stresses, creep crack tests were carried out on the tension creep specimens, in which the residual stresses were generated by local remelting and cooling. Residual stresses in the specimens were measured using Synchrotron X-ray diffraction techniques. The fracture surface of the creep specimen was analyzed using statistical methods and fractal analysis. The relation between fractal dimension of the fracture surface and fracture mode of the creep specimen was discussed. Due to different fracture mechanisms, the probability density functions of the height coordinates vary with the intergranular crack percentage. Good fitting was found between Gaussian distribution and the probability function of height coordinates of the high percentage intergranular crack surface.
Keywords: Creep damage; Fracture surface; Fractal dimension; Fracture toughness; Gaussian distribution; Residual stresses;

Interaction study on bovine serum albumin physically binding to silver nanoparticles: Evolution from discrete conjugates to protein coronas by Jun Guo; Ruibo Zhong; Wanrong Li; Yushuang Liu; Zhijun Bai; Jun Yin; Jingran Liu; Pei Gong; Xinmin Zhao; Feng Zhang (82-88).
With the non-uniform coating of amphiphilic polymer, the silver nanoparticles (AgNPs) can form protein coronas which can become discrete protein–nanoparticle conjugates when controlling the protein–nanoparticle molar ratios. The protein's conformational changes upon binding NPs was also studied by both circular dichroism and three-dimensional fluorescence spectroscopy.The nanostructures formed by inorganic nanoparticles together with organic molecules especially biomolecules have attracted increasing attention from both industries and researching fields due to their unique hybrid properties. In this paper, we systemically studied the interactions between amphiphilic polymer coated silver nanoparticles and bovine serum albumins by employing the fluorescence quenching approach in combination with the Stern-Volmer and Hill equations. The binding affinity was determined to 1.30 × 107  M−1 and the interaction was spontaneously driven by mainly the van der Waals force and hydrogen-bond mediated interactions, and negatively cooperative from the point of view of thermodynamics. With the non-uniform coating of amphiphilic polymer, the silver nanoparticles can form protein coronas which can become discrete protein–nanoparticle conjugates when controlling their molar ratios of mixing. The protein's conformational changes upon binding nanoparticles was also studied by using the three-dimensional fluorescence spectroscopy.
Keywords: Silver nanoparticle; Bovine serum albumin; Discrete conjugate; Fluorescence quenching; Conformational change;

Superhydrophobic surfaces arranged by hierarchical porous particles were prepared using modified hydrothermal routes under the effect of sodium citrate. Two particle samples were generated in the medium of hexamethylenetetramine (P1) and urea (P2), respectively. X-ray diffraction, scanning electron microscope, and transmission electron microscope were adopted for the investigation, and results revealed that the P1 and P2 particles are porous microspheres with crosslinked extremely thin (10–30 nm) sheet crystals composed of Zn5(OH)8Ac2·2H2O and Zn5(CO3)2(OH)6, respectively. The prepared particles were treated with a fluoroethylene vinyl ether derivative and studied using Fourier transform infrared spectroscopy and energy-dispersive X-ray spectrometer. Results showed that the hierarchical surfaces of these particles were combined with low-wettable fluorocarbon layers. Moreover, the fabricated surface composed of the prepared hierarchical particles displayed considerably high contact angles, indicating great superhydrophobicity for the products. The wetting behavior of the particles was analyzed with a theoretical wetting model in comparison with that of chestnut-like ZnO products obtained through a conventional hydrothermal route. Correspondingly, this study provided evidence that high roughness surface plays a great role in superhydrophobic behavior.
Keywords: Superhydrophobic material; Hydrothermal process; Hierarchical structure; Surface modification;

Molecular mechanisms for surfactant-aided oil removal from a solid surface by Shumeng Wang; Zhi Li; Bei Liu; Xianren Zhang; Qingyuan Yang (98-105).
In this work, the detachment mechanism of oil molecules from the hydrophobic solid surface in the aqueous surfactant solution is studied with lattice Monte Carlo simulations. Three different mechanisms for oil removal, including oil carrying microemulsion model, oil film stripping model, and surfactant-aided diffusion model are identified. The molecular mechanisms that agree with experimental observations are found to be dependent sensitively on surfactant structure.
Keywords: Surfactant; Oil removal; Hydrophobic surface; Lattice Monte Carlo simulation;

Polysulfide ligand exchange on zinc sulfide nanocrystal surfaces for improved film formation by Steven M. Herron; Qudus O. Lawal; Stacey F. Bent (106-113).
The physical and chemical properties of nanocrystals can be modified by changing the ligands attached at their surfaces. A ligand exchange procedure with ammonium polysulfides has been developed to replace the native ligands on cubic zinc sulfide nanocrystals. Several mixtures of polysulfides in formamide and other solvents were prepared with different average chain lengths and used to achieve high yield ligand exchange, as confirmed by UV–vis spectroscopy, infrared spectroscopy and X-ray photoelectron spectroscopy. The results show that polysulfide content can be increased with longer surface ligands and that the exchange process yields compositionally pure surfaces before and after high temperature anneals. X-ray diffraction and scanning electron microscopy show that, when annealed in nitrogen at 525 °C, polysulfide ligands lead to average crystal sizes 2–3 times larger than in the un-exchanged control sample. The ligand exchange procedure itself does not alter nanocrystal size. Nanocrystal inks prepared from the exchanged samples form thin films that exhibit superior grain growth, morphology, mass retention, and composition compared to the un-exchanged material. Overall, polysulfide species are demonstrated as alternative ligands for the surfaces of metal chalcogenide nanocrystals which, when incorporated in an efficient ligand-exchange procedure, can improve the quality of ZnS nanocrystal inks.
Keywords: Polysulfide; Nanocrystal ink; Ligand exchange; Zinc sulfide;

Hydrothermal synthesis of h-MoO3 microrods and their gas sensing properties to ethanol by Yueli Liu; Shuang Yang; Yu Lu; Natal’ya V. Podval’naya; Wen Chen; Galina S. Zakharova (114-119).
Hexagonal molybdenum trioxide (h-MoO3) microrods were successfully synthesized via a novel and facile hydrothermal route from peroxomolybdate solution with the presence of NH4Cl as the mineralizer. A variety of the techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry combined with the thermal gravimetric analysis (DSC–TG) were used to characterize the product. The gas sensing test indicates that h-MoO3 microrods have a good response to 5–500 ppm ethanol in the range of 273–380 °C, and the optimum operating temperature is 332 °C with a high sensitivity of 8.24 to 500 ppm ethanol. Moreover, it also has a good selectivity toward ethanol gas if compared with other gases, such as ammonia, methanol and toluene. The sensing mechanism of h-MoO3 microrods to ethanol was also discussed.
Keywords: Hydrothermal method; h-MoO3 mcirorods; Gas sensor; Ethanol; Sensitivity;

One-pot hydrothermal growth of raspberry-like CeO2 on CuO microsphere as copper-based catalyst for Rochow reaction by Zheying Jin; Jing Li; Laishun Shi; Yongjun Ji; Ziyi Zhong; Fabing Su (120-129).
In this work, we prepared a novel structure comprising of raspberry-like CeO2 deposited on CuO microspheres (Ce–CuO) for Rochow reaction. The synthesis was carried out via a facile one-pot hydrothermal reaction without using any template, in which, the basic copper carbonate microspheres were first formed via self-assembly of basic copper carbonate nanorods, followed with deposition of cerium hydroxide. After calcination, they were transformed into Ce–CuO but still maintained the hierarchical structure, and meanwhile, mesoporous structure was formed (for simplicity, we will only state them as metal oxide in the following context). The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. When used as a Cu-based catalyst, Ce–CuO exhibited superior catalytic property to the single CuO, CeO2 and their physically mixture in the Rochow reaction with dimethyldichlorosilane (M2) selectivity increased from ca. 65 to 83.7%. The higher M2 selectivity of Ce–CuO is mainly due to its larger surface area and the synergistic effect between CuO and CeO2. This work demonstrates that catalytic performance of the Cu-based can be improved by adding Ce rare-earth element and by carefully controlling their structures.
Keywords: Hydrothermal synthesis; Cerium-copper catalysts; Composites; Rochow reaction;

Luminescent monolayer MoS2 quantum dots produced by multi-exfoliation based on lithium intercalation by Wen Qiao; Shiming Yan; Xueyin Song; Xing Zhang; Xueming He; Wei Zhong; Youwei Du (130-136).
An effective multi-exfoliation method based on lithium (Li) intercalation has been demonstrated for preparing monolayer molybdenum disulfide (MoS2) quantum dots (QDs). The cutting mechanism of MoS2 QDs may involve the complete breakup around the defects and edges during the reaction of Li x MoS2 with water and its following ultrasonication process. The multiply exfoliation make the MoS2 fragile and easier to break up. After the third exfoliation, a large number of monolayer MoS2 QDs is formed. The as-prepared MoS2 QDs show photoluminescence (PL) inactive due to the existence of 1T phase. After heating treatment, the PL intensity excited at 300 nm is enhanced by five times. The MoS2 QDs solution has an excitation-dependent luminescence emission which shifts to longer wavelengths when the excitation wavelength changes from 280 nm to 370 nm. The optical properties are explored based on the quantum confinement and edge effect.
Keywords: MoS2 QDs; Photoluminescence; Chemical exfoliation;

Surface free radicals detection using molecular scavenging method on black spruce wood treated with cold, atmospheric-pressure plasmas by Jean-Michel Hardy; Olivier Levasseur; Mirela Vlad; Luc Stafford; Bernard Riedl (137-142).
Formation of surface free radicals on wood surfaces during plasma treatment could be an important factor when it comes to wood coating adhesion enhancement. In order to explore this aspect, freshly sanded black spruce (Picea mariana) wood samples were exposed to either plane-to-plane atmospheric-pressure dielectric barrier discharge (AP-DBD) or the flowing afterglow of an AP-DBD and then dipped in a 2,2-diphenyl-1-picrylhydrazyl (DPPH) solution. Wood veneers (extracted to eliminate small molecules prior to each plasma treatment) showed an increase of their reaction rate toward DPPH after treatment in the AP-DBD operated in nominally pure He; a feature ascribed to the plasma-assisted formation of free radicals on the wood surface. Addition of trace amounts (0.1%) of O2 in the He plasma produced a decrease in DPPH reactivity, suggesting that oxygen–spruce interaction during plasma treatment quenches free radicals formation. Similar experiments performed using the flowing afterglow of AP-DBD operated in either N2 or N2/O2 showed that both treatments do not generate significant amount of surface free radicals. This partially results from oxygen–wood interactions due to the open-air configuration of the afterglow reactor.
Keywords: Surface free radicals; Wood; DPPH; Atmospheric-pressure dielectric barrier discharges; Plasmas;

Effect of calcium carbonate on low carbon steel corrosion behavior in saline CO2 high pressure environments by Lisiane Morfeo Tavares; Eleani Maria da Costa; Jairo José de Oliveira Andrade; Roberto Hubler; Bruno Huet (143-152).
The CaCO3 influence on the corrosion properties of low carbon steel in aqueous solutions saturated with CO2 and NaCl at 80 °C and 15 MPa was investigated over time with respect to morphology, thickness, structure, chemical composition and corrosion rate. The corrosion product formed in CaCO3-based solution was a calcium-enriched siderite and the scales were thinner and more porous than the ones formed in solutions without CaCO3. The CaCO3 reduced the corrosion rate, but the scales produced in the presence of this compound presented depassivation followed by formation of pits during electrochemical measurements effectuated on corroded samples.
Keywords: Corrosion scale; Calcium carbonate; Iron carbonate; Steel corrosion; CO2 corrosion;

Display OmittedMXenes are found to be promising electrode materials for energy storage applications. Recent theoretical and experimental studies indicate the possibility of using these novel low dimensional materials for metal-ion batteries. Herein, we use density-functional theory in combination with the nonequilibrium Green's function formalism to study the effect of lithium and sodium ion adsorption on the electronic transport properties of the MXene, Ti3C2. Oxygen, hydroxyl and fluorine terminated species are considered and the obtained results are compared with the ones for the pristine MXene. We found that the ion adsorption results in reduced electronic transport in the pristine MXene: depending on the type of the ions and the bias voltage, the current in the system can be reduced by more than 30%. On the other hand, transport properties of the oxygen terminated sample can be improved by the ion adsorption: for both types of ions the current in the system can be increased by more than a factor of 4. However, the electronic transport is less affected by the ions in fluorinated and hydroxylated samples. These two samples show enhanced electronic transport as compared to the pristine MXene. The obtained results are explained in terms of electron localization in the system.
Keywords: MXenes; Electronic transport; DFT;

The fluoride ion in artificial saliva significantly changed semiconductor characteristic of the passive film formed on the surface of 316L stainless steels. The electrochemical results showed that nanocrystalline α′-martensite improved corrosion resistance of the stainless steel in a typical artificial saliva compared with coarse grained stainless steel. Moreover, comparing with nitrided coarse grained stainless steel, corrosion resistance of the nitrided nanocrystalline stainless steel was also improved significantly, even in artificial saliva solution containing fluoride ion. The present study showed that the cryogenic cold rolling and electrochemical nitridation improved corrosion resistance of 316L stainless steel for the dental application.
Keywords: Stainless steel; EIS; Raman spectroscopy; Passive films; XPS;

Effects of benzotriazole on the magnesium phosphate coating by Juan Zuo; Fen Guo; Junqiu Zhu; Ajiao Chen; Yanling Hu; Changjian Lin; Chunhai Jiang (166-171).
Magnesium phosphate coatings are extensively used on carbon steel to improve their corrosion resistance. The effect of benzotriazole on the magnesium phosphate coating was investigated. The phosphate coatings were deposited on carbon steel at different bath temperature, room temperature (RM), 60 °C and 80 °C. The change of crystalline phase, morphology, the sludge weight, bath efficiency factor, and corrosion behavior of the coatings after the addition of benzotriazole (BTAH) were investigated by means of Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and potentiodynamic polarization methods. The adsorption of BTAH during the formation of magnesium phosphate coating was also investigated by means of XPS. The effect of BTAH on the formation of magnesium phosphate coating was discussed. The adsorbed BTAH layer could favor the nucleation of phosphate coating by supplying more nuclei centers which leads to the formation of more compact phosphate coating. Meanwhile, the adsorbed atoms can block the active sites and generate a barrier to reduce the transport of corrosive species to the metal surface and hence improve the corrosion behavior of carbon steels.
Keywords: Magnesium phosphate coating; Carbon steel; Benzotriazole; Anti-corrosion property;

Three dimensional nickel oxides/nickel structure by in situ electro-oxidation of nickel foam as robust electrocatalyst for oxygen evolution reaction by Guan-Qun Han; Yan-Ru Liu; Wen-Hui Hu; Bin Dong; Xiao Li; Xiao Shang; Yong-Ming Chai; Yun-Qi Liu; Chen-Guang Liu (172-176).
Three dimensional (3D) nickel oxide/nickel (NiO x /Ni) structure has been synthesized through a facile in situ electro-oxidation method. The formation of NiO x through the electro-oxidation process has been proved by SEM and EDX, with some dense black dots appearing on the surface of Ni foam and the molar ratio of O/Ni increasing, which is nearly 7 times larger than the pure Ni foam. The increase in O content indicates the formatted black particles on the surface of Ni foam are composed of NiO x . The electrocatalytic property of the obtained 3D NiO x /Ni structure has been measured and it can be used as a highly active electrocatalyst for oxygen evolution reaction (OER). The overpotential to reach j  = 10 mA cm−2 is 0.39 V. And after the long-term It measurement, extremely high electrochemical and physical stability are exhibited in the 3D structure, keeping electrochemical activity and morphology the same. The excellent OER properties may be attributed to the 3D structure and the interface effect of NiO x /Ni.
Keywords: NiO x /Ni; Three dimensional; In situ electro-oxidation; Oxygen evolution reaction;

This paper presents the results of a study on the influence of tungsten as a structure promoter in the carbothermal reduction of silica. The morphology and surface structure of the obtained materials were analyzed using XRD, SEM-EDS, TEM and FTIR techniques. Surface area and porosity were evaluated on the basis of low temperature adsorption of nitrogen. The WC-W2C-β-SiC nanostructured composite material formed from the carbothermal reduction of SiO2 promoted with tungsten had a larger surface area (25.8 m2  g−1) in comparison to that measured for a β-SiC sample obtained by the simple carbothermal reduction of silica. Based on the results of this research, tungsten promoted carbothermal reduction of silica appears as a relatively simple procedure for obtaining valuable materials with a sufficiently high surface area to be used in catalysis.
Keywords: Whiskers; Carbothermal reduction; β-SiC; Tungsten;

A facile approach is demonstrated to synthesize a series of magnetite/graphene nanocomposites by solvothermal method, which can be easily collected after removal of pollutants without secondary pollution of graphene powders. Raman and FT-IR analyses show that the reduction of the mixing vapor of ammonia and hydrazine at different reaction periods generates the discrepancy of oxidation degree for reduced graphene oxide (rGO), which can be kept after the solvothermal synthesis of Fe3O4/rGO nanocomposites. Batch adsorption experiments indicate that the nanocomposite with maximum oxidation degree of rGO presents the largest magnetization of 35.4 emu g−1 and adsorption capacity of 59.2 mg g−1 for Cu2+, while the one with minimum oxidation degree exhibits the strongest adsorption of 39.0 mg g−1 for methylene blue accompanied with appropriate magnetization of 9.0 emu g−1, and only 23% of initial capacity was lost after seven recycling use. The adsorption kinetics of the both composites follows the pseudo-second-order model, suggestive of physical and chemical interactions between the pollutants and adsorbent. The results suggest that the oxidation degree of the rGO substrate can apparently influence both the structure and the adsorbing behavior of Fe3O4/rGO nanocomposites, which allows the control over the adsorbent performance according to the pollutant of interest.
Keywords: Nanocomposite; Magnetite; Graphene; Oxidation degree; Adsorption;

Surface modification of polyester fabric with plasma pretreatment and carbon nanotube coating for antistatic property improvement by C.X. Wang; J.C. Lv; Y. Ren; T. Zhi; J.Y. Chen; Q.Q. Zhou; Z.Q. Lu; D.W. Gao; L.M. Jin (196-203).
This study introduced a green method to prepare antistatic polyester (PET) fabrics by plasma pretreatment and single-walled carbon nanotube (SWCNT) coating. The influences of plasma conditions and SWCNT coating parameters on antistatic property of PET fabrics were investigated. PET fabrics were pretreated under various plasma conditions such as different treatment times, output powers and working gases, and then SWCNT coating on the plasma treated PET fabrics was carried out by coating-dry-cure using various coating parameters including different SWCNT concentrations, curing times and curing temperatures. PET fabrics were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and volume resistivity. SEM and XPS analysis of the plasma treated PET fabrics revealed the increase in surface roughness and oxygen/nitrogen containing groups on the PET fiber surface. SEM and XPS analysis of the plasma treated and SWCNT coated PET fabrics indicated the SWCNT coating on PET fiber surface. The plasma treated and SWCNT coated PET fabrics exhibited a good antistatic property, which increased and then decreased with the increasing plasma treatment time and output power. The antistatic property of the O2 plasma treated and SWCNT coated PET fabric was better and worse than that of N2 or Ar plasma treated and SWCNT coated PET fabric in the shorter treatment time and the longer treatment time, respectively. In addition, the antistatic property of the plasma treated and SWCNT coated PET fabrics also increased with the increasing SWCNT concentration, curing time and curing temperature in the range studied. Plasma conditions and SWCNT coating parameters had signally influence on the antistatic property of plasma treated and SWCNT coated PET fabrics. Therefore, adequate parameters should be carefully selected for the optimum antistatic property of the plasma treated and SWCNT coated PET fabrics.
Keywords: Plasma surface modification; Carbon nanotube coating; Polyester fabric; Antistatic property; SEM; XPS;

We present a novel method capable of measuring surface roughness of deposited thin films. The method was tested with 4 sets of SiN thin films deposited using a plasma-enhanced chemical vapor deposition system. The range of surface roughness measured over 3 sets of data with atomic force microscopy (AFM) was between 0.13 and 1.66 nm. The remaining one data set had a greater roughness range of 1.63–5.43 nm. The roughness calculated with an algorithm demonstrated a strong correlation with AFM measurement in all the comparisons. This was attributed to the formation of spatial height differences between positive light matter (particles) and negative surface plasmon carriers both comprising a speckle pattern. This indicates that the proposed method can effectively characterize surface roughness tendency with the accuracy comparable to AFM.
Keywords: Surface roughness; Speckle pattern; Laser; Light matter; Surface plasmon carriers; Film;

A smart surface with thermo-responsive wettability was fabricated on the cross section of wood with simple bench chemistry. The surface showed fast response between superhydrophobic and hydrophilic under different temperatures. The reversible wettability from superhydrophobicity to hydrophilicity can be easily achieved by adjusting the temperature between 25 and 60 °C. This reversible wettability is resulted from the synergistic effect of the crystallinity transition of the polymer coated on the surface and the optimized roughness controlled by the silica particles with different sizes. Furthermore, the modified wood surface showed an excellent chemical stability to corrosive liquids under ambient conditions.
Keywords: Superhydrophobic; Hydrophilic; Wettability switch; Temperature control; Composite film;

Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study by Fabjola Bilo; Laura Borgese; Josef Prost; Mirjam Rauwolf; Anna Turyanskaya; Peter Wobrauschek; Peter Kregsamer; Christina Streli; Ugo Pazzaglia; Laura E. Depero (215-220).
We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co–Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO2. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO2 layer, the lower is the metal migration.
Keywords: Co–Cr alloy; Bone; TiO2; ALD; TXRF; μ-XRF;

3-D periodic mesoporous nickel oxide for nonenzymatic uric acid sensors with improved sensitivity by Wei Huang; Yang Cao; Yong Chen; Yang Zhou; Qingyou Huang (221-226).
The enzyme-less amperometric sensor based on 3-D periodic mesoporous NiO nanomaterials used in the detection of uric acid with detection limit of 0.005 μM (S/N = 3) over wide linear detection ranges up to 0.374 mM and with a high sensitivity of 756.26 μA mM−1  cm−2.3-D periodic mesoporous nickel oxide (NiO) particles with crystalline walls have been synthesized through the microwave-assisted hard template route toward the KIT-6 silica. It was investigated as a nonenzymatic amperometric sensor for the detection of uric acid. 3-D periodic nickel oxide matrix has been obtained by the hard template route from the KIT-6 silica template. The crystalline nickel oxide belonged to the Ia3d space group, and its structure was characterized by X-ray diffraction (XRD), N2 adsorption–desorption, and transmission electron microscopy (TEM). The analysis results showed that the microwave-assisted mesoporous NiO materials were more appropriate to be electrochemical sensors than the traditional mesoporous NiO. Cyclic voltammetry (CV) revealed that 3-D periodic NiO exhibited a direct electrocatalytic activity for the oxidation of uric acid in sodium hydroxide solution. The enzyme-less amperometric sensor used in the detection of uric acid with detection limit of 0.005 μM (S/N = 3) over wide linear detection ranges up to 0.374 mM and with a high sensitivity of 756.26   μA mM−1  cm−2, and a possible mechanism was also given in the paper.
Keywords: Uric acid; Biosensors; Nonenzymatic; Mesoporous materials;

Activity and stability of the oxygen evolution reaction on electrodeposited Ru and its thermal oxides by Jin Yeong Kim; Jihui Choi; Ho Young Kim; Eunkyoung Hwang; Hyoung-Juhn Kim; Sang Hyun Ahn; Soo-Kil Kim (227-235).
The activity and stability of Ru metal and its thermal oxide films for the oxygen evolution reaction (OER) were investigated. The metallic Ru films were prepared by electrodeposition on a Ti substrate and then thermally oxidized at various temperatures under atmospheric conditions. During long-term operation of the OER with cyclic voltammetry (CV) in H2SO4 electrolyte, changes in the properties of the Ru and its thermal oxides were monitored in terms of their morphology, crystal structure, and electronic structure. In the initial stages of the OER, all of the Ru thermal oxide films underwent an activation process that was related to the continuous removal of low-activity Ru oxides from the surface. With further cycling, the OER activity decreased. The rate of decrease was different for each Ru film and was related to the annealing temperatures. Monitoring of material properties indicates that the amount of stable anhydrous RuO2 is important for OER stability because it prevents both the severe dissolution of metallic Ru beneath the oxide surface and the formation of a less active hydrous RuO2 at the surface.
Keywords: Water splitting; Oxygen evolution reaction; Electrodeposited ruthenium catalyst; Anhydrous ruthenium oxide;

During uniaxial planar compression of annealed aluminium alloys, a novel approach to determine the surface asperity flattening (roughness R a ) is employed by analyzing the evolution of the surface's micro-texture. With an increase in compression strain, the surface asperity tends to be flattened, and strain hardening increases. Lubrication can constrain the surface asperity flattening process and hinder the progress of grain surface flattening. The development of surface texture shows an obvious dependency: under the influence of friction, the normal deformation texture component (brass orientation { 0 1 1} 〈1 1 2〉) can be generated easily, while lubrication can hinder this texture component generation. Simulated results show a good agreement with experimental results which predicated brass orientation. However, due to the limitation of the FCC Taylor model, the other orientation components cannot be predicted.
Keywords: Crystal plasticity finite element model; Texture; Cold uniaxial planar compression (CUPC); Flow stress; Friction;

Superhydrophobic coating to delay drug release from drug-loaded electrospun fibrous materials by Botao Song; Shichen Xu; Suqing Shi; Pengxiang Jia; Qing Xu; Gaoli Hu; Hongxin Zhang; Cuiyu Wang (245-251).
The drug-loaded electrospun fibrous materials showed attractive applications in biomedical fields; however, the serve burst release of drug from this kind of drug carrier limited its further applications. In this study, inspired by water strong repellency of superhydrophobic surface, the drug-loaded electrospun fibrous mat coated with superhydrophobic layer was constructed to retard and control drug release. The results indicated that the superhydrophobic coating could be simply fabricated on the drug-loaded electrospun mat by the electrospray approach, and the thickness of the superhydrophobic coating could be finely controlled by varying the deposition time. It was further found that, as compared with drug-loaded electrospun mats, drug released sustainably from the samples coated with superhydrophobic layer, and the drug release rate could be controlled by the thickness of superhydrophobic layer. In summary, the current approach of coating a superhydrophobic layer on the drug-loaded electrospun fibrous materials offered a fundament for drug sustained release.
Keywords: Burst release; Sustained release; Electrospinning; Superhydrophobic;

Hydrophilicity improvement in polyphenylsulfone nanofibrous filtration membranes through addition of polyethylene glycol by Shirin Kiani; Seyed Mahmoud Mousavi; Nasser Shahtahmassebi; Ehsan Saljoughi (252-258).
Novel hydrophilic polyphenylsulfone (PPSU) nanofibrous membrane was prepared by electrospinning of the PPSU solution blended with polyethylene glycol 400 (PEG 400). The influence of the PEG concentration on the membrane characteristics was studied using scanning electron microscopy (SEM), water contact angle measurement, and tensile test. Filtration performance of the membranes was investigated by measurement of pure water flux (PWF) and determination of the rejection values of the pollution indices during treatment of canned beans production wastewater. According to the results, blending the PPSU solution with 10 wt.% PEG 400 resulted in formation of a nanofibrous membrane with high porosity and increased mechanical strength which exhibited a low water contact angle of 8.9° and high water flux of 7920 L/m2h. Flux recovery of the mentioned membrane which was assessed by filtration of a solution containing bovine serum albumin (BSA) was 83% indicating a noticeable antifouling property.
Keywords: Electrospinning; Nanofiber; Polyphenylsulfone; Polyethylene glycol; Filtration;

Surface properties, simultaneous photocatalytic and magnetic activities of Ni2FeVO6 nanoparticles by Xuebin Qiao; Yanlin Huang; Han Cheng; Hyo Jin Seo (259-265).
Nickel-ferro-vanadium oxide Ni2FeVO6 nanoparticles were prepared by the sol–gel film coating and subsequent sintering method. The phase formation was investigated X-ray polycrystalline diffraction (XRD) measurement. The surface characteristics were measured by scanning electron microscope (SEM), transmission electron microscopy (TEM), specific surface area, energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). This vanadate has a narrow band-gap energy of 1.784 eV. The investigations concluded that Ni2FeVO6 nanoparticles have photocatalytic ability under visible-light irradiation. The ferromagnetic behavior of the nanoparticles was confirmed by the magnetic hysteresis loops. The nanoparticles can be magnetically recoverable after photocatalytic reactions. The photocatalytic activities were discussed on the base of the multivalent cations in crystal lattices.
Keywords: Semiconductors; Nanostructures; Photocatalysis; Optical properties; Surface properties;

Correlation between structural and electrical properties of PLD prepared ZnO thin films used as a photodetector material by C. Triolo; E. Fazio; F. Neri; A.M. Mezzasalma; S. Trusso; S. Patanè (266-271).
The electrical transport properties of a set of zinc oxide (ZnO) thin films, prepared by pulsed laser ablation, were investigated at the temperatures of 30 K and 300 K. Information about the structural and morphological properties of the samples were obtained by means of atomic force microscopy (AFM) and X-ray diffraction (XRD). A significant variation in the surface morphology and photoresponse characteristics of the ZnO thin films were observed as a function of the deposition temperature. Upon increasing the deposition temperature, the surface topography changes from a more fine-grained to a more coarse-grained structure, showing a tetragonal wurtzite crystalline structure. Time resolved photocurrent measurements showed significantly variations as function of the observed samples morphologies. A photocurrent value of about three order of magnitude larger is observed for samples showing a more coarse-grained structure with respect to the fine-grained ones. Such a result is interpreted as due to the contributions of both “bulk” and defect centers that affect the conduction mechanisms and influence both the photoconductivity values and the photoresponse speed. The observed decay times are very long with respect to films grown by other techniques, due to the reduction of the surface localized centers of defect available for recombination. In this context, the sample morphology appears to be a key parameter to control the photoconductivity in ZnO thin films.
Keywords: ZINC oxide; THIN films; Photoconductivity;

Polypyrrole layered SPEES/TPA proton exchange membrane for direct methanol fuel cells by S. Neelakandan; P. Kanagaraj; R.M. Sabarathinam; A. Nagendran (272-279).
Hybrid membranes based on sulfonated poly(1,4-phenylene ether ether sulfone) (SPEES)/tungstophosphoric acid (TPA) were prepared. SPEES/TPA membrane surfaces were modified with polypyrrole (Ppy) by in situ polymerization method to reduce the TPA leaching. The morphology and electrochemical property of the surface coated membranes were studied by SEM, AFM, water uptake, ion exchange capacity, proton conductivity, methanol permeability and tensile strength. The water uptake and the swelling ratio of the surface coated membranes decreased with increasing the Ppy layer. The surface roughness of the hybrid membrane was decreased with an increase in Ppy layer on the membrane surface. The methanol permeability of SPEES/TPA-Ppy4 hybrid membrane was significantly suppressed and found to be 2.1 × 10−7  cm2  s−1, which is 1.9 times lower than pristine SPEES membrane. The SPEES/TPA-Ppy4 membrane exhibits highest relative selectivity (2.86 × 104  S cm−3  s) than the other membrane with low TPA leaching. The tensile strength of hybrid membranes was improved with the introduction of Ppy layer. Combining their lower swelling ratio, high thermal stability and selectivity, SPEES/TPA-Ppy4 membranes could be a promising material as PEM for DMFC applications.
Keywords: SPEES; PEM; TPA; Polypyrrole; AFM; DMFC;

A novel Ag catalyzation process using swelling impregnation method for electroless Ni deposition on Kevlar® fiber by Hongwei Pang; Ruicheng Bai; Qinsi Shao; Yufang Gao; Aijun Li; Zhiyong Tang (280-287).
Schematic diagram illustration of electroless nickel plating process on Kevlar fiber.A novel Ag catalyzation process using swelling impregnation pretreatment method was developed for electroless nickel (EN) deposition on Kevlar fiber. Firstly, the fiber was immersed into an aqueous dimethylsulfoxide (DMSO) solution of silver nitrate to impart silver nitrate into the inner part of the fiber near the surface. Subsequently silver nitrate was reduced to metal silver nanoparticles on the fiber surface by treatment with aqueous solution of sodium borohydride. After electroless plating, a dense and homogeneous nickel coating was obtained on the fiber surface. The silver nanoparticles formed at the fiber surface functioned as a catalyst for electroless deposition as well as an anchor for the plated layer. The study also revealed that the incorporation of surfactant sodium dodecyl sulfate (SDS) in electroless nickel plating bath can enhance the adhesion strength of EN layer with the fiber surface and minimize the surface roughness of the EN coating. The Ni plated Kevlar fiber possessed excellent corrosion resistance and high tensile strength.
Keywords: Silver catalysts; Kevlar®; Swelling impregnation; Electroless plating; Surfactant;

The potentiodynamic polarization curve shows that the SM-DCPD coating can dramatically enhance the corrosion potential (E corr) value and meanwhile decrease the corrosion current density (I corr) of C/C composites.Trace elements substituted apatite coatings have received a lot of interest recently as they have many benefits. In this work, strontium and magnesium substituted DCPD (SM-DCPD) coatings were deposited on carbon/carbon (C/C) composites by pulsed electrodeposition method. The morphology, microstructure, corrosion resistance and in vitro bioactivity of the SM-DCPD coatings are analyzed. The results show that the SM-DCPD coatings exhibit a flake-like morphology with dense and uniform structure. The SM-DCPD coatings could induce the formation of apatite layers on their surface in simulated body fluid. The electrochemical test indicates that the SM-DCPD coatings can evidently decrease the corrosion rate of the C/C composites in simulated body fluid. The SM-DCPD has potential application as the bioactive coatings.
Keywords: Carbon/carbon composites; Dicalcium phosphate dehydrate; Pulsed electrodeposition; Bioactivity; Corrosion;

The photodegradation of 4-nitrophenol in aqueous solution was studied by using titania-based photocatalysts, in particular standard commercial titania samples (anatase and rutile, Hunstmann; P25 and Aeroxide VP P90, Evonik) and a mesoporous and nanocrystalline titania synthesized under hydrothermal conditions. A comparison between the commercial products and our preparations made evident a different particle size and phase composition. Moreover, in order to investigate a possible synergism between TiO2 and carbon nanotubes (CNTs), further two samples were purposely synthesized by adding to the reaction mixture used for the catalyst preparation a small amount of single-walled or multi-walled carbon nanotubes (SWCNTs and MWCNTs). Among the investigated solids, the nanocrystalline titania resulted to be the most active photocatalysts. The less active solids were rutile and mesoporous titania. The addition of a small amount of MWCNTs further increased the photoactivity of the nanocrystalline titania.
Keywords: TiO2 photocatalysts; Nanocrystalline titania; Mesoporous titania; Carbon nanotubes; 4-Nitrophenol photo-degradation;

The extraction of depth profiles from simulated ARXPS data: From parametric models to regularization methods by Carlos Palacio; Gonzalo Camacho; Carlos García-Rodríguez (306-314).
Trade-off between the residual norm and the regularization parameter α: (1) no regularization, (2) optimal value of α, (3) over regularization.The extraction of concentration depth profiles from ARXPS data has been carried out using noisy simulated data and two different approaches, using either simple parametric models or general algorithms with Tikhonov regularization schemes. Among the single parametric models the only one that is stable and robust against noise is that using only one parameter, with the uncertainty of the parameter displaying a linear dependence on the input noise level. For Tikhonov regularization schemes, a guide is given to choose the appropriate regularization parameter, which is based on the use of the S-curve in conjunction with the constraints introduced by χ 2, and which provides user-independent results.
Keywords: Concentration depth profiles; Angle resolved X-ray photoelectron spectroscopy; Parametric models; Regularization methods; S-curve;

TEM image of metal incorporated with TiO2 nanoparticles (left side). And in the (right side) is the schematic diagram of the dye sensitized solar cell including the plasmonic metals incorporated with TiO2 nanoparticles.In this article, a low cost mesoporous Fe2O3-TiO2 nanoparticles has been synthesized from Abu Ghalaga ilmenite ore, Egypt using simple hydrothermal route. Meanwhile, silver, platinum and palladium metals nanoparticles from spent catalysts have been extracted and deposited between the anatase TiO2 particles using in situ reduction step. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopic (TEM), N2 adsorption–desorption isotherm (S BET) and X-ray photoelectron spectroscopy (XPS). The as-prepared materials were applied as photoanodes in dye-sensitized solar cells (DSSCs), whose photocurrent–voltage J–V characteristic curves measurements were consistently performed. The 0.5% precious metal doped samples NPs exhibit absorption enhancement over a broad wavelength range due to the excitation of localized surface plasmons (LSPs) at different wavelengths which also exhibited very good and enhanced photovoltaic performance as a result of the strong scattering lightresulting of noticeable enhancement of charge transfer rates. Indeed, the Ag@Fe2O3-TiO2 sample exhibited the maximum overall conversion efficiency (η % = 4.5%) and it can be considered as a cost-effective photoanode for DSSCs.
Keywords: Cost-effective synthesis; Mesoporous materials; Photovoltaic performance; Dye-sensitized solar cells (DSSCs);

Combined modification of fly ash with Ca(OH)2/Na2FeO4 and its adsorption of Methyl orange by Mengfan Gao; Qingliang Ma; Qingwen Lin; Jiali Chang; Weiren Bao; Hongzhu Ma (323-330).
Fly ash resulted during the coal burning for energy production is a waste that can be used in wastewater treatment for removal of dyes. Fly ash (FA) modified by Ca(OH)2/Na2FeO4 was used as adsorbent for methyl orange (MO) wastewater treatment. The effect of parameters (contact time, dosage of adsorbent, initial concentration of MO) on MO adsorption are optimized. At the optimized conditions: 4.00 × 10−3  g/mL of adsorbent, 50 mg/L MO, 40 min, the raw pH value (pH = 10), 99.2% color removal was achieved at room temperature. The thermodynamic and kinetic of the adsorption processes were also studied, and further discussed correlated with the surface structure (XRD) and morphology (SEM, BET). The results indicate that the Ca(OH)2/Na2FeO4 modified FA can be used as an efficient and low cost adsorbent for removal of dyes.
Keywords: Adsorption; Methyl orange; Fly ash; Ca(OH)2/Na2FeO4;

Electrochemical and surface studies of some Porphines as corrosion inhibitor for J55 steel in sweet corrosion environment by Ambrish Singh; Yuanhua Lin; K.R. Ansari; M.A. Quraishi; Eno. E. Ebenso; Songsong Chen; Wanying Liu (331-339).
Corrosion inhibition of J55 steel in 3.5 wt.% NaCl solution saturated with CO2 by the three Porphines 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (P1), 5,10,15,20-Tetraphenyl-21H,23H-porphine (P2), 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (P3), electrochemical impedance spectroscopy (EIS), contact angle measurement, scanning electrochemical microscopy (SECM), and atomic force microscopy (AFM).Corrosion inhibition of J55 steel in 3.5 wt.% NaCl solution saturated with CO2 by the three Porphines 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (P1), 5,10,15,20-Tetraphenyl-21H,23H-porphine (P2), 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (P3), electrochemical impedance spectroscopy (EIS), Contact angle measurement, scanning electrochemical microscopy (SECM), and atomic force microscopy (AFM). Adsorption of such Porphines on the J55 steel surface obeyed to the Langmuir adsorption isotherm. Atomic force microscopy (AFM), SECM, and Contact angle results confirm the formation of inhibitor film on J55 steel surface thereby mitigating corrosion.
Keywords: J55 steel; Porphines; EIS; SECM; AFM; Corrosion;

The effect of graphene content and sliding speed on the wear mechanism of nickel–graphene nanocomposites by H. Algul; M. Tokur; S. Ozcan; M. Uysal; T. Cetinkaya; H. Akbulut; A. Alp (340-348).
Nickel–graphene metal matrix composite coatings were fabricated by pulse electrodeposition technique from a Watt's type electrolyte. Effect of the graphene concentration in the electrolyte on the microstructure, microhardness, tribological features of nanocomposite coatings were evaluated in details. Microhardness of the composite coating was measured using a Vicker's microhardness indenter. The surfaces of the samples were characterized by scanning electron microscopy (SEM). Raman spectroscopy, EDS and XRD analysis were used to determine chemical composition and structure of composite coatings. The tribological behavior of the resultant composite coating was tested by a reciprocating ball-on disk method at constant load but varying sliding speeds for determination the wear loss and friction coefficient features against a counterface. The wear and friction variations of the electrodeposited nickel graphene nanocomposite coatings sliding against an M50 steel balls were carried out on a CSM Instrument. The friction and wear properties of the coatings were examined without any lubrication at room temperature in the ambient air. The change in wear mechanisms by changing graphene nanosheets content was also comprehensively studied.
Keywords: Ni/graphene composites; Microstructure; Pulse electrodeposition; Wear resistance; Friction coefficient;

The inner surface of micro-PVC tube was modified by APPJ and AA monomer, and a higher density of cell was attached on the treated tube surface.In this paper, the successful deposition of acrylic acid polymer (PAA) nano-cones on the inner surface of a polyvinyl chloride (PVC) tube using an atmospheric pressure pulsed plasma jet (APPJ) with acrylic acid (AA) monomer is presented. Optical emission spectroscopy (OES) measurements indicated that various reactive radicals, such as •OH and •O, existed in the plasma jet. Moreover, the pulsed current proportionally increased with the increase in the applied voltage. The strengthened stretching vibration of the carbonyl group (C=O) at 1700 cm−1, shown in the ATR-FTIR spectra, clearly indicated that the PAA was deposited on the PVC surface. The maximum height of the PAA nano-cones deposited by this method ranged from 150 to 200 nm. FTIR and XPS results confirmed the enhanced exposure of the carboxyl groups on the modified PVC surface, which was considered highly beneficial for successfully immobilizing a high density of biomolecules. The XPS data showed that the carbon ratios of the C―OH/R and COOH/R groups increased from 7.03% and 2.6% to 18.69% and 6.81%, respectively (more than doubled) when an Ar/O2 plasma with AA monomer was applied to treat the inner surface of the PVC tube. Moreover, the enhanced attachment density of MC3T3-E1 bone cells was observed on the PVC inner surface coated with PAA nano-cones.
Keywords: Plasma polymerization; Nano-cone; Cell immobilization; Plasma jet;

The photoluminescence properties of undoped & Eu-doped ZnO thin films grown by RF sputtering on sapphire and silicon substrates by Samah M. Ahmed; Paul Szymanski; Mostafa A. El-Sayed; Yehia Badr; Lotfia M. El-Nadi (356-363).
We have reported on the effects of the substrate type on the structural and photoluminescence properties of undoped and Eu-doped ZnO thin films, grown by RF sputtering on c-plane sapphire and silicon substrates. As revealed by the XRD, all films are highly textured and have a preferred orientation along the c-axis perpendicular to the substrate. XPS analysis confirms the incorporation of Eu ions into the ZnO matrix. Also, all thin films are O-rich, with increasing oxygen content after annealing in oxygen atmosphere. The annealed thin films on sapphire substrates are found to have more excess oxygen than those on silicon substrates. The AFM images showed that the substrate type and Eu-doping affect the surface morphology of the thin films. The photoluminescence measurements showed that the intensity ratio of the defect-related visible emission to the UV excitonic emission of ZnO, as well as the red emission intensity of Eu3+ ions were affected by the substrate type. Our results point out that, for luminescent devices based on the UV emission of ZnO thin films, silicon is a promising, cost-effective substrate. On the other hand, for efficient red emission of Eu3+ ions in Eu-doped ZnO thin films, c-plane sapphire substrate is more favorable.
Keywords: Zinc oxide; Europium; Thin films; Energy transfer; Photoluminescence;

Preparation of Langmuir–Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties by Mustafa Ozmen; Zikriye Ozbek; Mevlut Bayrakci; Seref Ertul; Mustafa Ersoz; Rifat Capan (364-371).
Organic vapor sensing properties of Langmuir–Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure–area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.
Keywords: Calixarene; Vapor sensing; Langmuir–Blodgett; QCM;

Anisotropy in Ostwald ripening and step-terraced surface formation on GaAs(0 0 1): Experiment and Monte Carlo simulation by D.M. Kazantsev; I.O. Akhundov; N.L. Shwartz; V.L. Alperovich; A.V. Latyshev (372-379).
Display OmittedOstwald ripening and step-terraced morphology formation on the GaAs(0 0 1) surface during annealing in equilibrium conditions are investigated experimentally and by Monte Carlo simulation. Fourier and autocorrelation analyses are used to reveal surface relief anisotropy and provide information about islands and pits shape and their size distribution. Two origins of surface anisotropy are revealed. At the initial stage of surface smoothing, crystallographic anisotropy is observed, which is caused presumably by the anisotropy of surface diffusion at GaAs(0 0 1). A difference of diffusion activation energies along [1 1 0] and [1  1 ¯  0] axes of the (0 0 1) face is estimated as ΔE d  ≈ 0.1 eV from the comparison of experimental results and simulation. At later stages of surface smoothing the anisotropy of the surface relief is determined by the vicinal steps direction. At the initial stage of step-terraced morphology formation the kinetics of monatomic islands and pits growth agrees with the Ostwald ripening theory. At the final stage the size of islands and pits decreases due to their incorporation into the forming vicinal steps.
Keywords: Surface smoothing; GaAs; Step-terraced morphology; Monte Carlo simulation; Ostwald ripening;

Novel functional silica nanoparticles (SiO2-NBS-F) with irreversible light-responsive wettability were prepared by grafting of a light-responsive silane coupling agent (NBS) and further bonding with hydrophobic segments via a click reaction. The NBS was synthesized using an o-nitrobenzyl alcohol derivative of the photolabile protecting group. The SiO2-NBS-F nanoparticles exhibited considerable change of wettability from near-superhydrophobicity to near-superhydrophilicity after UV irradiation. The changing mechanism of wettability was confirmed by UV–Vis absorption spectra and X-ray photoelectron spectra. The SiO2-NBS-F nanoparticles were incorporated into fluorocarbon FEVE coatings by simple mixing. The nanoparticles occurred at the surface of the dried coatings even though their content was as low as 5 wt%, being due to their low surface free energy. The wettability of the SiO2-NBS-F filled FEVE coatings could transform from hydrophobicity (WCA 106.4°) to hydrophilicity (WCA 33.3°) after UV irradiation. It demonstrates that SiO2-NBS-F nanoparticles are useful to acquire highly hydrophilic surface for organic coatings.
Keywords: o-nitrobenzyl alcohol derivative; Light-responsive wettability; FEVE coatings; Highly hydrophilicity;

Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements by Khaled Almuhammadi; Lakshmi Selvakumaran; Marco Alfano; Yang Yang; Tushar Kanti Bera; Gilles Lubineau (388-397).
Display OmittedElectrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.
Keywords: Laminates; Electrical properties; Surface electrodes; Laser ablation;

Electron emission properties of materials are highly dependent to the surface and the first nanometres subsurface. Technical materials, i.e. used within applications are ordinarily exposed to atmosphere, which interacts with the surface. The contamination layer building up at the surface of materials and/or oxidation layer affects dramatically the electron emission proprieties. In this paper, starting from 99.99% pure silver sample, exposed 4 years to ambient atmosphere, we monitored the variations of the electron emission properties and the surface composition during step by step ion etching procedure.
Keywords: Electron emission; Electron beam surface interaction; AES; Contamination; Surface modification;

Synchronised electrical current and high speed video information are presented from individual discharges on Al substrates during PEO processing. Exposure time was 8 μs and linear spatial resolution 9 μm. Image sequences were captured for periods of 2 s, during which the sample surface was illuminated with short duration flashes (revealing bubbles formed where the discharge reached the surface of the coating). Correlations were thus established between discharge current, light emission from the discharge channel and (externally-illuminated) dimensions of the bubble as it expanded and contracted. Bubbles reached radii of 500 μm, within periods of 100 μs, with peak growth velocity about 10 m/s. It is deduced that bubble growth occurs as a consequence of the progressive volatilisation of water (electrolyte), without substantial increases in either pressure or temperature within the bubble. Current continues to flow through the discharge as the bubble expands, and this growth (and the related increase in electrical resistance) is thought to be responsible for the current being cut off (soon after the point of maximum radius). A semi-quantitative audit is presented of the transformations between different forms of energy that take place during the lifetime of a discharge.
Keywords: Plasma electrolytic oxidation; Electrical discharges; Bubbles; High speed photography;

Pulse electrodeposition of self-lubricating Ni–W/PTFE nanocomposite coatings on mild steel surface by S. Sangeetha; G. Paruthimal Kalaignan; J. Tennis Anthuvan (412-419).
Ni–W/PTFE nanocomposite coatings with various contents of PTFE (polytetafluoroethylene) particles were prepared by pulse current (PC) electrodeposition from the Ni–W plating bath containing self lubricant PTFE particles to be co-deposited. Co-deposited PTFE particulates were uniformly distributed in the Ni–W alloy matrix. The coatings were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), X-ray Diffractometry (XRD) and Vicker's micro hardness tester. Tafel Polarization and electrochemical Impedance methods were used to evaluate the corrosion resistance behaviour of the nanocomposite coatings in 3.5% NaCl solution. It was found that, the Ni–W/PTFE nanocomposite coating has better corrosion resistance than the Ni–W alloy coating. Surface roughness and friction coefficient of the coated samples were assessed by Mitutoyo Surftest SJ-310 (ISO1997) and Scratch tester TR-101-M4 respectively. The contact angle (CA) of a water droplet on the surface of nanocomposite coating was measured by Optical Contact Goniometry (OCA 35). These results indicated that, the addition of PTFE in the Ni–W alloy matrix has resulted moderate microhardness, smooth surface, less friction coefficient, excellent water repellency and enhanced corrosion resistance of the nanocomposite coatings.
Keywords: Ni–W/PTFE nanocomposite coatings; Coefficient of friction; Microhardness; Electrochemical characterization; Contact angle;

An AlN interlayer was fabricated by filtered vacuum arc evaporation as a diffusion barrier (DB) between Ni + CrAlYSiHfN composite coating and K417G superalloy. Microstructure changes of the AlN DB were investigated after exposure at 1000 and 1100 °C. Amorphous structure was found in the as-deposited AlN DB, which went through crystallization when exposing at high temperature. The AlN DB suppressed interdiffusion between overlayer and substrate effectively after 200 h exposure at both 1000 °C and 1100 °C. A few substrate element precipitates were observed within the grain boundary of the AlN DB after exposure at 1100 °C for 200 h.
Keywords: Diffusion barrier; Nanocomposite coating; TEM; High temperature;

Five selected amine-derivatives of phenothiazine were electropolymerized on an ITO/glass substrate and then used in the daylight-activated process to produce in situ singlet oxygen which degrades phenol in a solution. The phenothiazines were immobilized in a simple electrochemical procedure in an acidic solution which led to the formation of an ultrathin transparent polymeric film. All films obtained on the ITO substrate including azure A (AA), azure C (AC), methylene blue (MB), toluidine blue (TBO), and thionine (Th) had a comparable surface coverage at the level of picomoles/cm2. The activity of these materials was then compared and presented in terms of an efficiency of the phenol degradation process in an aqueous solution by photogenerated singlet oxygen. That efficiency was determined by the UV–vis spectroscopy employing a phenol/4-aminoantipyrine complex. All the phenothiazine ultrathin polymeric films were capable of generating the singlet oxygen in the aqueous solution under daylight activation, which was used in the consecutive process of phenol degradation. The highest efficiency at a level of 51.4% and 45.4% was found for the AC/ITO and MB/ITO layers, respectively.
Keywords: Phenol degradation; Phenothiazines; Singlet oxygen; Photochemical generation; Electropolymerization;

Bias induced cutoff redshift of photocurrent in ZnO ultraviolet photodetectors by Man Zhao; Xin Wang; Guang Yang; Mai-Yu Zhou; Wen-Jing Liu; Tian-Wen Luo; Hai-Feng Tan; Xiao-Rui Sun (432-434).
A ZnO film with a c-axis preferred orientation was prepared on quartz using the radio frequency (RF) magnetron sputtering technique. Then, a metal-semiconductor-metal (MSM)-structured ultraviolet (UV) photodetector was fabricated on the film. It was found that the cutoff wavelength of the photocurrent redshifted from 361 to 379 nm when the bias increased from 5 to 30 V. The origin of the redshift has been interpreted in terms of a qualitative model considering the declining band gap caused by the bias. This method opens up the possibility of tuning the cutoff redshift of ZnO UV photodetectors.
Keywords: ZnO; Redshift; Photocurrent;

Facile one-pot fabrication and high photocatalytic performance of vanadium doped TiO2-based nanosheets for visible-light-driven degradation of RhB or Cr(VI) by Dingze Lu; Bin Zhao; Pengfei Fang; Shengbin Zhai; Delong Li; Zhiqiang Chen; Wenhui Wu; Wuqiong Chai; Yichu Wu; Ning Qi (435-448).
Vanadium doped TiO2-based nanosheets (V-TNSs) with different V/Ti ratios were prepared by a facile one-pot hydrothermal method using vanadium nitrate and P25 as the vanadium precursor and titanium precursor, respectively. The results indicated that as-synthesized photocatalysts exhibited sheet-like structure with large specific surface area (270–340 cm2/g) and small thickness (4–5 nm). XPS results revealed that vanadium exists in the form of V4+ and V5+, and the binding energies of Ti―O bonds have been changed with the concentration of vanadium. Vanadium doping resulted in considerable enhancement of visible light absorption, red-shift, and the band-gap of photocatalysts reduced from 3.18 eV to 2.91 eV. The density functional theory (DFT) calculations for band structure and total energy also provided a good explanation and further confirmation for the experimental results. It has been found that the photo-activity increased gradually with the concentration of vanadium, and then decreased after attaining a maximum with an optimal content of vanadium at 1.0 at.% for RhB or Cr(VI). The reaction rate K app of 1.0%-V-TNSs are 9.27-fold and 3.26-fold as compared to undoped TNSs under UV–vis and visible light irradiation, respectively. The cyclic tests that performed six times demonstrated high stability and reusability of the photocatalysts. A possible alternate mechanism for the enhancement of the photocatalytic activity under visible-light irradiation was also proposed.
Keywords: TiO2-based nanosheets; Vanadium doping; Radicals; Photodegradation of RhB; Cr(VI) reduction;

Multi-pulse LIBDE of fused silica at different thicknesses of the organic absorber layer by Yunxiang Pan; Martin Ehrhardt; Pierre Lorenz; Bing Han; Bela Hopp; Csaba Vass; Xiaowu Ni; Klaus Zimmer (449-454).
Laser-induced etching techniques feature several unique characteristics that enable ultraprecise machining of transparent materials. However, LIBDE (laser-induced back side dry etching) and LIBWE (laser-induced back side wet etching) are preferentially studied due to experimental feasibilities either using a very thin or a bulk absorber at the rear side of the transparent material. This study aims to fill the gap by examining the thickness dependence of the absorbing material. Multi-pulse-LIBDE (MP-LIBDE) of fused silica using different thick photoresist absorber layers (d L  = 0.2–11.7 μm) was performed with a KrF excimer laser (λ  = 248 nm, t p  ≈ 20 ns). The influence of several experimental parameters, such as laser fluence, pulse number, film thickness, on the ablation morphology and the etching rate were investigated. Especially at moderate fluences (F  = 0.7–1.5 J/cm2) MP-LIBDE and LIBWE show several similar process characteristics such as the etching rate dependence on the laser fluence and the pulse number with a typical etching rate of approx. 12 nm at 1 J/cm2. However, the specific etching rate values depend on the absorber layer thickness, for instance. The morphology of the etched surface is smooth with a roughness of below 5 nm rms. Further, the modification of the surface has been observed and will be discussed in relation to the multi-pulse laser etching mechanism.
Keywords: Laser; Laser ablation; Laser etching; LIBDE; Photoresist; Confinement;

The reduced graphene oxide-ZnFe2O4 composite was successfully prepared by chemistry co-precipitation, which shows the excellent adsorption, photocatalytic and antibacterial properties.Magnetic reduced graphene oxide-ZnFe2O4 composites (RG/ZF) were successfully prepared through a simple chemical co-precipitation method, and their composition, structure, and morphology were characterized by XRD, Raman, SEM, TEM and STEM. These results indicated that the as-prepared RGO with some defects and few reactive groups containing oxygen possessed the few-layered crystal structure, and the ZnFe2O4 nanoparticles with spinel structure were homogeneously dispersed in the interlayer of graphene sheets. The interactions between two components had been investigated by TG and FT-IR. Importantly, kinetic researches indicated that the adsorption behavior of RG/ZF composite could be well described by the second-order kinetic model. Their adsorption effect on RhB conformed to the Langmuir model and belonged to the monolayer chemical adsorption, which were illustrated by thermodynamic experiment. In addition, RG/ZF composites with different mass ratio of RG to ZF (m RG/ZF) presented good photocatalytic activity, and their photocatalytic behavior could be described by the first-order kinetic model under different pH. Among all composites, the RG/ZF composite with m RG/ZF  = 0.4 showed the best photocatalytic activity under pH = 1. However, the enhanced photocatalytic activity may arise from the effective separation of photogenerated e-h+ pairs and the positive synergetic effect between two components. Moreover, the obtained optimum RG/ZF composite had the saturation magnetization (9.8747 emu/g) enough to make it easy to be separated from solution by means of an external magnetic field. On the other hand, the antibacterial testing implied that the antibacterial properties of composite were depended on the m RG/ZF, and the RG/ZF with m RG/ZF  = 0.4 likewise presented the most excellent antibacterial activity, especially to the C. albicans (its IZD and MID was respectively up to 34.5 mm and 12.5 μg/mL). Finally, the possible mechanisms of photocatalysis and antibacterial have been discussed.
Keywords: Reduced graphene oxide; ZnFe2O4; Adsorption; Photocatalysis; Antibacterial;

Origin of (0 0 1) orientation and superlattice structure identification in L10-FePt/B4C multilayer thin films by Jun Zhang; Jian Xie; Yi Wang; Hanbin Wang; Xiang Liu; Cong Ye; Hao Wang (469-473).
(0 0 1) textured L10 FePt/B4C multilayer thin films have been prepared on amorphous substrates by magnetron sputtering. High resolution transmission electron microscopy investigation indicates that the Fe and Pt atoms stacked alternately along the c-axis of L10 FePt, confirming the formation of the superlattice structure of L10-ordered FePt. The internal stress calculation and geometrical phase analysis confirm the existence of the in-plane tensile strain in the L10 FePt thin films. The diffusion of the B and C atoms into the FePt layers results in expansion of the FePt unit cells in the interfaces, which induces an in-plane tensile strain in the adjacent deep parts of FePt layer. Such an in-plane tensile strain creates a favorable condition for the FePt films to stabilize the (0 0 1) texture because it relaxes the ordering strain energy of FePt during phase transformation.
Keywords: FePt; (0 0 1) texture; Strain; Superlattice structure;

Silica-based mesoporous materials have been recently proposed as an efficient support for the controlled release of a popular anticancer drug, 5-fluorouracil (5-FU). Although the relevance of this topic, the atomistic details about the specific surface-drug interactions and the energy of adsorption are almost unknown. In this work, theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) applying Grimme's—D2 correction were performed to elucidate the drug–silica interactions and the host properties that control 5-FU drug adsorption on β-cristobalite (1 1 1) hydroxylated surface. This study shows that hydrogen bonding, electron exchange, and dispersion forces are mainly involved to perform the 5-FU adsorption onto silica. This phenomenon, revealed by favorable energies, results in optimum four adsorption geometries that can be adopted for 5-FU on the hydroxylated silica surface. Silanols are weakening in response to the molecule approach and establish H-bonds with polar groups of 5-FU drug. The final geometry of 5-FU adopted on hydroxylated silica surface is the results of H-bonding interactions which stabilize and fix the molecule to the surface and dispersion forces which approach it toward silica (1 1 1) plane. The level of hydroxylation of the SiO2 (1 1 1) surface is reflected by the elevated number of hydrogen bonds that play a significant role in the adsorption mechanisms.
Keywords: H-bond interaction; 5-Fluorouracil; Hydroxylated silica; Drug delivery; DFT;

Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition by Juan de la Figuera; Adrián Quesada; Laura Martín-García; Mikel Sanz; Mohamed Oujja; Esther Rebollar; Marta Castillejo; Pilar Prieto; Ángel Muñoz-Martín; Lucía Aballe; José F. Marco (480-485).
Display OmittedWe have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO3 by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.
Keywords: Magnetite; Cobalt ferrite; Spinel; Thin film; Mössbauer spectroscopy; Pulsed laser deposition;

The present investigation is focused on evaluation of self-assembling ability in aqueous solutions of two water soluble polymers: poly(aspartic acid) (PAS) and Pluronic F127 (PL). The intermolecular complexes, realized between polyacid and neutral copolymer surfactant in different ratios, have been studied by combining various characterization techniques as rheology, DLS, spectroscopy, microscopy, chemical imaging, and zeta potential determination, measurements performed in static and/or dynamic conditions. In static conditions, when the equilibrium state between PAS/PL polymeric pair was reached, and depending on the polymers mixture composition, and of experimental rheological conditions, positive or negative deviations from the additive rule are registered. Conformational changes of the macromolecular chains and correspondingly physical interactions are generated between PL and PAS for self-assembly and the formation of interpolymer complex as suprastructure with micellar configuration. The phenomenon was better evidenced in case of 1/1 wt ratio between the two polymers. In dynamic conditions of determination, during “in situ” evaluation of the hydrodynamic diameter, zeta potential and conductivity, when the equilibrium state is not reached and as result either the intermolecular bonds are not achieved, the self-assembling process is not so obvious evidenced.
Keywords: Self-assembling; Poly(aspartic acid); Pluronic F127; Aqueous solution;

The fabrication and comparative studies of vertically-grown and horizontally-dispersed fully nanowire-based photodetectors are reported. The detectors both consist of transparent electrodes made by Ag nanowires and active region fabricated by GaN nanowires. The performances of the nanowire-based detectors are strongly affected by desorption and absorption of oxygen. Although the photocurrent sensitivity are similar, the horizontal structured photodetector owns larger of both of photo- and dark current which is due to the better carrier pathways and larger area that can be illuminated. The vertically structured photodetector shows a self-powered effect which is caused by diversity of the two GaN-Ag Schottky contacts.
Keywords: Fully nanowire-based; Photodetector; GaN; Chemical vapor deposition;

Synthesis of multiwall carbon nanotube wrapped Co(OH)2 flakes: A high-performance supercapacitor by Chanchal Mondal; Debasis Ghosh; Mainak Ganguly; Anup Kumar Sasmal; Anindita Roy; Tarasankar Pal (500-507).
The problem of poor electron conductivity is always associated with pseudocapacitive electrode material that deters full utilization of the active material. To have a viable solution to this problem, we report fabrication of a composite material bringing highly conductive carbon nanotube (CNT) wrapped pseudocapacitive with Co(OH)2 nanoflakes. An in situ growth route evolves the supercapacitor via our laboratory developed modified hydrothermal reaction condition (MHT). An electrochemical investigation substantiates that the composite material electrode is highly active, which delivers a maximum specific capacitance of 603 F g−1 (at 1 mV s−1 scan rate), outstanding long-term cyclic stability with 96% retention at a constant current density of 1.5 A g−1 after 1000 cycles of operation. Thus it offers almost an effortless approach to fabricate high-power and high-energy density supercapacitors. By virtue of having high-capacity of pseudocapacitive hydroxides and desirable conductivity of carbon-based materials, the as-synthesized material could be a promising candidate for the development of supercapacitor electrode material.
Keywords: Pseudocapacitance; Conductivity; Composite; Cyclic voltammetry; Specific capacitance; Electrode material;

Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings by Blaise-Alexis Fouetio Kengne; Abdulbaset M. Alayat; Guanqun Luo; Armando G. McDonald; Justin Brown; Hayden Smotherman; David N. McIlroy (508-514).
The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co3O4 spinel phase. A two-step reduction of Co3O4 to CoO and then to Co0 is observed, which is consistent with the results of H2-temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10−6  Torr of H2 revealed signatures of Co0, CoO, and Co3O4. The reduction saturates at a Coo concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H2, the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C6-C17 hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

Development of multilayer oxidation resistant coatings on Cr–50Nb alloy by Haizhong Zheng; Lingling Xiong; Qinhao Luo; Shiqiang Lu (515-520).
To protect Cr–50Nb alloys from high-temperature oxidation, the Al2O3/Si–Al multilayer coatings were produced by pack cementation process, followed by sol–gel process and hot pressing. The results indicate that the multilayer coating is dense and exhibits good adherence to the substrate, which consists of a compact Al2O3 outer layer and an inner layer composed of Si, Al, Cr, Nb. Uncoated Cr–50Nb alloy occurs catastrophic oxidation at the initial oxidation stage at 1200 °C. However, the scale spalling resistance of the multilayer coating is improved significantly, and the multilayer coating exhibits good resistance to oxidation. During cyclic oxidation in air at 1200 °C for 100 h, the weight loss is 0.13 mg/cm2 and the mass gain is 3.38 mg/cm2.
Keywords: Al2O3/Si–Al multilayer coating; Microstructure; Oxidation;

Effect of negative bias on the composition and structure of the tungsten oxide thin films deposited by magnetron sputtering by Meihan Wang; Hao Lei; Jiaxing Wen; Haibo Long; Yutaka Sawada; Yoichi Hoshi; Takayuki Uchida; Zhaoxia Hou (521-525).
Tungsten oxide films deposited at different negative bias voltages by reactive magnetron sputtering transfer from amorphous to crystalline (monoclinic + hexagonal) after annealing at 500 °C in air atmosphere. Furthermore, the crystallized tungsten oxide films show different preferred orientation.Tungsten oxide thin films were deposited at room temperature under different negative bias voltages (V b , 0 to −500 V) by DC reactive magnetron sputtering, and then the as-deposited films were annealed at 500 °C in air atmosphere. The crystal structure, surface morphology, chemical composition and transmittance of the tungsten oxide thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometer. The XRD analysis reveals that the tungsten oxide films deposited at different negative bias voltages present a partly crystallized amorphous structure. All the films transfer from amorphous to crystalline (monoclinic + hexagonal) after annealing 3 h at 500 °C. Furthermore, the crystallized tungsten oxide films show different preferred orientation. The morphology of the tungsten oxide films deposited at different negative bias voltages is consisted of fine nanoscale grains. The grains grow up and conjunct with each other after annealing. The tungsten oxide films deposited at higher negative bias voltages after annealing show non-uniform special morphology. Substoichiometric tungsten oxide films were formed as evidenced by XPS spectra of W4f and O1s. As a result, semi-transparent films were obtained in the visible range for all films deposited at different negative bias voltages.
Keywords: Tungsten oxide thin films; Magnetron sputtering; Negative bias voltage (V b ); Structure; Composition;

Chromium depletion, Δx  =  x k  −  x, in Fe100−x Cr x (x  = 2.2, 3.9, 6.4, 8.5, 10.25, 10.75, 14.9, 15.15) alloys quenched into LN (left panel) and those quenched onto brass (right panel) as found from CEMS (pre surface zone) and TRANS (bulk) Mössbauer spectra (x k – Cr content in the pre surface or bulk as estimated from the average hyperfine field found for the quenched samples).Effect of a quenching medium (water, liquid nitrogen and block of brass) on a distribution of Cr atoms in the surface zone of Fe100−x Cr x (x  ≤ 19) alloys was studied with the Mössbauer spectroscopy. The distribution of Cr atoms was expressed in terms of the Cowley–Warren short-range order (SRO) parameters: 〈α1〉 for the first neighbor-shell, 〈α2〉 for the second neighbor-shell and 〈α12〉 for both neighbor-shells. It was revealed that none of the quenching media resulted in a random distribution of atoms, yet the degree of randomness was the highest for the samples quenched onto the block of brass. The quenching into water and liquid nitrogen caused a partial oxidation of samples’ surface accompanied by a chromium depletion of the bulk. Quantitative analysis of various phases in the studied samples both in their bulk as well as in pre surface zones was carried out.
Keywords: Fe–Cr alloys; Short-range order; Conversion electrons Mössbauer spectroscopy;

Some residual OH ligands originating from incomplete reaction between TMA and surface species of OH* during ALD process induce the defects in deposited Al2O3 films. Three possible types of defects are suggested. The analytic results indicate the defects are Type-I and/or Type-II but do not directly expose the substrate, like pinholes (Type-III).Al2O3 films with various thicknesses were deposited by the atomic layer deposition (ALD) technique on pure copper at temperatures of 100–200 °C. Oxidation trials were conducted in air at 200 °C to investigate the defects in these films. The analytic results show that the defects have a looser micro-structure compared to their surroundings, but do not directly expose the substrate, like pinholes. The film's crystallinity, mechanical properties and oxidation resistance could also be affected by these defects. Superficial contamination particles on the substrate surface are confirmed to be nucleation sites of the defects. A model for the mechanism of defect formation is proposed in this study.
Keywords: Atomic layer deposition; Al2O3 film; Copper; Oxidation; Defect;

The study presents a direct process for surface patterning of multilayer graphene on the glass substrate as a biosensing device. In contrast to lithography with etching, the proposed process provides simultaneous surface patterning of multilayer graphene through nanosecond laser irradiation. In this study, the multilayer graphene was prepared by a screen printing process. Additionally, the wavelength of the laser beam was 355 nm. To perform the effective laser process with the small heat affected zone, the surface patterns on the sensing devices could be directly fabricated using the laser with optimal control of the pulse overlap at a fluence threshold of 0.63 J/cm2. The unique patterning of the laser-ablated surface exhibits their electrical and hydrophilic characteristics. The hydrophilic surface of graphene-based sensing devices was achieved in the process with the pulse overlap of 90%. Furthermore, the sensing devices for controlling the electrical response of glucose by using glucose oxidase can be used in sensors in commercial medical applications.
Keywords: Surface patterning; Multilayer graphene; Laser irradiation; Sensing devices;

Investigations of the composition of macro-, micro- and nanoporous silicon surface by ultrasoft X-ray spectroscopy and X-ray photoelectron spectroscopy by A.S. Lenshin; V.M. Kashkarov; E.P. Domashevskaya; A.N. Bel’tyukov; F.Z. Gil’mutdinov (550-559).
The features of atomic and electron structure and phase composition of the surface in the samples of macro-, micro- and nanoporous silicon and their changes with depth were investigated with the use of X-ray photoelectron spectroscopy, ultrasoft X-ray emission spectroscopy and scanning electron microscopy. Analysis of the X-ray emission spectra applying the simulation method allowed to follow the trends in the changes of the composition for the investigated samples starting from the surface and into the bulk and to show the differences in the phase composition between the samples of porous silicon with different pores size.
Keywords: Porous silicon; Electron spectroscopy; Oxidation.;

Improving the efficiency of perovskite solar cells through optimization of the CH3NH3PbI3 film growth in solution process method by Ying Zhao; Jian Liu; Xinrong Lu; Yandong Gao; Xiaozeng You; Xiangxing Xu (560-566).
Perovskite-structured organic–inorganic materials such as CH3NH3PbI3 are attracting much interest in the scientific community because of their abilities to function as revolutionary light harvesters and charge transfer materials for solar cells. To achieve high power conversion efficiency (PCE), it is critical to optimize the perovskite film layer. This paper reports the temperature and concentration controls on the two-step solution process. A diffusion-controlled growth mechanism is proposed for this process in tuning the morphology and purity of the perovskite film, which are proven to be important factors contributing to the photovoltaic performance. The highest PCE of 11.92% is achieved with an optimized perovskite crystal size of ∼150 nm and an appropriate amount of residual PbI2. This study sheds light on the design and fabrication of highly efficient, low-cost, solution-processed perovskite solar cells.
Keywords: Organic–inorganic perovskite; Solar cell; Two-step solution method; Morphology; Diffusion controlled growth; Thin film;

Laser patterning of very thin indium tin oxide thin films on PET substrates by C. McDonnell; D.Milne; C. Prieto; H. Chan; D. Rostohar; G.M. O’Connor (567-575).
This work investigates the film removal properties of 30 nm thick Indium Tin Oxide (ITO) thin films, on flexible polyethylene terephthalate (PET) substrates, using 355, 532 and 1064 nm nanosecond pulses (ns), and 343 and 1064 nm femtosecond pulses. The ablation threshold was found to be dependent on the applied wavelength and pulse duration. The surface topography of the laser induced features were examined using atomic force microscopy across the range of wavelengths and pulse durations. The peak temperature, strain and stress tensors were examined in the film and substrate during laser heating, using finite element computational methods. Selective removal of the thin ITO film from the polymer substrate is possible at all wavelengths except at 266 nm, were damage to substrate is observed. The damage to the substrate results in periodic surface structures (LIPPS) on the exposed PET, with a period of twice the incident wavelength. Fragmented crater edges are observed at all nanosecond pulse durations. Film removal using 1030 nm femtosecond pulses results in clean crater edges, however, minor 5 nm damage to the substrate is also observed. The key results show that film removal for ITO on PET, is through film de-lamination across all wavelengths and pulse durations. Film de-lamination occurs due to thermo-elastic stress at the film substrate interface region, as the polymer substrate expands under heating from direct laser absorption and heat conduction across the film substrate interface.
Keywords: ITO; Thin films; Flexible substrate; Ablation; Delamination; Transparent conductive layers; Nanosecond; Finite element model;

The effect of β-halogen substitutions on the thermal chemistry of 1-propanol over Ni(1 1 1) and Cu(1 1 1) single-crystal surfaces was investigated using the method of unity bond index-quadratic exponential potential (UBI-QEP). This method was employed to investigate the energetics of the catalytic conversion routes of the ad-molecule mainly at the zero-coverage limit by calculating activation barriers and enthalpy changes for surface reactions. The alcohol molecule can be oxidized partially and totally over the Ni surface, however, the molecule is rather inactive on Cu. The β-halogen substitution makes extensive conversion of the alcohol possible on the Cu surface and changes conversion pathways on the Ni surface. It was found that halogen substitution as well as hydrogen bonding can affect the reactivity and conversion routes of the molecules on Ni and Cu surfaces. On account of energetic criteria, the predicted routes for decompositions and the TPD patterns for the surface species are in accord with the available experimental observations.
Keywords: UBI-QEP theory; Catalytic decomposition; Halo-propanol; Ni; Cu;

A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH3) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc―N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.
Keywords: Scandium nitride (ScN); Electron beam (e-beam) evaporator; Rock salt grains-like structure; Ammonia (NH3) annealing;

Surface functionalization of solid state ultra-high molecular weight polyethylene through chemical grafting by Tauqir A. Sherazi; Tayyiba Rehman; Syed Ali Raza Naqvi; Ahson Jabbar Shaikh; Sohail Anjum Shahzad; Ghazanfar Abbas; Rizwan Raza; Amir Waseem (593-601).
The surface of ultra-high molecular weight polyethylene (UHMWPE) powder was functionalized with styrene using chemical grafting technique. The grafting process was initiated through radical generation on base polymer matrix in the solid state by sodium thiosulfate, while peroxides formed at radical sites during this process were dissociated by ceric ammonium nitrate. Various factors were optimized and reasonably high level of monomer grafting was achieved, i.e., 15.6%. The effect of different acids as additive and divinyl benzene (DVB) as a cross-linking agent was also studied. Post-grafting sulfonation was conducted to introduce the ionic moieties to the grafted polymer. Ion-exchange capacity (IEC) was measured experimentally and is found to be 1.04 meq g−1, which is in close agreement with the theoretical IEC values. The chemical structure of grafted and functionalized polymer was characterized by attenuated total reflection infrared spectroscopy (ATR-FTIR) and thermal properties were investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Thermal analysis depicts that the presence of radicals on the polymer chain accelerates the thermal decomposition process. The results signify that the chemical grafting is an effective tool for substantial surface modification and subsequent functionalization of polyethylene.
Keywords: Chemical grafting; Styrene; Ultra-high molecular weight polyethylene; Surface modification; Thermal stability; Ion-exchange resin;

An organic–inorganic core/shell structure, γ-Fe2O3/polyrhodanine nanocomposite with γ-Fe2O3 nanoparticle as core with average diameter of 15 nm and polyrhodanine as shell with thickness of 1.5 nm, has been synthesized via chemical oxidation polymerization and applied for adsorption of Zn ions from aqueous solution in a fixed-bed column. The properties of nanocomposite were characterized with transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). The performance of the column was assessed under variable bed heights (10, 15 and 20 cm) and influent Zn concentrations (50, 100 and 150 ppm) at a constant flow rate (0.5 mL/min). The results demonstrated that the breakthrough curves are S-shaped and the breakthrough time increases with increasing bed height and decreases with increasing influent concentration. Moreover, the dynamics of the adsorption process were evaluated by using Adams–Bohart, bed depth service time (BDST), Thomas and Yoon–Nelson kinetic models. The models were nearly in good agreement with the experimental data.
Keywords: Synthetic nanocomposite; Maghemite; Polyrhodanine; Adsorption; Fixed bed column; Breakthrough curve;

KIT-6 is a cage type three dimensional cubic mesoporous silicate with Ia3d type structure, which shows scintillating promise in nanocasting, surface functionality, metal incorporation, and pharmaceutics. Nevertheless, little attention was paid to its application as support in heterogeneous catalysts. Cu-containing cobaltosic oxide spinel composite supported by mesoporous silica KIT-6 was synthesized via impregnation method and subsequent calcination under different temperatures. The prepared ordered materials were characterized by X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy, atomic adsorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results showed that Cu2+ was successfully embedded in spinel structure when calcined at 550 °C, in contrast, the samples through thermal treatment at 250 °C remained hybrid composition of CuO and Co3O4. Catalytic performance of mesoporous materials was evaluated for epoxidation of styrene in the presence of tert-butylhydroperoxide as oxidant. Among a range of prepared materials, a significant enhancement in styrene conversion and selectivity of styrene oxide was obtained for Cu-spinel catalysts, in comparison with hybrid oxide. A dramatic decrease in catalytic activities was found while KIT-6 support was removed, due to the partial destruction of ordered structure of Cu–Co oxide. Consequently, the catalytic behaviors were chiefly ascribed to copper species and their textural properties.
Keywords: Copper–cobalt oxides catalysts; Mesoporous materials; Spinel phase; Epoxidation; Styrene;

Thin polycrystalline diamond films protecting zirconium alloys surfaces: From technology to layer analysis and application in nuclear facilities by P. Ashcheulov; R. Škoda; J. Škarohlíd; A. Taylor; L. Fekete; F. Fendrych; R. Vega; L. Shao; L. Kalvoda; S. Vratislav; V. Cháb; K. Horáková; K. Kůsová; L. Klimša; J. Kopeček; P. Sajdl; J. Macák; S. Johnson; I. Kratochvílová (621-628).
Zirconium alloys can be effectively protected against corrosion by polycrystalline diamond (PCD) layers grown in microwave plasma enhanced linear antenna chemical vapor deposition apparatus. Standard and hot steam oxidized PCD layers grown on Zircaloy2 surfaces were examined and the specific impact of polycrystalline Zr substrate surface on PCD layer properties was investigated. It was found that the presence of the PCD coating blocks hydrogen diffusion into the Zircaloy2 surface and protects Zircaloy2 material from degradation. PCD anticorrosion protection of Zircaloy2 can significantly prolong life of Zircaloy2 material in nuclear reactors even at temperatures above Zr phase transition temperatures.
Keywords: Metal coatings; Thin polycrystalline diamond film; Impedance spectroscopy; Raman spectroscopy; XPS;

The method of distributed calibration of a probe microscope scanner consists in a search for a net of local calibration coefficients (LCCs) in the process of automatic measurement of a standard surface, whereby each point of the movement space of the scanner can be defined by a unique set of scale factors. Feature-oriented scanning (FOS) methodology is used to implement the distributed calibration, which permits to exclude in situ the negative influence of thermal drift, creep and hysteresis on the obtained results. The sensitivity of LCCs to errors in determination of position coordinates of surface features forming the local calibration structure (LCS) is eliminated by performing multiple repeated measurements followed by building regression surfaces. There are no principle restrictions on the number of repeated LCS measurements. Possessing the calibration database enables correcting in one procedure all the spatial distortions caused by nonlinearity, nonorthogonality and spurious crosstalk couplings of the microscope scanner piezomanipulators. To provide high precision of spatial measurements in nanometer range, the calibration is carried out using natural standards – constants of crystal lattice. The method may be used with any scanning probe instrument.
Keywords: STM; AFM; SPM; Scanner; Calibration; Drift; Creep; Nonlinearity; Nonorthogonality; Crosstalk coupling; Graphite; HOPG; Recognition; Feature-oriented scanning; FOS; Counter-scanning; Counter-scanned images; Nanometrology; Surface characterization; Nanotechnology;

Emerging interface dipole versus screening effect in copolymer/metal nano-layered systems by V. Torrisi; F. Ruffino; A. Liscio; M.G. Grimaldi; G. Marletta (637-642).
Despite to the importance on the charge carrier injection and transport at organic/metal interface, there is yet an incomplete estimation of the various contribution to the overall dipole. This work shows how the mapping of the surface potential performed by Kelvin Probe Force Microscopy (KPFM) allows the direct observation of the interface dipole within an organic/metal multilayered structure. Moreover, we show how the sub-surface sensitivity of the KPFM depends on the thickness and surface coverage of the metallic layer. This paper proposes a way to control the surface potential of the exposed layer of an hybrid layered system by controlling the interface dipole at the organic/metal interface as a function of the nanometer scale thickness and the surface coverage of the metallic layer.We obtained a layered system constituted by repeated sequence of a copolymer film, poly(n-butylacrylate)-b-polyacrilic acid, and Au layer. We compared the results obtained by means of scanning probe microscopy technique with the results of the KPFM technique, that allows us to obtain high-contrast images of the underlying layer of copolymer behind a typical threshold, on the nanoscale, of the thickness of the metal layer. We considered the effect of the morphology of the gold layer on the covered area at different thicknesses by using the scanning electron microscopy technique.This finding represents a step forward towards the using of dynamic atomic force microscopy based characterization to explore the electrical properties of the sub-surface states of layered nanohybrid, that is a critical point for nanohybrid applications in sensors and energy storage devices.
Keywords: KPFM; Au layer; Contact potential difference; Thickness; Nanoscale; Surface coverage;

The effect of hydroxylation on CNT to form Chitosan-CNT composites: A DFT study by Rui Yu; Maofei Ran; Jie Wen; Wenjing Sun; Wei Chu; Chengfa Jiang; Zhiwei He (643-650).
The effect of types of CNTs (pristine and hydroxylated) on the synthesis of Chitosan-CNT (CS-CNT) composites was investigated theoretically. The adsorption energy (E ads) of CS on the pristine CNT and hydroxylated CNTs (CNT-OH n , n  = 1–6) as well as the structural and electronic properties of said composites have been investigated. Results show that the adsorption of CS on CNT and CNT-OH n is thermodynamically favored. The E ads of CS on CNTs was calculated to be −20.387 kcal/mol from electrostatic interactions. For CS adsorbed into CNT-OH n , E ads ranges from −20.612 to −37.567 kcal/mol. Hydroxyl groups on CNT are the main adsorption sites for CS loading onto CNT-OH n via hydrogen-bond interactions. The CS-CNT-OH3 is the most sable composite among tested complexes. The energy gap (ΔE gap) of CS-CNT-OH3 was calculated less than pristine CNT and CNT-OH3, indicative of the composites being more reactive than that of pristine CNTs and CNT-OH3. It was proved that CS can transfer electron to the hydroxylated CNTs, thus overcoming the drawbacks of CNTs being chemically inert.
Keywords: Density functional theory; Carbon nanotubes (CNT); Hydroxylation; Chitosan; Composites;

Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium by R.M. Abdel Hameed; Amani E. Fetohi; R.S. Amin; K.M. El-Khatib (651-663).
Physical and electrochemical properties of Pt/C, Pt–MnO2/C-1 and Pt–MnO2/C-2 electrocatalysts.The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt–MnO2/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO2 improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt–MnO2/C towards methanol oxidation in H2SO4 solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO2 is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt–MnO2/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt–MnO2/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).
Keywords: Platinum; Manganese oxide; Reducing agent; Chemical synthesis; Fuel cells;

Performance of colloidal silica and ceria based slurries on CMP of Si-face 6H-SiC substrates by Guomei Chen; Zifeng Ni; Laijun Xu; Qingzhong Li; Yongwu Zhao (664-668).
There was a significant difference in the CMP performance of 6H-SiC between silica and ceria based slurries. For the ceria based slurries, a higher MRR was obtained, especially in strong acid KMnO4 environment.Colloidal silica and ceria based slurries, both using KMnO4 as an oxidizer, for chemical mechanical polishing (CMP) of Si-face (0 0 0 1) 6H-SiC substrate, were investigated to obtain higher material removal rate (MRR) and ultra-smooth surface. The results indicate that there was a significant difference in the CMP performance of 6H-SiC between silica and ceria based slurries. For the ceria based slurries, a higher MRR was obtained, especially in strong acid KMnO4 environment, and the maximum MRR (1089 nm/h) and a smoother surface with an average roughness Ra of 0.11 nm was achieved using slurries containing 2 wt% colloidal ceria, 0.05 M KMnO4 at pH 2. In contrast, due to the attraction between negative charged silica particles and positive charged SiC surface below pH 5, the maximum MRR of silica based slurry was only 185 nm/h with surface roughness Ra of 0.254 nm using slurries containing 6 wt% colloidal silica, 0.05 M KMnO4 at pH 6. The polishing mechanism was discussed based on the zeta potential measurements of the abrasives and the X-ray photoelectron spectroscopy (XPS) analysis of the polished SiC surfaces.
Keywords: Chemical mechanical polishing (CMP); Silicon carbide (SiC); Silica; Ceria;

SnO2 and Stainless Steel 316 (Sst) films are useful materials for the production of interferential decorative coatings because they provide a high sputtering rate and low cost respectively. Multilayers of SnO2 and Stainless Steel 316 were deposited using DC pulsed magnetron sputtering, and oxygen diffusion processes were studied in the interface. Studies were made at selected temperatures between 450 °C and 650 °C for different exposure times: 0, 15, 30, 60 and 120 min. TOF-SIMS depth profiles determined the oxygen penetration in Sst films and evidenced the formation of a chromium oxide film. This method is noted for its simplicity for a full study at different temperatures and exposure times with few TOF-SIMS measurements. Oxidation kinetics can be described by two different contributions: a fast oxide film formation and parabolic growth. Results are useful for predicting the thickness of the chromium oxide film and the degradation of the coating at high temperatures.
Keywords: DC pulsed magnetron sputtering; Oxidation kinetics; TOF-SIMS depth profile; Decorative coatings; Thin films;

Effect of doping on the morphology of GaSb/GaAs nanostructures for solar cells by N. Fernández-Delgado; M. Herrera; S.I. Molina; C. Castro; S. Duguay; J.S. James; A. Krier (676-678).
Keywords: Electron microscopy; Crystal structure; Epitaxial growth; Thin films; Solar cells;

Formation of Mach angle profiles during wet etching of silica and silicon nitride materials by M. Ghulinyan; M. Bernard; R. Bartali; G. Pucker (679-686).
Display OmittedIn integrated circuit technology peeling of masking photoresist films is a major drawback during the long-timed wet etching of materials. It causes an undesired film underetching, which is often accompanied by a formation of complex etch profiles. Here we report on a detailed study of wedge-shaped profile formation in a series of silicon oxide, silicon oxynitride and silicon nitride materials during wet etching in a buffered hydrofluoric acid (BHF) solution. The shape of etched profiles reflects the time-dependent adhesion properties of the photoresist to a particular material and can be perfectly circular, purely linear or a combination of both, separated by a knee feature. Starting from a formal analogy between the sonic boom propagation and the wet underetching process, we model the wedge formation mechanism analytically. This model predicts the final form of the profile as a function of time and fits the experimental data perfectly. We discuss how this knowledge can be extended to the design and the realization of optical components such as highly efficient etch-less vertical tapers for passive silicon photonics.
Keywords: Integrated optics materials; Material processing; Etching; Silica glass; Silicon nitride; Buffered hydrofluoric acid;

Quantum states of hydrogen atom on Pd(1 1 0) surface by Allan Abraham B. Padama; Hiroshi Nakanishi; Hideaki Kasai (687-691).
The quantum states of adsorbed hydrogen atom on Pd(1 1 0) surface are investigated in this work. From the calculated potential energy surface (PES) of hydrogen atom on Pd(1 1 0), the wave functions and eigenenergies in the ground and few excited states of protium (H) and deuterium (D) are calculated. Localized wave functions of hydrogen atom exist on pseudo-threefold and long bridge sites of Pd(1 1 0). The short bridge site is a local minimum from the result of PES, however, quantum behavior of hydrogen revealed that its vibration would allow it to hop to other pseudo-threefold site (that crosses the short bridge site) than to stay on the short bridge site. Exchange of ordering of the wave functions between H and D is attributed to the difference in their masses. The calculated eigenenergies are found to be in fair agreement with experimental data based from the identified vibrations of hydrogen with component perpendicular to the surface. The activation barriers measured from the eigenenergies are in better agreement with experimental findings in comparison to the data gathered from PES.
Keywords: Quantum states; Hydrogen atom; Surface diffusion; Pd(1 1 0) surface; Metal hydride;

Electroless nickel–boron coatings are widely used in industrial on various substrates: ferrous and non-ferrous alloys mainly but also in some cases non-metallic materials. However, their growth process is still not fully understood and the influence of the nature of the substrate on this process is completely unknown.The formation of electroless nickel–boron was observed on five ferrous alloys: a mild steel, a high carbon unalloyed steel, a cryogenic steel (that contains 9 wt.% nickel), an austenitic stainless steel and an austeno-ferritic (duplex) stainless steel.Nickel–boron films were prepared by electroless deposition, using sodium borohydride as a reducing agent. Samples were immersed in a plating bath for times ranging from 5 s to 60 min. The influence of the nature of the substrate on the initial deposition of the coatings was investigated in detail: the initiation mechanism was identified for all substrates and it was found to be related to catalytic oxidation of the reducing agent rather than to a displacement process.The delay before initiation was influenced by the nickel content of the coating and by a high number of grain boundaries.In all cases, the plating rate varied with plating time, with a slower period during the first 10 min that corresponds to morphological modification of the coating.
Keywords: Electroless nickel–boron; Initiation; Roughness; Plating rate; Substrate; Steel;

Investigations of the polymer/magnetic interface of organic spin-valves by N.A. Morley; R. Dost; A.S.V. Lingam; A.J. Barlow (704-713).
This work investigates the top interface of an organic spin-valve, to determine the interactions between the polymer and top magnetic electrode. The polymers studied are regio-regular poly(3-hexylthiophene) (RR-P3HT) and poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and the magnetic top electrodes are NiFe and Fe. X-ray photoelectron spectroscopy (XPS) is used to determine the bonding at the interface, along with the extent of how oxidised the magnetic layers are, while atomic force microscopy (AFM) is used to determine the surface roughness. A magneto-optic Kerr effect (MOKE) magnetometer is used to study the magnetic properties of the top electrode. It is shown that at the organic–magnetic interface the magnetic atoms interact with the polymer, as metallic–sulphide and metallic-carbide species are present at the interface. It is also shown that the structure of the polymer influences the anisotropy of the magnetic electrode, such that the magnetic electrodes grown on RR-P3HT have uniaxial anisotropy, while those grown on PBTTT are isotropic.
Keywords: Organic spintronics; Interfaces; XPS; Chemical bonding;

The hybrid magnetic Sr5x Ba3x (PO4)3(OH)/Fe3O4 (SBPF) nanorod was prepared and characterized using different techniques, such as SEM, EDS, TEM, SAED, HRTEM, XRD, and FT-IR. Adsorption studies of acid fuchsin (AF) from aqueous solution with respect to the pH, temperature, time, initial dye concentration, and sorbent dosage were investigated. The Freundlich adsorption model was applied to describe the equilibrium isotherms. The maximal AF uptake by SBPF was 1590 mg/g in the test. Kinetics parameters of the adsorption process indicated that it followed the pseudo-second order equation, and the maximum sorption capacity calculated from the pseudo-second-order rate equation was 909 mg/g which was close to the experimental value. Adsorption thermodynamics study indicated the spontaneous nature and exothermic of the adsorption process. The removal of AF was attributed to the hydrogen bond and ionic interactions. Moreover, SBPF was easily recovered, and the adsorption capacity was approximately 97.7% of the initial saturation adsorption capacity after being used five times.
Keywords: Magnetic nanorod; Acid fuchsin; Adsorption; Mechanism;

The preparation of Fe3O4 cube-like nanoparticles via the ethanol reduction of α-Fe2O3 and the study of its electromagnetic wave absorption by Lili Zhang; Peng Dai; Xinxin Yu; Yang Li; Zhiwei Bao; Jin Zhu; Kerong Zhu; Mingzai Wu; Xiansong Liu; Guang Li; Hong Bi (723-728).
Cube-like Fe3O4 nanoparticles with size between 60 nm and 80 nm were reduced via ethanol using α-Fe2O3 nanocubes as precursors at 350 °C. The possible mechanism for the CH3CH2OH reduction of α-Fe2O3 into Fe3O4 was discussed. Electromagnetic wave absorption test showed that these Fe3O4 nanoparticles possessed excellent microwave absorption performance due to its complementary effect of dielectric loss and magnetic loss. The minimum absorption reflection loss value is −47.8 dB for Fe3O4 nanoparticles/paraffin wax composite sample with thickness of 4 mm, much higher than that of the commercial microwave absorber [Fe, Ni].
Keywords: Fe2O3; Fe3O4; Ethanol reduction; Electromagnetic wave absorption;

The structures of Au n clusters (n  = 1–20) supported on rutile TiO2 (1 1 0) surfaces were investigated using density functional theory. The supported Au n clusters were found to prefer planar or quasi-planar structures. We found that the supported Au n clusters lay flat on the TiO2 (1 1 0) surfaces, which agrees well with the experimental results. The dispersion interaction dominates the interactions between the Au n clusters and the TiO2 surface and causes the planar growth patterns of the supported Au n clusters. All of the supported Au n clusters possess a positive net charge, and the charges show an odd-even oscillation behavior with increasing n, especially when n  > 12. Obvious charge nonuniformities of the Au n clusters with an even value of n were observed. In some Au n clusters with an even value of n, some of the Au atoms possess large negative charges.
Keywords: Au n cluster; TiO2 surface; Growth pattern; Dispersion interaction;

Wetting process of copper filling in through silicon vias by Junhong Zhang; Wei Luo; Yi Li; Liming Gao; Ming Li (736-741).
In this paper, wetting process of copper filling in through silicon vias was investigated by agitation and vacuum pretreatment. Copper filling followed the pretreatment was fabricated in electrolyte with optimal additives concentration. By agitation pretreatment, a large void was observed at the bottom of the vias where the copper seed layer was clearly seen, which was attributed to the insufficient wetting of vias. In the blind vias with higher aspect ratio, the ambient gas phase was difficult to be completely removed from the vias by agitation. This resulted in electrolyte having better wettability does not reach all the places of the vias by capillarity. The vacuum pretreatment results suggested that the air inside the vias was almost completely evacuated. Hence, the deionized water used as wetting solution easily permeated the blind vias relying on atmospheric pressure. Consequently, the uniform, complete and void-free copper filling was achieved due to better wettability of 273 K deionized water. Nevertheless, deionized water with temperature higher than the critical vaporization temperature yielded a void formation at the bottom of the vias, which resulted from the insufficient wetting caused by the vaporization of deionized water. The conclusions drawn by the experimental results were employed in the through silicon vias, and void-free copper filling in the vias having aspect ratio as high as 16 was fabricated.
Keywords: Vacuum pretreatment; Wetting process; Copper filling; Through silicon vias;

Role of the substrate on the magnetic anisotropy of magnetite thin films grown by ion-assisted deposition by Pilar Prieto; José Emilio Prieto; Raquel Gargallo-Caballero; José Francisco Marco; Juan de la Figuera (742-748).
Magnetite (Fe3O4) thin films were deposited on MgO (0 0 1), SrTiO3 (0 0 1), LaAlO3 (0 0 1) single crystal substrates as well on as silicon and amorphous glass in order to study the effect of the substrate on their magnetic properties, mainly the magnetic anisotropy. We have performed a structural, morphological and compositional characterization by X-ray diffraction, atomic force microscopy and Rutherford backscattering ion channeling in oxygen resonance mode. The magnetic anisotropy has been investigated by vectorial magneto-optical Kerr effect. The results indicate that the magnetic anisotropy is especially influenced by the substrate-induced microstructure. In-plane isotropy and uniaxial anisotropy behavior have been observed on silicon and glass substrates, respectively. The transition between both behaviors depends on grain size. For LaAlO3 substrates, in which the lattice mismatch between the Fe3O4 films and the substrate is significant, a weak in-plane fourfold magnetic anisotropy is induced. However when magnetite is deposited on MgO (0 0 1) and SrTiO3 (0 0 1) substrates, a well-defined fourfold in-plane magnetic anisotropy is observed with easy axes along [1 0 0] and [0 1 0] directions. The magnetic properties on these two latter substrates are similar in terms of magnetic anisotropy and coercive fields.
Keywords: Magnetite thin films; Magnetic anisotropy;

Double surface plasmon enhanced organic light-emitting diodes by gold nanoparticles and silver nanoclusters by Chia-Yuan Gao; Ying-Chung Chen; Kan-Lin Chen; Chien-Jung Huang (749-753).
The influence of gold nanoparticles (GNPs) and silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The GNPs are doped into (poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)) (PEDOT: PSS) and the SNCs are introduced between the electron-injection layer and cathode alumina. The power efficiency of the device, at the maximum luminance, with double surface plasmon resonance and buffer layer is about 2.15 times higher than that of the device without GNPs and SNCs because the absorption peaks of GNPs and SNCs are as good as the photoluminescence peak of the emission layer, resulting in strong surface plasmon resonance effect in the device. In addition, the buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated.
Keywords: Gold nanoparticles; Silver nanoclusters; Surface plasmon resonance effect; Power efficiency;

Fabricating high-k conductor/polymer composites with low dielectric loss and percolation threshold is still a challenge, while the electric conductor is the key factor of determining the dielectric behavior of composites. A novel hybridized conductor with “sandwich” structure (rPANI@CNT-rGO) and active groups was prepared by introducing polyaniline coated carbon nanotube (rPANI@CNT) on the surface of reduced graphene oxide (rGO) through electrostatic and π–π conjugate forces. And the rPANI@CNT-rGO hybrids with different loadings of rPANI@CNT were introduced into epoxy resin (EP) to prepare a series of rPANI@CNT-0.75rGO/EP composites; meanwhile rPANI@CNT and rGO were mechanically blended with EP to prepare rPANI@CNT/0.75rGO/EP composites for comparison. rPANI@CNT/0.75rGO/EP composites have low dielectric constant (10–20), whereas the dielectric constant at 100 Hz of the 7rPANI@CNT-0.75rGO/EP composite with 0.75 wt% rPANI@CNT is as high as 210, much larger than those of rPANI@CNT/EP, 0.75rGO/EP and rPANI@CNT/0.75rGO/EP composites. Meanwhile, the dielectric loss at 100 Hz of 7rPANI@CNT-0.75rGO/EP composite is only 17% of that of 0.75rGO/EP, indicating that the dielectric behavior of rPANI@CNT-0.75rGO/EP composites is not originated from a simple addition of basic components, but has an obvious synergistic effect. The percolation threshold of rPANI@CNT-0.75rGO/EP composites is only 1.1 wt%. The origin of these attractive dielectric properties was revealed through systematically discussing the structures and simulated circuits of rPANI@CNT-0.75rGO/EP composites.
Keywords: Carbon-based nanostructures; Dielectric property; Synergism; Composites;

Vinyltrimethoxysilane-modified zinc oxide quantum dots with tuned optical properties by Aurel Tăbăcaru; Viorica Muşat; Nicolae Ţigău; Bogdan Ştefan Vasile; Vasile-Adrian Surdu (766-773).
Surface modification of zinc oxide nanoparticles (ZnO NPs) with covalently attachable organosilane species is a promising route for the preparation of hybrid nanomaterials in which optical and physico-chemical properties can be easily tuned. As a continuation of our ongoing studies regarding the surface modification of ZnO NPs with adjustable optical properties, we here report a novel series of hybrid zinc oxide quantum dots (ZnO QDs) modified with vinyltrimethoxysilane (VTMS). The modified ZnO QDs, with sizes spanning the range 3–4 nm, were obtained through a simple and low-cost precipitation method. They were morpho-structurally characterized by means of X-ray diffraction, high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy, while their optical properties were studied by UV–vis spectroscopy. When applied as thin films on glass substrate, the obtained ZnO QDs showed excellent optical transmittance between 85 and 90%, and low reflectance in the visible domain. The photoluminescence spectra showed a significant blue-shift of the emission bands, from 578 nm for unmodified ZnO to 540 nm for ZnO modified with 10% VTMS. A new opposite trend of band gap variation from 3.494 eV for unmodified ZnO to 3.32 eV for ZnO modified with 10% VTMS was detected, while an organosilane loading higher than 10% was found to reincrease both nanoparticles size and band gap energy. These results highlighted the better ability of VTMS to attain a higher degree of nanoparticles size reduction, along with the tuning of the optical properties, with respect to the previously reported ZnO-MPS series.
Keywords: Zinc oxide quantum dots; Vinyltrimethoxysilane; Surface modification; Photoluminescence; Band gap energy;

Visual representation of the PS interface interacting with mixed gas configurations. The red dots correspond to nanostructured metal oxides. Each combination of distinct molecules are labeled below the pores, which are oversized in the figure.A unique MEMS/NEMS approach is presented for the modeling of a detection platform for mixed gas interactions. Mixed gas analytes interact with nanostructured decorating metal oxide island sites supported on a microporous silicon substrate. The Inverse Hard/Soft acid/base (IHSAB) concept is used to assess a diversity of conductometric responses for mixed gas interactions as a function of these nanostructured metal oxides. The analyte conductometric responses are well represented using a combination diffusion/absorption-based model for multi-gas interactions where a newly developed response absorption isotherm, based on the Fermi distribution function is applied. A further coupling of this model with the IHSAB concept describes the considerations in modeling of multi-gas mixed analyte–interface, and analyte–analyte interactions. Taking into account the molecular electronic interaction of both the analytes with each other and an extrinsic semiconductor interface we demonstrate how the presence of one gas can enhance or diminish the reversible interaction of a second gas with the extrinsic semiconductor interface. These concepts demonstrate important considerations in the array-based formats for multi-gas sensing and its applications.
Keywords: Interfaces; Nanoparticles; Gas-phase interactions; IHSAB; Nanostructures;

The influence of molybdenum disulfide nanoplatelets on the dispersion of nano silica in natural rubber composites by Peijin Weng; Qiuyan Wei; Zhenghai Tang; Tengfei Lin; Baochun Guo (782-789).
The dispersion of nanofiller in polymer composites is critical in governing the ultimate performances. Present study aimed to improve the dispersion of silica in elastomeric materials based on natural rubber (NR) composites using the nanoplatelets of molybdenum disulfide (MoS2), a graphene-like layered inorganic. NR latex was co-coagulated with MoS2 suspension to form NR/MoS2 compounds (1∼5 phr). Then silica (30 phr) was incorporated into NR/MoS2 compounds, followed by curing with sulfur, to obtained NR/MoS2/silica composites. The dispersion state of silica in the composites was examined by TEM and the effects of MoS2 on the performance of the composites were investigated. It was found that a small amount of MoS2 nanoplatelets significantly improved the silica dispersion. Consequently, the static and dynamic mechanical properties of the crosslinked natural rubber materials were greatly enhanced. The improved dispersion of silica is associated with charge transfer interaction, giving rise to electrostatic repulsion among silica.
Keywords: Nanocomposite; Silica; Molybdenum sulfide; Dispersion; Reinforcement; Dynamic property;

Deposition of adherent diamond films on cobalt-cemented tungsten carbide substrates has been realized by application of diamond/beta-silicon carbide composite interlayers. Diamond top layers and the interlayers were deposited in one single process by hot filament chemical vapor deposition technique. Two different kinds of interlayers have been employed, namely, gradient interlayer and interlayer with constant composition. The distribution of diamond and beta-silicon carbide phases was precisely controlled by manipulating the gas phase composition. X-ray diffraction and Raman spectroscopy were employed to determine the existence of diamond, beta-silicon carbide and cobalt silicides (Co2Si, CoSi) phases, as well as the quality of diamond crystal and the residual stress in the films. Rockwell-C indentation tests were carried out to evaluate the film adhesion. It is revealed that the adhesion of the diamond film is drastically improved by employing the interlayer. This is mainly influenced by the residual stress in the diamond top layer, which is induced by the different thermal expansion coefficient of the film and the substrate. It is even possible to further suppress the stress by manipulating the distribution of diamond and beta-silicon carbide in the interlayer. The most adhesive diamond film on cemented carbide is thus obtained by employing a gradient composite interlayer.
Keywords: Diamond/β-SiC composite; Interlayer; Diamond film; Adhesion; Residual stress; HFCVD;

Facile, soot free approach toward synthesis of carbon nanoropes via chemical vapor deposition of acetylene in the presence of MnFe2O4 coated on stainless steel by Vivek Dhand; S. Bharadwaj; K. Amareshwari; V. Himabindu; Kyong Yop Rhee; Soo-Jin Park; David Hui (797-804).
High density, soot free, novel and a facile approach toward synthesis of carbon nanoropes (CNRs) were successfully carried out in a chemical vapor deposition (CVD) process. Manganese ferrite (MnFe2O4) coated on stainless steel foil (SS 316 grade) was used as a catalyst to initiate the growth of CNR. The coated catalyst was introduced into the CVD and the chamber temperature was set at 700 °C later followed with the release of acetylene (50 sccm) and nitrogen (500 sccm) gas, respectively. Total reaction continued until 30 min. No purification or oxidation process of the soot was involved. Analysis reveals the presence of intermingled CNRs with semi crystalline nature of the sample. The elemental analysis confirms the presence of manganese and iron whereas Raman spectrum shows the characteristic narrow G and D bands. The sample displays a super-paramagnetic behavior and is thermally stable up to 500–550 °C presenting a strong exothermic reaction.
Keywords: Carbon nanorope; Chemical vapor deposition; Raman spectroscopy; Manganese ferrite; Super-paramagnetism;

An enhanced photoelectrochemical activity for water splitting was achieved over porous Ti-doped α-Fe2O3 nanocubes.Ti-doped α-Fe2O3 nanocubes on FTO substrate was prepared by hydrothermal deposition β-FeOOH onto FTO glass with a solution of FeCl3, TiOCl2 and NaF, followed by an appropriate annealing. In comparison to Ti-doped α-Fe2O3 nanorods Ti-doped α-Fe2O3 nanocubes showed an enhanced photoelectrochemical activity for water splitting, with a remarkable IPCE of 25.2% at 340 nm at the potential of 1.23 V vs. RHE. The hematite films were studied in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy and electrochemical impedance spectroscopy. On the basis of the obtained results, the improved performance of Ti-doped α-Fe2O3 nanocubes can be ascribed to the porous structure, good electrical conductivity and fast charge transportation of hematite.
Keywords: Hematite; NaF-assisted; Photoelectrochemical; Water splitting;

A facile strategy for generating dendrimers onto carbon fibers, in order to functionalize them, was reported. Dendrimers were propagated on the surface of carbon fibers by in situ polymerization with Michael addition. The changes in morphology, surface composition and surface energy, which were studied by atomic force microscope (AFM), dynamic contact angle analysis test (DCAT) and x-ray photoelectron microscopy (XPS), were related to the interfacial performance of model composites. In addition, the level of fiber-matrix adhesion was determined by the interlaminar shear strength (ILSS) test. Experimental results indicated that some dendritic polymer was successfully grown on the fiber surface through the chemical reaction, and this significantly enhanced the interfacial bonding of the carbon fiber composites.
Keywords: Carbon fiber; Mechanical properties; Interface/interphase; Surface treatments;

We investigate the effect of yttrium-doping on the microstructures and semiconductor-metal phase transition characteristics of polycrystalline VO2 thin films prepared by reactively co-sputtering process. XPS analyses indicate the existence of Y3+ in the Y-doped VO2 films, but Y-doping hardly influences the chemical states of V and O elements. X-ray diffraction patterns and Raman spectra reveal that both undoped and Y-doped VO2 thin films have a polycrystalline structure of monoclinic VO2. The introduction of Y greatly reduces the grain size of VO2 thin films as evidenced by scanning electron microscopy analyses. The relationship between the hysteresis width and doping level is not monotonic although the grain size is monotonically reduced with increasing the doping level. Y-doped VO2 films with optimal doping level (1.82 at%) have a notably narrower hysteresis width (4.6 °C) than undoped VO2 films (10.7 °C). This is ascribed to increased heterogeneous nucleation centers due to Y in the VO2 lattice. With the further increase of doping level, the size effect gradually plays a prominent role in SMPT, and the hysteresis width of Y-doped VO2 films increases instead. The SMPT temperature of Y-doped VO2 films obviously decreases compared with undoped VO2 films due to reduced grain size and deformation of local structure around Y atom.
Keywords: VO2 thin film; Polycrystalline; Microstructure; Semiconductor-metal phase transition; Yttrium doping;

Optical transparency, mechanical flexibility, and fast regeneration are important factors to expand the application of superhydrophobic surfaces. Herein, we fabricated highly transparent, stable, and superhydrophobic coatings through a novel gradient structure design by versatile dip-coating of silica colloid particles (SCPs) and diethoxydimethysiliane cross-linked silica nanoparticles (DDS-SNPs) on polyethylene terephthalate (PET) film and glass, followed by the modification of octadecyltrichlorosiliane (OTCS). When the DDS concentration reached 5 wt%, the modified SCPs/DDS-SNPs coating exhibited a water contact angle (WCA) of 153° and a sliding angle (SA) <5°. Besides, the average transmittance of this superhydrophobic coating on PET film and glass was increased by 2.7% and 1% in the visible wavelength, respectively. This superhydrophobic coating also showed good robustness and stability against water dropping impact, ultrasonic damage, and acid solution. Moreover, the superhydrophobic PET film after physical damage can quickly regain the superhydrophobicity by one-step spray regenerative solution of dodecyltrichlorosilane (DTCS) modified silica nanoparticles at room temperature. The demonstrated method for the preparation and regeneration of superhydrophobic coating is available for different substrates and large-scale production at room temperature.
Keywords: Superhydrophobic; Highly transparent; Gradient structure; Flexible substrate; Fast regeneration;

Metal organic framework derived magnetically separable 3-dimensional hierarchical Ni@C nanocomposites is a multifunctional adsorbent.Design an effective absorbent that has high surface area, and perfect recyclable is imperative for pollution elimination. Herein, we report a facile two-step strategy to fabricate magnetically separable 3-dimensional (3D) hierarchical carbon-coated nickel (Ni@C) nanocomposites by calcinating nickel based metal organic framework (Ni3(OH)2(C8H4O4)2(H2O)4). SEM and TEM images illuminate that the nanocomposites were constructed by 8 nm nickel nanoparticle encapsulated in 3D flake like carbon. The specific surface area of the obtained nanocomposites is up to 120.38 m2  g−1. Room temperature magnetic measurement indicates the nanocomposites show soft magnetism property, which endows the nanocomposites with an ideal fast magnetic separable property. The maximum adsorption capacity of the nanocomposites for rhodamine B is 84.5 mg g−1. Furthermore, the nanocomposites also exhibit a high adsorption capacity for heavy metal ions. The adsorbent can be very easily separated from the solution by using a common magnet without exterior energy. The as-prepared Ni@C nanocomposites can apply in waste water treatment on a large-scale as a new adsorbent with high efficiency and excellent recyclability.
Keywords: Metal organic framework; Ni@C nanocomposites; Adsorption;

Titanium doped tungsten oxide (Ti:WO3) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O2 atmosphere. Ti:WO3 thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10−3–5.0 × 10−3  mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm2) and tungsten (3 W/cm2) were kept constant. Ti:WO3 films deposited at an oxygen pressure of 5 × 10−3  mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ  = 550 nm), coloration efficiency (60 cm2/C at λ  = 550 nm), electron/ion storage and removal capacity (Qc: −22.01 mC/cm2, Qa: 17.72 mC/cm2), reversibility (80%) and methylene blue decomposition rate (−1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO3 films.
Keywords: Thin films; Sputtering; Oxides; Surfaces; Electrochemical properties; Catalytic properties;

The properties of gallium oxide thin film grown by pulsed laser deposition by Qian Feng; Fuguo Li; Bo Dai; Zhitai Jia; Wenlin Xie; Tong Xu; Xiaoli Lu; Xutang Tao; Jincheng Zhang; Yue Hao (847-852).
Ga2O3 films were deposited on MgAl6O10(1 0 0) substrates by means of pulsed laser deposition (PLD). The influence of oxygen pressure on crystal quality, surface morphology and transmittance were investigated by means of X-ray diffraction (XRD), atomic force microscope (AFM) and spectrophotometer. The results showed that the grain size increased, the surface roughness and FWHM of X-ray rocking curve reduced with the oxygen pressure decreasing. Furthermore, the photoluminescence spectra were recorded as a function of excitation power and temperature. A blue shift of the visible luminescence at higher excitation power was observed, indicating that donor–acceptor transitions were responsible for the visible emissions. The thermal quenching of the blue and green bands corresponded to the activation energies of 0.028 eV, 0.037 eV and 0.034 eV, respectively.
Keywords: Beta-Ga2O3; Epitaxy film; Optical transmittance; Photoluminescence;

Preparation of sensitive and recyclable porous Ag/TiO2 composite films for SERS detection by Zhengyi Zhang; Jiajie Yu; Jingying Yang; Xiang Lv; Tianhe Wang (853-859).
Porous Ag/TiO2 composite films were prepared by spin coating of titania on normal glass slides and subsequent photochemical deposition of silver nanoparticles (AgNPs). The films were characterized by XRD and FESEM to reveal micro structural and morphological differences between films obtained under varied conditions. The SERS properties of these films were investigated using aqueous crystal violet (CV) as probe molecules. The results indicate that the content of polyethylene glycol (PEG) and photo-reduction time had significant influences on both the microstructure and SERS performance of Ag/TiO2 films. The highest SERS sensitivity that allowed as low as 10−10  M aqueous CV to be detected, was achieved with the PEG/(C4H9O)4Ti molar ratio being 0.08% and with 30 min of UV irradiation. With this film a linear relationship was established through experiment between SERS intensity and CV concentration from 10−10 to 10−5  M, which could be used as a calibration curve for CV concentration measurement. In addition, the film could be reused as a SERS substrate for up to four times without significantly losing SERS sensitivity if a simple regeneration was followed. It is visualized that the Ag/TiO2 film on glass has potentials for being developed into a practical SERS substrate with high sensitivity and good reusability.
Keywords: Ag/TiO2 film; SERS; Crystal violet; Recyclability;

Improved liquid phase deposition of anatase TiO2 hollow microspheres with exposed {0 0 1} facets and their photocatalytic activity by Cai-Xia Lei; Xiao-Long Jiang; Xu Huang; Xiang Liu; De-Qian Zeng; Ya-Ting Ma; Lai-Sen Wang; Dong-Liang Peng (860-867).
An improved liquid phase deposition (LPD) method was developed to prepare the TiO2 microspheres with enhanced crystallinity in this study. The as-prepared samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nitrogen adsorption and desorption instrument, as well as the UV-Vis absorption spectroscopy. The results showed that the samples prepared at various precursor concentrations were identified as the well-crystalline anatase TiO2 exposed with reactive {0 0 1} facets, which was caused by the introduction of fluorine during the hydrolysis process of (NH4)2TiF6 precursor solution. Moreover, with increased concentration of precursor solution, the dissolution of {0 0 1} facets occurred and the typical hollow spherical structure was also found. The photocatalytic experiments revealed that the as-prepared anatase TiO2 microspheres exhibited an effective photocatalytic activity during the process of Rhodamine B (RhB) degradation.
Keywords: TiO2 microspheres; Photocatalytic activity; Liquid phase deposition;

Preparation and photocatalytic activity of TiO2-exfoliated graphite oxide composite using an ecofriendly graphite oxidation method by Vanessa Zanon Baldissarelli; Thiago de Souza; Luisa Andrade; Luiz Fernando Cappa de Oliveira; Humberto Jorge José; Regina de Fátima Peralta Muniz Moreira (868-874).
A simple and effective stepwise-method was developed to produce expanded exfoliated graphite oxide (EGO). Using a combination of ozone exposure and thermal treatment we demonstrate that a graphite surface can be modified to generate a graphene-like surface containing oxygen and sp3 carbon. This expanded exfoliated graphite oxide is useful for the production, through thermal treatment, of photocatalytic TiO2-EGO composites which are more active than those produce by the Hummers method. The photocatalytic activity of TiO2-EGO in methylene blue (MB) bleaching under UV light is enhanced in comparison with TiO2 P25.
Keywords: Exfoliated graphite oxide; Photocatalysis; TiO2; Composite; Methylene blue;

A simple and novel Si surface modification on LiFePO4@C electrode and its suppression of degradation of lithium ion batteries by Wenyu Yang; Zhenyuan Zhuang; Xiang Chen; Mingzhong Zou; Guiying Zhao; Qian Feng; Jiaxin Li; Yingbin Lin; Zhigao Huang (875-882).
A simple and novel surface modification device of the electrodes based on the ultrasonic spray technique was set up, which is considered to have the enormous prospect of industrial application due to its simpleness and high efficiency. Then, the nano-sized Si nanoparticles were deposited uniformly on the LiFePO4@C electrodes. In comparison with pristine LiFePO4@C electrode, the surface modification of the nano-sized Si with crystalline Si core and amorphous Si shell on the electrode surface exhibits less coarsening degree, higher rate capability, better cyclicity at high charge/discharge rate, especially at elevated temperature. Moreover, Raman spectra of LiFePO4@C, LiFePO4@C/Si electrodes before cycles and after 100 cycles at 1 C and 60 °C were measured. It is found that the FePO4 and α-Fe2O3 phases exist in LiFePO4@C after 100 cycles. On the contrary, there hardly exists the FePO4 and α-Fe2O3 phases, which means that the nano Si surface modification suppresses the degradation of lithium ion batteries. At last, the schematic and phenomenological resistance models of LiFePO4@C electrode modified by the nano-sized silicon particles have been suggested, which is responsible for the enhancement of the electrochemical performances after nano-sized Si surface modification.
Keywords: LiFePO4 cathode; Nano-sized Si surface modification; Lithium ion batteries; Ultrasonic spray;

Surface modification of mixed-phase hydrogenated TiO2 and corresponding photocatalytic response by Emy Marlina Samsudin; Sharifah Bee Abd Hamid; Joon Ching Juan; Wan Jefrey Basirun; Ahmad Esmaeiljadeh Kandjani (883-896).
Preparation of highly photo-activated TiO2 is achievable by hydrogenation at constant temperature and pressure, with controlled hydrogenation duration. The formation of surface disorders and Ti3+ is responsible for the color change from white unhydrogenated TiO2 to bluish-gray hydrogenated TiO2. This color change, together with increased oxygen vacancies and Ti3+ enhanced the solar light absorption from UV to infra-red region. Interestingly, no band gap narrowing is observed. The photocatalytic activity in the UV and visible region is controlled by Ti3+ and oxygen vacancies respectively. Both Ti3+ and oxygen vacancies increases the electron density on the catalyst surface thus facilitates •OH radicals formation. The lifespan of surface photo-excited electrons and holes are also sustained thus prevents charge carrier recombination. However, excessive amount of oxygen vacancies deteriorates the photocatalytic activity as it serves as charge traps. Hydrogenation of TiO2 also promotes the growth of active {0 0 1} facets and facilitates the photocatalytic activity by higher concentration of surface OH radicals. However, the growth of {0 0 1} facets is small and insignificant toward the overall photo-kinetics. This work also shows that larger role is played by Ti3+ and oxygen vacancies rather than the surface disorders created during the hydrogenation process. It also demonstrates the ability of hydrogenated TiO2 to absorb wider range of photons even though at a similar band gap as unhydrogenated TiO2. In addition, the photocatalytic activity is shown to be decreased for extended hydrogenation duration due to excessive catalyst growth and loss in the total surface area. Thus, a balance in the physico-chemical properties of hydrogenated TiO2 is crucial to enhance the photocatalytic activity by simply controlling the hydrogenation duration.
Keywords: TiO2; Hydrogenation; Defects; Photocatalysis; Atrazine;

Photophysical and adsorption properties of pyronin B in natural bentonite clay dispersion by Mohammad Reza Rostami; Mehmet Kaya; Bahri Gür; Yavuz Onganer; Kadem Meral (897-904).
The molecular aggregation of PyB in bentonite aqueous dispersion is observed by using molecular absorption spectrum.The present study focused on the adsorption and photophysical properties of pyronin B (PyB) in bentonite aqueous dispersion. The photophysical properties of PyB in the aqueous dispersion were studied by using UV–vis absorption, steady-state and time-resolved fluorescence spectroscopy techniques. In this concept, the interaction of the dye with bentonite particles in the aqueous dispersion was spectroscopically followed depending on certain parameters such as interaction time, pH and the dye concentration. Obtained spectral data revealed that the aggregate structures (H-type) of PyB in the aqueous dispersion were formed in the dye concentration range studied. The non-fluorescence nature of H-aggregates and the clay minerals governed the fluorescence property of PyB. The mentioned non-radiative processes caused the fluorescence lifetime of the dye to decrease compared to that in water. The adsorption process of PyB on bentonite was examined depending on contact time and initial adsorbate concentration. An adsorption isotherm was good-fitted by the Freundlich model with a linear regression correlation value of 0.999. The adsorption of PyB on bentonite particles was in agreement with pseudo second-order kinetics.
Keywords: H-aggregation; Time-resolved fluorescence; Xanthene dyes; Bentonite; Adsorption;

Fabrication of superhydrophobic textured steel surface for anti-corrosion and tribological properties by Hongmei Zhang; Jin Yang; Beibei Chen; Can Liu; Mingsuo Zhang; Changsheng Li (905-910).
We describe a simple and rapid method to fabricate superhydrophobic textured steel surface with excellent anti-corrosion and tribological properties on S45C steel substrate. The steel substrate was firstly ground using SiC sandpapers, and then polished using diamond paste to remove scratches. The polished steel was subsequently etched in a mixture of HF and H2O2 solution for 30 s at room temperature to obtain the textured steel surface with island-like protrusions, micro-pits, and nano-flakes. Meanwhile, to investigate the formation mechanism of the multiscale structures, the polished steel was immersed in a 3 wt% Nital solution for 5 s to observe the metallographic structures. The multiscale structures, along with low-surface-energy molecules, led to the steel surface that displayed superhydrophobicity with the contact angle of 158 ± 2° and the sliding angle of 3 ± 1°. The chemical stability and potentiodynamic polarization test indicated that the as-prepared superhydrophobic surface had excellent corrosion resistance that can provide effective protection for the steel substrate. The tribological test showed that the friction coefficient of the superhydrophobic surface maintained 0.11 within 6000 s and its superhydrophobicity had no obvious decrease after the abrasion test. The theoretical mechanism for the excellent anti-corrosion and tribological properties on the superhydrophobic surface were also analyzed respectively. The advantages of facile production, anti-corrosion, and tribological properties for the superhydrophobic steel surface make it to be a good candidate in practical applications.
Keywords: Superhydrophobic; Anti-corrosion; Tribological; Microstructure; Steel;

Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 h) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with ρ  = 0.51. The ratio of k p to k t, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.
Keywords: ATRP; Surface polymerization; Substituent effect and Hammett relation;

Facile synthesis of porous TiO2 photocatalysts using waste sludge as the template by Xiaopeng Wang; Shouqiang Huang; Nanwen Zhu; Ziyang Lou; Haiping Yuan (917-922).
Waste sludge is introduced to synthesize the waste sludge templated TiO2 photocatalyst with porous structure, which possesses better photocatalytic activity compared to pure TiO2.A resource utilization method of waste sludge is present by the synthesis of waste sludge templated TiO2 photocatalysts. The organic materials in waste sludge are used as the pore-forming agents, and the transition metals included in the remaining waste sludge through calcination (WSC) can serve as the dopants for the WSC-TiO2 (WSCT) photocatalyst. The visible and UV–visible light driven photocatalytic activities of WSCT are much better compared to those of pure TiO2 and WSC, and it is originated from the higher light absorption property and the efficient electron–hole pair separation provided by waste sludge.
Keywords: Waste sludge; TiO2; Dopants; Porous structure; Photocatalytic activities;

Ferroelectric properties of manganese doped (Bi1/2Na1/2)TiO3 and (Bi1/2Na1/2)TiO3–BaTiO3 epitaxial thin films by A. Gallegos-Melgar; D.G. Espinosa-Arbelaez; F.J. Flores-Ruiz; A. Lahmar; J.-L. Dellis; N. Lemée; F.J. Espinoza-Beltran; J. Muñoz-Saldaña (923-930).
The effects of Manganese doped (Bi1/2Na1/2)TiO3 and (Bi1/2Na1/2)TiO3–BaTiO3 epitaxial thin films on the structure, dielectric, ferroelectric and piezoelectric properties are reported. The thin films were grown by pulsed laser deposition on (Lao.5Sr0.5)CoO3 (LSCO) electrode LaAlO3 (LAO) substrates using homemade ceramic targets. The (La0.5Sr0.5)CoO3 (LSCO)/LaAlO3/system was chosen based on the adequate coupling conditions to grow high quality epitaxial films with desired properties. The dielectric and ferroelectric properties are all self-consistent to each other, despite the morphotropic phase boundary effect in Mn doped BNT-BT thin film. Even when remanent polarizations of 17 and 25 μC/cm2 from BNT-Mn and BNT-BT-Mn thin films were respectively obtained from well-defined PE hysteresis curves and the corresponding values of coercive field for BNT-Mn and BNT-BT-Mn thin films are 93 and 150 kV/cm, respectively, no significant changes are observed suggesting that the effect of MPB composition is not fully activated due to Mn additions. In the ceramics, the vibrational modes associated to Mn interactions with the oxygen octahedral were identified with Raman spectroscopy. Finally, the local piezoelectric constants (d 33) as measured by PFM are 60 and 124 pm/V for BNT-Mn and BNT-BT-Mn thin films, respectively. Thus, BNT-Mn and BNT-BT-Mn thin films are potential candidates to be used in lead-free piezoelectric devices.
Keywords: Bismuth; Lead-free thin film; Mn-doping; Piezoelectric properties; Ferroelectric properties;

The application of micro/nanostructured materials to combustion enables distinctive chemical reactions that can be used to modulate the reaction rates. Simultaneously, combustion is capable of changing the intrinsic properties of micro/nanostructured materials based on chemical interactions in high-temperature conditions. In this work, we investigate the structural–chemical transition of copper oxide microstructures exposed to interfacially driven combustion waves. The high thermal energy and exchange of chemical compounds resulting from the instant combustion waves cause direct transition without any further processes. The precise characterization of the structural and chemical transitions in the copper oxide microstructures and chemical fuels confirm that the self-propagating combustion waves in the layered composites of Cu/Cu2O/CuO microparticle-based films and the chemical fuel layers yield the direct synthesis of Cu(OH)2 flower-like structures and nanowires. The propagation of combustion waves at the interface induces an increase of the surface temperatures over 650 °C and the direct interaction between the copper oxide and chemical compounds of the fuel layers. Further application of these interfacially driven combustion waves will contribute to the development of one-step, fast, low-cost methods for the synthesis of micro/nanostructured materials.
Keywords: Combustion wave; Exothermic chemical reaction; Copper oxide; Combustion synthesis; Thermal transport;

Anodic aluminum oxide (AAO) is well known as an important nanostructured material, and a useful template in the fabrication of nanostructures. Nanoporous anodic alumina (PAA) with high open porosity was prepared by adopting three de-anodizing regimes following the first anodizing step and preceding the second one. The de-anodizing methods include electrolytic etching (EE) and chemical etching using either phosphoric acid (PE) or sodium hydroxide (HE) solutions. Three of the obtained AAO samples were black colored by electrodeposition of copper nanoparticles in their pores. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to characterize the electrochemical performance of the two sets of the prepared samples. In general, the data obtained in aggressive aerated 0.5 M HCl solution demonstrated dissimilar behavior for the three prepared samples despite that the second anodizing step was the same for all of them. The data indicated that the resistance and thickness of the inner barrier part of nano-PAA film, are the main controlling factors determining its stability. On the other hand, coloring the film decreased its stability due to the galvanic effect. The difference in the electrochemical behavior of the three colored samples was discussed based on the difference in both the pore size and thickness of the outer porous part of PAA film as supported by SEM, TEM and cross-sectional micrographs. These results can thus contribute for better engineering applications of nanoporous AAO.
Keywords: Nonporous AAO; Black colored films; Anodization; De-anodizing techniques; Electrochemical impedance spectroscopy;