Applied Surface Science (v.378, #C)

Poly(ethylene oxide)/clay nanaocomposites: Thermal and mechanical properties by Mehtap Ejder-Korucu; Ahmet Gürses; Semra Karaca (1-7).
Poly(ethylene oxide) (PEO)/clay nanocomposites were prepared by a solution intercalation method using chloroform as a solvent. The nanocomposites were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and also investigation of some mechanical properties of the composites. Formation of nanocomposite was confirmed by XRD analysis. The increasing tendency of exfoliation degree with an increase in clay content may be attributed to easier diffusion of PEO chains to interlayer regions. An increase in PEO crystallinity in case of nanocomposite, was confirmed by an increase in the heat of melting as indicated by DSC. Improvement in tensile properties in all respect was observed for nanocomposites with clay content.
Keywords: PEO; Nano composites; Organoclay; CTAB;

Display OmittedSeparation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO2) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet–visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.
Keywords: Silicon carbide-titanium dioxide nanocomposite; Dye sensitized solar cells; Photo-conversion; Pulsed laser ablation in liquid;

In situ growth of NixSy controlled by surface treatment of nickel foam as efficient electrocatalyst for oxygen evolution reaction by Xiao Shang; Xiao Li; Wen-Hui Hu; Bin Dong; Yan-Ru Liu; Guan-Qun Han; Yong-Ming Chai; Yun-Qi Liu; Chen-Guang Liu (15-21).
Display OmittedIn situ growth of NixSy with different crystal phases supported on different surface-treated (acidification or oxidation) nickel foam (NF) has been successfully achieved by a facile solvothermal process. XRD and SEM results show that crystal phase and morphology of NixSy have been greatly affected by the surface treatment of NF. XRD results show that the mixture crystal phases of NixSy have been obtained on both acid-treated NF (NF(a)) and oxidant treated NF (NF(o)). NixSy/NF(a) contains Ni3S2 and NiS, whereas NixSy/NF(o) has Ni3S2 and NiS2, implying different crystal phases derived from different surface treatment of NF. SEM images also reveal the different morphology of two samples based on pre-treatment support. NixSy/NF(a) displays unique conical agglomeration surrounded by porous structure. NixSy/NF(o) has the disorder stacking structure of nanosheets. Electrochemical measurements for oxygen evolution reaction (OER) show the enhanced performances of NixSy/NF(a) than NixSy/NF(o) and pure Ni3S2/NF as contrast samples, implying that NiS outperforms other types of NixSy. The mechanisms of sulfurization path of different surface-treated NF have been discussed. The facile surface treatment of NF may provide a new strategy to prepare excellent electrocatalysts for OER.
Keywords: Surface treatment; In situ growth; Crystal structure; Solvothermal process;

The PEGylated graphene oxides with high water dispersibility, good biocompatibility as well as high drug loading capability were fabricated via “one-pot” SET-LRPDisplay OmittedGraphene oxide (GO) based polymer nanocomposites have attracted extensive research interest recently for their outstanding physicochemical properties and potential applications. However, surface modification of GO with synthetic polymers has demonstrated to be trouble for most polymerization procedures are occurred under non-aqueous solution, which will in turn lead to the restacking of GO. In this work, a facile and efficient “one-pot” strategy has been developed for surface modification of GO with synthetic polymers through single-electron-transfer living radical polymerization (SET-LRP). The GO based polymer nanocomposites were obtained via SET-LRP in aqueous solution using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the monomer and 11-bromoundecanoic acid as the initiator, which could be effectively adsorbed on GO through hydrophobic interaction. The successful preparation of GO based polymer nanocomposites was confirmed by a series of characterization techniques such as 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The resultant products exhibit high water disperisibility, excellent biocompatibility and high efficient drug loading capability, making these PEGylated GO nanocomposites promising candidates for biomedical applications.
Keywords: Graphene oxide; Surface modification; Single-electron-transfer living radical polymerization; Polymer nanocomposites; Drug delivery;

Impact of temperature-induced coalescence on SERS properties of Au nanoparticles deposited on GaN nano-columns by Igor Dzięcielewski; Julita Smalc-Koziorowska; Małgorzata Bańkowska; Tomasz Sochacki; Alexandr Khachapuridze; Jan Weyher (30-36).
Display OmittedNanostructured GaN surfaces sputtered with Au provide very promising and reproducible platforms for surface enhanced Raman scattering (SERS). The enhancement factor (EF) in SERS is expected to depend strongly on the local metal (Au) surface structure (size, distribution and morphology). Herein we show how temperature-induced coalescence followed by recrystallization of Au on GaN nano-columns occurs well below the melting point of gold. This process is reflected in SEM, TEM images and SERS spectra of Au/GaN – bound p‐mercaptobenzoic acid (4-MBA), a model Raman scatterer. SERS signals of 4-MBA bound to Au/GaN reach minimum for platforms exposed to t = 350 °C before regaining the intensity when annealed in the range of 450–900 °C. The results have been discussed in the light of the nature of SERS active sites – so called “hot spots” and structure of Au nanoparticles.

The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO2 by radiolytic method by Marek Klein; Joanna Nadolna; Anna Gołąbiewska; Paweł Mazierski; Tomasz Klimczuk; Hynd Remita; Adriana Zaleska-Medynska (37-48).
Display OmittedTiO2 (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV–vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO2 co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15–30 nm) on TiO2 surface and enhances the Vis-induced activity of Ag/Pd-TiO2 up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV–vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for visible light photoactivity, whereas superoxide radicals (such as O2• and •OOH) are responsible for pollutants degradation over metal-TiO2 composites.
Keywords: TiO2; Bimetallic nanoparticle deposition; Noble metals; Toluene; Photocatalysis;

Display OmittedHollow-spherical composites of polyaniline/cobalt sulfide/carbon nanodots (PANI/CoS/CDs-0.5T) have been synthesized by in situ polymerization under an applied magnetic field (MF) of 0.5 T. As a control, PANI/CoS/CDs-0T composites have been synthesized without a MF. Both composites acting as electrodes present obvious magnetocapacitances at a scan rate of 100 mV s−1 while the electrochemical cell tested under an external MF of 0.5 T. Notably, PANI/CoS/CDs-0.5T composites show larger magnetocapacitances than PANI/CoS/CDs-0T composites at different scan rates from 5 to 100 mV s−1. Electrochemical impedance spectroscopy (EIS) results indicate that MF can reduce charge transfer resistance at electrode/electrolyte interface. More importantly, PANI/CoS/CDs-0.5T composites show a much stronger electromagnetic wave (EMW) absorbing capability than PANI/CoS/CDs-0T in the range of 2–18 GHz which is attributed to an increased dielectric loss and a magnetic loss in low frequency range of 2–12.5 GHz. MF-induced ferromagnetic nanodomains of Co2+ clusters in the PANI/CoS/CDs-0.5T composites increase the complex permittivity and create more interfacial polarizations or the Maxwell–Wagner effect, which leads to increased dielectric loss. Compared with PANI/CoS/CDs-0T composites with diamagnetic behaviour, MF-induced weak ferromagnetism of CoS in the PANI/CoS/CDs-0.5T composites has caused additional magnetic loss. This work provides an efficient way for modulating electrochemical or electromagnetic properties of inorganic/polymer nanocomposites by employing an external MF.
Keywords: Polyaniline; Elelctromagnetic wave absorption; Magnetocapacitance; Magnetic field; Hollow-spherical;

Molecular dynamics study of nanojoining between axially positioned Ag nanowires by Jianlei Cui; Barayavuga Theogene; Xuewen Wang; Xuesong Mei; Wenjun Wang; Kedian Wang (57-62).
The miniaturization of electronics devices into nanometer scale is indispensable for next-generation semiconductor technology. Ag nanowires (Ag NWs) are considered to be the promising candidates for future electronic circuit owing to the excellent electrical and thermal properties. The nanojoining of axially positioned Ag NWs was performed by molecular dynamics simulation. Through the detailed atomic evolution during the nanojoining, the results indicate that the temperature and the distance between Ag NWs in axial direction have a great impact on nanojoining effect. When the nanojoining temperature is relatively high, the atoms are disordered and the atomic queues become to distort with strong thermodynamic properties and weak effect of metal bonds. At the relatively low temperature, the Ag NWs can be well connected with good junction quality and their own morphology, which is similar to the cold welding without fusion, while the distance between Ag NWs should be controlled for interaction and diffusion of interfacial atoms at nanowires head. When the Ag NWs are placed on Si and SiO2 substrate, because the atomic species and lattice structure of substrate material can differently affect the motions of Ag atoms through the interactive force between the atoms, the nanojoining quality of Ag NWs on Si substrate is better than that on the SiO2 substrate. So, for getting effective and reliable nanojoining without nanosolders and other materials, the temperature, distance and substrate surface should be reasonably controlled and selected, providing helpful theoretical guidance for experiment and application of nanojoining.
Keywords: Nanojoining; Ag nanowires; Atomic configuration; Molecular dynamics;

Tuning surface porosity on vanadium surface by low energy He+ ion irradiation by J.K. Tripathi; T.J. Novakowski; A. Hassanein (63-72).
In the present study, we report on tuning the surface porosity on vanadium surfaces using high-flux, low-energy He+ ion irradiation as function of sample temperature. Polished, mirror-finished vanadium samples were irradiated with 100 eV He+ ions at a constant ion-flux of 7.2 × 1020  ions m−2  s−1 for 1 h duration at constant sample temperatures in the wide range of 823–1173 K. Our results show that the surface porosity of V2O5 (naturally oxidized vanadium porous structure, after taking out from UHV) is strongly correlated to the sample temperature and is highly tunable. In fact, the surface porosity significantly increases with reducing sample temperature and reaches up to ∼87%. Optical reflectivity on these highly porous V2O5 surfaces show ∼0% optical reflectivity at 670 nm wavelength, which is very similar to that of “black metal”. Combined with the naturally high melting point of V2O5, this very low optical reflectivity suggests potential application in solar power concentration technology. Additionally, this top-down approach guarantees relatively good contact between the different crystallites and avoids electrical conductivity limitations (if required). Since V2O5 is naturally a potential photocatalytic material, the resulting sub-micron-sized cube-shaped porous structures could be used in solar water splitting for hydrogen production in energy applications.
Keywords: Plasma facing and solar materials; Vanadium; Surface porosity; Ion irradiation; Atomic force microscopy; X-ray photoelectron spectroscopy; Optical reflectivity;

Display OmittedThe effect of temperature, humidity and incident UV light on the photocatalytic activity of two TiO2 films with different microstructures (dense and mesoporous) was explored in terms of stearic acid degradation. Previous works reported in the literature suggest that the activity of TiO2 films does not only depend on single factors but also on interactions between them. Hence, the design of experiments (DoE) approach was used in this work to plan the experiments in a systematic way, simultaneously considering several variables. This approach provided an efficient working strategy to explore both individual and interaction effects on the photocatalytic activity of the films. The statistical evidence found here revealed that single factors temperature and mesoporous microstructure have the strongest positive effect on the efficiency of the films. In the case of temperature, this was explained by easier degradation and/or desorption of reaction intermediates. On the other hand, the positive effect of the mesoporous microstructure was correlated with its large surface area. An interaction factor between temperature and incident UV light also affects the activity of the films. Results suggest that this phenomenon depends of the degree of film hydration before the deposition of SA.
Keywords: Titanium dioxide; Dense; Mesoporous; Design of experiments; Interaction factor; Water;

Facile synthesis of Fe3O4-graphene@mesoporous SiO2 nanocomposites for efficient removal of Methylene Blue by Xi-Lin Wu; Yanpeng Shi; Shuxian Zhong; Hongjun Lin; Jian-Rong Chen (80-86).
Display OmittedHerein, we have developed a facile and low-cost method for the synthesis of novel graphene based nanosorbents. Firstly, well-defined Fe3O4 nanoparticles were decorated onto graphene sheets, and then a layer of mesoporous SiO2 were deposited on the surface of the Fe3O4-graphene composites. The obtained Fe3O4-graphene@mesoporous SiO2 nanocomposites (denoted as MG@m-SiO2) were characterized by scanning electron microscopic (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The adsorptive property was investigated by using MG@m-SiO2 as sorbents and Methylene Blue (MB), a common dye, as model of the organic pollutants. Adsorption kinetics, isotherms, thermodynamics as well as effects of pH and adsorbent dose on the adsorption were studied. The adsorption isotherms and kinetics are better described by Langmuir isotherm model and pseudo-second-order kinetic model, respectively. Thermodynamic studies suggest that the adsorption of MB onto the MG@m-SiO2 is endothermic and spontaneous process. The results imply that the MG@m-SiO2 can be served as a cost-effective adsorbent for the removal of organic pollutants from aqueous solutions.
Keywords: Magnetic graphene; Composites; Adsorption; Methylene blue;

Display OmittedNew theoretical model describing the sampling depth of elastic peak electron spectroscopy (EPES) has been proposed. Surface sensitivity of this technique can be generally identified with the maximum depth reached by trajectories of elastically backscattered electrons. A parameter called the penetration depth distribution function (PDDF) has been proposed for this description. Two further parameters are descendant from this definition: the mean penetration depth (MPD) and the information depth (ID). From the proposed theory, relatively simple analytical expressions describing the above parameters can be derived. Although the Monte Carlo simulations can be effectively used to estimate the sampling depth of EPES, this approach may require a considerable amount of computations. In contrast, the analytical model proposed here (AN) is very fast and provides the parameters PDDF, MPD and ID that very well compare with results of MC simulations. As follows from detailed comparisons performed for four elements (Al, Ni, Pd and Au), the AN model practically reproduced complicated emission angle dependences of the MPDs and the IDs, correctly indicating numerous maximum and minimum positions. In the energy range from 200 eV to 5 keV, the averaged percentage differences between MPDs obtained from the MC and the AN models were close to 4%. An important conclusion resulting from the present studies refers to the procedure of determination of the inelastic mean free path (IMFP) from EPES. Frequently, the analyzed sample is deposited as a thin overlayer on a smooth substrate. From an analysis of the presently obtained IDs, is follows that 99% of trajectories in analyzed experimental configurations reaches depth not exceeding 2.39 in units of IMFP. Thus, one can postulate that a safe minimum thickness of an overlayer should be larger than about 3 IMFPs. For example, the minimum thickness of an Al overlayer shoud be about 8 nm at 5000 eV.
Keywords: Theory of electron transport in solids; Monte Carlo simulations; Penetration depth of backscattered electrons; Inelastic mean free path;

Spatter generated during laser irradiation of an aluminium alloy nanocomposite (AlMg5 reinforced with Al2O3 nanoparticles) was monitored by high speed imaging. Droplets trajectory and speed were assessed by computerized image analysis. The effects of laser peak power and laser focusing on the plume expansion and expulsed droplet speeds were studied in air or under argon flow. It was found that the velocity of visible droplets expulsed laterally or at the end of the plume emission from the metal surface was not dependent on the plasma plume speed. The neighbouring area of irradiation sites was studied by optical and scanning electron microscopy. Droplets deposited on the surface were classified according to their size and counted using a digital image processing software. It was observed that the number of droplets on surface was 1.5–3 times higher when the laser beam was focused in depth as compared to focused beams, even though the populations average diameter were comparable. Three methods were selected for removing droplets in situ, during plume expansion: an argon gas jet crossing the plasma plume, a fused silica plate collector transparent to the laser wavelength placed parallel to the irradiated surface and a mask placed onto the aluminium composite surface. The argon gas jet was efficient only for low power irradiation conditions, the fused silica plate failed in all tested conditions and the mask was successful for all irradiation regimes.
Keywords: Aluminium composite; Laser ablation; Spatter; High speed imaging;

Structural and magnetic studies of thin Fe57 films formed by ion beam assisted deposition by N.M. Lyadov; V.V. Bazarov; F.G. Vagizov; I.R. Vakhitov; E.N. Dulov; R.N. Kashapov; A.I. Noskov; R.I. Khaibullin; V.A. Shustov; I.A. Faizrakhmanov (114-119).
Thin Fe57 films with the thickness of 120 nm have been prepared on glass substrates by using the ion-beam-assisted deposition technique. X-ray diffraction, electron microdiffraction and Mössbauer spectroscopy studies have shown that as-deposited films are in a stressful nanostructured state containing the nanoscaled inclusions of α-phase iron with the size of ∼10 nm. Room temperature in-plane and out-of-plane magnetization measurements confirmed the presence of the magnetic α-phase in the iron film and indicated the strong effect of residual stresses on magnetic properties of the film as well. Subsequent thermal annealing of iron films in vacuum at the temperature of 450 °C stimulates the growth of α-phase Fe crystallites with the size of up to 20 nm. However, electron microdiffraction and Mössbauer spectroscopic data have shown the partial oxidation and carbonization of the iron film during annealing. The stress disappeared after annealing of the film. The magnetic behaviour of the annealed samples was characterized by the magnetic hysteresis loop with the coercive field of ∼10 mT and the saturation magnetization decreased slightly in comparison with the α-phase Fe magnetization due to small oxidation of the film.
Keywords: IBAD technique; Nano crystalline iron films; Structure; Magnetic properties; Out-of-plane magnetic anisotropy;

Evolution and mechanism of the periodical structures formed on Ti plate under femtosecond laser irradiation by Dong Liu; Chuansong Chen; Baoyuan Man; Xue Meng; Yanna Sun; Feifei Li (120-129).
This work investigates the femtosencond laser (fs-laser) induced periodical surface structures (FLIPSS) on titanium plate including the concentric rings, microgrooves and subwavelength ripples. The evolution of the three types of the structures at different laser fluence and shot number is investigated experimentally in detail. The competition mechanisms exist among the different FLIPSS. A processing window for each resulting FLIPSS is obtained. In order to give an overall understanding of the FLIPSS, the formation mechanisms of each type of FLIPSS are discussed. The formation of the ripples is well explained by the propagating of the surface plasma wave (SPW) on the air/Ti interface. The evolutions of the ripple distribution are well understood according to this model as well. It is concluded that the interaction of the scattered wave of the laser light with the surface wave is concluded to give rise to the microgroove structure. According to our observation, the shape of the concentric rings does not change with the variation of the laser fluence and pulse number. The structure could be originated from the optical interference between the transmitted and reflected laser beams by the two surfaces of the biconvex lens. This investigation could not only make a further understanding of the formations of FLIPSS but also provide the possibility to control the surface morphologies in laser processing.
Keywords: Laser induced periodic surface structures; Laser processing window; Ripples; Surface plasma wave;

Display OmittedEffects of catalyst concentration and ultraviolet intensity on chemical mechanical polishing (CMP) of GaN were deeply investigated in this paper. Working as an ideal homogeneous substrate material in LED industry, GaN ought to be equipped with a smooth and flat surface. Taking the strong chemical stability of GaN into account, photocatalytic oxidation technology was adopted in GaN CMP process to realize efficient removal. It was found that, because of the improved reaction rate of photocatalytic oxidation, GaN material removal rate (MRR) increases by a certain extent with catalyst concentration increasing. Cross single line analysis on the surface after polishing by Phase Shift MicroXAM-3D was carried out to prove the better removal effect with higher catalyst concentration. Ultraviolet intensity field in H2O2-SiO2-based polishing system was established and simulated, revealing the variation trend of ultraviolet intensity around the outlet of the slurry. It could be concluded that, owing to the higher planarization efficiency and lower energy damage, the UV lamp of 125 W is the most appropriate lamp in this system. Based on the analysis, defects removal model of this work was proposed to describe the effects of higher catalyst concentration and higher power of UV lamp.
Keywords: GaN; Chemical mechanical polishing; Catalyst concentration; Photocatalytic oxidation; Ultraviolet intensity;

Micro-oxidation treatment to improve bonding strength of Sr and Na co-substituted hydroxyapatite coatings for carbon/carbon composites by Leilei Zhang; Hejun Li; Kezhi Li; Yulei Zhang; Shoujie Liu; Qian Guo; Shaoxian Li (136-141).
To improve the bonding strength of Sr and Na co-substituted hydroxyapatite (SNH) coatings for carbon/carbon composites, carbon/carbon composites are surface modified by micro-oxidation treatment. The micro-oxidation treatment could generate large number of pores containing oxygenic functional groups on the surface of carbon/carbon composites. SNH is nucleated on the inwall of the pores and form a flaky shape coating with 10–50 nm in thickness and 200–900 nm in width. The bonding strength between SNH coating and carbon/carbon composites increases from 4.27 ± 0.26 MPa to 10.57 ± 0.38 MPa after the micro-oxidation treatment. The promotion of bonding strength is mainly attributed to the pinning effect caused by the pores and chemical bonding generated by the oxygenic functional groups.
Keywords: Hydroxyapatite; Carbon/carbon composites; Micro-oxidation; Electrodeposition;

Wear behavior and microstructure of hypereutectic Al-Si alloys prepared by selective laser melting by Nan Kang; Pierre Coddet; Hanlin Liao; Tiphaine Baur; Christian Coddet (142-149).
Display OmittedThis work investigates the microstructure and wear behavior of hypereutectic Al-Si alloys, in-situ fabricated using selective laser melting of a mixture of eutectic Al-12Si (wt.%) and pure Si powders. The first observation was that the size and morphology of the Si phase are strongly influenced by the laser power. In addition, it was also observed that a high laser power causes serious evaporation of aluminum during the remelting process. Dry sliding wear test and Vickers microhardness measurements were employed to characterize the mechanical properties of the material. The lowest wear rate of about 7.0 × 10−4  mm3  N−1  m−1 was observed for samples having the highest value of relative density (96%) and microhardness (105 Hv0.3).
Keywords: Hypereutectic Al-Si alloy; Microstructure; Wear behavior; Selective laser melting;

In-rich In x Al1−x N thin films were deposited on quartz substrate at various nitrogen flow rates by plasma-assisted dual source reactive evaporation technique. The elemental composition, surface morphology, structural and optical properties of the films were investigated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray diffraction (XRD), UV–vis spectrophotometer and photoluminescence (PL) measurements. XPS results revealed that the indium composition (x) of the In x Al1−x N films increases from 0.90 to 0.97 as the nitrogen flow rate is increased from 40 to 100 sccm, respectively. FESEM images of the surface and cross-sectional microstructure of the In x Al1−x N films showed that by increasing the N2 flow rate, the grown particles are highly agglomerated. Raman and XRD results indicated that by increasing nitrogen flow rate the In-rich In x Al1−x N films tend to turn into amorphous state. It was found that band gap energy of the films are in the range of 0.90–1.17 eV which is desirable for the application of full spectra solar cells.
Keywords: In x Al1−x N; Plasma-assisted deposition; Raman spectra; Band gap;

Nanofrictional behavior of amorphous, polycrystalline and textured Y-Cr-O films by J.J. Gervacio-Arciniega; F.J. Flores-Ruiz; C.J. Diliegros-Godines; E. Broitman; C.I. Enriquez-Flores; F.J. Espinoza-Beltrán; J. Siqueiros; M.P. Cruz (157-162).
Differences in friction coefficients (μ) of ferroelectric YCrO3, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB® software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO3 film deposited on a Pt(150 nm)/TiO2(30 nm)/SiO2/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO3 (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO3 films seem to be the best candidates due to their lower μ.
Keywords: Friction; Ferroelectrics; AFM; Lead-free;

Direct evidence of reactive ion etching induced damages in Ge2Sb2Te5 based on different halogen plasmas by Juntao Li; Yangyang Xia; Bo Liu; Gaoming Feng; Zhitang Song; Dan Gao; Zhen Xu; Weiwei Wang; Yipeng Chan; Songlin Feng (163-166).
Display OmittedThe work we did was used to investigate the reactive ion etching (RIE) induced damages in Ge2Sb2Te5 (GST) based on different halogen plasmas (CF4, Cl2 and HBr). The figure showed here revealed the cross-sectional TEM images of the patterned GST samples: (a) Cl2-based plasma, (b) CF4-based plasma, (c) HBr-based plasma. The (b) and (c) show the cross section of TEM images for GST lines etched by CF4 and HBr gases. The etching sidewalls are both vertical and smooth with CF4 and HBr gases. However, it can be founded that an obvious damaged layer was observed near the boundary of sidewall in CF4 etched sample, which can be attributed to the high reactivity of F and its penetrability.Chalcogenide glasses based on Ge-Te-Sb are processed using reactive ion etching (RIE) in the fabrication of phase change memory (PCM). These materials are known to be halogenated easily and apt to be damaged when exposed to halogen gas based plasmas which can cause severe halogenation-induced degradation. In this paper, we investigate the RIE induced damage of popular phase change material Ge2Sb2Te5 (GST) in different halogen based plasmas (CF4, Cl2 and HBr) highly diluted by argon. After blanket etching, results of scanning electron microscopy and atomic force microscopy directly showed that the surface of Cl2 etched samples were roughest with a Ge deficient damaged layer. X-ray photoelectron spectroscopy was performed to investigate the chemical shift of constituent elements. Selected scans over the valence band peaks of Te 3d revealed that electrons were transferred from chalcogenide to halogen and the highest halogenation was observed on the GST etched by CF4. The GST films masked with patterned TiN were also etched. High-resolution transmission electron microscopy and surface scan directly showed the line profile and the damaged layer. Almost vertical and smooth sidewall without damaged layer makes HBr a promising gas for GST etch in the fabrication of high-density memory devices.
Keywords: Ge2Sb2Te5; Reactive ion etching; Etch damage; Phase change memory;

Display OmittedA series of Mn-Ce/TiO2 catalysts were synthesized through an impregnation method and used for low temperature selective catalytic reduction (SCR) of NOx with ammonia (NH3). Na2SO4 was added into the catalyst to simulate the combined effects of alkali metal and SO2 in the flue gas. Experimental results showed that Na2SO4 had strong and fluctuant influence on the activity of Mn-Ce/TiO2, because the effect of Na2SO4 included pore occlusion and sulfation effect simultaneously. When Na2SO4 loading content increased from 0 to 1 wt.%, the SCR activities of Na2SO4-doped catalysts decreased greatly. With further increasing amount of Na2SO4, however, the catalytic activity increased gradually. XRD results showed that Na2SO4 doping could induce the crystallization of MnOx phases, which were also confirmed by TEM and SEM results. BET results showed that the surface areas decreased and a new bimodal mesoporous structure formed gradually with the increasing amount of Na2SO4. XPS results indicated that part of Ce4+ and Mn3+ were transferred to Ce3+ and Mn4+ due to the sulfation after Na2SO4 deposition on the surface of the catalysts. When the doped amounts of Na2SO4 increased, NH3-TPD results showed that the Lewis acid sites decreased and the Brønsted acid sites of Mn-Ce/TiO2 increased quickly, which could be considered as another reason for the observed changes in the catalytic activity. The decreased Mn and Ce atomic concentration, the changes of their oxidative states, and the variation in acidic properties on the surface of Na2SO4-doped catalysts could be the reasons for the fluctuant changes of the catalytic activity.
Keywords: Low temperature SCR; Mn-Ce/TiO2; Alkali metal; SO2; Deactivation;

An efficient hydrothermal method was used to fabricate the superparamagnetic and red luminescent bifunctional Fe3O4@Mn2(*)+-doped NaYF4:Yb/Er nanoparticles (NPs) with core@shell structures through a seed-growth procedure. Then using PEG phosphate ligand to displace oleate from the as-synthesized NPs, hydrophilic Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs with good water solubility are obtained.Display OmittedWe report the use of an efficient hydrothermal method to synthesize superparamagnetic and red luminescent bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er nanoparticles (NPs) with core@shell structures via a seed-growth procedure. Oleic acid coated Fe3O4 (OA-Fe3O4) NPs were initially synthesized using a coprecipitation method. The as-synthesized OA-Fe3O4 NPs were then used as seeds, on which the red upconversion luminescent shell (Mn2+-doped NaYF4:Yb/Er) was formed. Furthermore, hydrophobic to hydrophilic surface modification of the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs was achieved via a ligand exchange method where oleic acid was displaced by a PEG phosphate ligand [PEG = poly(ethylene glycol)]. These materials were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). The Fe3O4 cores were uniformly coated with a Mn2+-doped NaYF4:Yb/Er shell, and the bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs were monodispersed. Furthermore, the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs exhibited a saturated magnetization value of 6.2 emu/g and emitted red luminescence under a 980 nm laser. The obtained bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs may find potential applications in drug targeting, bioseparation, and diagnostic analysis. The synthetic method may be employed for the preparation of other bifunctional nanomaterials.
Keywords: Fe3O4; NaYF4:Yb/Er; Upconversion luminescence; Mn2+ doping; Core@shell structure;

Display OmittedThis study reported the improved Raman enhancement ability of silver nanoparticles (Ag NPs) decorated on surface mesoporous silica microspheres (MSiO2@Ag) than that of Ag NPs on solid silica microspheres (SSiO2@Ag). These two kinds of hybrid structures were prepared by a facile single-step hydrothermal reaction with polyvinylpyrrolidone (PVP) serves as both a reductant and stabilizer. The as-synthesized MSiO2@Ag microspheres show more significant surface-enhanced Raman scattering (SERS) activity for 4-mercaptobenzoic acid (4MBA) than SSiO2@Ag microspheres with enhancement factors as 9.20 × 106 and 4.39 × 106, respectively. The proposed reason for the higher SERS activity is estimated to be the contribution of more Raman probe molecules at the mesoporous channels where an enhanced electromagnetic field exists. Such a field was identified by theoretical calculation result. The MSiO2@Ag microspheres were eventually demonstrated for the SERS detection of a typical chemical toxin namely methyl parathion with a detection limit as low as 1 × 10−3  ppm, showing its promising potential in biosensor application.
Keywords: Silver nanoparticles; Mesoporous silica; Surface plasmon resonance; SERS;

Structure analysis of bimetallic Co–Au nanoparticles formed by sequential ion implantation by Hua-jian Chen; Yu-hua Wang; Xiao-jian Zhang; Shu-peng Song; Hong chen; Ke Zhang; Zu-zhao Xiong; Ling-ling Ji; Hou-mei Dai; Deng-jing Wang; Jian-duo Lu; Ru-wu Wang; Li-rong Zheng (191-195).
Co–Au alloy Metallic nanoparticles (MNPs) are formed by sequential ion implantation of Co and Au into silica glass at room temperature. The ion ranges of Au ions implantation process have been displayed to show the ion distribution. We have used the atomic force microscopy (AFM) and transmission electron microscopy (TEM) to investigate the formation of bimetallic nanoparticles. The extended X-ray absorption fine structure (EXAFS) has been used to study the local structural information of bimetallic nanoparticles. With the increase of Au ion implantation, the local environments of Co ions are changed enormously. Hence, three oscillations, respectively, Co–O, Co–Co and Co–Au coordination are determined.
Keywords: Nanomaterials; Microstructure; X-ray techniques;

A facile strategy for fabrication of nano-ZnO/yeast composites and their adsorption mechanism towards lead (II) ions by Wei Zhang; Lingyin Meng; Guiqin Mu; Maojun Zhao; Ping Zou; Yunsong Zhang (196-206).
Nano-ZnO/yeast composites were successfully fabricated by one-step alkali hydrothermal method, and their adsorption properties for Pb2+ ions were also evaluated. Various influencing parameters of nano-ZnO/yeast composites, such as initial pH, contact time and initial Pb2+ concentration were investigated, respectively. The maximum adsorption capacity of nano-ZnO/yeast composites for Pb2+ (31.72 mg g−1) is 2.03 times higher than that of pristine yeast (15.63 mg g−1). The adsorption mechanism of nano-ZnO/yeast composites was studied by a series of techniques. Scanning electron microscopy (SEM) showed that nano-ZnO is evenly deposited on yeast surface. Atomic force microscopy (AFM) analysis exhibited that the yeast surface is rougher than that of pristine yeast. Energy dispersive X-ray detector (EDX) and X-ray diffraction (XRD) indicated the existence of nano-ZnO on yeast surface. Additionally, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) measurements further illustrated that alkali hydrothermal method causes not only the generation and anchorage of nano-ZnO on yeast surface but also the exposure of more functional groups (such as amino, carboxyl groups etc.) on yeast surface, both of which could adsorb Pb2+ via synergistic effect.
Keywords: Hydrothermal method; Nano-ZnO; Yeast; Pb2+; Synergistic effect;

Synthesis by anodic-spark deposition of Ca- and P-containing films on pure titanium and their biological response by Oksana Banakh; Tony Journot; Pierre-Antoine Gay; Joël Matthey; Catherine Csefalvay; Oleg Kalinichenko; Olha Sereda; Mira Moussa; Stéphane Durual; Lyubov Snizhko (207-215).
The purpose of this work is to characterize the anodized layers formed on titanium by anodic-spark deposition in an electrolyte containing Ca and P ions, Ca3(PO4)2, studied for the first time. The oxidation experiments were performed at different periods of time and using different concentrations of electrolyte. The influence of the process parameters (time of electrolysis and electrolyte concentration) on the surface morphology and chemical composition of the anodized layers was studied. It has been found that it is possible to incorporate Ca and P into the growing layer. A response of the anodized layers in a biological medium was evaluated by their immersion in a simulated body fluid. An enrichment of titanium and a simultaneous loss of calcium and phosphorus in the layer after immersion tests indicate that these coatings should be bioresorbable in a biological medium. Preliminary biological assays were performed on some anodized layers in order to assess their biocompatibility with osteoblast cells. The cell proliferation on one selected anodized sample was assessed up to 21 days after seeding. The preliminary results suggest excellent biocompatibility properties of anodized coatings.
Keywords: Titanium; Calcium-phosphate coating; Anodization; Anodic-spark deposition; SBF test;

Cerium, gallium and zinc containing mesoporous bioactive glass coating deposited on titanium alloy by S. Shruti; F. Andreatta; E. Furlani; E. Marin; S. Maschio; L. Fedrizzi (216-223).
Display OmittedSurface modification is one of the methods for improving the performance of medical implants in biological environment. In this study, cerium, gallium and zinc substituted 80%SiO2-15%CaO-5%P2O5 mesoporous bioactive glass (MBG) in combination with polycaprolactone (PCL) were coated over Ti6Al4 V substrates by dip-coating method in order to obtain an inorganic—organic hybrid coating (MBG-PCL). Structural characterization was performed using XRD, nitrogen adsorption, SEM-EDXS, FTIR. The MBG-PCL coating uniformly covered the substrate with the thickness found to be more than 1 μm. Glass and polymer phases were detected in the coating along with the presence of biologically potent elements cerium, gallium and zinc. In addition, in vitro bioactivity was investigated by soaking the coated samples in simulated body fluid (SBF) for up to 30 days at 37 °C. The apatite-like layer was monitored by FTIR, SEM-EDXS and ICP measurements and it formed in all the samples within 15 days except zinc samples. In this way, an attempt was made to develop a new biomaterial with improved in vitro bioactive response due to bioactive glass coating and good mechanical strength of Ti6Al4 V alloy along with inherent biological properties of cerium, gallium and zinc.
Keywords: Mesoporous bioactive glass with Ce2O3; Ga2O3 or ZnO; Ti6Al4 V substrate; Polycaprolactone; Dip coating; In vitro bioactivity;

Hot corrosion behavior of Ni based Inconel 617 and Inconel 738 superalloys by G.A. El-Awadi; S. Abdel-Samad; Ezzat S. Elshazly (224-230).
Superalloys are extensively used at high temperature applications due to their good oxidation and corrosion resistance properties in addition to their high stability were made at high temperature. Experimental measurements of hot corrosion at high temperature of Inconel 617 and Inconel 738 superalloys. The experiments were carried out at temperatures 700 °C, 800 °C and 900 °C for different exposure times to up to 100 h. The corrosive media was NaCl and Na2SO4 sprayed on the specimens. Seven different specimens were used at each temperature. The corrosion process is endothermic and the spontaneity increased by increasing temperature. The activation energy was found to be Ea = 23.54 and Ea  = 25.18 KJ/mol for Inconel 738 and Inconel 617 respectively. X-ray diffraction technique (XRD) was used to analyze the formed scale. The morphology of the specimen and scale were examined by scanning electron microscopy (SEM). The results show that the major corrosion products formed were NiCr2O4, and Co Cr2O4 spinles, in addition to Cr2O3.
Keywords: Ni-super alloys; Hot corrosion; Oxidation;

Facile synthesis of well-dispersed Bi2S3 nanoparticles on reduced graphene oxide and enhanced photocatalytic activity by Yajie Chen; Guohui Tian; Guijie Mao; Rong Li; Yuting Xiao; Taoran Han (231-238).
Display OmittedHere we present a facile method for the synthesis of highly dispersed Bi2S3 nanoparticles (Bi2S3 NPs) with an average diameter of ca. 25 ± 3 nm on the surface of reduced graphene oxide (RGO) via a poly(sodium-p-styrenesul-fonate) (PSS) asisted hydrothermal process. Such synthetic strategy can avoid excess aggregates of Bi2S3 nanoparticles, meanwhile from effective interfacial contact between Bi2S3 nanoparticles and RGO nanosheets, and inhibit the recombination of photogenerated charges. The enhanced charge transfer properties were proved by photoluminescence (PL) measurement. The obtained Bi2S3 NPs/RGO composites showed more significant visible light photoactivity for the degradation of 2,4-dichlorophenol and Rhodamine B than that pure Bi2S3 and the control sample prepared in the absence of PSS. The enhanced photocatalytic performance could be attributed to the synergistic effect of efficient separation of photogenerated electron-hole pairs, increased catalytic active sites and visible light utilization.
Keywords: Bi2S3; Reduced graphene oxide; Visible light photocatalysis; Synergistic effect;

Effect of a novel chelating agent on defect removal during post-CMP cleaning by Jiao Hong; Xinhuan Niu; Yuling Liu; Yangang He; Baoguo Zhang; Juan Wang; Liying Han; Chenqi Yan; Jin Zhang (239-244).
Chemical mechanical polishing (CMP) has become widely accepted for the planarization of device interconnect structures in deep submicron semiconductor manufacturing. However, during CMP process the foreign particles, metal contaminants, and other chemical components are introduced onto the wafer surface, so CMP process is considered as one of the dirtiest process to wafer surface defects which may damage the GLSI patterns and the metallic impurities can induce many crystal defects in wafers during the following furnace processing. Therefore, the post-CMP cleaning of wafers has become a key step in successful CMP process and the polyvinyl alcohol (PVA) brush cleaning is the most effective method for post-CMP in situ cleaning. In this study, the effect of the chelating agent with different concentrations on defect removal by using PVA brush cleaning was discussed emphatically. It can be seen from the surface images obtained by scanning electron microscopy and KLA digital comparison system analysis confirmed that the chelating agent can effectively act on the defect removal.
Keywords: Post-CMP cleaning; Alkaline chemicals; Defect removal; PVA brush cleaning;

Display OmittedCuO-PANI nanostructure has been demonstrated as the solar selective absorber coating for the first time. The effortless chemical methods and easily scalable techniques such as precipitation, in-situ polymerization and spray coating were adopted for the fabrication of CuO nanorods and CuO-PANI nanostructures for solar application. The synthesis was carried out without using any template. The morphology and phase structure of fabricated CuO nanorods and CuO-PANI nanostructure coatings were studied by atomic force microscopy, scanning electron microscopy and X-ray diffraction analysis. The energy dispersive X-ray spectra and elemental mapping confirm the presence of the chosen elements in the nanostructure. The solar absorptance (αs), thermal emittance (εt) and selectivity (ξ) of the nanostructure coatings on glass substrate were optimized to 0.94, 0.01 and 94 respectively by changing the polyaniline content on the surface of the CuO nanorods. The efficiency of the solar selective coatings were evaluated. The optimized solar absorber coating of CuO-PANI nanostructure is highly promising for its selective optical properties.
Keywords: Solar selective absorber; CuO; Polyaniline; Solar selectivity; Absorber efficiency;

Anisotropic behavior of layer-by-layer films using highly disordered copper hexacyanoferrate(II) nanoparticles by Rafael N. Soek; Ariane Schmidt; Herbert Winnischofer; Marcio Vidotti (253-258).
Display OmittedCopper hexacyanoferrate(II) (Cuhcf(II)) nanoparticles (NPs) were synthesized by using a simple and straightforward methodology using aqueous solution without the need of any further passivating agent. The 15 nm NPs (obtained by TEM) were fully characterized by XRD, FTIR and Raman spectroscopy that revealed a high number of structural defects. These structural defects are responsible to produce a strong internal dipole moment. This leads to an anisotropic growth onto the electrode surface by using the layer-by-layer technique. Specular Reflectance FTIR corroborates with our assumption. The defects are also responsible for the high electroactivity of the Cuhcf(II)NPs modified electrodes in sodium based electrolytes. Our results contrast with others in which the authors attributed the cell distortion as the main phenomenon.
Keywords: Copper hexacyanoferrate nanoparticles; Structural defects; Layer-by-Layer; Anisotropic behavior; FTIR reflectance;

Flexible supercapacitor based on electrochemically synthesized pyrrole formyl pyrrole copolymer coated on carbon microfibers by Mehrdad Gholami; Pooria Moozarm Nia; Leila Narimani; Mehran Sokhakian; Yatimah Alias (259-269).
Display OmittedThe main objective of this work is to prepare a flexible supercapacitor using electrochemically synthesized pyrrole formyl pyrrole copolymer P(Py-co-FPy) coated on the carbon microfibers. Due to difficulties of working with carbon microfibers, glassy carbon was used to find out optimized conditions by varying mole ratio of pyrrole and formyl pyrrole monomers on the capacitance value. The prepared electrodes were characterized using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FESEM), Brunauer–Emmett–Teller (BET) analysis, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Then the X-ray photoelectron spectroscopy (XPS) was used to characterize the optimized electrode. The specific capacitance is calculated using cyclic voltammetry, charge/discharge method, and impedance spectroscopy. The charge/discharge study reveals that the best specific capacitance is estimated to be 220.3 mF cm−2 for equal mole fraction of pyrrole and formyl pyrrole Py (0.1)-FP (0.1) at discharge current of 3 × 10−4  A. This optimized electrode keeps about 92% of its capacitance value in high current of discharging. The specific capacitances calculated by all the mentioned methods are in agreement with each other. Finally, the found optimized conditions were successfully applied to produce a flexible supercapacitor on the surface of carbon microfibers.
Keywords: Supercapacitor; Pyrrole; Formyl pyrrole; Pyrrole formyl pyrrole copolymer; Conducting polymer; Carbon microfibers;

Density functional theory study on the interaction of CO2 with Fe3O4(111) surface by Tongming Su; Zuzeng Qin; Guan Huang; Hongbing Ji; Yuexiu Jiang; Jianhua Chen (270-276).
Display OmittedCO2 adsorption on the Fetet1- and Feoct2-tet1-terminated Fe3O4(111) surface was investigated in order to understand the adsorption mechanism of CO2 by using density functional theory (DFT). Both weak and strong adsorptions exist between the CO2 and the Fe3O4(111) surface. The preferred adsorption site was found to be the Od site on the Feoct2-tet1-termination, after adsorption, the CO2 molecule was bent and the C―O bond was elongated, indicating the activation of CO2. And it is found that Feoct2-tet1-terminated Fe3O4(111) surface is more active than Fetet1-terminated surface, CO2 serves as a charge acceptor to withdraw electrons from the Feoct2-tet1-terminated Fe3O4(111) surface. In addition, partial density of states, electron localization function and difference electron density reveal that covalent bond was formed between the C atom of CO2 and the surface O atom. These results provide fundamental insight into the CO2 adsorption mechanism on Fe3O4(111) surface and potential application on the activation of CO2.
Keywords: Fe3O4(111); Carbon dioxide; DFT; Charge transfer; Chemisorption;

Surface modification of parylene-N films for the culture of osteoblast-like cells (MG-63) by Usman Liaqat; Hyuk Ko; Hwal Suh; Misu Lee; Jae-Chul Pyun (277-285).
Display OmittedThe influence of microenvironments on the culture of osteoblast-like cells (MG-63) has been investigated using parylene films with different surfaces, such as parylene-N film, UV-modified parylene-N film, functional parylene film with amine groups (parylene-A), and UV-modified parylene-A film. In this work, parylene-N film was found to induce dramatic changes in cell adhesion and cell viability before and after UV-treatment with respect to the culture of osteoblast-like cells (MG-63). The influences of such a chemical environment on cell culture were investigated in relation to the cell proliferation (viability and proliferation rate) and the cell physiology (cell cycle, protein synthesis, and differentiation) of cells grown on parylene-N film, UV-modified parylene-N film, parylene-A film, and UV-modified parylene-A film in comparison with cells grown on a polystyrene surface.
Keywords: Osteoblast; MG-63; Parylene; Adhesion; UV-treatment;

Display OmittedThe preferred binding site of H/Pt(111) has been shown to be change from the on-top to FCC as the Pt(111) surface goes approximately from a state of compressive to tensile strain. A chemical analysis of the system has shown that for both FCC and on-top bound cases the H s―Pt s and H s―Pt d interactions have a similar importance in determining the preferred binding position. It has been seen that FCC-bound H forms a distinct state below the Pt d-band, whereas the on-top bound H does not.
Keywords: Hydrogen; Platinum; Surface segregation; Strain engineering;

Display OmittedIt was demonstrated experimentally that doping Zr into TiAlN coatings at room temperature will detriment its oxidation resistance. On the other hand, there are evidences that doping Zr into TiAlN at high temperature will improve coating's oxidation resistance. In the present work, we address the effect of Zr on the oxidation resistance of TiAlN by means of ab initio molecular dynamics simulations. The TiAlN and TiAlZrN (1 Zr atom replacing 1 Ti atom) surfaces covered with 4 oxygen atoms at 300 K and 1123 K were simulated. Based on the analysis of the atomic motion, bond formation after relaxation, and the charge density difference maps we find that at 300 K, the addition of Zr induces escape of Ti atoms from the surface, resulting in formation of surface vacancies and subsequently TiO2. Comparison of metal-oxygen dimers in the vacuum and above the TiAlZrN surface further shows that the addition of Zr in the TiAlN surface will change the lowest bonding energy sequence from Zr―O < Ti―O < Al―O in the vacuum to Ti―O < Zr―O < Al―O above the TiAlZrN surface. From Molecular Dynamics simulations at 1123 K, it is find that no Ti vacancies were generated in the surface. Moreover, less charge is transferred from metal to N atoms and the bond lengths between Ti and O atoms become shorter at 1123 K as compared with 300 K, suggesting that the addition of Zr atom promotes the interaction of Ti and O at TiAlZrN surface at 1123 K, leading to a more stable surface. Our simulation explains why Zr-doping at 1123 K increases TiAlN coating's oxidation resistance while at 300 K reduces its oxidation resistance.
Keywords: TiAlN; TiAlZrN; Oxidation; Ab initio molecular dynamics;

Silicon epitaxy on H-terminated Si (100) surfaces at 250 °C by Xiao Deng; Pradeep Namboodiri; Kai Li; Xiqiao Wang; Gheorghe Stan; Alline F. Myers; Xinbin Cheng; Tongbao Li; Richard M. Silver (301-307).
Display OmittedLow temperature Si epitaxy has become increasingly important due to its critical role in the encapsulation and performance of buried nanoscale dopant devices. We demonstrate epitaxial growth up to nominally 25 nm, at 250 °C, with analysis at successive growth steps using STM and cross section TEM to reveal the nature and quality of the epitaxial growth. STM images indicate that growth morphology of both Si on Si and Si on H-terminated Si (H: Si) is epitaxial in nature at temperatures as low as 250 °C. For Si on Si growth at 250 °C, we show that the Si epitaxial growth front maintains a constant morphology after reaching a specific thickness threshold. Although the in-plane mobility of silicon is affected on the H: Si surface due to the presence of H atoms during initial sub-monolayer growth, STM images reveal long range order and demonstrate that growth proceeds by epitaxial island growth albeit with noticeable surface roughening.
Keywords: Low temperature Si epitaxy; Scanning tunneling microscope; H terminated Si surfaces;

Display OmittedSolid lubricant particles are commonly used as oil additives for low friction and wear. Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxides (LDH) were synthesized by coprecipitation method. The benefits of LDH nanoparticles are that they can be synthesized using chemical methods where size and shape can be controlled, and can be modified organically to allow dispersal in fluids. The LDH nanoparticles were characterized by X-ray diffraction, scanning electron microscope, thermogravimetry, and differential scanning calorimetry. A pin-on-disk friction and wear tester was used for evaluating the friction and wear properties of LDH nanoparticles as lubricant additives. LDH nanoparticles have friction-reducing and anti-wear properties compared to oil without LDHs. Mg/Al-LDH has the best lubrication, possibly due to better thermal stability in severe conditions.
Keywords: Lubricant additives; Layered double hydroxides; Friction performance; Thermal analysis; Lubrication mechanism;

Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods by Zhi Cao; Michael Daly; Lopez Clémence; Luke M. Geever; Ian Major; Clement L. Higginbotham; Declan M. Devine (320-329).
Display OmittedCalcium carbonate (CaCO3) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO3 thermoplastic composite’s interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the “complex” process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the “complex” surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the “complex” treatment process, the CaCO3 particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the “wet” and “complex” treated CaCO3 composites had a significantly higher heat of fusion and moisture resistance compared to the “dry” treated CaCO3 composites. Furthermore, “wet” and “complex” treated CaCO3 composites have a significantly higher tensile strength than the composites containing untreated and “dry” treated CaCO3. This is mainly because the “wet” and “complex” treatment processes have increased adsorption density of stearate, which enhances the interfacial interaction between matrix and filler. These results confirm that the chemical adsorption of the surfactant ions at the solid-liquid interface is higher than at other interface. From this study, it was concluded that the utilization of the “complex” method minimised the negative effects of void coalescence provides key information for the improvement of existing processes.
Keywords: Calcium carbonate; Stearic acid; Treatment method; Void content;

Structural, optical, magnetic and photocatalytic properties of Co doped CuS diluted magnetic semiconductor nanoparticles by N. Sreelekha; K. Subramanyam; D. Amaranatha Reddy; G. Murali; S. Ramu; K. Rahul Varma; R.P. Vijayalakshmi (330-340).
Display OmittedPristine and Co doped covellite CuS nanoparticles were synthesized in aqueous solution by facile chemical co-precipitation method with Ethylene Diamine Tetra Acetic Acid (EDTA) as a stabilizing agent. EDAX measurements confirmed the presence of Co in the CuS host lattice. Hexagonal crystal structure of pure and Co doped CuS nanoparticles were authenticated by XRD patterns. TEM images indicated that sphere-shape of nanoparticles through a size ranging from 5 to 8 nm. The optical absorption edge moved to higher energies with increase in Co concentration as indicated by UV–vis spectroscopy. Magnetic measurements revealed that bare CuS sample show sign of diamagnetic character where as in Co doped nanoparticles augmentation of room temperature ferromagnetism was observed with increasing doping precursor concentrations. Photocatalytic performance of the pure and Co doped CuS nanoparticles were assessed by evaluating the degradation rate of rhodamine B solution under sun light irradiation. The 5% Co doped CuS nanoparticles provide evidence for high-quality photocatalytic activity.
Keywords: Chemical synthesis; Co doped CuS; RTFM; Photocatalytic dye degradation;

Enhancing the oxidation resistance of graphite by applying an SiC coat with crack healing at an elevated temperature by Jae-Won Park; Eung-Seon Kim; Jae-Un Kim; Yootaek Kim; William E. Windes (341-349).
The potential of reducing the oxidation of the supporting graphite components during normal and/or accident conditions in the Very High Temperature Reactor (VHTR) design has been studied. In this work efforts have been made to slow the oxidation process of the graphite with a thin SiC coating (∼ 10 μm). Upon heating at ≥ 1173 K in air, the spallations and cracks were formed in the dense columnar structured SiC coating layer grown on the graphite with a functionally gradient electron beam physical vapor deposition (EB-PVD. In accordance with the formations of these defects, the sample was vigorously oxidized, leaving only the SiC coating layer. Then, efforts were made to heal the surface defects using additional EB-PVD with ion beam bombardment and chemical vapor deposition (CVD). The EB-PVD did not effectively heal the cracks. But, the CVD was more appropriate for crack healing, likely due to its excellent crack line filling capability with a high density and high aspect ratio. It took ∼ 34 min for the 20% weight loss of the CVD crack healed sample in the oxidation test with annealing at 1173 K, while it took ∼ 8 min for the EB-PVD coated sample, which means it took ∼4 times longer at 1173 K for the same weight reduction in this experimental set-up.
Keywords: Oxidation protection; Graphite; SiC coating; Crack healing; EBPVD; CVD;

First-principles studies on substitutional doping by group IV and VI atoms in the two-dimensional arsenene by Juan Du; Congxin Xia; Tianxing Wang; Xu Zhao; Xiaoming Tan; Shuyi Wei (350-356).
The electronic characteristics of group IV and VI atoms-doped arsenene are investigated by means of first-principles methods. The results show that the influences of group IV and VI impurities are obvious on electronic structures in the arsenene. The spin-up and spin-down states induced by C, Si, Ge and O substituting As atoms lie on the both sides of Fermi level in the arsenene, and induce deeper impurity states with total magnetic moment 1 μB. However, Te substituting As atom is the most possible n-type doping due to the shallowest transition level. These results are useful to further investigate experimentally the electronic structures and magnetic properties of group IV and VI atoms-doped arsenene nanosheets.
Keywords: Arsenene; Electronic structures; First-principle methods;

Damage caused by a nanosecond UV laser on a heated copper surface by V. Henč-Bartolić; T. Bončina; S. Jakovljević; P. Panjan; F. Zupanič (357-361).
Display OmittedThis work studied the effect of thin copper plate temperature on its surface morphology after irradiation using a pulsed nanosecond UV laser. The surface characteristics were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam and stylus profilometry. When a target was at room temperature, a crater and the radial flow of molten Cu from the crater was observed. When the thin target was warm (about 360 °C ± 20 °C), a crater was smaller, and quasi-semicircular waves with the periodicity of around 3 μm appeared in its vicinity. The origin of the waves is Marangoni effect, causing thermocapillary waves, which in same occasions had a structure of final states of chaos in Rayleigh–Bénard convection.
Keywords: Nanosecond laser; Capillary waves; Copper; Surface topography;

Morphology and magnetic properties of the ethylene-co-vinyl acetate/iron nanocomposite films prepared by implantation with Fe6+ ions by Dušan K. Božanić; Ilija Draganić; Nataša Bibić; Adriaan S. Luyt; Zorica Konstantinović; Vladimir Djoković (362-367).
Display OmittedEthylene-co-vinyl acetate/iron nanocomposite films were fabricated by implantation with multiple charged ions at different fluencies. The films obtained with ion fluency of 1 × 1017  cm−2 were used for specific studies. It was found that spherical ∼1.5 nm diameter nanoparticles were formed upon implantation. They were clustered into a single 80 nm wide strip about 40 nm beneath the film surface. The magnetic measurements of the film showed that the particles exhibit superparamagnetic behavior with a blocking temperature below 5 K. A second type of the samples was also prepared with ion fluency of 1 × 1017  cm−2, but prior to implantation, the iron was evaporated onto the co-polymer surface. A nanocomposite film of different morphology was obtained upon the implantation and the particles were much smaller (∼0.8 nm). The magnetic behavior of both the films was that of isolated nanoparticles, despite the high ion fluency of 1 × 1017  cm−2.
Keywords: Ion implantation; Nanocomposite; Iron; Multiple charged ions; Magnetic properties; Ion beam mixing;

Display OmittedIn this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).
Keywords: RGO/ZnO:B; Hydrothermal method; Supercapacitor; Boron;

The synthesis of Au@C@Pt core-double shell nanocomposite and its application in enzyme-free hydrogen peroxide sensing by Yayun Zhang; Yuhui Li; Yingying Jiang; Yancai Li; Shunxing Li (375-383).
A novel Au@C@Pt core-double shell nanocomposite was synthesized and used to fabricate enzyme-free electrochemical sensor for rapid and sensitive detection of hydrogen peroxide (H2O2). The well-designed Au@C@Pt core-double shell nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy-dispersed spectrum (EDS). The Au@C@Pt core-double shell nanocomposite modified glassy carbon electrode (Au@C@Pt/GCE) exhibits good electrocatalytic activity towards H2O2 reduction at 0.0 V and can be used as H2O2 sensor. The sensor displays two wide linear ranges towards H2O2 detection. The one is 9.0 μM–1.86 mM with high sensitivity of 144.7 μA mM−1  cm−2, and the other is 1.86 mM–7.11 mM with sensitivity of 80.1 μA mM−1  cm−2. When signal to noise (S/N) is 3, the calculated detection limit (LOD) is 0.13 μM. Furthermore, the interference from the common interfering species such as glucose, ascorbic acid, dopamine and uric acid can be effectively avoided to H2O2 detection. Additionally, the H2O2 sensor also displays good stability and reproducibility.
Keywords: Au@C@Pt core-double shell nanocomposite; Electrocatalytic reduction; Hydrogen peroxide; Enzyme-free sensor;

The impact of wafering on organic and inorganic surface contaminations by S. Meyer; S. Wahl; S. Timmel; R. Köpge; B.-Y. Jang (384-387).
Display OmittedBeside the silicon feedstock material, the crystallization process and the cell processing itself, the wafer sawing process can strongly determine the final solar cell quality. Especially surface contamination is introduced in this process step because impurities from sawing meet with a virgin silicon surface which is highly reactive until the oxide layer is formed. In this paper we quantitatively analysed both, the organic and inorganic contamination on wafer surfaces and show that changes of process parameters during wafering may cause dramatic changes in surface purity. We present powerful techniques for the monitoring of wafer surface quality which is essential for the production of high efficiency and high quality solar cells.
Keywords: Wafer surface; Organic and inorganic impurities; Quantitative determination;

Superhydrophobic surface fabricated on iron substrate by black chromium electrodeposition and its corrosion resistance property by Bo Zhang; Haitao Feng; Feng Lin; Yabin Wang; Liping Wang; Yaping Dong; Wu Li (388-396).
Display OmittedThe fabrication of superhydrophobic surface on iron substrate is carried out through 20 min black chromium electrodeposition, followed by immersing in 0.05 M ethanolic stearic acid solution for 12 h. The resultant superhydrophobic complex film is characterized by scanning electron microscope (SEM), disperse Spectrometer (EDS), atomic force microscope (AFM), water contact angle (CA), sliding angle (SA) and X-ray photoelectron spectroscope (XPS), and its corrosion resistance property is measured with cyclic voltammetry (CV), linear polarization and electrochemical impedance spectroscopy (EIS). The results show that the fabricated superhydrophobic film has excellent water repellency (CA, 158.8°; SA, 2.1°) and significantly high corrosion resistance (1.31 × 106  Ω cm−2) and excellent corrosion protection efficiency (99.94%).
Keywords: Superhydrophobic; Iron substrate; Black chromium; Stearic acid; Corrosion resistance;

Structural and electronic characterization of graphene grown by chemical vapor deposition and transferred onto sapphire by Frédéric Joucken; Jean-François Colomer; Robert Sporken; Nicolas Reckinger (397-401).
We present a combination of magnetotransport and local probe measurements on graphene grown by chemical vapor deposition on copper foil and subsequently transferred onto a sapphire substrate. A rather strong p-doping is observed (∼9 × 1012  cm−2) together with quite low carrier mobility (∼1350 cm2/V s). Atomic force and tunneling imaging performed on the transport devices reveals the presence of contaminants between sapphire and graphene, explaining the limited performance of our devices. The transferred graphene displays ridges similar to those observed whilst graphene is still on the copper foil. We show that, on sapphire, these ridges are made of different thicknesses of the contamination layer and that, contrary to what was reported for hBN or certain transition metal dichalcogenides, no self-cleansing process of the sapphire substrate is observed.
Keywords: Graphene; CVD; Transfer; Sapphire; STM; Transport;

A facile and green method towards coal-based fluorescent carbon dots with photocatalytic activity by Shengliang Hu; Zhijia Wei; Qing Chang; Adrian Trinchi; Jinlong Yang (402-407).
Display OmittedOne of the most widely used methods for exfoliating crystalline nanocarbon is via strong oxidizing acid treatment of bulk carbon sources, such as graphite, carbon black and coal. Not only is such method dangerous and accompanied by the liberation of toxic gases, it is also plagued by issues of purity, requiring the thorough and costly removal of the excess oxidizing acids and salts formed during the process. Herein we report a facile, green and inexpensive top-down strategy towards fluorescent carbon dots (CDs) from coal without incurring the burden of tedious or inefficient post-processing steps and facing the danger of highly toxic gas liberation. The presented approach shows a high yield and great potential for carbon dot production scale-up using coal, one of our most abundant and low-cost resources. The prepared CDs demonstrate photocatalytic behavior capable of rapidly degrading organic dyes under visible light. Our findings may lead to alternative uses of coal, particularly for applications including the treatment of environmental pollution, solar energy conversion or storage, and highlight coal’s applicability in areas other than energy producing via burning of this great resource.
Keywords: Carbon dots; Coal chemistry; Photocatalysis; Luminescence;

Microstructure and mechanical properties of sputter deposited Ni/Ni3Al multilayer films at elevated temperature by Chao Zhang; Kai Feng; Zhuguo Li; Fenggui Lu; Jian Huang; Yixiong Wu (408-417).
Display OmittedNano-structured Ni/Ni3Al multilayer was prepared by magnetron sputtering, with individual layer thicknesses h varying from 10 to 160 nm. The microstructure and hardness of Ni/Ni3Al multilayer were investigated by X-ray diffraction, transmission electron microscopy and nanoindentation. The results show that the hardness increases with decreasing h for as-deposited and 500 °C annealed multilayers. When annealed at 700 °C, the hardness approach a peak value at h  = 40 nm with followed by softening at smaller h. The influence of individual layer thickness, grain size as well as formation of ordered Ni3Al on strengthening mechanisms of Ni/Ni3Al multilayers at elevated temperature are discussed.
Keywords: Ni/Ni3Al multilayer; Magnetron sputtering; Hardness; Microstructure; Ordering transformation;

Display OmittedIn the present study, by means of density functional theory (DFT) calculations, the catalytic oxidation of CO by O2 molecule is investigated over Al- and Ge-embedded graphene. The large atomic radius of these dopant atoms can induce a local surface curvature and modulate the electronic structure properties of the graphene sheet through the charge redistribution. It is found that the adsorption of molecular O2 over Al- or Ge-embedded graphene is stronger than that of CO molecule. The CO oxidation reaction by molecular O2 on Al- and Ge-embedded graphene is comparably studied. The results indicate that a two-step process can occur, namely, CO + O2  → CO2  + Oads and CO + Oads  → CO2. Furthermore, the computed activation energy (Eact) for the first reaction on Ge-doped graphene is lower than that of Al-doped one, and the formation of second CO2 molecule on both surfaces can occur rapidly due to its low energy barrier (0.1 eV).
Keywords: CO oxidation reaction; Al-embedded graphene; Ge-embedded graphene; DFT; LH mechanism; ER mechanism;

Microfabrication of polymeric surfaces with extreme wettability using hot embossing by Salma Falah Toosi; Sona Moradi; Marzieh Ebrahimi; Savvas G. Hatzikiriakos (426-434).
Hot embossing was utilized to imprint topographical metallic patterns on the surfaces of thermoplastic polymers in order to create superhydrophobic and superoleophobic polymeric surfaces. The stainless steel (SS) micro/nano structured templates were fabricated using femtosecond laser ablation. The SS laser ablated templates were employed to imprint micron/submicron periodic structures onto the surface of high density polyethylene (HDPE), polylactic acid (PLA), and medical PVC at temperatures slightly above their melting points and pressures in the range of 3–12 MPa. Results have shown that the water contact angle (CA) of imprinted polymers increased to above 160° in the case of PLA and HDPE, while their water contact angle hysteresis (CAH) were significantly below 10°. In the case of medical-PVC, imprinting produced morphologies with high CA and high CAH (petal effect) due to the adhesion forces developed at the interface between the hydrophilic plasticizer of medical-PVC (TOTM) and water droplets. It is also noted that the re-entrant superoleophobic patterns created on HDPE through imprinting closely resemble the patterns found on the surface of filefish skin that is densely angled microfiber arrays. This bioinspired surface is highly capable of repelling both polar (water) and non-polar liquids of low surface tension and meets the superoleophobicity criteria.
Keywords: Hot embossing; Superhydrophobic; Superoleophobic; Polymer; Bio-inspired; Laser ablation; File-fish pattern;

Corrosion behaviors and effects of corrosion products of plasma electrolytic oxidation coated AZ31 magnesium alloy under the salt spray corrosion test by Yan Wang; Zhiquan Huang; Qin Yan; Chen Liu; Peng Liu; Yi Zhang; Changhong Guo; Guirong Jiang; Dejiu Shen (435-442).
The effects of corrosion products on corrosion behaviors of AZ31 magnesium alloy with a plasma electrolytic oxidation (PEO) coating were investigated under the salt spray corrosion test (SSCT). The surface morphology, cross-sectional microstructure, chemical and phase compositions of the PEO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD), respectively. Further, the corrosion process of the samples under the SSCT was examined in a non-aqueous electrolyte (methanol) using electrochemical impedance spectroscopy (EIS) coupled with equivalent circuit. The results show that the inner layer of the coating was destroyed firstly and the corrosion products have significant effects on the corrosion behaviors of the coating. The results above are discussed and an electrochemical corrosion model is proposed in the paper.
Keywords: Magnesium alloy; Plasma electrolytic oxidation; Salt spray test; Corrosion behavior;

A simple large-scale synthesis of mesoporous In2O3 for gas sensing applications by Su Zhang; Peng Song; Huihui Yan; Zhongxi Yang; Qi Wang (443-450).
Large-scale mesoporous In2O3 nanostructures for gas-sensing applications were successfully fabricated via a facile Lewis acid catalytic the furfural alcohol resin template route.Display OmittedIn this paper, large-scale mesoporous In2O3 nanostructures were synthesized by a facile Lewis acid catalytic the furfural alcohol resin (FAR) template route for the high-yield. Their morphology and structure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal and thermogravimetry analysis (DSC-TG) and the Brunauer-Emmett-Teller (BET) approach. The as-obtained mesoporous In2O3 nanostructures possess excellent mesoporous and network structure, which increases the contact area with the gases, it is conducive for adsorption-desorption of gas on the surface of In2O3. The In2O3 particles and pores were both about 15 nm and very uniform. In gas-sensing measurements with target gases, the gas sensor based on mesoporous In2O3 nanostructures showed a good response, short response-recovery time, good selectivity and stability to ethanol. These properties are due to the large specific surface area of mesoporous structure. This synthetic method could use as a new design concept for functional mesoporous nanomaterials and for mass production.
Keywords: Mesoporous; In2O3; Furfural alcohol; Gas sensors;

Short-range effect at the semi-coherent metal/its native oxide interface by Deqiang Yin; Mingxia Wu; Wanglai Cen; Hongping Li; Yi Yang; Hui Fang (451-459).
Display OmittedFundamentally understanding the variations of atomistic and electronic properties at the interface of metal/its native oxide systems plays a critical role in many important technological processes and applications, such as oxidization, corrosion, chemical catalysis, fuel reactions, and thin-film process. Here, we have adopted the representatively semi-coherent Cu2O(111)/Cu(100) interface and demonstrated, by first-principles calculations on energetic and electronic structures of a total 9 candidate interfacial models, that the preferred geometries (i.e., that having the largest adhesion energy) are those possess the shortest interfacial distance between O terminated Cu2O and substrate Cu. Using several analytic methods, we have thoroughly characterized the variation of electronic states from the interface to Cu2O constituent, and determined that the large degree of charge accumulation at the interface is at the expense of depletion of charge in both substrate Cu and neighboring Cu (Cu2O) to the interfacial O atoms. Strikingly, in Cu2O the conducting states appear only in monolayer proximal to Cu2O/Cu interface, as well, the second layer remains in semi-conducting state as its bulk, indicating a short-range effect in electronic properties induced by Cu substrate. The theoretical calculations provide insight into the complex electronic properties of the functional Cu2O/Cu interface, which was quite difficult to observe by experimental methods alone. The unique properties are of practical importance for further understanding and improvement of such a promising class of metal/native oxide interface at the atomic scale.
Keywords: Cu2O/Cu interface; Metal/its native oxide interface; Short-range effect; First principles calculations;

Synthesis and structural property of Si nanosheets connected to Si nanowires using MnCl2/Si powder source by Erchao Meng; Akiko Ueki; Xiang Meng; Hiroaki Suzuki; Hiroshi Itahara; Hirokazu Tatsuoka (460-466).
Si nanosheets connected to Si nanowires synthesized using a MnCl2/Si powder source with an Au catalyst avoid the use of air-sensitive SiH4 or SiCl4. It was evident from these structural features of the nanosheets (leaf blade) with nanowires (petiole) that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes of the Si(111) nanosheets was clearly explained by the interference with the extra diffraction spots that arose due to the reciprocal lattice streaking effect.Display OmittedSi nanosheets connected to Si nanowires were synthesized using a MnCl2/Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH4 or SiCl4. The existence of the Si nanosheets connected to the Si<111> nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of <211> perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.
Keywords: A1 low dimensional structures; A3Chemical vapor deposition processes; B1 nanomaterials; B2 semiconducting silicon;

Hydrophilic crosslinked-polymeric surface capable of effective suppression of protein adsorption by Yuri Kamon; Naoko Inoue; Erika Mihara; Yukiya Kitayama; Tooru Ooya; Toshifumi Takeuchi (467-472).
Display OmittedWe investigated the nonspecific adsorption of proteins towards three hydrophilic crosslinked-polymeric thin layers prepared by surface-initiated atom transfer radical polymerization using N,N′-methylenebisacrylamide, 2-(methacryloyloxy)ethyl-[N-(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC), or 6,6′-diacryloyl-trehalose crosslinkers. Protein binding experiments were performed by surface plasmon resonance with six proteins of different pI values including α-lactalbumin, bovine serum albumin (BSA), myoglobin, ribonuclease A, cytochrome C, and lysozyme in buffer solution at pH 7.4. All of the obtained crosslinked-polymeric thin layers showed low nonspecific adsorption of negatively charged proteins at pH 7.4 such as α-lactalbumin, BSA, and myoglobin. Nonspecific adsorption of positively charged proteins including ribonuclease A, cytochrome C, and lysozyme was the lowest for poly(MMPC). These results suggest poly(MMPC) can effectively reduce nonspecific adsorption of a wide range of proteins that are negatively or positively charged at pH 7.4. MMPC is a promising crosslinker for a wide range of polymeric materials requiring low nonspecific protein binding.
Keywords: Hydrophilic polymer; Crosslinker; Surface-initiated activator generated by electron transfer for atom transfer radical polymerization (SI-AGET ATRP); Nonspecific adsorption; Proteins;

Enhanced photocatalytic activity of supported TiO2 by selective surface modification of zeolite Y by Kiros Guesh; Carlos Márquez-Álvarez; Yonas Chebude; Isabel Díaz (473-478).
Zeolite Y was treated using ammonium acetate and ammonium fluoride sequentially. As a consequence the aluminum from the surface was selectively removed. Then, loading with TiO2 (20 wt%) led to a final photocatalyst. The samples were characterized by X-ray diffraction (XRD), elemental analysis (ICP-OES), N2 adsorption, diffuse reflectance UV–vis spectroscopy (DRS), photoluminescence spectroscopy (PL), and X-ray photoelectron spectroscopy (XPS). It was found that 50% of the Al atoms were removed from the surface of the zeolite without affecting the framework structure. The TiO2/treated zeolite sample yielded 92% photocatalytic degradation of 10 ppm methyl orange (MO), a model pollutant, while the TiO2/parent zeolite converted only 7.6%. The mass normalized turnover rate (TORm) of the treated zeolite loaded with TiO2 was about 12 times higher than that of the parent zeolite loaded with the same amount of TiO2 precursor. This higher photocatalytic activity of the TiO2 supported on treated zeolite can be attributed to a more efficient interaction of the TiO2 with the zeolite leading to higher adsorption capacity. Reusability of the photocatalysts was assessed by performing three consecutive reaction cycles that showed no significant loss of photocatalytic activity.
Keywords: Photocatalysis; Zeolite; Titanium oxide; Methyl orange; Dealumination;

Display OmittedA method to prepare a self-healing, antimicrobial polymer coating that retains efficacy against Escherichia coli O157:H7 in the presence of organic matter is reported. A coating composed of branched polyethyleneimine (PEI) and styrene maleic anhydride copolymer (SMA) was applied to a maleic anhydride functionalized polypropylene support. The chemistry of the polymer coating was designed to impart hydrophobicity due to the styrene subunits, intrinsic antimicrobial character (>99.9% reduction) from the cationic primary amine groups, and enhanced antimicrobial character ( > 99.99% reduction) after chlorination of N-halamine forming groups. Antimicrobial effectiveness was demonstrated under conditions of increasing organic load. Up to 500 ppm horse serum, chlorinated coatings retained full antimicrobial character (>99.99% reduction). Even at 50,000 ppm of horse serum, the coating provided ∼90% reduction as prepared, and between ∼75% and ∼80% reduction in the form of N-halamines. Microscopy confirmed no evidence of bacterial adhesion on the coating surface. Finally, the coating exhibited self-healing properties after exposure to acid and alkaline solutions and restoration by heat, as confirmed through spectroscopy from the rebuilding of characteristic chemical bonds. Such robust antimicrobial polymer coatings with efficacy under conditions of increasing organic load may support reducing microbial cross-contamination in food and biomedical industries.
Keywords: Antimicrobial material; N-halamines; Polycations; Self-healing material; Antimicrobial coating; Microbial cross-contamination;

Display OmittedThe La and/or Ni was introduced into alumina-promoted sulfated zirconia by impregnation and co-precipitation to improve the catalytic property of n-butane isomerization. Catalysts characterization shows that the addition of La/Ni has a remarkable influence on the surface and textual properties depending on the modification method. The impregnation of La/Ni facilitates the transformation of a small amount of tetragonal zirconia into monoclinic phase, while the co-precipitation improves the stability of tetragonal ZrO2. H2-TPR indicates that the addition of La/Ni changes the interaction between SO4 2− and supports, which affects the acidity on the surface. Specifically, the Lewis acidity is significantly enhanced by either modification method. The co-precipitation reserves almost all of the Brønsted acid sites, while the impregnation causes a remarkable decrease of Brønsted acid sites. Reaction results demonstrate that the co-precipitation exhibits a significant advantage over impregnation that the higher conversion of n-butane and selectivity to isobutane are obtained on the catalyst prepared by co-precipitation. The increase of catalytic activity is ascribed to the accelerated activation rate of n-butane molecules by hydride subtraction on the Lewis acid sites at higher reaction temperature. Furthermore, the addition of La/Ni improves the selectivity to isobutane by inhibiting the bimolecular reaction.
Keywords: Alumina-promoted sulfated zirconia; La; Ni; n-Butane isomerization; Impregnation; Co-precipitation;

Facile incorporation of hydroxyapatite onto an anodized Ti surface via a mussel inspired polydopamine coating by Wang Zhe; Chaofang Dong; Yang Sefei; Zhang Dawei; Xiao Kui; Li Xiaogang (496-503).
Display OmittedInspired by the porous morphology of anodized Ti and the adhesive versatility of polydopamine (PDA), which can induce apatite mineralization, we fabricated a novel interface by coating a porous anodized TiO2 layer with PDA to rapidly immobilize HA on Ti-based substrates. It was found that the as-prepared PDA/anodized (HD) surface exhibited nanoscale roughness, which possessed an excellent ability to form apatite when immersed in 1.5× simulated body fluid (SBF), as observed by AFM and FE-SEM. The morphology and composition of each layer were further confirmed by XPS, XRD and FTIR. The corrosion resistance of the multilayer was investigated using potentiodynamic polarization curve and electrochemical impedance spectra (EIS) measurements in a 0.9 wt% NaCl solution, the results suggested that the HA/PDA/anodized (HDA) layer increased the corrosion resistance of pure Ti with higher corrosion potential and lower passive current, the surface wettability was also enhanced with the incorporation of HA. In vitro cellular assays showed that the HDA layer stimulated cell attachment and improved the alkaline phosphate (ALP) activity. Overall, the PDA/anodized treatment provided a viable method to quickly integrate HA, and the obtained HDA layer improved both corrosion resistance and biocompatibility of the Ti surface.
Keywords: Ti; Polydopamine; Hydroxyapatite; Corrosion resistance; Biocompatibility;

Laser surface and subsurface modification of sapphire using femtosecond pulses by G. Eberle; M. Schmidt; F. Pude; K. Wegener (504-512).
Display OmittedTwo methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.
Keywords: Sapphire; Waterjet orifice; Laser; Femtosecond; Ablation; Etching;

The deactivation mechanism of Cl on Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3 by Ning-zhi Yang; Rui-tang Guo; Wei-guo Pan; Qi-lin Chen; Qing-shan Wang; Chen-zi Lu; Shu-xian Wang (513-518).
Display OmittedThe poisoning mechanism of Cl on Ce/TiO2 catalyst was investigated based on temperature programmed desorption (TPD) and the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) studies. The results of NH3-TPD and NO-TPD indicated that the addition of Cl on Ce/TiO2 catalyst would inhibit the adsorption of NH3 species and NOx species on it. As can be seen from the results of in situ DRIFT study, the NH3-SCR reaction over Ce/TiO2 and Ce/TiO2-Cl were all followed both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. And the decreased adsorption ability of NH3 species and NOx species on the surface of Ce/TiO2-Cl should be mainly responsible for its low SCR activity.
Keywords: Ce/TiO2; SCR; Cl; Deactivation; TPD; DRIFT;

Assembly of citrate gold nanoparticles on hydrophilic monolayers by Inger Vikholm-Lundin; Emil Rosqvist; Petri Ihalainen; Tony Munter; Anni Honkimaa; Varpu Marjomäki; Willem M. Albers; Jouko Peltonen (519-529).
Display OmittedSelf-assembled monolayers (SAMs) as model surfaces were linked onto planar gold films thorough lipoic acid or disulfide groups. The molecules used were polyethylene glycol (EG-S-S), N-[tris-(hydroxymethyl)methyl]acrylamide polymers with and without lipoic acid (Lipa-pTHMMAA and pTHMMAA) and a lipoic acid triazine derivative (Lipa-MF). All the layers, but Lipa-MF with a primary amino group were hydroxyl terminated. The layers were characterized by contact angle measurements and atomic force microscopy, AFM. Citrate stabilized nanoparticles, AuNPs in water and phosphate buffer were allowed to assemble on the layers for 10 min and the binding was followed in real-time with surface plasmon resonance, SPR. The SPR resonance curves were observed to shift to higher angles and become increasingly damped, while also the peaks strongly broaden when large nanoparticles assembled on the surface. Both the angular shift and the damping of the curve was largest for nanoparticles assembling on the EG-S-S monolayer. High amounts of particles were also assembled on the pTHMMAA layer without the lipoic acid group, but the damping of the curve was considerably lower with a more even distribution of the particles. Topographical images confirmed that the highest number of particles were assembled on the polyethylene glycol monolayer. By increasing the interaction time more particles could be assembled on the surface.
Keywords: Hydrophilic monolayers; Gold nanoparticles; Surface plasmon resonance (SPR); Atomic force microscopy (AFM); Contact angle;

Display OmittedA method of distributed calibration of a probe microscope scanner is suggested. The main idea 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 characterized by a unique set of scale factors. Feature-oriented scanning (FOS) methodology is used as a basis for implementation of the distributed calibration permitting to exclude in situ the negative influence of thermal drift, creep and hysteresis on the obtained results. Possessing the calibration database enables correcting in one procedure all the spatial systematic 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. One of the useful modes of the developed calibration method is a virtual mode. In the virtual mode, instead of measurement of a real surface of the standard, the calibration program makes a surface image “measurement” of the standard, which was obtained earlier using conventional raster scanning. The application of the virtual mode permits simulation of the calibration process and detail analysis of raster distortions occurring in both conventional and counter surface scanning. Moreover, the mode allows to estimate the thermal drift and the creep velocities acting while surface scanning. Virtual calibration makes possible automatic characterization of a surface by the method of scanning probe microscopy (SPM).
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;

3-D laser confocal microscopy study of the oxidation of NdFeB magnets in atmospheric conditions by J.P. Meakin; J.D. Speight; R.S. Sheridan; A. Bradshaw; I.R. Harris; A.J. Williams; A. Walton (540-544).
Neodymium iron boron (NdFeB) magnets are used in a number of important applications, such as generators in gearless wind turbines, motors in electric vehicles and electronic goods (e.g.— computer hard disk drives, HDD). Hydrogen can be used as a processing gas to separate and recycle scrap sintered Nd-Fe-B magnets from end-of-life products to form a powder suitable for recycling. However, the magnets are likely to have been exposed to atmospheric conditions prior to processing, and any oxidation could lead to activation problems for the hydrogen decrepitation reaction. Many previous studies on the oxidation of NdFeB magnets have been performed at elevated temperatures; however, few studies have been formed under atmospheric conditions.In this paper a combination of 3-D laser confocal microscopy and Raman spectroscopy have been used to assess the composition, morphology and rate of oxidation/corrosion on scrap sintered NdFeB magnets. Confocal microscopy has been employed to measure the growth of surface reaction products at room temperature, immediately after exposure to air. The results showed that there was a significant height increase at the triple junctions of the Nd-rich grain boundaries. Using Raman spectroscopy, the product was shown to consist of Nd2O3 and formed only on the Nd-rich triple junctions. The diffusion coefficient of the triple junction reaction product growth at 20 °C was determined to be approximately 4 × 10−13  cm2/sec. This value is several orders of magnitude larger than values derived from the diffusion controlled oxide growth observations at elevated temperatures in the literature. This indicates that the growth of the room temperature oxidation products are likely defect enhanced processes at the NdFeB triple junctions.
Keywords: NdFeB; Magnet; Oxidation; Confocal microscopy; Raman spectroscopy;

Phosphoric acid (PA) self-assembled monolayers (SAMs) have been developed for applications in organic field-effect transistors (OFETs). This efficient interface modification is helpful for semiconductor layer to form crystal thin film during vapor deposition. Results show that the PDI-i8C based OFETs with PA SAMs exhibit field-effect mobilities up to 0.014 cm2  V−1  s−1 (with ODPA as SAMs), which is over 500 times higher than the device without SAMs. Also, transistors with Naph6PA as SAMs show up to 1.5 × 10−3  cm2  V−1  s−1. By studying the morphology of semiconductor layer and SAMs surface, it is found that ODPA bilayer structure plays a key role in inducing PDI-i8C to form orderly crystal thin film.
Keywords: Thin film transistors; Self-assembled monolayer; Phosphonic acid derivative; Carrier mobility;

A novel molecular sieve supporting material for enhancing activity and stability of Ag3PO4 photocatalyst by Qiang Wu; Peifu Wang; Futao Niu; Cunping Huang; Yang Li; Weifeng Yao (552-563).
Display OmittedA small-pore silicon-substituted silicon aluminum phosphate (SAPO-34) molecular sieve, for the first time, is reported to significantly increase both the activity and life span of Ag3PO4 photocatalyst for visible-light degradation of methylene blue (MB) and rhodamine B (RhB). Results show that 60 wt.% Ag3PO4/SAPO-34 exhibits the highest photocatalytic degradation efficiencies for both MB (91.0% degradation within 2.0 min) and RhB (91.0% degradation within 7.0 min). In comparison, pure Ag3PO4 powder photocatalyst requires 8.0 min and 12.0 min for decomposing 91.0% of MB and RhB, respectively. During MB degradation the rate constant for 60 wt.% Ag3PO4/SAPO-34 increases 317.2% in comparison with the rate constant of pure Ag3PO4. This activity is also much higher than literature reported composite or supported Ag3PO4 photocatalysts. In three photocatalytic runs for the degradation of RhB, the rate constant for 60 wt.% Ag3PO4/SAPO-34 reduces from 0.33 to 0.18 min−1 (45.5% efficiency loss). In contrast, the rate constant of pure Ag3PO4 catalyst decreases from 0.2 to 0.07 min−1 (80.0% efficiency loss). All experimental results have shown that small pores and zero light absorption loss of SAPO-34 molecular sieves minimize Ag3PO4 loading, enhance photocatalytic activity and prolong the lifespan of Ag3PO4 photocatalyst.
Keywords: SAPO-34 molecular sieve; Silver phosphate (Ag3PO4); Rhodamine B (RhB); Methylene blue (MB); Photocatalytic degradation;

Laser surface pretreatment of 100Cr6 bearing steel – Hardening effects and white etching zones by Anna Buling; Hendrik Sändker; Jochen Stollenwerk; Ulrich Krupp; Angela Hamann-Steinmeier (564-571).
Display OmittedIn order to achieve a surface pretreatment of the bearing steel 100Cr6 (1–1.5 wt.% Cr) a laser-based process was used. The obtained modification may result in an optimization of the adhesive properties of the surface with respect to an anticorrosion polymer coating on the basis of PEEK (poly-ether-ether-ketone), which is applied on the steel surface by a laser melting technique. This work deals with the influence of the laser-based pretreatment regarding the surface microstructure and the micro-hardness of the steel, which has been examined by scanning electron microscopy (SEM), light microscopy and automated micro-hardness testing.The most suitable parameter set for the laser-based pretreatment leads to the formation of very hard white etching zones (WEZ) with a thickness of 23 μm, whereas this pretreatment also induces topographical changes. The occurrence of the white etching zones is attributed to near-surface re-austenitization and rapid quenching. Moreover, dark etching zones (DEZ) with a thickness of 32 μm are found at the laser path edges as well as underneath the white etching zones (WEZ). In these areas, the hardness is decreased due to the formation of oxides as a consequence of re-tempering.
Keywords: Laser pretreatment; Micro-hardness; White etching zones; Corrosion protection; Laser material processing;

Display OmittedIn this study, carboxylated quercetin (CQ) was conjugated to superparamagnetic iron oxide nanoparticles (SPIONs) which were modified by (3-aminopropyl) triethoxysilane (APTES), Folic acid (FA) and carboxylated Polyethylene glycol (PEG); (SPION@APTES@FA-PEG@CQ), nanodrug has been synthesized via polyol and accompanying by various chemical synthesis routes. The characterization of the final product was done via X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), Transmission electron spectroscopy (TEM) and Vibrating sample magnetometer (VSM). Its cytotoxic and apoptotic activities on over expressed folic acid receptor (FR + ) (MCF-7, HeLa) and none expressed folic acid receptor (FR-) (A549) cancer cell lines were determined by using MTT assay, Real-Time Cell Analysis, TUNEL assay, Annexin assay and RT-PCR analysis for Caspase3/7 respectively. SPION@APTES@FA-PEG@CQ nanodrug showed higher cytotoxicity against HeLa and MCF-7 cell lines as compared with A549 cell line. Moreover, SPION@APTES@FA-PEG@CQ nanodrug also caused higher apoptotic and necrotic effects in 100 μg/mL HeLa and MCF-7 cells than A549 cells. The findings showed that SPION@APTES@FA-PEG@CQ nanodrug has cytotoxic, apoptotic and necrotic effects on HeLa and MCF-7 which are FR over expressed cell lines and can be potentially used for the delivery of quercetin to cervical and breast cancer cells.
Keywords: SPION; Quercetin; Anticancer; Cytotoxicity; Cancer treatment; Nanodrug;