Applied Surface Science (v.369, #C)

Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation by Hua-Yue Zhu; Ru Jiang; Yong-Qian Fu; Rong-Rong Li; Jun Yao; Sheng-Tao Jiang (1-10).
Novel multifunctional NiFe2O4/ZnO hybrids were prepared by a hydrothermal method and their physicochemical properties were characterized by XRD, SEM, TEM, TGA, VSM, BET and UV–vis DRS. The adsorption and photocatalytic performance of NiFe2O4/ZnO hybrids were systematically investigated using congo red as a model contaminant. With the introduction of NiFe2O4, NiFe2O4/ZnO hybrids can absorb the whole light from 300 nm to 700 nm. The adsorption capacity (221.73 mg g−1) of NiFe2O4/ZnO hybrids is higher than those of NiFe2O4, ZnO and mechanically mixed NiFe2O4/ZnO hybrids. The removal of congo red solution (20 mg L−1) by NiFe2O4/ZnO hybrids was about 94.55% under simulated solar light irradiation for 10 min. •OH and h + play important roles in the decolorization of congo red solution by NiFe2O4/ZnO hybrids under simulated solar light irradiation. The decolorization efficiency of congo red solution is 97.23% for the fifth time by NiFe2O4/ZnO hybrids under simulate solar light irradiation, indicating the high photostability and durability. NO3 and Cl anions which are ubiquitous components in dye-containing wastewater have negligible influence on the effectiveness of NiFe2O4/ZnO hybrids. Moreover, the magnetic NiFe2O4/ZnO hybrids can be easily separated from the reacted solution by an external magnet.
Keywords: Photocatalysis; Adsorption; Congo red; Magnetic separation; NiFe2O4/ZnO hybrids;

Water contaminants, such as oils, dyes, arsenite ions and organic solvents can be efficiently sorbed by two kinds of 3D magnetite-graphene aerogels (M-RGOs) with the size of Fe3O4 NPs of about 10 nm.In order to develop efficient and environment benign sorbents for water purification, the macroscopic multifunctional magnetite-reduced graphene oxides aerogels (M-RGOs) with strong interconnected networks were prepared via a one pot solvothermal method of graphene oxide sheets adsorbing iron ions and in situ simultaneous deposition of Fe3O4 nanoparticles in ethylene glycol or triethylene glycol solvents. Such M-RGOs exhibited excellent sorption capacity to different contaminants, including oils, organic solvents, arsenite ions, as well as dyes. In addition, it was demonstrated that the M-RGOs could be used as column packing materials to manufacture column for water purification by filtration. The method proposed was proved to be versatile to induce synergistic assembly of RGO sheets with other functional metal oxides nanoparticles and as a kind of broad-spectrum sorbents for removing different types of contaminants in water purification, simultaneously.
Keywords: Graphene aerogels; Iron oxide nanoparticles; Solvothermal method; Broad-spectrum; Sorbents;

Modification of electrospun polyacrylonitrile nanofibers with EDTA for the removal of Cd and Cr ions from water effluents by Eutilério F.C. Chaúque; Langelihle N. Dlamini; Adedeji A. Adelodun; Corinne J. Greyling; J. Catherine Ngila (19-28).
Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning technique prior to surface modification with polyethylenediaminetetraacetic acid (EDTA) using ethylenediamine (EDA) as the cross-linker. The modified nanofibers (EDTA-EDA-PAN) were subsequently applied in the wastewater treatment for the removal of Cd(II) and Cr(VI). Textural and chemical characterizations of the nanofibers were carried out by analysis of the specific surface area (Brauner Emmet and Teller (BET)) and thermogravimetric analyses, scanning electron microscopy and Fourier transform infrared spectroscopy. From the adsorption equilibrium studies with Langmuir, Freundlich and Temkin isotherm models, Freundlich was found most suitable for describing the removal mechanism of the target metals as they collect on a heterogeneously functionalized polymer surface. The EDTA-EDA-PAN nanofibers showed effective sorption affinity for both Cd(II) and Cr(VI), achieving maximum adsorption capacities of 32.68 and 66.24 mg g-1, respectively, at 298 K. In furtherance, the nanofibers were regenerated by simple washing with 2 M HCl solution. Conclusively, the EDTA-EDA-PAN nanofibers were found to be efficient for the removal of Cd(II) and Cr(VI) in water effluents.
Keywords: Polyacrylonitrile; Nanofibers; Electrospinning; Adsorption; Trace metals; Water effluent;

Improving the work function of the niobium surface of SRF cavities by plasma processing by P.V. Tyagi; M. Doleans; B. Hannah; R. Afanador; C. McMahan; S. Stewart; J. Mammosser; M. Howell; J. Saunders; B. Degraff; S.-H. Kim (29-35).
An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature has been developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5–1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.
Keywords: SRF cavity; Plasma processing; Surface science; Hydrocarbons removal; Niobium surface; Secondary Ion Mass Spectroscopy; Scanning kelvin probe; Work function;

A novel hydrazine electrochemical sensor was developed based on gold nanoparticles and single-walled carbon nanohorns composite film. The sensor has the merits of wide linear range, fast response, high sensitivity, good selectivity and reproducibility. The diffusion coefficient of hydrazine was also studied.A novel electrochemical sensor was developed by electrodepositing gold nanoparticles on the single-walled carbon nanohorns modified glassy carbon electrode. We used the prepared sensor to determine hydrazine for the first time. The results show that the modified electrode has good electrocatalytic activity toward the oxidation of hydrazine. Under the optimized conditions, two wide linear segments were observed between the catalytic currents and the concentration of hydrazine within the range of 0.005–3.345 mM with a detection limit of 1.1 μM (s/n = 3). The diffusion coefficient of hydrazine was also estimated using chronoamperometry. Additionally, the sensor showed excellent sensitivity, selectivity, and reproducibility properties.
Keywords: Single-walled carbon nanohorns; Gold nanoparticles; Hydrazine sensor; Electrocatalytic oxidation;

Adsorption study of copper phthalocyanine on Si(111)(√3 × √3)R30°Ag surface by S. Menzli; B. Ben Hamada; I. Arbi; A. Souissi; A. Laribi; A. Akremi; C. Chefi (43-49).
The adsorption of copper phthalocyanine (CuPc) molecules on Si(111)(√3 × √3)R30°Ag surface is studied at room temperature under ultra high vacuum. Crystallographic, chemical and electronic properties of the interface are investigated by low energy electron diffraction (LEED), ultraviolet and X-ray photoemission spectroscopies (UPS, XPS) and X-ray photoemission diffraction (XPD). LEED and XPD results indicate that after one monolayer deposition the molecular layer is highly ordered with a flat lying adsorption configuration. The corresponding pattern reveals the coexistence of three symmetrically equivalent orientations of molecules with respect to the substrate. XPS core level spectra of the substrate reveal that there is no discernible chemical interaction between molecules and substrate; however there is evidence of Fermi level movement. During the growth, the work function was found to decrease from 4.90 eV for the clean substrate to 4.35 eV for the highest coverage (60 monolayers). Within a thickness of two monolayer deposition an interface dipole of 0.35 eV and a band bending of 0.2 eV have been found. UPS spectra indicate the existence of a band bending of the highest occupied molecular orbital (HOMO) of 0.55 eV. The changes in the work function, in the Fermi level position and in the HOMO state have been used to determine the energy level alignment at the interface.
Keywords: Copper-phthalocyanine; Si(111)(√3 × √3)R30°Ag surface; LEED; XPS; XPD; UPS;

Hydrogenated fullerenes are detected in the Universe in space but their identification is still unsolved task. Therefore, this paper provides useful information about hydrogenated fullerenes (dimer, peanut and capsule) using DFT method at the B3LYP/6-31G(d) level of theory. The stability, geometric structures, hydrogen adsorption energies and NMR chemical shifts are calculated. The results show that the energy of most stable isomer of C118 dimer is lower than the energies sum of C60 and C58 cages by 1.77 eV and the energy per carbon atom of C144 capsule is more stable than C60 cage by 126.98 meV. Also, endohedral Ti-doped C118 dimer and C128 peanut are found to be most stable structures than exohedral Ti-doped C118 dimer and C128 peanut by 2.19 eV/Ti and 3.52 eV/Ti, respectively. The hydrogenation process is found to be enhanced (especially at the caps) for endohedral Ti-doped C118 dimer and C128 peanut through electronic surface modifications. The most active hydrogenation sites are selected and it is found that the most stable hydrogenation sites are H out s 1 and H out s 3 for fullerenes and endohedral Ti-doped fullerenes, respectively.
Keywords: Endohedral Ti-doped fullerenes; 13C NMR chemical shifts; Hydrogenated fullerenes; Fullerenes in space; DFT;

The effect of microstructural properties of CoCr2O4 spinel oxides on catalytic combustion of dichloromethane by Jing-Di Liu; Ting-Ting Zhang; Ai-Pin Jia; Meng-Fei Luo; Ji-Qing Lu (58-66).
It was found that a series of spinel CoCr2O4 oxides were very active and selective for dichloromethane combustion, and the best performance was obtained on a catalyst calcined at 600 °C (with a areal specific reaction rate of 3.41 × 10−8  molCH2Cl2  s−1  m−2 at 220 °C). Quantitative analyses revealed that Cr3+/Cr6+ cations could partially substitute Co3+ cations in the octahedral sites of the spinel oxide at high-temperature calcination and thus to enhanced reducibility and surface acidity of the oxide, which synergistically governed the observed catalytic behaviors. Moreover, it was found that high valent Cr species (Cr6+) played very important role in the reaction, with a much higher turnover frequency (2.2 × 10−3  s−1) than that of the Cr3+ (0.56 × 10−3  s−1).
Keywords: Dichloromethane combustion; CoCr2O4; Microstructure; Reducibility; Surface acidity;

TiN-buffered substrates for photoelectrochemical measurements of oxynitride thin films by Markus Pichler; Daniele Pergolesi; Steve Landsmann; Vipin Chawla; Johann Michler; Max Döbeli; Alexander Wokaun; Thomas Lippert (67-75).
Display OmittedDeveloping novel materials for the conversion of solar to chemical energy is becoming an increasingly important endeavour. Perovskite compounds based on bandgap tunable oxynitrides represent an exciting class of novel photoactive materials. To date, literature mostly focuses on the characterization of oxynitride powder samples which have undeniable technological interest but do not allow the investigation of fundamental properties such as the role of the crystalline quality and/or the surface crystallographic orientation toward photo-catalytic activity. The challenge of growing high quality oxynitride thin films arises from the availability of a suitable substrate, owing to strict material and processing requirements: effective lattice matching, sufficiently high conductivities, stability under high temperatures and in strongly reducing environments. Here, we have established the foundations of a model system incorporating a TiN-buffer layer which enables fundamental investigations into crystallographic surface orientation and crystalline quality of the photocatalyst against photo(electro)chemical performance to be effectively performed. Furthermore, we find that TiN as current collector enables control over the nitrogen content of oxynitride thin films produced by a modified pulsed laser deposition method and allows the growth of highly ordered LaTiO3−x N x thin films.
Keywords: Solar Water splitting; Titanium nitride; Oxynitride; Pulsed laser deposition; Photoelectrochemistry;

Electronic and optical properties of 2D graphene-like ZnS: DFT calculations by Hamed Lashgari; Arash Boochani; Ashkan Shekaari; Shahram Solaymani; Elmira Sartipi; Rohollah Taghavi Mendi (76-81).
Density-functional theory has been applied to investigate the electronic and optical properties of graphene-like two-dimensional ZnS in the (0001) direction of its Wurtzite phase. A comparison with 3D-ZnS has been carried out within the PBE- and EV-GGA. The electronic properties of 2D- and 3D-ZnS have been derived by the examination of the electronic band structures and density of states. The optical properties have been determined through the study of the dielectric function, reflectivity, electron loss function, refractive and extinction indices, the absorption index and optical conductivity. It is found that the transparency of 2D-ZnS is greater than the 3D over the visible range. A thorough study of the dielectric function has been performed so that the peaks and the transition bands have been specified. The electron loss function demonstrates that the plasmonic frequency for 2D- and 3D-ZnS is accrued at 11.22 and 19.93 eV within the PBE-GGA, respectively.
Keywords: Two-dimensional ZnS; Graphene-like; Optical properties; Density functional theory;

To improve the dispersion and interfacial interaction between halloysite nanotubes (HNTs) and poly(l-lactide) (PLLA) matrix, and hence to increase the mechanical properties and cytocompatibility of the HNTs/PLLA composite, a facile approach was developed to prepare polydopamine-coated HNTs (D-HNTs) by the self-polymerization of dopamine (DOPA), and then HNTs and D-HNTs were further introduced into PLLA matrix to fabricate HNTs/PLLA and D-HNTs/PLLA fiber membranes based on electrospinning technique. The successful immobilization of the polydopamine (PDOPA) coating on the surfaces of HNTs was confirmed, and such PDOPA coating played an important role in improving the interfacial interaction between the nanotubes and PLLA matrix. The D-HNTs were dispersed in the matrix more uniformly than untreated HNTs, and relative smooth and uniform fiber were obtained for the D-HNTs/PLLA fiber membrane. As a result, the tensile strength and modulus of the D-HNTs/PLLA fiber membrane were obviously superior to those of the HNTs/PLLA fiber membrane. Cell culture results revealed that D-HNTs/PLLA fiber membrane was more effectively to promote MC3T3-E1 cells adhesion and proliferation than neat PLLA and HNTs/PLLA fiber membrane.
Keywords: Poly(l-lactide); Halloysite nanotubes; Dopamine; Electrospinning; Properties;

Effect of Ca addition on the corrosion behavior of Mg–Al–Mn alloy by Jiang Yang; Jian Peng; Eric A. Nyberg; Fu-sheng Pan (92-100).
The microstructures and corrosion resistance of magnesium–5 wt% aluminum–0.3 wt% manganese alloys (Mg–Al–Mn) with different Ca additions (0.2–4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.
Keywords: Mg–Al–Mn alloy; Ca addition; Microstructure; Corrosion resistance;

Spherical carbonaceous adsorbents (CS n ) with micro-porosity developed for CO2 capture were prepared by a simple hydrothermal carbonization of carboxymethylcellulose (CMC) in the presence of urea, and activated in a high temperature N2 atmosphere. The effects of specific surface area, pore structure, and N content on the CO2 adsorption capacity were systematically investigated. Urea was found to react with surface carbonyl groups and other intermediate products generated by CMC hydrothermal carbonization, which produced highly spherical morphologies that also exhibited some ordered lattice structures. The particle size of N-doped CS n was larger than that of particles prepared without urea. Nitrogen was mainly present in pyridine (N-6), pyrrolic/pyridone (N-5) and quaternary (N-Q) forms. The high CO2 capture capacity was produced by a combination of N-doping and developing micro-pore structures. At an adsorption pressure of 1 bar, the capacity was dominated by the micro-porosity. However, during initial, lower pressures the N content dominated the CO2 adsorption capacity.
Keywords: Spherical carbonaceous adsorbents; CO2 capture; N-doping; Hydrothermal carbonization;

Fabrication and photoelectrochemical characteristics of In2S3 nano-flower films on TiO2 nanorods arrays by Minmin Han; Limin Yu; Wenyuan Chen; Wenzhen Wang; Junhong Jia (108-114).
The In2S3 nano-flower films on TiO2/FTO (Fluorine-doped tin oxide) substrates were synthesized via hydrothermal method and the photoelectrochemical performances of In2S3/TiO2 photoelectrodes were characterized. The roles of PSS (poly(sodium-p-styrenesul-fonate)) and PEG (polyethylene glycol) on the structure controlling of In2S3 films were also discussed. The results show that the In2S3 nano-flower films consisted of ultrathin nanoflakes with a thickness of 5 nm are successfully grew on the surface of TiO2 nanorod arrays. PEG could play a role as the morphology-directing agent by confining crystal growth in certain directions, while PSS could provide coordination sites with long chains and lead to the formation of spherical structure. The energy conversion efficiency of In2S3 nano-flower/TiO2 photoelectrodes enhances thrice compared with that of bare TiO2 photoelectrode. This research presents further insight for improving the efficiency of semiconductors by using the suitable electron transfer channels, which may be promising for rational construction of solar conversion and storage devices.
Keywords: In2S3 nano-flower; Morphology-directing agent; Energy conversion efficiency; Hydrothermal method; Crystal growth;

Structural studies on drop-cast film based on functionalized gold nanoparticles network: The effect of thermal treatment by Laura Fontana; Ilaria Fratoddi; Iole Venditti; Dmitriy Ksenzov; Maria Vittoria Russo; Souren Grigorian (115-119).
In the present work the role of the thermal treatment on the reorganization of gold nanoparticles (AuNPs) functionalized with a π-conjugated dithiol ligand, namely 9,9-didodecyl-2,7-bis-thiofluorene, is studied by grazing incidence X-ray diffraction technique. For a detailed investigation of the structural changes and reorganization occurring in the AuNPs network and of the monitoring of complex interactions between nanoparticles, the line profiles are analyzed in out-of-plane and in-plane directions. The obtained data support the idea of the formation of a uniform network of nanoparticles that after annealing are extended from hexagonal to cubic arrangement.
Keywords: Gold nanoparticles network; In situ annealing; GIXD; Nanoparticles reorganization;

Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica–carbon nanocomposites were prepared by sol–gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica–carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.
Keywords: Silica–carbon; Nanocomposite; Surface; Copper catalyst; Reduction of NO;

Fe-based metal–organic frameworks (MOFs) including MIL-101(Fe), MIL-100(Fe), MIL-53(Fe), and MIL-88B(Fe) prepared via a facile solvothermal process were introduced as both adsorbents and catalysts to generate powerful radicals from persulfate for acid orange 7 (AO7) removal in aqueous solution. Various catalysts were described and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectra. Because of the high specific surface area of the materials, we studied the adsorption isotherms of the four MILs by the fitting of Langmuir adsorption isotherm. Meanwhile, the catalytic activities in persulfate oxidation system were investigated. The results showed that the sequence of the materials ability in the combination of adsorption and degradation was MIL-101(Fe) > MIL-100(Fe) > MIL-53(Fe) > MIL-88B(Fe), which had a close connection with the activity of metal ion in active site of the catalysts and their different cages in size. Moreover, the reactive species in MILs/persulfate system were identified as sulfate radicals and hydroxyl radicals. The reaction mechanism for persulfate activation over MILs was also studied.
Keywords: Metal–organic frameworks; Catalyst; Adsorption; Sulfate radicals; Degradation;

Diffusion barrier characteristics of co monolayer prepared by Langmuir Blodgett technique by Sumit Sharma; Mukesh Kumar; Sumita Rani; Dinesh Kumar (137-142).
Thermal stability of structures (a) Cu/SiO2/Si and (b) Cu/Co/SiO2/Si, indicating that presence of thin cobalt layer improves the thermal stability of the structure up to 600 °C.Monolayers of Co over SiO2/Si substrate were deposited using Langmuir Blodgett (LB) technique. The diffusion barrier capability of Co layer was evaluated against copper diffusion. The structure of the deposited Co layer was analyzed using X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS) and Atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO2/Si and Cu/Co/SiO2/Si test structures was studied and compared using X-ray diffraction (XRD), scanning electron microscope (SEM) and four probe techniques. The samples were annealed at different temperatures starting from 200 °C up to 700 °C in vacuum for 30 min. XRD results indicated that combination of Co/SiO2 worked as diffusion barrier up to 550 °C whereas SiO2 alone could work as barrier only up to 300 °C. Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. CV curves of these structures under the influence of Biased Thermal Stress (BTS) were analyzed. BTS was applied at 2.5 MV cm−1 at 150 °C. Results showed that in the presence of Co barrier layer there was no shift in the CV curve even after 90 min of BTS while in the absence of barrier there was a significant shift in the CV curve even after 30 min of BTS. Further these test structures were examined for leakage current density (j L) at same BTS conditions and leakage current density (j L) was plotted against the BTS duration. It was found that the Cu/Co/SiO2/Si test structure could survive about one and half time more than the Cu/SiO2/Si test structure.
Keywords: Langmuir Blodgett technique; Monolayer diffusion barrier; Biased thermal stress; XRD; C–V and leakage current characterization;

Transparent film with inverted conical microholes array for reflection enhancement by Biao Lei; Hongzhong Liu; Weitao Jiang; Bangdao Chen; Yongsheng Shi; Lei Yin; Xiaokang Liu (143-150).
PDMS has been widely utilized for microfluidic chips and microchannel detections, as its good optical properties are the prerequisite to achieve accurate and efficient detection. However, it is difficult to obtain effective information for opaque liquids. With the development of microchannel detection for wider fields, it is imperative to obtain more comprehensive information of the observed objects by integrating high transmission with enhanced reflection. This article investigates reflection enhancement by Polydimethylsiloxane (PDMS) film with inverted conical microholes array. PDMS film with inverted conical microholes array is fabricated by replication from the silicon mold with inverted microcones array which is prepared by Inductively Coupled Plasma (ICP) etch tool. The monolayer PDMS film with inverted conical microholes array shows a two-fold effectively increase in reflection, approximately up to 15%, at a broad wavelength range of 637–1131 nm and 1214–1350 nm, compared with bare PDMS film. In addition, the reflection can be further enhanced by multilayered lamination of PDMS film with inverted conical microholes array, and the enhancement is also dependent on the lamination way, i.e., for bilayer laminations, the maximum reflection enhancement occurs when with face-to-back lamination, and 32.79% larger than that with back-to-face lamination. From the experiments, the maximum reflectivity of 8-layered PDMS films can obtain 64.4% while the maximum reflectivity of monolayer PDMS film barely has 17.5%. The transparent film with inverted conical microholes array for reflection enhancement may find a variety of applications in optical devices, microchips, and energy conservation technologies etc.
Keywords: PDMS film; Inverted conical microholes array; Reflection enhancement;

A novel GR based zinc oxide nanorods nanocomposite modified glassy carbon electrode (GR/ZnORs/GCE) sensor has been developed for electroquantification of tizanidine in micellar medium.A new graphene/zinc oxide nanorods modified glassy carbon electrode (GR/ZnORs/GCE) based electrochemical sensor has been developed for the sensitive determination tizanidine (TZ) in solubilized system. The fabricated sensor was characterized by various electrochemical methods. Different kinetic parameters affecting the monitored electrocatalytic response were investigated and optimized for tizanidine determination at fabricated GR/ZnORs/GCE sensor and successfully compared with the results obtained at GR/SiO2/GCE, GR/GCE and at bare GCE. Under optimized conditions the square wave current is linear over the concentration range 0.80 ng mL−1 to 10.0 μg mL−1 with detection limit and quantification limit of 0.10 ng mL−1 and 3.45 ng mL−1 respectively. The applicability of proposed method is further extended to in vitro determination of the drug in pharmaceutical formulation with an acceptable recovery from 97.89% to 101.09%.
Keywords: Tizanidine (TZ); Graphene/zinc oxide nanorods modified glassy carbon electrode (GR/ZnORs/GCE); CTAB; Voltammetry; Sensors;

Impact of substrate nitridation on the growth of InN on In2O3(111) by plasma-assisted molecular beam epitaxy by YongJin Cho; Sergey Sadofev; Sergio Fernández-Garrido; Raffaella Calarco; Henning Riechert; Zbigniew Galazka; Reinhard Uecker; Oliver Brandt (159-162).
Display OmittedWe study the growth of InN films on In2O3(111) substrates by plasma-assisted molecular beam epitaxy under N excess. InN films deposited directly on In2O3(111) exhibit a strongly faceted morphology. A nitridation step prior to growth is found to convert the In2O3(111) surface to InN{0001}. The morphology of InN films deposited on such nitridated In2O3(111) substrates is characteristic for growth by instable step-flow and is thus drastically different from the three-dimensional growth obtained without nitridation. We show that this change originates from the different polarity of the films: while InN films deposited directly on In2O3(111) are In-polar, they are N-polar when grown on the nitridated substrate.
Keywords: InN; In2O3; MBE; Nitridation; Polarity;

One-step fabrication of nickel nanocones by electrodeposition using CaCl2·2H2O as capping reagent by Jae Min Lee; Kyung Kuk Jung; Sung Ho Lee; Jong Soo Ko (163-169).
In this research, a method for the fabrication of nickel nanocones through the addition of CaCl2·2H2O to an electrodeposition solution was proposed. When electrodeposition was performed after CaCl2·2H2O addition, precipitation of the Ni ions onto the (2 0 0) crystal face was suppressed and anisotropic growth of the nickel electrodeposited structures was promoted. Sharper nanocones were produced with increasing concentration of CaCl2·2H2O added to the solution. Moreover, when temperature of the electrodeposition solutions approached 60 °C, the apex angle of the nanostructures decreased. In addition, the nanocones produced were applied to superhydrophobic surface modification using a plasma-polymerized fluorocarbon (PPFC) coating. When the solution temperature was maintained at 60 °C and the concentration of the added CaCl2·2H2O was 1.2 M or higher, the fabricated samples showed superhydrophobic surface properties. The proposed nickel nanocone formation method can be applied to various industrial fields that require metal nanocones, including superhydrophobic surface modification.
Keywords: Nanocone; CaCl2·2H2O; Electrodeposition; Nickel nanostructure; Superhydrophobic;

Template-free synthesis of hierarchical TiO2 hollow microspheres as scattering layer for dye-sensitized solar cells by Yichuan Rui; Linlin Wang; Jiachang Zhao; Hongzhi Wang; Yaogang Li; Qinghong Zhang; Jingli Xu (170-177).
Hierarchical TiO2 hollow microspheres were synthesized by a 2-step process consisting of thermal hydrolysis and subsequent solvothermal reaction. Quasi-monodispersed solid TiO2 microspheres aggregated by amorphous particles were firstly obtained by the controlled thermal hydrolysis of titanium sulfate, and then the solid structures transformed to hollow ones and crystallized during the subsequent solvothermal treatment. SEM and TEM images of the samples revealed that the morphological evolution was in perfect accordance with the inside-out Ostwald ripening mechanism. The rich porosity and unique hierarchical hollow structure endow the TiO2 microspheres with a large specific surface area of 108.0 m2  g−1. As an effective anode material for dye-sensitized solar cells, TiO2 hollow microspheres showed good capability of dye adsorption and strong light scattering, leading to a comparable energy conversion efficiency to the commercial 18NR-T transparent titania. Finally, a high efficiency of 7.84% was achieved for the bi-layer DSSC by coating the hollow microspheres on top of the 18NR-T titania as the light scattering layer.
Keywords: TiO2 hollow microspheres; Dye-sensitized solar cells; Ostwald ripening; Scattering; Photoelectrochemical efficiency;

Electrodeposition of silver nanoparticle arrays on transparent conductive oxides by Dezhong Zhang; Yang Tang; Fuguo Jiang; Zhihua Han; Jie Chen (178-182).
In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.
Keywords: Sliver nanoparticle; Electrodeposition and aluminum-doped zinc oxide;

The thin film containing CuS and In2S3 can be converted into CuInS2 by irradiation of intense pulses of light.In this paper, we demonstrate the use of high intensity pulsed light technique for the synthesis of phase pure CuInS2 (CIS) thin film at room temperature. The intense pulse of light is used to induce sintering of binary sulfides CuS and In2S3 to produce CIS phase without any direct thermal treatment. Light energy equivalent to the 706 mJ/cm2 is found to be the best energy to convert the CIS precursor film deposited at room temperature into CIS pure phase and well crystalline film. The CIS absorber film thus prepared is useful in making printed solar cell at room temperature on substrate with large area.
Keywords: Deposition; Thin film; Photovoltaic; Sintering; Low temperature solar cell;

Effect of fluorination on the mechanical behavior and electromagnetic interference shielding of MWCNT/epoxy composites by Si-Eun Lee; Man Young Lee; Min-Kyung Lee; Euigyung Jeong; Young-Seak Lee (189-195).
MWCNTs were fluorinated using various fluorine concentrations and used as a reinforcing material to improve the mechanical properties and electromagnetic shielding effect of epoxy composites.Multi-walled carbon nanotube (MWCNT)/epoxy composites were prepared using MWCNT fluorinated to different extents. The mechanical properties, fracture surface morphologies and electromagnetic interference shielding efficiency (EMI-SE) of these composites were evaluated for epoxy matrices containing MWCNT with degrees of fluorination. The tensile strengths of the MWCNT/epoxy composites improved by 31% with treated MWCNT compared to that of the epoxy composites with untreated MWCNT. The EMI-SE values of the fluorinated MWCNT/epoxy composites improved up to 26% with increasing fluorination extent. The mechanical and electrical properties enhancement of the composites were attributed to the fluorinated MWCNT, which improved both the dispersion of the MWCNT in epoxy matrix and interfacial interactions between the MWCNT and the epoxy matrix.
Keywords: Carbon nanotube; Polymer-matrix composites (PMCs); Electrical properties; Mechanical properties; Surface treatments;

Microstructure and properties of SiC-coated carbon fibers prepared by radio frequency magnetron sputtering by Yong Cheng; Xiaozhong Huang; Zuojuan Du; Jianrong Xiao; Shan Zhou; Yongshan Wei (196-200).
SiC-coated carbon fibers are prepared at room temperature with different radio-frequency magnetron sputtering powers. Results show that the coated carbon fibers have uniform, continuous, and flawless surfaces. The mean strengths of the coated carbon fibers with different sputtering powers are not influenced by other factors. Filament strength of SiC-coated carbon fibers increases by approximately 2% compared with that of uncoated carbon fibers at a sputtering power of <200 W. The filament strengths of the coated fibers increase by 9.3% and 12% at sputtering powers of 250 and 300 W, respectively. However, the mean strength of the SiC-coated carbon fibers decreased by 8% at a sputtering power of 400 W.
Keywords: SiC coating; Carbon material; Strength; Sputtering;

Effective water splitting using CuO x /TiO2 composite films: Role of Cu species and content in hydrogen generation by Qianqian Hu; Jiquan Huang; Guojing Li; Jian Chen; Zhaojun Zhang; Zhonghua Deng; Yabin Jiang; Wang Guo; Yongge Cao (201-206).
We have fabricated a series of CuO x /TiO2 composite films composed of TiO2 nanorods and CuO x nanopariticles with copper content in the range of 0–4.75 at.% by a facile magnetron sputtering method for hydrogen generation from water splitting. By virtue of the one-dimensional TiO2 nanostructures, all the nanorods films show excellent photocatalytic activity. Especially, there appear to be an optimum Cu content of 2.72 at.% giving the H2 evolution rate of 53 mmol m−2  h−1, which is about 15 times higher than that of pristine anatase TiO2 nanorods film. To evaluate the effect of foreign copper on the photocatalytic properties, comprehensive structural, morphology and surface characterizations of catalysts have been carried out. It is found that CuO is an unstable species which is inevitably reduced to Cu2O during the initial stage of photocatalytic reaction, and the occurrence of highly disperse Cu2O species is responsible for the improved photocatalytic activity.
Keywords: TiO2 nanorods; Copper; Efficient water splitting;

Tunable fabrication of hierarchical hybrids via the incorporation of poly(dopamine) functional interlayer by Ting Xu; Xin Zhao; Junxian Zhang; Jie Dong; Qinghua Zhang (207-214).
Display OmittedTwo kinds of ternary hybrids were prepared by anchoring different shapes and loadings of Au nanoparticles (NPs) on poly(dopamine) (PDA) functionalized polystyrene (PS) microspheres with two different strategies, i.e., in situ reduction and self-assembly approach. PDA coatings were firstly introduced to functionalize the hydrophobic PS surface with sufficient amino and hydroxyl groups, which enhanced the interaction between Au NPs and the polymer spheres. Thus, Au NPs could be easily immobilized onto the surface of the PDA/PS microspheres, and the hierarchical composite microspheres exhibited a well-defined core/shell structure without sacrificing the spherical PS morphology. PS/PDA/Au-R and PS/PDA/Au-A microspheres fabricated by in situ reduction and self-assembly approach showed different distinct Au nano-shell morphology with the corresponding optical, catalytic and electrochemical properties. Field emission scanning electron microscopy and transmission electronic microscopy verified these hierarchical structures with the ultrathin PDA film incorporating between the inner PS core and the outer Au NPs shell. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the presence of PDA and Au layer on the surface of the composite particles. These green and facile methods with mild experimental conditions can extend to fabricate other polymer or inorganic substrates coated by various noble metals.
Keywords: Au nanoparticles; Polydopamine; Core–shell conducting spheres; Polymer microsphere;

Enhanced removal of Cd(II) and Pb(II) by composites of mesoporous carbon stabilized alumina by Weichun Yang; Qiongzhi Tang; Jingmiao Wei; Yajun Ran; Liyuan Chai; Haiying Wang (215-223).
A novel adsorbent of mesoporous carbon stabilized alumina (MC/Al2O3) was synthesized through one-pot hard-templating method. The adsorption potential of MC/Al2O3 for Cd(II) and Pb(II) from aqueous solution was investigated compared with the mesoporous carbon. The results indicated the MC/Al2O3 showed excellent performance for Cd(II) and Pb(II) removal, the adsorption capacity reached 49.98 mg g−1 for Cd(II) with initial concentration of 50 mg L−1 and reached 235.57 mg g−1 for Pb(II) with initial concentration of 250 mg L−1, respectively. The kinetics data of Cd(II) adsorption demonstrated that the Cd(II) adsorption rate was fast, and the removal efficiencies with initial concentration of 10 and 50 mg L−1 can reach up 99% within 5 and 20 min, respectively. The pseudo-second-order kinetic model could describe the kinetics of Cd(II) adsorption well, indicating the chemical reaction was the rate-controlling step. The mechanism for Cd(II) and Pb(II) adsorption by MC/Al2O3 was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR), and the results indicated that the excellent performance for Cd(II) and Pb(II) adsorption of MC/Al2O3 was mainly attributed to its high surface area and the special functional groups of hydroxy-aluminum, hydroxyl, carboxylic through the formation of strong surface complexation or ion-exchange. It was concluded that MC/Al2O3 can be recognized as an effective adsorbent for removal of Cd(II) and Pb(II) in aqueous solution.
Keywords: Enhanced removal; Cd(II); Pb(II); Mesoporous carbon stabilized alumina; Hydroxy-aluminum (Al-OH);

Electrodeposition and characterization of Ni–Mo–ZrO2 composite coatings by A. Laszczyńska; J. Winiarski; B. Szczygieł; I. Szczygieł (224-231).
Ni–Mo–ZrO2 composite coatings were produced by electrodeposition technique from citrate electrolytes containing dispersed ZrO2 nanopowder. The influence of deposition parameters i.e. concentration of molybdate and ZrO2 nanoparticles in the electrolyte, bath pH and deposition current density on the composition and surface morphology of the coating has been investigated. The structure, microhardness and corrosion properties of Ni–Mo–ZrO2 composites with different molybdenum and ZrO2 content have been also examined. It was found that ZrO2 content in the deposit is increased by rising the nanoparticles concentration in the plating solution up to 20 g dm−3. An increase in molybdate concentration in the electrolyte affects negatively the amount of codeposited ZrO2 nanoparticles. The correlation between the deposition current efficiency and ZrO2 content in the composite coating has been also observed. A decrease in deposition current efficiency leads to deposition of Ni–Mo–ZrO2 composite with low nanoparticles content. This may be explained by formation of higher amounts of gas bubbles on the cathode surface, which prevent the adsorption of ZrO2 nanoparticles on the growing deposit. The XRD analysis revealed that all the studied Ni–Mo–ZrO2 coatings were composed of a single, nanocrystalline phase with FCC structure. It was found that the incorporation of ZrO2 nanoparticles into Ni–Mo alloy matrix affects positively the microhardness and also slightly improves the corrosion properties of Ni–Mo alloy coating.
Keywords: Electrodeposition; Ni–Mo alloy; Composite coating; X-ray diffraction; Microhardness;

Structure and antireflection properties of SiNWs arrays form mc-Si wafer through Ag-catalyzed chemical etching by Shaoyuan Li; Wenhui Ma; Xiuhua Chen; Keqiang Xie; Yuping Li; Xiao He; Xi Yang; Yun Lei (232-240).
A simple and low cost MACE method was demonstrated for efficiently texturing commercial mc-Si wafer at room temperature. The effects of fabrication parameters (deposition time, HF concentration, H2O2 concentration, and etching time) on the morphology structure, antireflection property of textured mc-Si were carefully studied. The large scale SiNWs arrays with different structure can be obtained under various fabrication conditions. Meanwhile, the results indicate that the fabricate parameters have important effect on the reflectance of textured mc-Si sample in the order of etching time > deposition time > H2O2 concentration > HF concentration. The comprehensive research results indicate that it is more beneficial for the nanowire arrays with tapering structure and the length of 13 μm to obtain excellent antireflection property. Under these optimization conditions, the textured mc-Si shows an outstanding anti-reflectance ability of ∼5.6%, which indicates that the Ag-catalysis etched mc-Si shows a huge potential application in high-efficiency polysilicon solar cells.
Keywords: Multi-crystalline silicon (mc-Si); Ag-catalyzed chemical etching; SiNWs films; Structural characterization; Anti-reflectance;

Hydration effects and antifouling properties of poly(vinyl chloride-co-PEGMA) membranes studied using molecular dynamics simulations by Abdul Rajjak Shaikh; Saeid Rajabzadeh; Ryuichi Matsuo; Hiromitsu Takaba; Hideto Matsuyama (241-250).
Hydration has a significant effect on surface of the copolymer membranes.Polyvinyl chloride (PVC) membranes are widely used in water treatment because of their low cost and chemical stability. However, PVC membranes can become fouled, and this restricts their applications in membrane technology. In order to enhance the antifouling property of PVC membranes, copolymers such as poly(vinyl chloride-co-poly(ethylene glycol)methyl ether methacrylate) (poly(VC-co-PEGMA)) with different PEGMA segment percentages were synthesized in our previous work. Experimentally, it was observed that the poly(VC-co-PEGMA) copolymer has better antifouling properties than those of PVC membranes. Here, we explore effect of the PEGMA segment percentage on the surface hydration properties of poly(VC-co-PEGMA) copolymers. Density functional theory calculations and molecular dynamics simulations were carried out to understand the interactions between PVC and PEGMA. Model structures of these systems were validated by comparing the simulated values of their volumetric properties with the experimental values. MD studies showed that increasing PEGMA percentage in the copolymer increases the interaction with water molecules, leading to improved resistance to fouling. The antifouling mechanism is also discussed with respect to surface hydration and water dynamicity. This study could form a basis for the systematic studies of polymeric membranes as well as their stability from the extent of solvent–polymer, solvent–solvent, and polymer–polymer interactions.
Keywords: Molecular dynamics; Hydration; Membrane surface; Antifouling; Density functional theory; Swelling;

AB stacked few layer graphene growth by chemical vapor deposition on single crystal Rh(1 1 1) and electronic structure characterization by Apostolis Kordatos; Nikolaos Kelaidis; Sigiava Aminalragia Giamini; Jose Marquez-Velasco; Evangelia Xenogiannopoulou; Polychronis Tsipas; George Kordas; Athanasios Dimoulas (251-256).
Graphene synthesis on single crystal Rh(1 1 1) catalytic substrates is performed by Chemical Vapor Deposition (CVD) at 1000 °C and atmospheric pressure. Raman analysis shows full substrate coverage with few layer graphene. It is found that the cool-down rate strongly affects the graphene stacking order. When lowered, the percentage of AB (Bernal) -stacked regions increases, leading to an almost full AB stacking order. When increased, the percentage of AB-stacked graphene regions decreases to a point where almost a full non AB-stacked graphene is grown.For a slow cool-down rate, graphene with AB stacking order and good epitaxial orientation with the substrate is achieved. This is indicated mainly by Raman characterization and confirmed by Reflection high-energy electron diffraction (RHEED) imaging. Additional Scanning Tunneling Microscopy (STM) topography data confirm that the grown graphene is mainly an AB-stacked structure. The electronic structure of the graphene/Rh(1 1 1) system is examined by Angle resolved Photo-Emission Spectroscopy (ARPES), where σ and π bands of graphene, are observed. Graphene's ΓK direction is aligned with the ΓK direction of the substrate, indicating no significant contribution from rotated domains.
Keywords: Graphene; Rhodium; CVD; Stacking; ARPES; STM;

Insight into the Reaction Mechanisms of Methanol on PtRu/Pt(111): A Density Functional Study by Qiuyue Ding; Wenbin Xu; Pengpeng Sang; Jing Xu; Lianming Zhao; Xiaoli He; Wenyue Guo (257-266).
Periodic DFT calculations have been performed to systematically investigate the mechanisms of methanol decomposition and oxidation on the PtRu/Pt(111) surface. Geometries and energies for the primary species involved are analyzed and the reaction network has been mapped out. The calculation shows that among three initial C―H, O―H, and C―O bond scissions of methanol, the O―H bond scission is found to be the most favorable and bears a lower energy barrier than the desorption of methanol. The decomposition of CH3O occurs via the path CH3O → CH2O → CHO → CO with the limiting step of the first dehydrogenation. Although the oxidation of CO is hindered by a high barrier, the CHO oxidation to CHOOH could occur facilely. Further decomposition of formic acid to CO2 and/or CO could occur via four possible pathways, that is, initial C―H, O―H, and C―O bond activations as well as simultaneous activation of C―H and C―O bonds, where the first pathway, HCOOH → COOH → CO2, is the most favorable from a kinetic point of view. Compared to that on Pt(111), methanol on PtRu/Pt(111) prefers to decomposition rather than desorption and then oxidation via the favorable non-CO path with a lower rate-determining energy barrier of CH3O → CH2O for the whole reaction, which indicates that PtRu alloy can improved tolerance toward CO poisoning compared with pure Pt.
Keywords: Reaction mechanism; Methanol oxidation; PtRu alloy; Surface modification;

Multifunctional nanocomposites Fe3O4@SiO2-EDTA for Pb(II) and Cu(II) removal from aqueous solutions by Yu Liu; Ruiqi Fu; Yue Sun; Xiaoxin Zhou; Shams Ali Baig; Xinhua Xu (267-276).
In this study, EDTA-functionalized Fe3O4 (Fe3O4@SiO2-EDTA) was prepared by silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (EDTA-silane) and hydroxyl groups for Pb(II) and Cu(II) removal from aqueous solutions. Fe3O4@SiO2-EDTA composites were characterized using SEM, TEM, EDX, FTIR, XPS, TGA and saturated magnetization techniques. Maximum Pb(II) adsorption capacity was found to be 114.94 mg g−1 with SiO2/EDTA molar ratio of 2.5:1. The adsorption rate was significantly fast and the equilibrium was reached within 10 min. The optimum pH was recorded to be 5.0. The maximum adsorption capacity of the studied heavy metal ions calculated by Langmuir model followed the order: Cu(II) (0.58 mmol g−1) > Pb(II) (0.55 mmol g−1) ≈ Ni(II) (0.55 mmol g−1) > Cd(II) (0.45 mmol g−1). Moreover, Pb(II) and Cu(II) adsorption capacities were not significantly affected by co-existing cations and NOM. These results suggested that this adsorbent can be considered as a promising adsorbent to remove Pb(II) and Cu(II) from wastewaters.
Keywords: Fe3O4 nanoparticles; EDTA; Functionalization; Heavy metals; Adsorption;

Facile fabrication of iron-based superhydrophobic surfaces via electric corrosion without bath by Qinghe Sun; Hongtao Liu; Tianchi Chen; Yan Wei; Zhu Wei (277-287).
Superhydrophobic surface is of wide application in the field of catalysis, lubrication, waterproof, biomedical materials, etc. The superhydrophobic surface based on hard metal is worth further study due to its advantages of high strength and wear resistance. This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion and studies the properties of as-prepared superhydrophobic surface. The hydrophobic properties were characterized by a water sliding angle (SA) and a water contact angle (CA) measured by the Surface tension instrument. A Scanning electron microscope was used to analyze the structure of the corrosion surface. The surface compositions were characterized by an Energy Dispersive Spectrum. The Electrochemical workstation was used to measure its anti-corrosion property. The anti-icing performance was characterized by a steam-freezing test in Environmental testing chamber. The SiC sandpaper and 500 g weight were used to test the friction property. The research result shows that the superhydrophobic surface can be successfully fabricated by electrocorrosion on carbon steel substrate under appropriate process; the contact angle of the as-prepared superhydrophobic surface can be up to 152 ± 0.5°, and the sliding angle is 1–2°; its anti-corrosion property, anti-icing performance and the friction property all show an excellent level. This method provides the possibility of industrialization of superhydrophobic surface based on iron substrate as it can prepare massive superhydrophobic surface quickly.
Keywords: Superhydrophobic; Electric corrosion; Hard metal; The contact angle; Corrosion resistance;

Improving the forming capability of laser dynamic forming by using rubber as a forming medium by Zongbao Shen; Huixia Liu; Xiao Wang; Cuntang Wang (288-298).
Laser dynamic forming (LDF) is a novel high velocity forming technique, which employs laser-generated shock wave to load the sample. The forming velocity induced by the high energy laser pulse may exceed the critical forming velocity, resulting in the occurrence of premature fracture. To avoid the above premature fracture, rubber is introduced in LDF as a forming medium to prolong the loading duration in this paper. Laser induced shock wave energy is transferred to the sample in different forming stages, so the forming velocity can be kept below the critical forming velocity when the initial laser energy is high for fracture. Bulge forming experiments with and without rubber were performed to study the effect of rubber on loading duration. The experimental results show that, the shock wave energy attenuates during the propagation through the rubber layer, the rubber can avoid the premature fracture. So the plastic deformation can continue, the forming capability of LDF is improved. Due to the severe plastic deformation under rubber compression, adiabatic shear bands (ASB) occur in LDF with rubber. The material softening in ASB leads to the irregular fracture, which is different from the premature fracture pattern (regular fracture) in LDF without rubber. To better understand this deformation behavior, Johnson–Cook model is used to simulate the dynamic response and the evolution of ASB of copper sample. The simulation results also indicate the rubber can prolong the loading duration.
Keywords: Laser dynamic forming; Rubber; Loading duration; Forming capability; Material softening; Dynamic fracture;

Co-production of hydrogen and carbon nanotubes on nickel foam via methane catalytic decomposition by Dan Ping; Chaoxian Wang; Xinfa Dong; Yingchao Dong (299-307).
The co-production of CO x -free hydrogen and carbon nanotubes (CNTs) was achieved on 3-dimensional (3D) macroporous nickel foam (NF) via methane catalytic decomposition (MCD) over nano-Ni catalysts using chemical vapor deposition (CVD) technique. By a simple coating of a NiO–Al2O3 binary mixture sol followed by a drying–calcination–reduction treatment, NF supported composite catalysts (denoted as Ni y AlO x /NF) with Al2O3 transition-layer incorporated with well-dispersed nano-Ni catalysts were successfully prepared. The effects of Ni loading, calcination temperature and reaction temperature on the performance for simultaneous production of CO x -free hydrogen and CNTs were investigated in detail. Catalysts before and after MCD were characterized by XRD, TPR, SEM, TEM, TG and Raman spectroscopy technology. Results show that increasing Ni loading, lowering calcination temperature and optimizing MCD reaction temperature resulted in high production efficiency of CO x -free H2 and carbon, but broader diameter distribution of CNTs. Through detailed parameter optimization, the catalyst with a Ni/Al molar ratio of 0.1, calcination temperature of 550 °C and MCD temperature of 650 °C was favorable to simultaneously produce CO x -free hydrogen with a growth rate as high as 10.3% and CNTs with uniform size on NF.
Keywords: Nickel foam; Carbon nanotubes; NiO–Al2O3 transition-layer; Methane catalytic decomposition;

Low temperature processed planar heterojunction perovskite solar cells employing silver nanowires as top electrode by Jianhua Zhang; Fushan Li; Kaiyu Yang; Chandrasekar Perumal Veeramalai; Tailiang Guo (308-313).
In this paper, we reported a low temperature processed planar heterojunction perovskite solar cell employing silver nanowires as the top electrode and ZnO nanoparticles as the electron transport layer. The CH3NH3PbI3 perovskite was grown as the light absorber via two-step spin-coating technique. The as-fabricated perovskite solar cell exhibited the highest power conversion efficiency of 9.21% with short circuit current density of 19.75 mA cm−2, open circuit voltage of 1.02, and fill factor value of 0.457. The solar cell's performance showed negligible difference between the forward and reverse bias scan. This work paves a way for realizing low cost solution processable solar cells.
Keywords: Perovskite; Solar cells; Planar; Silver nanowire;

Fe2O3 coated TiO2 nanotube (Fe2O3@TiO2 nanotube) composites anodes for lithium-ion batteries (LIBs) have been prepared by hydrothermal and atomic layer deposition (ALD) method. The composites anodes show a reversible capacity of 450 mAh g−1 after 150 cycles at the current density of 200 mA g−1, which is approximately two times of pure TiO2 nanotubes. Even at a high current density of 3200 mA g−1, the composite anodes still exhibit a good capacity of 198 mAh g−1, more than three times higher than that of pure TiO2 nanotubes. The good reversible capacity and rete capability of composite anodes indicate the cumulative effect of Fe2O3 on TiO2 nanotube by the integration of structural stability of TiO2 and high theoretical capacity of Fe2O3.
Keywords: Fe2O3; TiO2 nanotube; Atomic layer deposition (ALD); Lithium ion battery;

Corrosion behavior of niobium coated 304 stainless steel in acid solution by T.J. Pan; Y. Chen; B. Zhang; J. Hu; C. Li (320-325).
The niobium coating is fabricated on the surface of AISI Type 304 stainless steel (304SS) by using a high energy micro arc alloying technique in order to improvecorrosion resistance of the steel against acidic environments. The electrochemical corrosion resistance of the niobium coating in 0.7 M sulfuric acid solutions is evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and the open circuit potential versus time. Electrochemical measurements indicate that the niobium coating increases the free corrosion potential of the substrate by 110 mV and a reduction in the corrosion rate by two orders of magnitude compared to the substrate alone. The niobium coating maintains large impedance and effectively offers good protection for the substrate during the long-term exposure tests, which is mainly ascribed to the niobium coating acting inhibiting permeation of corrosive species. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion resistance behavior of the niobium coating in acid solutions.
Keywords: Niobium coating; Acid corrosion; Electrochemical measurement; High energy micro arc alloying;

Binding profiles of creatinine on MIP and NIP using 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) and aluminium ion (Al3+) as the cross-linkers.In this study, sol–gel processing was proposed to prepare a creatinine (Cre)-imprinted molecularly imprinted polymer (MIP). The intermolecular interaction constituted by the cross-linkers, i.e., 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) and aluminium ion (Al3+), was studied and compared in order to form a confined matrix that promises the effectiveness of molecular imprinting. In view of the shape recognition, the hydrogen bonded Cre-AMPS did not demonstrate good recognition of Cre, with Cre binding found only at 5.70 ± 0.15 mg g−1 of MIP. Whilst, MIP cross-linked using Al3+ was able to attain an excellent Cre adsorption capacity of 19.48 ± 0.64 mg g−1 of MIP via the stronger ionic interaction of Cre-Al3+. Based on the Scatchard analysis, a higher Cre concentration in testing solution required greater driving force to resolve the binding resistance of Cre molecules, so as to have a precise Cre binding with shape factor. The molecular recognition ability of Cre-MIP in present work was shape-specific for Cre as compared to its structural analogue, 2-pyrrolidinone (2-pyr), by an ideal selectivity coefficient of 6.57 ± 0.10. In overall, this study has come up with a practical approach on the preparation of MIP for the detection of renal dysfunction by point-of-care Cre testing.
Keywords: Molecularly imprinted polymer; Creatinine; Intermolecular interaction; Shape recognition; Mass transfer resistance; Driving force;

Ba0.85Ca0.15Ti0.9−x Zr0.1Cu x O3 (x  = 0.2, 0.4, 0.6, 0.8 and 1%) ceramics are prepared from nanopowders synthesized using a hydrothermal method at low sintering temperature of 1300 °C for 3 h. The samples are dense microstructures investigated by scanning electron microscopy (SEM). The dielectric constants, ferroelectric hysteresis loops of Ba0.85Ca0.15Ti0.9−x Zr0.1Cu x O3 ceramics are well character.Ba0.85Ca0.15Ti0.9Zr0.1−x Cu x O3 (BCTZC) nanopowders were synthesized using a hydrothermal method after which they were pressed into discs and sintered in air at 1300 °C for 3 h to form ceramic samples. The phase and microstructure of the powder and ceramic samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results indicated that the ceramic samples exhibited a tetragonal structure and that CuO, BaZrO3 or CaTiO3 impurity phases, which had been present in the powder samples, were not observed. The average grain sizes in the ceramic samples were found to be 17.0, 16.1, 20.0, 18.1 and 19.6 μm for Cu mole fractions x of 0.002, 0.004, 0.006, 0.008 and 0.01, respectively. The dielectric constants, ferroelectric hysteresis loops and piezoelectric charge coefficients of the BCZTC ceramic samples were also investigated. Optimum values for the relative dielectric constant (ɛ′), tan  δ and piezoelectric charge coefficient (d 33) of the samples were 3830, 0.03 and 306 pC/N, respectively, in the Cu mole fraction samples with x  = 0.002.
Keywords: Ba0.85Ca0.15Ti0.9Zr0.1−x Cu x O3; Lead-free ceramics; Hydrothermal method; Dielectric constant; Ferroelectric hysteresis loop; Piezoelectric charge coefficient;

Rapid synthesis of inherently robust and stable superhydrophobic carbon soot coatings by Karekin D. Esmeryan; Carlos E. Castano; Ashton H. Bressler; Mehran Abolghasemibizaki; Reza Mohammadi (341-347).
The fabrication of superhydrophobic coatings using a candle flame or rapeseed oil has become very attractive as a novel approach for synthesis of water repellent surfaces. Here, we report an improved, simplified and time-efficient method for the preparation of robust superhydrophobic carbon soot that does not require any additional stabilizers or chemical treatment. The soot's inherent stabilization is achieved using a specially-designed cone-shaped aluminum chimney, mounted over an ignited paper-based wick immersed in a rapeseed oil. Such configuration decreases the level of oxygen during the process of combustion; altering the ratio of chemical bonds in the soot. As a result, the fractal-like network of the carbon nanoparticles is converted into dense and fused carbon chains, rigidly coupled to the substrate surface. The modified carbon coating shows thermal sustainability and retains superhydrophobicity up to ∼300 °C. Furthermore, it demonstrates a low contact angle hysteresis of 0.7–1.2° accompanied by enhanced surface adhesion and mechanical durability under random water flows. In addition, the soot's deposition rate of ∼1.5 μm/s reduces the exposure time of the substrate to heat and consequently minimizes the thermal effects, allowing the creation of superhydrophobic coatings on materials with low thermal stability (e.g. wood or polyethylene).
Keywords: Superhydrophobicity; Carbon soot; Rapeseed oil; Cone-shaped chimney;

Ultra-multiple and reproducible resistance levels based on intrinsic crystallization properties of Ge1Sb4Te7 film by You Yin; Shota Iwashita; Sumio Hosaka; Tao Wang; Jingze Li; Yang Liu; Qi Yu (348-353).
Ge1Sb4Te7 (GST147) was adopted as the storage media for multiple resistance levels. It was exhibited that the resistivity of GST147 gradually dropped by about 3–4 orders of magnitude due to crystallization with the annealing temperature, which is critical to realize multiple resistance levels. The ultra-multiple 27 resistance levels in TiSi3/GST147 lateral phase-change memory device were demonstrated simply by controlling the maximum sweeping currents for programming the device resistance. Furthermore, the reproducibility of the six resistance levels was demonstrated and these levels were distinguishable from each other. This study indicates that GST147 is a media suitable for stable ultra-multiple level storage, enabling low-cost ultrahigh-density nonvolatile memory.
Keywords: Phase-change memory; Nonvolatile memory; Multilevel storage;

Display OmittedThis paper investigates the contact characteristics between a copper workpiece and a diamond tool in a force sensor-integrated fast tool servo (FS-FTS) for single point diamond microcutting and in-process measurement of ultra-precision surface forms of the workpiece. Molecular dynamics (MD) simulations are carried out to identify the subnanometric elastic-plastic transition contact depth, at which the plastic deformation in the workpiece is initiated. This critical depth can be used to optimize the FS-FTS as well as the cutting/measurement process. It is clarified that the vibrations of the copper atoms in the MD model have a great influence on the subnanometric MD simulation results. A multi-relaxation time method is then proposed to reduce the influence of the atom vibrations based on the fact that the dominant vibration component has a certain period determined by the size of the MD model. It is also identified that for a subnanometric contact depth, the position of the tool tip for the contact force to be zero during the retracting operation of the tool does not correspond to the final depth of the permanent contact impression on the workpiece surface. The accuracy for identification of the transition contact depth is then improved by observing the residual defects on the workpiece surface after the tool retracting.
Keywords: Molecular dynamics; Microcutting; Measurement; Contact depth; Elastic-plastic transition; Fast tool servo; Surface damage;

Two-sided and simultaneous laser shock peening impacts is considered as a novel surface treatment technology for the turbine blade and thin-walled component. In this paper, tensile properties of Mg–Al–Mn alloy specimens with different sheet thickness under two kinds of laser shock peening strategies were investigated, and an overlapping three-dimension axisymmetric numerical model was developed to analyze the effects of sheet thickness on residual stress distributions. Meanwhile, special attentions were paid to the in-depth microstructural evolution as a function of sheet thickness. Results showed that sheet thickness had an important influence on the tensile properties of Mg–Al–Mn alloy, and the generated residual stress distribution and grain arrangement were two important factors. The corresponding influence mechanism of sheet thickness on the tensile properties of Mg–Al–Mn alloy was also presented, and the optimal thickness of Mg–Al–Mn alloy sheet may be 4 mm or more.
Keywords: Mg–Al–Mn alloy; Laser shock peening; Stress–strain curve; Residual stress distribution; Grain arrangement; Ultimate tensile strength;

Improving the ALD-grown Y2O3/Ge interface quality by surface and annealing treatments by C. Zimmermann; O. Bethge; K. Winkler; B. Lutzer; E. Bertagnolli (377-383).
Metal Oxide Semiconductor capacitors are investigated, employing ALD grown Y2O3 as gate dielectric, and n-type (1 0 0) germanium as channel substrate. The effect of post deposition annealing (PDA) in oxygen and forming gas atmosphere using a thin catalytically acting platinum (Pt)-layer on the Y2O3/Ge interface is electrically analyzed for buffered hydrofluoric (BHF) and thermally pre-treated Ge-surfaces.The Pt-assisted PDA ensures even for BHF pre-treated samples very low values for the interface trap density D it of 1.55 × 1011  eV−1  cm−2 and low leakage current densities J of <7 × 10−9  A/cm2 outperforming conventional PDA treatments. The interfacial formation of GeO2 and yttrium germanate after PDA is proven by using X-ray Photoelectron Spectroscopy measurements.
Keywords: ALD; Y2O3; XPS-measurements; Surface pre-treatment; Improvement of interfacial layer; Germanium MOSCAPs;

Smart epoxy coating containing Ce-MCM-22 zeolites for corrosion protection of Mg-Li alloy by Yanli Wang; Yanhao Zhu; Chao Li; Dalei Song; Tao Zhang; Xinran Zheng; Yongde Yan; Meng Zhang; Jun Wang; Dmitry G. Shchukin (384-389).
The epoxy coatings containing MCM-22 and Ce-MCM-22 zeolites were prepared by coating method on the Mg-Li alloy surface. The influence of MCM-22 and Ce-MCM-22 zeolites on corrosion protection of the epoxy coating was studied. The epoxy coating containing Ce-MCM-22 zeolites showed high corrosion resistance. Artificial defects in the epoxy coating containing Ce-MCM-22 zeolites on the Mg-Li surface were produced by the needle punching. The results show that the epoxy coating containing Ce-MCM-22 zeolites exhibits self-healing corrosion inhibition capabilities. It is ascribed to the fact that the Ce3+ ions are released from MCM-22 zeolites based on ion exchange of zeolite in the corrosion process of the Mg-Li alloy substrate. MCM-22 zeolites as reservoirs provided a prolonged release of cerium ions.
Keywords: MCM-22 zeolite; Cerium; Self-healing; Corrosion; Mg-Li alloy;

Ammonia-treated porous carbon derived from ZIF-8 for enhanced CO2 adsorption by Xiancheng Ma; Liqing Li; Shaobin Wang; Mingming Lu; Hailong Li; Weiwu Ma; Tim C. Keener (390-397).
The role of nitrogen species in increasing CO2 adsorption capacity has been explained with the mechanisms of base–acid interaction, as well as hydrogen bonds interaction.A porous carbon (ZC) was prepared at 900 °C using zeolitic imidazolate framework-8 (ZIF-8) as a solid template for CO2 adsorption. The ZC was further treated by ammonia functionalization to improve CO2 uptake. The textural and surface characteristics of ZC samples were determined by X-ray diffraction (XRD), N2 adsorption, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It was revealed that ammonia treatment at 600 °C considerably enhanced the specific surface area and N-content of ZC. However, the pyrrolic-N group was decreased, yet the pyridinic-N group was increased with an increased temperature. The pyrrolic-N significantly enhanced CO2 adsorption. The ammonia treatment, on the one hand, increases the alkalinity of ZC sample and the base–acid interaction between N-containing functional groups with CO2. On the other hand, the ammonia treatment increased pyrrolic-N group (NH) into carbon surface facilitating the hydrogen-bonding interactions between proton of pyrrolic-N and CO2 molecules.
Keywords: ZIF-8; Porous carbon; Ammonia modification; Adsorption; CO2;

Amino and thiol modified magnetic multi-walled carbon nanotubes for the simultaneous removal of lead, zinc, and phenol from aqueous solutions by Lili Jiang; Shujun Li; Haitao Yu; Zongshu Zou; Xingang Hou; Fengman Shen; Chuantong Li; Xiayan Yao (398-413).
The novel functionalization of multi-walled carbon nanotubes (MWCNTs) was synthesized by reacting trimethoxysilylpropanethiol (MPTs), hydrazine, ammonium ferrous sulfate, and ammonium ferric sulfate in sequence as efficient ways to introduce Fe3O4, amino and thiol groups onto the nanotubes sidewalls. The magnetic MWCNTs composite material (N2H4–SH–Fe3O4/o-MWCNTs) was characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, thermo-gravimetric analysis, x-ray photoelectron spectroscopy, Fourier transformation infrared spectroscopy and magnetization curve. The results revealed that MPTs and hydrazine were coated on the surface of N2H4–SH–Fe3O4/o-MWCNTs. A series of batch adsorption experiments were conducted to study the experimental conditions, such as pH, contact time, initial concentrations and temperatures, which affected the adsorption process. The adsorption experiment results showed that the maximum equilibrium adsorption capacity of N2H4–SH–Fe3O4/o-MWCNTs for lead, zinc and phenol was 195.81 mg/g, 169.89 mg/g and 38.97 mg/g at pH 6, respectively. The adsorption isotherm was better fitted by the Freundlich model, and the adsorption kinetics was consistent with pseudo-second order kinetics model. Furthermore, thermodynamic data showed that the adsorption process was spontaneous and exothermic. These results indicated that N2H4–SH–Fe3O4/o-MWCNTs may be promising surface modified materials for removing heavy metal ions and phenol from aqueous solutions.
Keywords: Multi-walled nanotube; Adsorption; Thermodynamics; Dynamics;

Effect of residual stress on the microstructure of GaN epitaxial films grown by pulsed laser deposition by Haiyan Wang; Wenliang Wang; Weijia Yang; Yunnong Zhu; Zhiting Lin; Guoqiang Li (414-421).
The stress-free GaN epitaxial films have been directly grown by pulsed laser deposition (PLD) without any interlayer, and the effect of different stress on the microstructure of as-grown GaN epitaxial films has been explored in detail. The as-grown stress-free GaN epitaxial films of ∼320 nm-thick exhibit very smooth surface without any particles and grains with the root-mean-square surface roughness of 2.3 nm measured by atomic force microscopy. The relatively high crystalline quality is confirmed by the smaller full-width at half maximum values of GaN(0002) and GaN ( 10 1 ¯ 2 ) X-ray rocking curves as 0.27° and 0.68°, respectively.The stress-free GaN epitaxial films have been directly grown by pulsed laser deposition (PLD) at 850 °C, and the effect of different stress on the microstructure of as-grown GaN epitaxial films has been explored in detail. The as-grown stress-free GaN epitaxial films exhibit very smooth surface without any particles and grains, which is confirmed by the smallest surface root-mean-square roughness of 2.3 nm measured by atomic force microscopy. In addition, they also have relatively high crystalline quality, which is proved by the small full-width at half maximum values of GaN(0002) and GaN ( 10 1 ¯ 2 ) X-ray rocking curves as 0.27° and 0.68°, respectively. However, when the growth temperature is lower or higher than 850 °C, internal or thermal stress would be increased in as-grown GaN epitaxial films. To release the larger stress, a great number of dislocations are generated. Many irregular particulates, hexagonal GaN gains and pits are therefore produced on the films surface, and the crystalline quality is greatly reduced consequently. This work has demonstrated the direct growth of stress-free GaN epitaxial films with excellent surface morphology and high crystalline quality by PLD, and presented a comprehensive study on the origins and the effect of stress in GaN layer. It is instructional to achieve high-quality nitride films by PLD, and shows great potential and broad prospect for the further development of high-performance GaN-based devices.
Keywords: GaN; Pulsed laser deposition; Stress-free; Surface roughness; Crystalline quality;

Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation by Gastón A. Primo; Cecilia I. Alvarez Igarzabal; Gustavo A. Pino; Juan C. Ferrero; Maximiliano Rossa (422-429).
This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.
Keywords: Surface morphological modification; UV–vis nanosecond pulsed laser irradiation; Laser ablation craters; Laser foaming; Crosslinked hydrophilic co-polymers; Swell/dried hydrogels;

Growth of nanotubular oxide layer on Ti-Ni alloys with different Ni contents by Min-Su Kim; Hiroaki Tsuchiya; Shinji Fujimoto (430-435).
Anodization of near-equiatomic Ti-Ni alloys was performed in an ethylene glycol based electrolyte under various conditions in order to investigate the effects of crystal structure and chemical composition of the Ti-Ni alloy on the morphology of the resulting oxide layers. X-ray diffraction patterns revealed that Ti-Ni substrates with Ni content lower than 50.0 at.% were in the martensitic phase, while substrates with Ni content higher than 50.0 at.% were in the austenitic phase. Oxide layers formed at 20 or 35 V for 5 min exhibited no distinct nanotubular structures; however, at 50 V, nanotubular oxide layers were formed. After anodization at 50 V for 20 min, the growth of an irregular-shaped porous layer underneath the nanotubular oxide layer was observed for Ti-Ni alloys with Ni content lower than 52.2 at.%, whereas the oxide layer consisted of only irregular-shaped porous structures for the Ti-52.5 at.% Ni alloy. Further anodization resulted in the formation of irregular-shaped porous oxide layers on all Ti-Ni alloys examined. Energy-dispersive X-ray analysis indicated that this morphological transition is related to Ni accumulation in the vicinity of the interface between the bottoms of the oxide layers and the surfaces of the substrate alloys. Therefore, nanotubular oxide layers cannot be grown, and instead irregular-shaped porous oxide layers are formed underneath the nanotubular layers. These results indicate that the morphology of anodic oxide layers formed on the near-equiatomic Ti-Ni alloys is not affected by their crystal structure, but by Ni content and anodization time.
Keywords: Ti-Ni alloy; Anodization; Nanotube; Chemical composition; Crystal structure;

Lead selenide (PbSe) thin films were deposited on fluorine doped tin oxide (FTO) glass by a facile one-step pulse voltage electrodeposition method, and used as counter electrode (CE) in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). A power conversion efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells, which is much better than that of 2.39% received using Pt CEs. The enhanced performance is attributed to the extended absorption in the near infrared region, superior electrocatalytic activity and p-type conductivity with a reflection of the incident light at the back electrode in addition. The physical and chemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), reflectance spectra, electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The present work provides a facile pathway to an efficient CE in the QDSSCs.
Keywords: Lead selenide thin films; Pulse voltage electrodeposition; Counter electrode; Quantum dot sensitized solar cells;

Selective hydrogen gas sensor using CuFe2O4 nanoparticle based thin film by Mohammad Abu Haija; Ahmad I. Ayesh; Sadiqa Ahmed; Marios S. Katsiotis (443-447).
Hydrogen gas sensors based on CuFe2O4 nanoparticle thin films are presented in this work. Each gas sensor was prepared by depositing CuFe2O4 thin film on a glass substrate by dc sputtering inside a high vacuum chamber. Argon inert gas was used to sputter the material from a composite sputtering target. Interdigitated metal electrodes were deposited on top of the thin films by thermal evaporation and shadow masking. The produced sensors were tested against hydrogen, hydrogen sulfide, and ethylene gases where they were found to be selective for hydrogen. The sensitivity of the produced sensors was maximum for hydrogen gas at 50 °C. In addition, the produced sensors exhibit linear response signal for hydrogen gas with concentrations up to 5%. Those sensors have potential to be used for industrial applications because of their low power requirement, functionality at low temperatures, and low production cost.
Keywords: CuFe2O4; Nanoparticle; Hydrogen sensor; Thin film;

Tribological properties of SiC-based MCD films synthesized using different carbon sources when sliding against Si3N4 by Xinchang Wang; Xiaotian Shen; Tianqi Zhao; Fanghong Sun; Bin Shen (448-459).
Micro-crystalline diamond (MCD) films are deposited on reactive sintering SiC substrates by the bias enhanced hot filament chemical vapor deposition (BE-HFCVD) method, respectively using the methane, acetone, methanol and ethanol as the carbon source. Two sets of standard tribotests are conducted, adopting Si3N4 balls as the counterpart balls, respectively with the purpose of clarifying differences among tribological properties of different MCD films, and studying detailed effects of the carbon source C, normal load F n and sliding velocity v based on orthogonal analyses. It is clarified that the methane-MCD film presents the lowest growth rate, the highest film quality, the highest hardness and the best adhesion, in consequence, it also performs the best tribological properties, including the lowest coefficient of friction (COF) and wear rate I d , while the opposite is the methanol-MCD film. Under a normal load F n of 7 N and at a sliding velocity v of 0.4183 m/s, for the methane-MCD film, the maximum COF (MCOF) is 0.524, the average COF during the relatively steady-state regime (ACOF) is 0.144, and the I d is about 1.016 × 10−7  mm3/N m; and for the methanol-MCD film, the MCOF is 0.667, the ACOF is 0.151, and the I d is 1.448 × 10−7  mm3/N m. Moreover, the MCOF, ACOF, I d and the wear rate of the Si3N4 ball I b will all increase with the F n , while the v only has significant effect on the ACOF, which shows a monotone increasing trend with the v.
Keywords: Diamond film; Carbon source; Tribological property; Normal load; Sliding velocity;

High capacity and high rate capability of nitrogen-doped porous hollow carbon spheres for capacitive deionization by Shanshan Zhao; Tingting Yan; Hui Wang; Guorong Chen; Lei Huang; Jianping Zhang; Liyi Shi; Dengsong Zhang (460-469).
In this work, nitrogen-doped porous hollow carbon spheres (N-PHCS) were well prepared by using polystyrene (PS) spheres as hard templates and dopamine hydrochloride as carbon and nitrogen sources. Field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate that the N-PHCS have a uniform, spherical and hollow structure. Nitrogen adsorption–desorption analysis shows that the N-PHCS have a high specific area of 512 m2/g. X-ray photoelectron spectroscopy result reveals that the nitrogen doping amount is 2.92%. The hollow and porous structure and effective nitrogen doping can contribute to large accessible surface area, efficient ion transport and good conductivity. In the electrochemical tests, we can conclude that the N-PHCS have a high specific capacitance value, a good stability and low inner resistance. The N-PHCS electrodes present a high salt adsorption capacity of 12.95 mg/g at a cell voltage of 1.4 V with a flow rate of 40 mL/min in a 500 mg/L NaCl aqueous solution. Moreover, the N-PHCS electrodes show high salt adsorption rate and good regeneration performance in the CDI process. With high surface specific area and effective nitrogen doping, the N-PHCS is promising to the CDI and other electrochemical applications.
Keywords: Carbon; Nitrogen doping; Electrosorption; Capacitive deionization;

Corrosion performance of bi-layer Ni/Cr2C3–NiCr HVAF thermal spray coating by E. Sadeghimeresht; N. Markocsan; P. Nylén; S. Björklund (470-481).
The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3–NiCr coatings, and C: bi-layer Ni/Cr2C3–NiCr coating) was comparatively studied using immersion, salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3–NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3–NiCr and single-layer Cr2C3–NiCr coatings were around 194 and 38 kΩ cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.
Keywords: Thermal spray; HVAF; Corrosion; EIS; Polarization; Immersion test;

Completely homogenous films formed via the layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDADMAC) and the poly(styrene sulfonate) were successfully obtained on plasma-treated poly(dimethylsiloxane) (PDMS) substrates. To modify the hydrophobicity of the PDMS surface, a cold plasma treatment was previously applied to the membrane, which led to the creation of hydrophilic groups on the surface of the membrane. PDMS wettability and surface morphology were successfully correlated with the plasma parameters. A combination of contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis was used to demonstrate that homogeneous and hydrophilic surfaces could be achieved on PDMS cold-plasma-treated membranes. The stability of the assembled PEL layer on the PDMS was evaluated using a combination of pull-off testing and X-ray photoelectron spectroscopy (XPS), which confirmed the relevance of a plasma pre-treatment as the adhesion of the polyelectrolyte multilayers was greatly enhanced when the deposition was completed on an activated PDMS surface at 80 W for 5 min.
Keywords: Layer-by-layer assembly; Poly(dimethylsiloxane) (PDMS); Polymer plasma processing; Polyelectrolyte; Surface modification;

In this work, magnetic Fe3O4 nanoparticles (NPs) were utilized to improve the mechanical and antibacterial properties of chitosan (CS)/gelatin (GE) composite nanofiber membranes. Homogeneous Fe3O4/CS/GE nanofibers were electrospun successfully. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the presence of well-dispersed Fe3O4 NPs in the composite nanofibers. Fourier transform infrared spectroscopy (FTIR) spectra revealed the effective interactions of Fe3O4 NPs to the composite matrix through hydrogen bonding. The improvement on the thermal stability of the Fe3O4/CS/GE was observed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), which is tightly correlated to strong filler-matrix adhesion. The incorporation of Fe3O4 NPs resulted in a substantial enhancement of mechanical properties. The optimum mechanical performance was demonstrated on 1 wt% Fe3O4/CS/GE nanofiber membranes, achieving 155% augment of Young's modulus, 128% increase of tensile strength, and 100% boost of toughness from CS/GE. The excellent mechanical enhancement can be explained by the effective dispersion of fillers and the filler-matrix interactions, which ensures the efficient load transfer from CS/GE matrix to Fe3O4 nanofillers. Moreover, zones of inhibition for Escherichia coli and Staphylococcus aureus expanded markedly with the supplement of Fe3O4 NPs. In all, nanofiber membranes made of Fe3O4/CS/GE composite with tailored mechanical and antibacterial properties appear a promising wound dressing material.
Keywords: Composite nanofiber; Iron oxide nanoparticles; Chitosan; Mechanical property; Antibacterial property;

Apatite layer growth on glassy Zr48Cu36Al8Ag8 sputtered titanium for potential biomedical applications by S. Thanka Rajan; M. Karthika; Avi Bendavid; B. Subramanian (501-509).
The bioactivity of magnetron sputtered thin film metallic glasses (TFMGs) of Zr48Cu36Al8Ag8 (at.%) on titanium substrates was tested for bio implant applications. The structural and elemental compositions of TFMGs were analyzed by XRD, XPS and EDAX. X-ray diffraction analysis displayed a broad hump around the incident angle of 30–50°, suggesting that the coatings possess a glassy structure. An in situ crystal growth of hydroxyapatite was observed by soaking the sputtered specimen in simulated body fluid (SBF). The nucleation and growth of a calcium phosphate (Ca–P) bone-like hydroxyapatite on Zr48Cu36Al8Ag8 (at.%) TFMG from SBF was investigated by using XRD, AFM and SEM. The presence of calcium and phosphorus elements was confirmed by EDAX and XPS. In vitro electrochemical corrosion studies indicated that the Zr-based TFMG coating sustain in the stimulated body-fluid (SBF), exhibiting superior corrosion resistance with a lower corrosion penetration rate and electrochemical stability than the bare crystalline titanium substrate.
Keywords: Amorphous materials; Glass; Surface treatments; Physical vapour deposition; Bioactivity;

Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres by Anne-Sophie Mamede; Nicolas Nuns; Anne-Lise Cristol; Laurent Cantrel; Sidi Souvi; Sylvain Cristol; Jean-François Paul (510-519).
In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8–12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe2O3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.
Keywords: Oxidation; Stainless steel; XPS; LEIS; ToF-SIMS;

Thermally assisted oxidation of GaSb(100) and the effect of initial oxide phases by J. Mäkelä; M. Tuominen; M. Yasir; M. Kuzmin; J. Dahl; M.P.J. Punkkinen; P. Laukkanen; K. Kokko (520-524).
Display OmittedThe oxidation of GaSb(100) surface has been widely studied because it affects the functionality of various devices. However even initial stages of the oxygen incorporation are not completely understood. To clarify this issue, we have investigated the oxidized GaSb(100) surfaces, which have been recently probed by scanning tunneling microscopy and spectroscopy, with high resolution synchrotron radiation photoelectron spectroscopy, in order to interconnect these different measurements. The results give a clear support that the oxidation initiates through saturation of available Ga bonds with; i.e., replacing some of the Sb―Ga bonds with O―Ga in the surface layers. Oxygen atoms have two different bonding environments in consistent with two dominating STM features. Also role of the plasmon features in the spectra have been elucidated.
Keywords: GaSb; Oxidation; Synchrotron radiation; Photoelectron spectroscopy; Core-level shifts;

Galvanic synthesis of Cu2−X Se thin films and their photocatalytic and thermoelectric properties by Amrita Ghosh; Chiranjit Kulsi; Dipali Banerjee; Anup Mondal (525-534).
Cu2−X Se thin film with cubic berzelianite phase was prepared by a simple, low-cost two electrode electrochemical technique and the photocatalytic and thermoelectric properties of the thin films were investigated. The results showed that Cu2−X Se crystallized in the cubic berzelianite phase and found to possess both direct and indirect band gaps of 2.9 and 1.05 eV respectively, covering almost the entire range of solar-spectrum. The photocatalytic discoloration of aqueous methylene blue (MB) and rose-bengal (RB) dyes over Cu2−X Se thin films were investigated under visible light irradiation. Cu2−X Se thin films showed higher catalytic activity for MB compared to RB in presence of H2O2. The photocatalytic discoloration followed first-order reaction kinetics. Complete removal of aqueous MB was realized after visible light irradiation for 150 min with Cu2−X Se thin film catalyst in presence of H2O2. Thermoelectric performances through power factor and figure of merit have been evaluated. Carrier concentration obtained from thermoelectric power was used to evaluate the mobility of carriers from electrical conductivity measurement.
Keywords: Thin film semiconductor; Galvanic synthesis; Photocatalytic property; Thermoelectric property;

The effect of Ni:Si ratio on microstructural properties of Ni/Si ohmic contacts to SiC by M. Wzorek; M.A. Borysiewicz; A. Czerwinski; M. Myśliwiec; M. Ekielski; J. Ratajczak; A. Piotrowska; J. Kątcki (535-544).
Detailed microstructural studies were performed on Ni/Si ohmic contacts to silicon carbide in order to investigate the effect of initial Ni:Si ratio in as-deposited structures on the occurrence of characteristic defects in Ni silicide layers, such as voids, layer discontinuities, rough surface or rough interface. The chosen range of investigated Ni:Si ratios corresponded to δ-Ni2Si as a dominant phase after complete annealing sequence. Strong effect of the initial stoichiometry on the ohmic contact's microstructure was observed. The highest Ni concentration significantly lowered the temperature at which roughening of the surface and the interface occurred. The middle value of investigated concentrations resulted in the rough interface after high temperature annealing, while the lowest investigated Ni content preserved smooth interface but introduced large voids and layer discontinuities. After the first annealing step, γ-Ni31Si12 and/or δ-Ni2Si phases were detected. In the ohmic contacts (after two-step annealing sequence), beside δ-Ni2Si, the metastable, high temperature phase θ-Ni2Si was detected (also referred to as Ni3Si2·h). This phase can exist within a relatively broad range of Ni:Si stoichiometry. The stoichiometry change toward higher Si content, which occurs during high temperature annealing, was realized through this phase. Superstructures were detected in θ-Ni2Si (Ni3Si2·h) and in γ-Ni31Si12 grains. The effect of the stoichiometry change on the morphology of the Ni silicide layers is discussed.
Keywords: Ohmic contact; Silicon carbide; Nickel silicides; Microstructure;

This paper describes the preparation, characterizations and the antireflection (AR) coating application in crystalline silicon solar cells of sol–gel derived SiC–SiO2 nanocomposite. The prepared SiC–SiO2 nanocomposite was effectively applied as AR layer on p-type Si-wafer via two step processes, where the sol–gel of precursor solution was first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to annealing at 450 °C for 1 h. The crystalline, and structural observations revealed the existence of SiC and SiO2 phases, which noticeably confirmed the formation of SiC–SiO2 nanocomposite. The SiC–SiO2 layer on Si solar cells was found to be an excellent AR coating, exhibiting the low reflectance of 7.08% at wavelengths ranging from 400 to 1000 nm. The fabricated crystalline Si solar cell with SiC–SiO2 nanocomposite AR coating showed comparable power conversion efficiency of 16.99% to the conventional Si x N x AR coated Si solar cell. New and effective sol–gel derived SiC–SiO2 AR layer would offer a promising technique to produce high performance Si solar cells with low-cost.
Keywords: Anti reflection coating; SiC–SiO2 nanocomposite; p-Type silicon wafer; Sol–gel process; Spin coating;

For the aim to give a new insight into the interactions between SO2 molecule and carbon surface and the effect of acidic oxygen-containing groups, density functional theory and noncovalent interaction analysis in terms of reduced density gradient were employed to investigate both the intensity and type of the interactions. The results indicate that the physisorption of SO2 molecule mainly occurs on the basal plane of pure carbon surface due to van der Waals interactions, however, when acidic oxygen-containing groups were decorated on the carbon surface, they would facilitate SO2 adsorption as a result of hydrogen bonding and dipole–dipole interactions. What's more, these groups could not affect the chemisorption of SO2 remarkably, no matter they are near the adsorption sites or not. In addition, calculation results show that the interactions between SO2 and acidic oxygen-containing groups are in physisorption nature, which challenges a long-held the viewpoint of irreversible chemisorption. Acidic oxygen-containing groups could boost the effective surface area of carbon by enhancing the physisorption on edge positions.
Keywords: SO2; Adsorption; DFT; Noncovalent interaction;

Zr(IV) surface-immobilized cross-linked chitosan/bentonite composite was synthesized by immersing cross-linked chitosan/bentonite composite in zirconium oxychloride solution, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy techniques. The adsorption of an anionic dye, Amido Black 10B, from aqueous solution by Zr(IV) loaded cross-linked chitosan/bentonite composite was investigated as a function of loading amount of Zr(IV), adsorbent dosage, pH value of initial dye solution, and ionic strength. The removal of Amido Black 10B increased with an increase in loading amount of Zr(IV) and adsorbent dosage, but decreased with an increase in pH or ionic strength. The adsorption of AB10B onto Zr(IV) loaded cross-linked chitosan/bentonite composite was favored at lower pH values and higher temperatures. The Langmuir isotherm model fitted well with the equilibrium adsorption isotherm data and the maximum monolayer adsorption capacity was 418.4 mg/g at natural pH value and 298 K. The pseudo-second-order kinetic model well described the adsorption process of Amido Black 10B onto Zr(IV) loaded cross-linked chitosan/bentonite composite. The possible mechanisms controlling Amido Black 10B adsorption included hydrogen bonding and electrostatic interactions.
Keywords: Zr(IV) surface-immobilized cross-linked chitosan/bentonite composite; Amido Black 10B; Adsorption;

A facile approach to fabricate a stable superhydrophobic composite comprising multi-walled carbon nanotubes and silicone rubber has been reported. Contact angle of de-ionized water droplets on the prepared surface was measured with the value of near 159°; while water droplets easily rolled off and bounced on it. Surface free energy of the superhydrophobic coating was examined by three methods about 26 mJ/m2. The prepared film shows good stability under high stress conditions such as ultraviolet exposure, heating, pencil hardness test, attacking with different pH value and ionic-strength solutions. In addition, remarkable stability of the coating was observed after soaking in condensed hydrochloric acid, 5 wt.% NaCl aqueous solution, boiling water and tape test.
Keywords: Superhydrophobic; Carbon nanotubes; Contact angle; Silicone rubber; Surface free energy;

Reduced graphene oxide/meso-TiO2/AuNPs (RGO/meso-TiO2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO2/AuNPs under a hydrothermal condition. The RGO/meso-TiO2/AuNPs ternary composites show high photocatalytic activity toward MB.Reduced graphene oxide/meso-TiO2/AuNPs (RGO/meso-TiO2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO2/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO2/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO2/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO2 and meso-TiO2/AuNPs.
Keywords: RGO/meso-TiO2/AuNPs; Ternary composites; Methylene blue; Photocatalytic degradation;

A novel approach based on molecular dynamics (MD) simulation has been proposed for the first time with the focus on quantifying the minimum feed (MF) in atomic force microscope (AFM) based nanochannel fabrication. This approach involves a coarse-to-fine criterion to determine MF so that regular nanochannel patterns can be obtained. The method is first introduced step by step and then confirmatory test is performed to demonstrate the capability of this contour-based method. MF judging studies are also performed systematically in which they vary in the aspects of scratching depth, tip angles, and tip shapes. Dislocations generation, surface quality, and scratching forces in the initial and subsequent scratches are investigated in detail. This method can overcome the drawbacks of high cost and low efficiency in experimental studies. Furthermore, our method sheds light on the manufacturing technique of nanochannels, which can help to obtain the surface morphologies with higher quality than traditional approaches.
Keywords: Nanochannels processing; Minimum feed; Atomic force microscope; MD simulation; Novel approach;