Applied Surface Science (v.360, #PA)

Based on the dispersion-corrected density functional calculations (DFT-D), we systematically studied the adsorption of noble metals (NM), Pd, Pt, Rh and Ir, on graphdiyne (GDY). We present a systematic study on the geometry, embedded adsorption energy and electronic structure of four different adatoms adsorbed on the GDY. The strong interaction between the NM adatoms and the GDY substrate is found with the NM embedded in the 18C-hexagon of the GDY. We investigated the mobility of the NM adatoms on the GDY, and found that the mobility barrier energy increases along with the increasing of the embedded adsorption energy. We present the NM adatoms growth of high concentrations on the GDY. Upon the analysis of the electronic structure and the frontier molecular orbitals, Rh and Ir adatoms of low concentrations (about 1.37 at%) on the GDY have the potential to be applied as single metal catalysts or gas molecule sensors.
Keywords: Interfacial properties; Graphdiyne; Noble metal; DFT-D;

Ultrathin NiO nanoflakes electrode materials for supercapacitors by Huanhao Xiao; Fengyu Qu; Xiang Wu (8-13).
Ultrathin NiO nanoflakes were synthesized through a facile and environmentally hydrothermal method. Electrochemical tests showed that ultrathin NiO nanoflakes as the electrode materials exhibited a high areal capacitance and excellent long cycle-life stability after 6000 cycles, which demonstrating high-performance capacitive behavior and could be used as excellent electrode material for electrochemical energy storage.In this work, large scale ultrathin NiO nanoflakes grown on nickel foam have been successfully obtained by a facile, low cost and eco-friendly route under mild temperature. The average thickness of the as-obtained NiO nanoflakes is about 10 nm. And they possess large surface area of 89.56 m2  g−1 and the dominant pore size of 2.313 nm. The electrochemical properties of the obtained product were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge measurement and electrochemical impedance spectroscopy (EIS). The electrochemical tests demonstrate the highest discharge areal capacitance of 870 mF cm−2 at 1 mA cm−2 and excellent long cycle-life stability with 84.2% of its discharge areal capacitance retention after 6000 cycles at the current density of 10 mA cm−2. The remarkable electrochemical capacitive performance revealed NiO nanoflakes grown on nickel foam might be promising supercapacitor electrode materials for future energy storage applications.
Keywords: NiO nanoflakes; Electrochemical; Supercapacitor electrode;

Fractional statistical theory of finite multilayer adsorption by E.A. Takara; E. Quiroga; D.A. Matoz-Fernandez; N.A. Ochoa; A.J. Ramirez-Pastor (14-19).
Display OmittedIn the present paper, finite multilayer adsorption is described as a fractional statistics problem, based on Haldane's statistics. In this scheme, the Helmholtz free energy and its derivatives are written in terms of a parameter g, which relates to the configuration of the molecules in the adsorbed state. For values of g ranging between 0 and 1 the formalism is used to model experimental data of bovine serum albumin (BSA) adsorbed onto an ion exchange resin for different values of pH and temperature. Excellent agreement between theory and experiments was found.
Keywords: Adsorption isotherms; Multilayer adsorption; Equilibrium thermodynamics and statistical mechanics; BSA protein adsorption;

To enhance the biocompatibility or extend the biomedical application of poly(caprolactone) (PCL), protein retention on PCL surface is often required. In this study, poly(acrylamide) (PAAm) brushes were grown from PCL surface via surface-initiated atom transfer radical polymerization (SI-ATRP) and served as a protein-capturing platform. Grafted PAAm was densely packed on surface and exhibited superior protein retention ability. Captured protein was found to be resistant to washing under detergent environment. Furthermore, protein structure after being captured was investigated by circular dichroism (CD) spectroscopy, and the CD spectra verified that secondary structure of captured proteins was maintained, indicating no denaturation of protein happened for retention process.
Keywords: Protein retention; Poly(caprolactone); Poly(acrylamide) brush; SI-ATRP;

The robust bio-immobilization based on pulsed plasma polymerization of cyclopropylamine and glutaraldehyde coupling chemistry by Anton Manakhov; Ekaterina Makhneva; Petr Skládal; David Nečas; Jan Čechal; Lukáš Kalina; Marek Eliáš; Lenka Zajíčková (28-36).
The performance of immunosensing devices crucially depends on the methodology of antibody or antigen immobilization on the sensor surface. Hence, the stable intermediate layers capable of specific and reproducible binding of antibodies are required. Herein, we introduce the amine rich (NH x concentration of 6 at.%) layers prepared by pulsed plasma polymerization of cyclopropylamine (CPA) for functionalization of the quartz crystal microbalance (QCM) surface by the antibody specific to human serum albumin. In these layers the amine groups serve as anchor for the antibody binding. The sensitivity of QCM sensors prepared in this way surpasses the one for the previously reported sensors functionalized by the thiol-based self-assembled monolayers by the factor of 2. Our results thus show that CPA plasma polymers have a significant potential for further development of the active layers for biosensing applications.
Keywords: Amine coating; Sensors; Bio-immobilization; Plasma polymerization; Cyclopropylamine; XPS; QCM;

The schematic drawings and fabrication process of three-dimensional interpenetrating network structure epoxy composites based on the modified carbon nanotube reinforced flexible polyurethane sponge.Three-dimensional (3D) interpenetrating network structure epoxy composites were fabricated based on the modified carbon nanotube (CNT) reinforced flexible polyurethane (PU) sponge. CNTs were first functionalized with polydopamine (PDA) as revealed by TEM imaging, which is formed via the oxidative self-polymerization of dopamine. Then the functionalized CNTs (CNT–PDA) were successfully anchored on the skeleton surfaces of sponge, forming a continuous 3D carbon network. The interfacial interaction between modified PU sponge and epoxy (EP) matrix was significantly enhanced due to the covalent linkage of PDA. Improvement in the thermal stability of CNT–PDA/PU3D/EP composites was observed by TG analysis and related to the CNTs anchored on the skeleton of sponge. The tribological properties of pure EP, PU3D/EP and CNT–PDA/PU3D/EP composites were comparatively investigated in terms of different loads and velocities. Results demonstrated that CNT–PDA/PU3D/EP composites exhibited the best tribological performance owing to the strong interfacial interaction and the 3D carbon network structure. In particular, the wear resistance of CNT–PDA/PU3D/EP composites was 6.2 times and 3 times higher than those of pure EP and PU3D/EP composites under the applied load of 1.6 MPa, respectively.
Keywords: Polymer-matrix composites; Three-dimensional polyurethane sponge; Dopamine functionalized carbon nanotubes; Interfacial interaction; Tribological behavior;

Through the exploration of modification mechanism, the hydrophilic properties of SiC/SiO2-KH570-OP-7 were far superior to SiC/SiO2-KH570.A thermochemical synthetic methodology for silicon carbide/silica (SiC/SiO2) powder modified by integrating γ-methacryloxypropyl trimethoxy silane (KH570) and octylphenol polyoxyethylene ether (7) (OP-7) with hydrophilic SiC/SiO2 particles is described. On account of weak hydrophobicity of SiC/SiO2 powder modified by KH570 (SiC/SiO2-KH570), the study focuses on the improvement of hydrophobicity utilizing alkylation reaction between OP-7 and KH570 at high temperature. Compared with using KH570 alone, SiC/SiO2 powder modified by KH570 and OP-7 (SiC/SiO2-KH570-OP-7) shows better water resistance, and also an increased contact angle from 73.8° to 136.4°, resulting thus an improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), as well as X-ray photoelectron spectroscopy (XPS), was utilized to characterize these surfaces, and the results indicated that KH570 and OP-7 can be covalently bonded on the surface of SiC/SiO2 powder. Furthermore, it has been deeply investigated in the paper not only the possible modes of non-oxidative thermal degradation of OP-7 and KH570, but also the formation mechanism of more hydrophobic SiC/SiO2-KH570-OP-7 powder, which probably will have a potential utility for other inorganic materials.
Keywords: SiC/SiO2 powder; Surfaces; XPS; Water resistance; Non-oxidative thermal deposition materials;

The correlation of structural, optical and electrical properties of amorphous carbon thin films deposited by ion beam sputtering technique on the glass substrate was investigated. The film thickness varied over a wide range from 57 to 408 nm by controlling the deposition time. Raman spectra and X-ray photoelectron spectroscopy showed that the size of the graphite crystallites with sp2 bonds (La) and the sp3/sp2 fraction are smaller than 1.5 nm and 1.4, respectively. The values of I D/I G ratio, the ‘G’ peak position, and surface roughness depend on the film thickness; all of them increased by increasing film thickness up to 360 nm, and then decreased by increasing time and thickness. Furthermore, the resistivity followed similar trends of these structural properties. According to Tauc equation the optical band gap of these films was in the range of 3.2–3.9 eV. A broad emission peak at around 2.94 eV was observed on a photoluminescence spectrum of amorphous carbon film with highest resistivity.
Keywords: Amorphous carbon (a-C); Ion beam sputtering deposition; Electrical resistivity; Optical band gap; Photoluminescence; Film thickness;

Spherical and non-spherical colloidal silica size and shape were characterized and its effects on aluminum alloy nickel plated (Al-NiP) hard disk substrate during chemical mechanical polishing (CMP) was investigated. Non-spherical colloidal silica slurry shows significantly higher material removal rate (MRR) with higher coefficient of friction (CoF) when compared to spherical colloidal silica of similar size. CMP evaluations on non-spherical colloidal silica slurry particle size distribution (PSD) reveal that MRR can be further increased by using wider PSD. Conventional slurry for Al-NiP hard disk substrates which use alumina–silica composite slurry induces embedded alumina thermal asperities (TA) defects which can cause reliability failure at product level. CMP comparison between conventional alumina–silica slurry and non-spherical colloidal silica slurry shows substrates polished by using non-spherical colloidal silica slurry have no embedded TA defects, lower surface roughness and lower surface defects.
Keywords: Chemical mechanical polishing (CMP); Non-spherical colloidal silica; Hard disk drive substrate; Surface roughness; Surface defects;

First-principles calculations showed that SiCNTs is a very promising candidate for metalloporphyrin adsorption and sensing/detection.In the present work, we report a detailed theoretical investigation of a series of metalloporphyrin, MP (M = FeP, CoP and ZnP), molecules interacting with silicon carbide nanotube (SiCNT) by means of density functional theory (DFT) calculations. In all calculations, we used the Perdew–Burke–Erzenhof (PBE) functional as employed in the SIESTA package. The detailed analysis of the structural and electronical properties of various optimized configurations is performed. The results show that among the MPs, adsorption of FeP molecule on the Si site with zigzag orientation is the most energetically preferable with a binding energy of −2.10 eV. Compared to SiCNTs, boron nitride nanotubes (BNNTs) have weaker interaction strength with the FeP molecule with −0.34 eV of binding energy. We have analyzed charge transfer between two interacting species trough well-known Mulliken, Hirshfeld and Voronoi charges analysis for aforementioned systems. The spin-polarized DFT calculations showed that the density of states (DOSs) are spin-polarized for the Fe-BNNT complex while the spin-polarization of the DOS spectra turn out to be less notable for MP-SiCNT complexes. Our results propose that FeP-SiCNT complex could be used for interesting applications in solar cell technology and nano-biosensors while FeP-BNNT complex might be considered for spintronic molecular devices.
Keywords: SiCNTs; BNNT; DFT; Metalloporphyrin; Adsorption; Nano-sensors;

Higher alcohols synthesis (HAS) is a strong exothermal reaction which leads to the formation of hotspots on the catalysts and the hotspots result in poor selectivity, and Cu–Co based catalysts are one of the most promising to which the formation of Cu–Co alloy is critical. Therefore a new scheme was proposed, based on the excellent thermal conductivity of carbon fibers (CFs) and the uniform mixing of metal ions in layered double hydroxides (LDHs), the latter favors the formation of metallic alloy. Nanocomposites of LDHs and CFs were prepared by using co-precipitation method and used for HAS, and characterized by using FTIR, N2 adsorption–desorption, XRD, TPR, SEM and TEM techniques. In the composites, nanosheets with the typical LDHs morphology are perpendicularly grown on the surface of CFs while intersecting each other, creating a highly open and porous structure. After reduction, Cu–Co-alloy nanoparticles are formed from the LDHs. The resultant catalysts showed high activity and much high selectivity to higher alcohols. The reported methods can be expanded to prepare other LDHs/CFs composites.
Keywords: Higher alcohols synthesis; Layered double hydroxides; Bimetallic CuCo-alloy; Carbon fibers; Syngas;

In this work, alkaline phosphatase (ALP) was covalently immobilized on carboxymethyl chitosan (CMCS)-coated polydopamine (PDA)-functionalized Ti to achieve a bifunctional surface. Our results showed ∼89% reduction in Staphylococcus epidermidis adhesion on this surface compared to that on pristine Ti. The ALP-modified Ti supported cell proliferation, and significantly enhanced cellular ALP activity and calcium deposition of osteoblasts, human mesenchymal stem cells (hMSCs) and human adipose-derived stem cells (hADSCs). The extent of enhancement in the functions of these cells is dependent on the surface density of immobilized ALP. The substrate prepared using an ALP solution of 50 μg/cm2 resulted in 44%, 54% and 129% increase in calcium deposited by osteoblasts, hMSCs and hADSCs, respectively, compared to those cultured on pristine Ti. The ALP-modified substrates also promoted the osteogenic differentiation of hMSCs and hADSCs by up-regulating gene expressions of runt-related transcription factor 2 (RUNX2), osterix (OSX), and osteocalcin (OC) in the two types of stem cells. The surface-immobilized ALP was stable after being subjected to 1 h immersion in 70% ethanol and autoclaving at 121 °C for 20 min. However, the enzymatic bioactivity of the surface-immobilized ALP was reduced by about 50% after these substrates were immersed in phosphate buffered saline (PBS) or PBS containing lysozyme for 14 days.
Keywords: Titanium; Alkaline phosphatase; Osteoblast; Stem cell; Carboxymethyl chitosan; Stability;

A ToF-SIMS investigation of the corrosion behavior of Mg alloy AM50 in atmospheric environments by M. Esmaily; P. Malmberg; M. Shahabi-Navid; J.E. Svensson; L.G. Johansson (98-106).
The redistribution of chloride and sodium ions after the NaCl-induced atmospheric corrosion of Mg alloy AM50 was investigated by means of Time-of-Flight Ion Mass Spectroscopy (ToF-SIMS). The samples were exposed at −4 and 22 °C in the presence of 400 ppm CO2. The results confirm the presence of less conductive electrolyte, and thus, less movement of ionic species (including sodium and chloride) in the electrolyte layer formed on the surface of samples exposed at the sub-zero temperature. Besides, ToF-SIMS analysis showed the presence of an Al-containing surface film formed on the alloy surface after exposure at high relative humidity.
Keywords: Tof-SIMS; Magnesium alloy; Atmospheric corrosion; Electrolyte; Sub-zero temperature;

Remarkable suppression of thermal conductivity by point defects in MoS2 nanoribbons by Yongchun Wang; Kaiwang Zhang; Guofeng Xie (107-112).
By molecular dynamics simulation, we demonstrate that both sulfur vacancies (VS) and oxygen substitutions to sulfur (SO) can significantly reduce thermal conductivity of monolayer MoS2 nanoribbons, but the suppression of thermal conductivity by vacancies is stronger than that by substitutions. We perform the vibrational eigenmodes analysis and find that the strong localization of phonons of all modes by defects results in the severe reduction of thermal conductivity of MoS2 nanoribbons. Further spectra analysis reveals that the localized modes are located in the sites of defects and the sites around defects, due to change of force constant at these sites.By applying non-equilibrium molecular dynamics simulation, we investigate the effect of point defects on thermal conductivity of MoS2 nanoribbons, such as sulfur vacancies (VS) and oxygen substitutions to sulfur (SO). It is found that both VS and SO can significantly reduce thermal conductivity of monolayer MoS2 nanoribbons, but the suppression of thermal conductivity by vacancies is stronger than that by substitutions. For armchair MoS2 nanoribbon of 41.1 nm length and 4.4 nm width, when defect density is only 1.5%, the reduction of thermal conductivity at room temperature by VS defects and SO defects is 42.3% and 35.1%, respectively. We perform the vibrational eigenmodes analysis and find that the strong localization of phonons of all modes by defects results in the severe reduction of thermal conductivity of MoS2 nanoribbons. Further spectra analysis reveals that the localized modes are located in the sites of defects and the sites around defects, due to the change of force constant at these sites. Our findings are helpful for understanding and tuning the thermal conductivity of MoS2 nanoribbons by defect engineering.
Keywords: Thermal conductivity; MoS2 nanoribbons; Point defects;

Submicron/nano-structured icephobic surfaces made from fluorinated polymethylsiloxane and octavinyl-POSS by Yancai Li; Chenghao Luo; Xiaohui Li; Kaiqiang Zhang; Yunhui Zhao; Kongying Zhu; Xiaoyan Yuan (113-120).
The submicron/nano-structured morphology induced by OVPOSS has a strong effect on ice attachment. The OVPOSS particles aggregated on the top surface could decrease the ice adhesion strength.Fluorinated hybrid films composed of fluorinated polymethylsiloxane (PMHS–xFMA, x  = 6, 13, 17) and octavinyl-polyhedral oligomeric silsesquioxanes (OVPOSS) were prepared for icephobic applications. PMHS–xFMA with diverse fluorinated side groups were synthesized via hydrosilylation of polymethylhydrosiloxane (PMHS) with fluorinated methacrylate (xFMA), i.e., hexafluorobutyl methacrylate (6FMA), tridecafluorooctyl methacrylate (13FMA) and heptadecafluorodecyl methacrylate (17FMA), respectively. Characterizations of atomic force microscope and scanning electron microscope indicated that surfaces of the hybrid films consisted of submicron/nano-scaled OVPOSS aggregates, and the root-mean-square roughness (S q ) could vary from 42.6 nm to 145.2 nm with various OVPOSS content (5–20 wt%). Wettability measurements of the prepared films demonstrated that the relatively longer fluorinated side groups in PMHS–17FMA were beneficial for decreasing surface energy and enhancing hydrophobic properties. However, the fluorinated hybrid films with PMHS–17FMA presented higher ice shear strengths due to the stronger interfacial interactions between the film surface and ice/water. The film prepared by PMHS–13FMA and 10 wt% of OVPOSS with proper roughness (90.2 nm) performed the lowest ice shear strength (188.2 ± 13.4 kPa) among all the samples. Dynamic water droplet impact measurement revealed that the rougher surface with the mass fraction of OVPOSS more than 10 wt% and S q larger than 90 nm could repel water droplets. The submicron/nano-structured surface of PMHS–xFMA and OVPOSS was expected for anti-icing applications.
Keywords: Hybrid films; Fluorinated polymethylsiloxane; OVPOSS; Icephobic properties;

Amine-functionalized, silver-exchanged zeolite NaY: Preparation, characterization and antibacterial activity by Siti Aishah Mohd Hanim; Nik Ahmad Nizam Nik Malek; Zaharah Ibrahim (121-130).
Amine-functionalized, silver-exchanged zeolite NaY (ZSA) were prepared with three different concentrations of 3-aminopropyltriethoxysilane (APTES) (0.01, 0.20 and 0.40 M) and four different concentrations of silver ions (25%, 50%, 100% and 200% from zeolite cation exchange capacity (CEC)). The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), surface area analysis, thermogravimetric analysis (TGA) and zeta potential (ZP) analysis. The FTIR results indicated that the zeolite was functionalized by APTES and that the intensity of the peaks corresponding to APTES increased as the concentration of APTES used was increased. The antibacterial activities of the silver-exchanged zeolite NaY (ZS) and ZSA were studied against Escherichia coli ATCC11229 and Staphylococcus aureus ATCC6538 using the disc diffusion technique (DDT) and minimum inhibitory concentration (MIC). The antibacterial activity of ZSA increased with the increase in APTES on ZS, and E. coli was more susceptible towards the sample compared to S. aureus. The FESEM micrographs of the bacteria after contact with the ZSA suggested different mechanisms of bacterial death for these two bacteria due to exposure to the studied sample. The functionalization of ZS with APTES improved the antibacterial activity of the silver-zeolite, depending on the concentration of silver ions and APTES used during modification.
Keywords: Zeolite NaY; Silver-exchanged zeolite; Amine-functionalized; 3-Aminopropyltriethoxysilane; Antibacterial agent; Antibacterial assay;

We report on our comprehensive experimental studies on 100 keV Kr+-ion irradiation induced nanoscale ripple pattern evolution on Ge surface over a large angular window and a wide range of ion fluence. Using the present experimental parameters, theoretical estimations have also been carried out in order to unveil the underlying physical processes causing the observed pattern formation. We observe the formation of periodic ripple patterns, with wave-vectors parallel to the ion-beam projection onto the surface, in the range of oblique incidence angles of 45–70°. On the other hand, for angles of incidence in the range of 80–85°, patterns having wave-vectors perpendicular to the projected ion-beam direction are seen to evolve. In contrast, the surface remains stable (no pattern is formed) for incidence angles between 0–40° and 75°. Corresponding theoretical estimations clearly demonstrate the simultaneous roles of curvature-dependent sputter erosion and ion-induced prompt atomic redistribution behind the morphological evolution, albeit sputter erosion becomes dominant at grazing angles of incidence. Consequently, observed patterning process of Ge surface at the present energies turns out to be analogous to those of Si and SiO2 in both medium (up to tens of keV) and low energy (up to a few keV) regimes. The present study, therefore, implies a generality in pattern evolution on these surfaces (for ion energies of few tens of keV) and thus, is significant towards taking a step ahead in understanding ion-induced pattern evolution on other solid surfaces as well in a universal framework. Further, investigations on temporal evolution of Ge ripples, in terms of surface roughness and slope distribution, reveal a transition from the linear to nonlinear regime, leading to a gradual transformation of sinusoidal surface patterns to faceted structures. Depending upon the ion fluence, the evolution of the faceted structures is attributed to the formation of undercompressive shocks and the ion-beam shadowing phenomenon.
Keywords: Nanoscale pattern evolution; Ion irradiation; Ge surface; Atomic force microscopy; Transmission electron microscopy;

A novel N-rGO-ZnO hybrid material was successfully synthesized by a two-step method and it exhibited large CO2 adsorption ability of 3.55 mmol/g at 298 K and 1 atm. Importantly, the CO2/N2 selectivity of N-rGO-ZnO was high up to be 35.84 determined by a slope method at 298 K.A novel kind of ZnO based N-doped reduced graphene oxide (N-rGO-ZnO) porous nanomaterial was successfully synthesized by a two-step method. CO2 and N2 adsorption–desorption measurements and pore size analysis of N-doped reduced graphene oxide (N-rGO) and N-rGO-ZnO have been investigated and compared. What's more, the adsorption isotherms of N-rGO-ZnO material were measured at different temperatures, and it exhibited a large CO2 adsorption ability of 3.55 mmol/g at 298 K and 1 atm. The impressive CO2 adsorption selectivity over N2 has also been calculated and determined to be 35.84 by a slope method, which indicates the potential application to separate CO2 from flue gases.
Keywords: N-doped; Reduced graphene oxide; Zinc oxide; Hybrid; Selectivity; Adsorption;

Synthesis of a bimodal porous Cu with nanopores on the inner surface of Gasar pores: Influences of preparation conditions by Ming Du; Hua-wei Zhang; Yan-xiang Li; Yuan Liu; Xiang Chen; Yun He (148-156).
A bimodal porous Cu with regular Gasar micrometer or millimeter pores and random dealloying nanometer pores was fabricated by chemical corrosion of Cu–Zn alloy layers on the inner surface of Gasar Cu pores. In order to accomplish this object, a two-step corrosion method was conducted, including the selective corrosion of Zn element from Cu–Zn alloy layers by NaOH solution, and the removal of the surface oxide obtained in the first step to expose the bottom nanoporous Cu films by HCl solution. Influences of preparation conditions, such as HCl solution concentration and processing time, NaOH solution dealloying time, Gasar pore diameter, and the distance from Gasar pore openings on the microstructure of the resulting nanoporous Cu films were discussed.
Keywords: Bimodal porous structure; Gasar; Dealloying;

MOVPE growth and characterization of heteroepitaxial germanium on silicon using iBuGe as precursor by G. Attolini; J.S. Ponraj; C. Frigeri; E. Buffagni; C. Ferrari; N. Musayeva; R. Jabbarov; M. Bosi (157-163).
Being an attractive and demanding candidate in the field of energy conversion, germanium has attained widespread applications. The present work is aimed at the study of metal organic vapour phase epitaxy of germanium thin films on (0 0 1) silicon at different growth temperatures using isobutyl germane as a precursor. The epilayers were characterized by X-ray diffraction, high resolution transmission electron microscopy, atomic force microscopy and scanning electron microscopy in order to understand the structural and morphological properties. The films were found to be epitaxially grown and single crystalline with slight misorientation (below 0.1 degrees). The interface between the film and substrate was analyzed in depth and different temperature dependent growth behaviours were evidenced. The major relevant lattice imperfections observed were attributed to planar defects and threading dislocations.
Keywords: Germanium; Epitaxy; Isobutyl germane; MOVPE; Characterization;

High solvent resistance PTFPMS/PEI hollow fiber composite membrane for gas separation by Yan Dai; Xuehua Ruan; Feng Bai; Miao Yu; Hao Li; Zongchang Zhao; Gaohong He (164-173).
Poly(fluoropropylmethylsiloxane) (PTFPMS), which had different properties with polydimethylsiloxane (PDMS) due to C―F bond. The limitation for PTFPMS membrane to achieve industrial-scale applications was the forms of membrane modules. Thus, PTSPMS/polyetherimide (PEI) hollow fiber composite membranes have been prepared. Effects of PTFPMS concentration, coating method, selective layer thickness, operating pressure and temperature on the separation performance of the composite membranes have been investigated. PTFPMS can form a top dense layer on PEI substrate under a suitable concentration. The gas permeation rates decrease in the following order: CO2  > C3H6  > H2  > O2  > CH4  > N2. Permeation rates of CO2 and C3H6 change significantly with the increase of operating pressure. Based on pure gas permeation rates, the selectivities range from 16.03 to 18.80 for CO2/N2 and 11.75–19.76 for C3H6/N2 under operating pressure ranging from 0.1 to 0.5 MPa. Operating temperature has significant impact on permeation rates of CO2, CH4, O2, H2 and N2. PTFPMS/PEI hollow fiber composite membrane exhibits stable separation performance after immersed in i-octane and petroleum ether. The selectivity decreases ratio of PTFPMS/PEI hollow fiber composite membranes varies in the range of 1.56–10.70%, much lower than those of PDMS/PEI membranes of 8.02–21.34%.
Keywords: Poly(trifluoropropylmethylsiloxane); Polyetherimide; Composite membrane; Solvent resistance; Gas separation;

Nano-Bi2WO6 functionalized flexible SiO2 fibrous film for water purification by Zhijun Ma; Zhongliang Hu; Xin He; Zaijin Fang; Yang Li; Jianrong Qiu (174-183).
Electrospinning-derived nanofibrous films functionalized by photocatalysts have been extensively studied in the applications of environmental remediation. In this investigation, we propose a simple strategy for preparation of flexible and chemically stable nanofibrous films with high photocatalytic efficiency. Specifically, SiO2 nanofibrous film modified with Bi2WO6 nanoparticles was studied as a representative. Flexible SiO2 nanofibers were derived through sol–gel and electrospinning techniques. By simple soaking in precursor solution of Bi2WO6 and calcination, the SiO2 nanofibrous film was functionalized by Bi2WO6 nanoparticles, forming hierarchically porous composite film. Micro morphology, mechanical property and photocatalytic performance were tuned via changing the concentration of the soaking solution. Photocatalytic removal of organic pollutant from water was performed using RhB (Rhodamine B) as a model. The strategy proposed here is also widely applicable for preparation of composite films modified with other kinds of photocatalysts. SiO2–Bi2MoO6, SiO2–TiO2 and SiO2–CuO composite films were prepared in a similar way to demonstrate the versatility of the proposed preparation strategy.
Keywords: SiO2 nanofiber; Electrospinning; Porous film; Bi2WO6; Photocatalysis;

Conformational change of oil contaminants adhered onto crystalline alpha-alumina surface in aqueous solution by Wenkun Xie; Yazhou Sun; Haitao Liu; Hongya Fu; Yingchun Liang (184-191).
Microscopic conformational change of oil contaminants adhered onto perfect α-Al2O3 (0001) surface in the aqueous solution was simulated by means of detailed fully atomistic molecular dynamics simulations. The main driving forces of the conformation change process of the oil contaminants were explored. The simulation results indicate that with submerging of the contaminated α-Al2O3 (0001) surface into the aqueous solution, the oil contaminants undertake an evident conformational change process. The dynamic process can be divided into several stages, including early penetration of water molecules, formation and widening of water channel, and generation of molecularly adsorbed hydration layers. Moreover, the oil contaminants on the α-Al2O3 surface are not fully removed from solid surface after a 10 ns relaxation, while a relatively stable oil/water/solid three-phase interface is gradually formed. Further, the residual oil contaminants are finally divided into several new ordered molecular adsorption layers. In addition, by systemically analyzing the driving forces for the conformational change of the oil contaminants, the penetration of water molecules is found to be the most important driving force. With penetrating of the water molecules, the dominating interactions controlling the conformational change of the oil contaminants have been changing over the whole simulation.
Keywords: Oil contaminants; Conformational change; Water penetration; Molecular dynamics simulation;

Facile patterning silicon wafer by Rochow reaction over patterned Cu-based catalysts by Wenfeng Ren; Yanhong Wang; Zailei Zhang; Qiangqiang Tan; Ziyi Zhong; Fabing Su (192-197).
Despite the promising application of patterned Si wafers (PSWs) in electrochemistry and photochemistry, the simple and environment-friendly fabrication of these PSWs is still a great challenge. Herein, we report a novel method for fabrication of PSWs via Rochow reaction, which is commonly used to produce organosilane monomers for synthesizing organosilane products in chemical industry. In this reaction, commercial Si wafers (SWs) reacted with gas CH3Cl over patterned various Cu-based catalyst to create regular patterns. PSWs were obtained after removal of Cu compounds followed with facile post treatment. Because of simplicity, low-cost and low-toxicity of this approach, the manufacture of PSWs on an industrial scale is highly possible, which can be realized by integrating the organosilane synthesis process and controlling the reaction conditions.
Keywords: Si wafers; Direct-pattern; Rochow reaction; Copper catalysts; CH3Cl;

A new method developed for the surface treatment of thermoplastic polymer substrates that increases their surface energies is introduced in this paper. The method is environmental friendly and low cost. In the proposed surface treatment method, nanoparticles are spread over the thermoplastic polyurethane (TPU) flexible substrate surface and then thermally fixed. This latter step allows the nanoparticles sinking-in on the polymer surface, resulting in a higher polymer–particle interaction at their interfacial region. The addition of nanoparticles onto the polymer surface increases surface roughness. The extent of the nanoparticles dispersion and sink-in in the substrate was evaluated through microscopy analysis (SEM). The roughness of the surface treated polymeric substrate was evaluated by AFM analysis. Substrate critical surface tension (ST) was measured by contact angle. In general, a homogeneous roughness form is achieved to a certain level. Great increase of the TPU surface roughness (by 621%) was induced by the propose method. The proposed surface treatment method increased significantly the substrate ST (by 45%) and consequently the TPU wettability. This novel surface treatment of thermoplastic polymers was applied to the inkjet printing of TPU substrates with conductive inks, and significant improvements on the printability were obtained.
Keywords: Surface treatment; Surface roughness; Thermoplastic polyurethane; Nanoparticles; Inkjet printing; Polymer conductive ink;

A simple one-step approach to fabrication of highly hydrophobic silk fabrics by Fengxiang Chen; Xin Liu; Huiyu Yang; Binghai Dong; Yingshan Zhou; Dongzhi Chen; Hang Hu; Xingfang Xiao; Difei Fan; Chunhua Zhang; Fan Cheng; Yunhe Cao; Tian Yuan; Zihui Liang; Jing Li; Shimin Wang; Weilin Xu (207-212).
Highly hydrophobic silk fabric surfaces were successfully fabricated using a simple one-step atomic layer deposition (ALD) process. The surface morphology, chemical composition, and structure of bare silk fabric and silk fabrics coated with titanium dioxide (TiO2) subjected to 800 and 1600 ALD cycles were measured using scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning probe microscopy (SPM). The surface wettability of the silk fabrics was evaluated by determining their static water contact angles (WCAs) and roll-off angles. The results suggest that the good hydrophilicity of the surfaces of bare silk fabrics can be changed to high hydrophobicity by the application of TiO2 nanoparticles to their surfaces using ALD. The high hydrophobicity achieved can be attributed to the increase in roughness of the silk fabric surface. The laundering durability of TiO2-coated silk fabrics is greatly improved by increasing the thickness of the ALD TiO2 films.
Keywords: Atomic layer deposition; Silk fabrics; TiO2; Hydrophobicity;

Electro-exfoliating graphene from graphite for direct fabrication of supercapacitor by A.A.B. Hamra; H.N. Lim; W.K. Chee; N.M. Huang (213-223).
A facile production of graphene via electro-exfoliation is demonstrated using different types of oxidizing agent (HNO3, NaNO3, H2SO4 and H2O2) in the presence of sodium dodecylbenzenesulfonate as a surfactant. Different types of surfactant–oxidizing agent solutions in different concentrations significantly influenced the electrochemical exfoliation of graphite rod. The surface morphology, layer thickness and defects of the as-produced graphene are further evaluated. Additionally, the as-produced graphene is fabricated as a supercapacitor electrode via direct vacuum filtration. Nylon membrane and polymer gel, each containing 2.0 M of potassium hydroxide, are utilized to investigate the influence of the electrolyte type on the capacitance performance. Upon 1000 charge/discharge cycles, the nylon membrane electrolyte recorded capacitance retention of 94%, whereas the polymer gel electrolyte recorded an impressive capacitance retention that exceeded 100%. The potential of the fabricated supercapacitor for real applications is manifested by its ability to light up a light-emitting diode upon charging.
Keywords: Graphene; Surfactant; Oxidizing agent; Electrochemical exfoliation; Supercapacitor;

The main advantages of magnetorheological finishing (MRF) are its high convergence rate of surface error, the ability of polishing aspheric surfaces and nearly no subsurface damage. However, common MRF produces directional surface texture due to the constant flow direction of the magnetorheological (MR) polishing fluid. This paper studies the mechanism of surface texture formation by texture modeling. Dual-rotation magnetorheological finishing (DRMRF) is presented to suppress directional surface texture after analyzing the results of the texture model for common MRF. The results of the surface texture model for DRMRF and the proposed quantitative method based on mathematical statistics indicate the effective suppression of directional surface texture. An experimental setup is developed and experiments show directional surface texture and no directional surface texture in common MRF and DRMRF, respectively. As a result, the surface roughness of DRMRF is 0.578 nm (root-mean-square value) which is lower than 1.109 nm in common MRF.
Keywords: Surface texture; Dual-rotation magnetorheological finishing; Surface roughness; Surface topography; Quantitative evaluation;

Facile synthesis of groove-like NiMoO4 hollow nanorods for high-performance supercapacitors by Liyang Lin; Tianmo Liu; Jianlin Liu; Rong Sun; Jinghua Hao; Kemeng Ji; Zhongchang Wang (234-239).
We report a successful growth of groove-like NiMoO4 hollow nanorods (NiMoO4-GHRs) via a facile and efficient one-pot hydrothermal approach, and test them as positive electrode materials for pseudocapacitors. We demonstrate that such hollow nanorods with a high aspect ratio (nearly ∼104) show a large specific surface area and electroactive surface area, giving rise to good electrochemical performance. Especially, the NiMoO4-GHRs electrode shows a high specific capacitance of 1102.2 F g−1 at a current density of 1 A g−1, a good rate capability by having 64.5% retention at a high current density of 20 A g−1, and an excellent cycling stability by retaining 90% of its original state even after 1000 cycles. The NiMoO4-GHRs with unique structures and enhanced electrochemical functionalities should be a promising electrode material for high-performance supercapacitors.
Keywords: NiMoO4; Hollow nanorods; Supercapacitor; Hydrothermal;

Adsorption and photocatalytic degradation of pharmaceuticals by BiOCl x I y nanospheres in aqueous solution by Xiaoning Wang; Wenlong Bi; Pingping Zhai; Xiaobing Wang; Hongjing Li; Gilles Mailhot; Wenbo Dong (240-251).
BiOCl x I y nanospheres have been synthesised via precipitation method in ethylene glycol (EG)-water (H2O) mixed solvent at 80 °C and ambient pressure. Results of BiOCl x I y characterisation showed that these composite materials well combined BiOCl with BiOI crystals, which displayed flower-like hierarchical nanospheres consisted of numerous nanosheets and possessed smaller particle size, higher surface area than those in previous papers. The great surface area resulted in its high adsorption abilities of hydroxyphenylacetic acid (p-HPA) in the dark, the adsorption process could be suitably described by a pseudo-second-order kinetics model and the adsorption isotherms could be well fitted with Freundlich and Langmuir equations. The photocatalytic degradation of p-HPA and acetaminophen (ACTP) were investigated under simulated solar and visible irradiation using BiOCl x I y catalyst for the first time. The combination of BiOCl and BiOI to a certain extent has largely improved the remove efficiency, and BiOCl0.75I0.25 was the optimal catalyst with almost 100% removal of p-HPA and 80% removal of ACTP under solar light for 3 h. Experimental results demonstrated that the photocatalytic degradation of p-HPA and ACTP followed pseudo-first-order kinetics and O2 and dissolved oxygen play predominant roles in photocatalytic process efficiency. This research will supply an environment-friendly photocatalyst for pharmaceutical wastewater treatment under sunlight.
Keywords: BiOCl x I y nanospheres; Composite materials; Adsorption; Photocatalytic degradation; Pharmaceuticals;

In present work, a multifunctional magnetic core–shell dendritic silica nanocatalyst Fe3O4@SiO2@Dendritic-SiO2-NH2-Ag with easy accessibility of active sites and convenient recovery was successfully fabricated by an oil–water biphase stratification coating strategy, and characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The as-synthesized nanocatalyst Fe3O4@SiO2@Dendritic-SiO2-NH2-Ag displayed excellent catalytic activity for the catalytic reduction of 4-nitrophenol and 2-nitroaniline using sodium borohydride in aqueous solution at room temperature due to easy accessibility of active sites. Interestingly, the novel catalyst could be conveniently recovered by magnetic separation from the reaction system and recycled for at least five times without significant loss in activity. These results indicate that the above mentioned approach based on magnetic core–shell dendritic silica Fe3O4@SiO2@Dendritic-SiO2 provided a useful platform for the preparation of noble metal nanocatalysts with easy accessibility, excellent catalytic activity and convenient recovery.
Keywords: Dendritic mesoporous silica; Core–shell structure; Nanocatalyst; Catalytic reduction; Nitro-compounds;

Surface modification of calcium sulfate whisker prepared from flue gas desulfurization gypsum by Chengjun Liu; Qing Zhao; Yeguang Wang; Peiyang Shi; Maofa Jiang (263-269).
In order to obtain hydrophobic whisker for preparing polymeric composite product, the calcium sulfate whisker (CSW) prepared from flue gas desulfurization (FGD) gypsum by hydrothermal synthesis was modified by various surfactants, and the effects of some modification conditions on the hydrophobic property of CSW were investigated in this study. Sodium stearate was considered to be a suitable surfactant and its reasonable dosage was 2% of ethanol solvent. Both physical and chemical absorptions were found in the surface modification process, and the later one was suggested to preferentially occur on the CSW surface. Moreover, modifying temperature, modifying duration, and agitation speed were experimentally found to have a remarkable influence on the modification behavior. Active ratio reached 0.845 when the modification process was conducted under reasonable conditions obtained in the current work. Finally, polypropylene sheet products were prepared from modified CSW showing an excellence mechanical property.
Keywords: Calcium sulfate whisker; Surfactant; Surface modification; Absorption; Mechanical property;

ZnO/RGO nanocomposites with different morphologies, including RGO/ZnO nanoparticles, RGO/ZnO nanosheets, RGO/ZnO nanospheres and RGO/ZnO nanorods were prepared through hydrothermal process, characterized by XRD, TEM, SEM, UV–vis spectra, electrochemical analysis, and tested in photocatalytic hydrogen production. It was found that the ZnO morphologies have great influence on photo absorption, separation efficiency of photo-generated charges and photocatalytic performance of ZnO/RGO nanocomposites. RGO/ZnO nanorods with a sandwich-like 3D structure, consisting of ZnO nanorods grown vertically on both sides of graphene sheets exhibited a highest photocatalytic H2 production rate of 610, which is about 1.1 times, 1.9 times and 2.6 times more active than ZnO/RGO particles, ZnO/RGO nanospheres and ZnO/RGO nanosheets, respectively. The results of PL, CV curves and photocurrent measurements show that the superior photocatalytic performances of RGO/ZnO nanorods and RGO/ZnO nanoparticles originate from the higher transfer rate of photo-generated electron from ZnO to RGO, and repressed recombination of the photoinduced hole–electron pairs of ZnO, which is closely related with the morphology of ZnO and the strength of chemical interaction between ZnO and RGO.
Keywords: Reductive graphene oxide; ZnO; Photocatalytic H2 production;

Nanocomposite synthesis and photoluminescence properties of MeV Au-ion beam modified Ni thin films by Vantari Siva; Debi P. Datta; Avanendra Singh; T. Som; Pratap K. Sahoo (276-282).
We report on the synthesis and properties of nano-composites from thin Ni films on Silica matrix using Au-ion beam. When 2.2 MeV Au-ions are irradiated on 5 nm Ni film on Silica, the surface morphology changes drastically with ion fluence. In fact, within a fluence range of 5 × 1014–1 × 1016 ions/cm2, a sharp increase in surface roughness follows after an initial surface smoothening. The depth profiles extracted from Rutherford backscattering spectra demonstrates the diffusion of Ni and Au into the silica matrix. The photoluminescence spectra of the irradiated samples reveal the development of two bands centered at 3.3 eV and 2.66 eV, respectively. Deconvolution of those bands shows five different emission peaks, corresponding to different luminescence centers, which confirms the existence of Ni–Au nanocomposites in silica matrix. The optical and structural modifications are understood in terms of ion induced local heating and mass transport due to thermal spikes, which leads to nanocomposite formation in silica.
Keywords: Nanocomposites; Ion implantation; RBS; AFM; Photoluminescence;

Photocatalytic degradation of brilliant green using undoped and Zn doped SnO2 nanoparticles under sunlight irradiation by N. Shanmugam; T. Sathya; G. Viruthagiri; C. Kalyanasundaram; R. Gobi; S. Ragupathy (283-290).
We formulate a simple chemical precipitation method for the preparation of undoped and Zn doped SnO2 nanocrystals. The X-ray diffraction (XRD) patterns revealed the crystalline nature of the prepared products. The diffusion reflectance spectra (DRS) show the optical properties and confirmation made by photoluminescence (PL) results. The scanning electron microscope (SEM) and transmission electron microscopic (TEM) results discussed more regarding the morphologies of the products. The photocatalytic performance of SnO2 studied by the degradation of brilliant green showed excellent activity on 0.075 M of zinc doping due to its reduced crystallite size and high surface area.
Keywords: SnO2; Tetragonal; Photocatalytic; Brilliant green; Charge carriers;

Co-deposition of tannic acid and diethlyenetriamine for surface hydrophilization of hydrophobic polymer membranes by Xi Zhang; Peng-Fei Ren; Hao-Cheng Yang; Ling-Shu Wan; Zhi-Kang Xu (291-297).
We report a novel approach toward the surface modification of commercial polymer membranes via co-deposition of tannic acid (TA) and diethlyenetriamine (DETA). Particle-free, superhydrophilic, and almost colorless coatings are fabricated on the surfaces of polypropylene, poly(vinylidene fluoride), and poly(tetrafluoroethlene) microfiltration membranes. Cross-linking between TA and DETA plays a crucial role during the co-deposition process, as well as the adhesion of TA on the hydrophobic membrane surfaces. Both the surface wettability and water permeation flux are dramatically improved for the studied membranes after the co-deposition. The results indicate that co-deposition of TA and DETA is great potential for the surface modification of hydrophobic membranes.
Keywords: Surface modification; Co-deposition; Hydrophobic membrane; Hydrophilization; Surface wettability;

Solvothermal synthesis of hierarchical TiO2 nanostructures with tunable morphology and enhanced photocatalytic activity by Zhenghua Fan; Fanming Meng; Miao Zhang; Zhenyu Wu; Zhaoqi Sun; Aixia Li (298-305).
This paper presents controllable growth and photocatalytic activity of TiO2 hierarchical nanostructures by solvothermal method at different temperatures. It is revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the morphology of TiO2 can be effectively controlled as rose-like, chrysanthemum-like and sea-urchin-like only changing solvothermal temperature. BET surface area analysis confirms the presence of a mesoporous network in all the nanostructures, and shows high surface area at relatively high temperature. The photocatalytic activities of the photocatalysts are evaluated by the photodegradation of RhB under UV light irradiation. The TiO2 samples exhibit high activity on the photodegradation of RhB, which is higher than that of the commercial P25. The enhancement in photocatalytic performance can be attributed to the synergetic effect of the surface area, crystallinity, band gap and crystalline size.
Keywords: Hierarchical nanostructures; TiO2; Crystal growth; Photocatalytic activity;

Solid-material-based coupling efficiency analyzed with time-of-flight secondary ion mass spectrometry by Bastian Muenster; Alexander Welle; Barbara Ridder; Daniela Althuon; Jakob Striffler; Tobias C. Foertsch; Lothar Hahn; Richard Thelen; Volker Stadler; Alexander Nesterov-Mueller; Frank Breitling; Felix F. Loeffler (306-314).
The coupling behavior of a microparticle embedded amino acid active-ester into a Poly(ethylene glycol)methacrylate-film, synthesized onto a silicon wafer by a grafting from approach, is characterized using dynamic time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze the 3d distribution of the amino acids in the polymer film. Besides standard solid phase peptide synthesis, employing solubilized amino acids in a solvent, we used solid polymer microparticles, incorporating the amino acids. These microparticles were especially designed for a new technique to produce high-density combinatorial peptide microarrays: upon heating, the particles become viscous, which releases the embedded amino acids to diffuse and couple to the surface. In the scope of the development of this new particle-based application, ToF-SIMS is used to analyze a complex chemically modified polymer surface layer. Due to depth profile measurements, it is possible to investigate the particle-based coupling reaction not only on the surface, but also into the depth of the PEGMA film.
Keywords: Secondary ion mass spectrometry; C60 depth profiling; Particle-based solid phase peptide synthesis; Functionalized PEGMA coated surfaces; High-density peptide arrays; Combinatorial laser fusing;

Fabrication of porous boron-doped diamond electrodes by catalytic etching under hydrogen–argon plasma by Chao Shi; Cuiping Li; Mingji Li; Hongji Li; Wei Dai; Yongheng Wu; Baohe Yang (315-322).
Porous boron-doped diamond (BDD) was prepared by hydrogen–argon plasma etching using electrodeposited Ni nanoparticles as a catalyst. The etching process and formation mechanism of porous BDD were investigated by changing the etching time from 30 s to 300 s. Pores were produced due to the C atoms around Ni nanoparticles are easy to react with hydrogen plasma and form methane. With the increase of etching time, the pore size increased, the pore density decreased, and the pore depth first increased and then maintained unchanged. The sp2-bonded graphitic carbons existing on the surface of BDD increase with increasing etching time due to the increase of surface area. No preferential etching was observed due to the high energy of argon plasma. The electrochemical behaviors of the pristine and porous BDD electrodes were characterized by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results showed that the porous BDD electrode exhibited high specific capacitance, which is attributed to its high electrical conductivity and large specific surface area. The highest specific capacitance of porous BDD electrode is 9.55 mF cm−2, which is 22 times higher than that of pristine BDD electrode. The specific capacitance retention of the porous BDD electrode reduced to 98.2% of the initial capacitance after 500 cycles and then increased to 120.0% after 10,000 cycles. For the first 500 cycles, the reduction of capacitance can be attributed to the dissolution of Ni nanoparticles that attached on the porous BDD surface or buried in the shallow layer. The capacitance increase after 10,000 cycles is due to the better contact of the electrolytic solution with the residual Ni with the increase of cycle number.
Keywords: Porous boron-doped diamond; Hydrogen–argon plasma; Catalytic etching; Electrochemical behavior;

Despite the great progress in the theory and experimental verification we made in past decade, the practical application of graphene is still hindered by the lack of efficient, economical, scalable, ease-processing exfoliation method. Herein, we propose a facile, low-cost, and efficient liquid-phase exfoliation process using low boiling-temperature solvent mixture to fabricate few-layer graphene in large scale. The Hansen solubility parameter theory was applied to help optimize the composition of solvent mixture. Aqueous-based ternary-solvent mixture, for the first time, was adapted to exfoliate graphene. We demonstrate that the exfoliation efficiency using ternary-solvent mixture surpasses that from binary-solvent approach. The final product concentration after optimization was over 260 μg/ml. The concentrated graphene dispersion was used to fabricate gas sensor for detecting volatile organic gases. Taking advantage of large surface area, large number of adsorption sites, and well-preserved basal plane, the mass-produced graphene nanosheets exhibited promising sensing potential toward ethanol and methanol vapors.
Keywords: Graphene; Liquid-phase exfoliation; Ternary-solvent strategy; Gas sensor; Volatile organic compounds;

CO2 sorption on surface-modified carbonaceous support: Probing the influence of the carbon black microporosity and surface polarity by Valentina Gargiulo; Michela Alfè; Paola Ammendola; Federica Raganati; Riccardo Chirone (329-337).
The use of solid sorbents is a convenient option in post-combustion CO2 capture strategies. Sorbents selection is a key point because the materials are required to be both low-cost and versatile in typical post-combustion conditions in order to guarantee an economically advantageous overall process. This work compares strategies to tailor the chemico-physical features of carbon black (CB) by surface-modification and/or coating with a CO2-sorbent phase. The influence of the CB microporosity, enhanced by chemical/thermal treatments, is also taken into account. Three CB surface modifications are performed and compared: (i) oxidation and functionalization with amino-groups, (ii) coating with iron oxides and (iii) impregnation with an ionic liquid (IL). The CO2 capture performance is evaluated on the basis of the breakthrough curves measured at atmospheric pressure and room temperature in a lab-scale fixed bed micro-reactor. Most of tested solids adsorb a CO2 amount significantly higher than a 13X zeolite and DARCO FGD (Norit) activated carbon (up to 4 times more in the best case). The sorbents bearing basic functionalities (amino-groups and IL) exhibit the highest CO2 sorption capacity. The use of a microporous carbonaceous support limits the accessibility of CO2 toward the adsorbing phase (IL or FM) lowering the number of accessible binding sites for CO2.
Keywords: Carbon black; CO2 capture; Solid sorbents; Magnetite; Ionic liquid;

Coexistence of bipolar and unipolar resistive switching behaviors in the double-layer Ag/ZnS-Ag/CuAlO2/Pt memory device by Lei Zhang; Haiyang Xu; Zhongqiang Wang; Hao Yu; Jiangang Ma; Yichun Liu (338-341).
The schematic diagrams of the resistive switching (RS) mechanism with the different compliance current (CC). The formation and rupture of Ag-CFs in the CuAlO2 layer should be accepted as the BRS behavior under the low CC of 1 mA, as shown in (a) and (b). A following transformation (“forming”) process is necessary to realize the BRS-to-URS transformation, as shown in (c) and (d). Afterward, the formation and rupture of Cu-vacancy-CFs are responsible for the URS behavior in the case of high CC (10 mA), as shown in (e) and (f).The coexistence of uniform bipolar and unipolar resistive-switching (RS) characteristics was demonstrated in a double-layer Ag/ZnS-Ag/CuAlO2/Pt memory device. By changing the compliance current (CC) from 1 mA to 10 mA, the RS behavior can be converted from the bipolar mode (BRS) to the unipolar mode (URS). The temperature dependence of low resistance states further indicates that the CFs are composed of the Ag atoms and Cu vacancies for the BRS mode and URS mode, respectively. For this double-layer structure device, the thicker conducting filaments (CFs) will be formed in the ZnS-Ag layer, and it can act as tip electrodes. Thus, the formation and rupture of these two different CFs are located in the CuAlO2 layer, realizing the uniform and stable BRS and URS.
Keywords: Resistive random access memory (RRAM); Bipolar and unipolar resistive switching (BRS and URS); Composition of conducting filaments;

An electrochemical quartz crystal microbalance study of magnesium dissolution by K.D. Ralston; S. Thomas; G. Williams; N. Birbilis (342-348).
A quartz crystal microbalance (QCM) was used in conjunction with electrochemical measurements to study dissolution of pure magnesium (Mg) sensors in dilute NaCl electrolytes. Open circuit potential and potentiodynamic polarisation experiments were conducted in 0.01 M NaCl, having pH values 3 (buffered) and 6 (unbuffered). In the pH 3 solution, the Mg sensor showed a net mass-loss during the electrochemical tests, whereas, in the unbuffered pH 6 solution Mg showed a net mass-gain, corresponding to the growth of an Mg(OH)2 film on its surface. The loss in the electrochemical efficiency of Mg dissolution due to such direct parasitic Mg(OH)2 growth has been estimated to be around 17–34%. This loss relates to the low capacities and voltage fluctuations reported during discharge of primary Mg batteries.
Keywords: Magnesium; QCM; EQCM; Anodic polarisation; Corrosion;

In this paper, the silver grids are prepared by thermal evaporation method and the electrical and optical characteristics of the samples are compared with those reported by the sputtering deposition method. The silver grids with 60 nm show the better figure of merit. Besides, we found that the surface contact, surface polarity and surface energy of the metal grid/organic layer increase with increasing the grid thickness due to increasing sulfur content.In this study, silver grid transparent conducting films are fabricated via the thermal deposition method. The proposed grid shows low sheet resistance and a good figure of merit. The sheet resistance decreased from 688 to 3.37 Ω/square when the thickness was increased from 30 to 70 nm. The samples are characterized in terms of the contact angle to calculate the surface energy and polarity. The surface energy and polarity of the samples increased from 8.15 to 58.029 mJ/m2 and 0.024 to 0.067, respectively, when the sulfur content was increased from 6.67 to 9.26% (thickness increased from 50 to 70 nm). The fabricated Ag grid transparent conducting films show good optical and electrical characteristics and have potential for application in optoelectronics.
Keywords: Silver grid; Surface energy; Polarity;

γ-Al2O3-supported nickel phosphides (mNi-Pn) were prepared by the TPR method and tested for the deoxygenation of methyl laurate to hydrocarbons. The effects of the P/Ni ratio (n  = 1.0–2.5) and Ni content (m  = 5–15 wt.%) in the precursors on their structure and performance were investigated. Ni/γ-Al2O3 was also studied for comparison. It was found that the formation of AlPO4 in the precursor inhibited the reduction of phosphate and so the formation of nickel phosphides. With increasing the P/Ni ratio and Ni content, the Ni, Ni3P, Ni12P5 and Ni2P phases orderly formed, accompanying with the increases of their particle size and the amount of weak acid sites (mainly due to P-OH group), while the CO uptake and the amount of medium strong acid sites (mainly related to Ni sites) reached maximum on 10%Ni-P1.5. In the deoxygenation reaction, compared with Ni/γ-Al2O3, the mNi-Pn catalysts showed much lower activities for decarbonylation, C―C hydrogenolysis and methanation due to the ligand and ensemble effects of P. The conversion and the selectivity to n-C11 and n-C12 hydrocarbons achieved maximum on 10%Ni-P 2.0 for the 10%Ni-Pn catalysts and on 8%Ni-P2.0 for the mNi-P2.0 catalysts, while the turnover frequency (TOF) of methyl laurate mainly increased with the P/Ni ratio and Ni content. We propose that TOF was influenced by the nickel phosphide phases, the catalyst acidity and the particle size as well as the synergetic effect between the Ni site and acid site. Again, the hydrodeoxygenation pathway of methyl laurate was promoted with increasing P/Ni ratio and Ni content, ascribed to the phase change in the order of Ni, Ni3P, Ni12P5 and Ni2P in the prepared catalysts.
Keywords: P/Ni ratio; Nickel content; Nickel phosphide; Methyl laurate; Hydrodeoxygenation; Decarbonylation;

Adsorption of sulfide ions on cerussite surfaces and implications for flotation by Qicheng Feng; Shuming Wen; Wenjuan Zhao; Jiushuai Deng; Yongjun Xian (365-372).
The adsorption of sulfide ions on cerussite surfaces and implications for flotation were studied by X-ray photoelectron spectroscopy (XPS) analysis, micro-flotation tests, and surface adsorption experiments. The XPS analysis results indicated that lead sulfide species formed on the mineral surface after treatment by Na2S, and the increase in the Na2S concentration was beneficial for sulfidization. In addition to the content of lead sulfide species, its activity, which was determined by the proportion of sulfide, disulfide and polysulfide, also played an important role in cerussite sulfidization. Micro-flotation tests results demonstrated that insufficient or excessive addition of Na2S in pulp solutions has detrimental effects on flotation performance, which was attributed to the dosage of Na2S and the activity of lead sulfide species formed on the mineral surface. Surface adsorption experiments of sulfide ions determined the residual S concentrations in pulp solutions and provided a quantitative illustration for the inhibition of cerussite flotation by excessive sulfide ions. Moreover, it also revealed that sulfide ions in the pulp solution were transformed onto the mineral surface and formed lead sulfide species. These results showed that both of lead sulfide species and its activity acted as an important role in sulfidization flotation process of cerussite.
Keywords: Cerussite; Sulfide ions; Adsorption; Lead sulfide species;

(3-Aminopropyl) triethoxysilane was grafted at the surface of GO in low and high different graft densities to yield GOHAL and GOHAH, respectively. Subsequently, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (RA) was attached at the surface of GOHAL and GOHAH by an amidation reaction to yield GOHRL and GOHRH, respectively. Then, GOHRL and GOHRH were used in grafting from RAFT polymerization of styrene.(3-Aminopropyl) triethoxysilane was grafted at the surface of GO in low and high different graft densities to yield GOHAL and GOHAH, respectively. Subsequently, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (RA) was attached at the surface of GOHAL and GOHAH by an amidation reaction to yield GOHRL and GOHRH, respectively. Then, GOHRL and GOHRH were used in grafting from RAFT polymerization of styrene. Grafting of APTES and RA was approved by Fourier transform infrared spectroscopy, X-ray photo electron spectroscopy, and Raman spectroscopy. Expansion of graphene interlayer by oxidation and functionalization processes was evaluated by X-ray diffraction. Conversion values of styrene were calculated using gas chromatography. Molecular weight and PDI values of attached polystyrene (PS) chains were studied by size exclusion chromatography. Thermogravimetric analysis was also used to investigate the degradation temperatures, char contents, and graft contents of modifiers and PS chains. GOHRH and GOHRL reach to char content of 55.3 and 45.2% at 600 °C, which shows that weight ratio of modifier (APTES and RA moieties) is 15.3 and 5.2%, respectively. Scanning and transmission electron microscopies show that graphite layers with flat and smooth surface wrinkled after oxidation and turned to opaque layers by grafting PS.
Keywords: Grafting from; Polystyrene; Graphene; RAFT polymerization;

Nanocomposited-coating was deposited on silicone hydrogel by using the matrix-assisted pulsed laser evaporation (MAPLE) process. The ZnO–PEG nanocomposited coating reduces over 50% protein absorption on silicone hydrogel, and can inhibit the bacterial growth efficiently.Zinc oxide (ZnO) nanoparticles incorporating with polyethylene glycol (PEG) were deposited together on the surface of silicone hydrogel through matrix-assisted pulsed laser evaporation (MAPLE). In this process, frozen nanocomposites (ZnO–PEG) in isopropanol were irradiated under a pulsed Nd:YAG laser at 532 nm for 1 h. Our results indicate that the MAPLE process is able to maintain the chemical backbone of polymer and prevent the nanocomposite coating from contamination. The ZnO–PEG nanocomposited coating reduces over 50% protein absorption on silicone hydrogel. The cytotoxicity study shows that the ZnO–PEG nanocomposites deposited on silicone hydrogels do not impose the toxic effect on mouse NIH/3T3 cells. In addition, MAPLE-deposited ZnO–PEG nanocomposites can inhibit the bacterial growth significantly.
Keywords: Matrix assisted pulsed laser evaporation (MAPLE); Nanoparticles; Hydrogels; Protein adsorption; Antimicrobial efficiency;

Anti-corrosive performance of electropolymerized phosphomolybdic acid doped PANI coating on 304SS by Yangzhi Gao; Junaid Ali Syed; Hongbin Lu; Xiangkang Meng (389-397).
A phosphomolybdic acid doped polyaniline (PANI) anti-corrosive coating was synthesized on stainless steel (304SS) by electropolymerization. The combination of phosphoric acid de-doping and phosphomolybdic acid re-doping processes leads to the direct and quick deposition of PANI-coating on 304SS without any residual oxidant impurities. The corrosion resistance of the coating was evaluated in 1 M H2SO4 solution by electrochemical techniques. The doping of phosphomolybdic acid enhances the corrosion resistance provided by the coating. The phosphomolybdic acid re-doped coating has a high R t of 1999 Ω cm2 in comparison with the phosphoric acid doped and re-doped coatings. The increase in corrosion resistance is due to the presence of phosphomolybdic acid that promotes the formation of oxides which not only fill the pores in the PANI coating but also forms an interfacial oxide layer and hence block the corrosion of 304SS in acidic medium.
Keywords: Electropolymerization; Polyaniline; Phosphomolybdic acid; Re-doping; Anti-corrosion;

The natural leather was modified through O2/H2O low-temperature plasma treatment. Surface morphology was characterized by scanning electron microscopy (SEM) and the results showed that the pores on the leather surface became deeper and larger with enhanced permeability of water and vapor. XPS and FTIR-ATR was performed to determine the chemical composition of natural leather surface. Oxygen-containing groups were successfully grafted onto the surface of natural leather and oxygen content increased with longer treatment time. After O2/H2O plasma treatment, initial water contact angle was about 21° and water contact angles were not beyond 55° after being stored for 3 days. Furthermore, the tensile test indicated that the resistance to deformation had a prominent transform without sacrificing the tensile strength.
Keywords: Natural leather; Plasma; Surface modification; Hydrophilicity; Deformation;

Comparison of corrosion behavior between coarse grained and nano/ultrafine grained alloy 690 by Lv Jinlong; Liang Tongxiang; Wang Chen; Guo Ting (403-408).
The effect of grain refinement on corrosion resistance of alloy 690 was investigated. The electron work function value of coarse grained alloy 690 was higher than that of nano/ultrafine grained one. The grain refinement reduced the electron work function of alloy 690. The passive films formed on coarse grained and nano/ultrafine grained alloy 690 in borate buffer solution were studied by potentiodynamic curves and electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The results showed that the grain refinement improved corrosion resistance of alloy 690. This was attributed to the fact that grain refinement promoted the enrichment of Cr2O3 and inhibited Cr(OH)3 in the passive film. More Cr2O3 in passive film could significantly improve the corrosion resistance of the nano/ultrafine grained alloy 690.
Keywords: EIS; Alloy 690; XRD; Passive films; X-ray photoelectron spectroscopy;

Structure, surface analysis, photoluminescent properties and decay characteristics of Tb3+-Eu3+ co-activated Sr2MgSi2O7 phosphor by M.A. Tshabalala; H.C. Swart; F.B. Dejene; E. Coetsee; O.M. Ntwaeaborwa (409-418).
Tb3+-Eu3+ co-activated Sr2MgSi2O7 powder phosphors were synthesized by a solid-state reaction method. The structure, stretching vibrations, chemical and electronic states, and photoluminescent properties were studied using X-ray powder diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Time-of-flight secondary ion mass spectrometer (TOF-SIMS) and Photoluminescence (PL) spectroscopy respectively. The XRD pattern of the Sr2MgSi2O7:Eu3+, Tb3+ phosphor resembles the standard tetragonal phase of Sr2MgSi2O7. The fitted XPS data demonstrated that there were two different Sr2+ sites in the host lattice and a site occupied by Mg+ cations which connects the Sr+ sites with the Si+ ions. The TOF-SIMS results demonstrated localization and distribution of various ions within the host lattice (Sr2MgSiO7) including the Tb3+ and Eu3+ dopants. The photoluminescence of Tb3+ single doped Sr2MgSi2O7 shown to emit blue and green emissions simultaneously with green emission more intense and the blue emission improving considerably when lower concentrations of Tb3+ were used. Only red emission was observed from the Eu3+ single doped Sr2MgSi2O7. Upon Tb3+-Eu3+ co-doping, simultaneous emissions of blue, green and red lines were observed resulting in white emission.
Keywords: Melilites; Phosphors; Mass spectroscopy; Photoelectron spectroscopy; Photoluminescence;

Silicon surface biofunctionalization with dopaminergic tetrahydroisoquinoline derivatives by A. Lucena-Serrano; C. Lucena-Serrano; R. Contreras-Cáceres; A. Díaz; M. Valpuesta; C. Cai; J.M. López-Romero (419-428).
In this work we grafted vinyl- and azido-terminated tetrahydroisoquinolines (compounds 1 and 2, respectively) onto H―Si(1 1 1) silicon wafers obtaining highly stable modified surfaces. A double bond was incorporated into the tetrahydroisoquinoline structure of 1 to be immobilized by a light induced hydrosilylation reaction on hydrogen-terminated Si(1 1 1). The best results were obtained employing a polar solvent (DMSO), rather than a non-polar solvent (toluene). The azide derivative 2 was grafted onto alkenyl-terminated silicon substrates with copper-catalyzed azide-alkyne cycloaddition (CuAAC). Atomic force microscopy (AFM), contact angle goniometry (CA) and X-ray photoemission spectroscopy (XPS) were used to demonstrate the incorporation of 1 and 2 into the surfaces, study the morphology of the modified surfaces and to calculate the yield of grafting and surface coverage. CA measurements showed the increase in the surface hydrophobicity when 1 or 2 were incorporated into the surface. Moreover, compounds 1 and 2 were prepared starting from 1-(p-nitrophenyl)tetrahydroisoquinoline 3 under smooth conditions and in good yields. The structures of 1 and 2 were designed with a reduced A-ring, two substituents at positions C-6 and C-7, an N-methyl group and a phenyl moiety at C-1 in order to provide a high affinity against dopaminergic receptors. Moreover, O-demethylation of 1 was carried out once it was adsorbed onto the surface by treatment with BBr3. The method presented constitutes a simple, easily reproducible and high yielding approach for grafting complex organic biomolecules with dopaminergic properties onto silicon surfaces.
Keywords: Silicon-wafer; Alkaloids; Phenylisoquinoline; Photografting; Hydrosilylation; Dopaminergic activity;

Fiber to rubber adhesion is an important subject in rubber composite industry. It is well known that surface physical, mechanical and chemical treatments are effective methods to improve interfacial bonding. Ultra violet (UV) light irradiation is an efficient method which is used to increase interfacial interactions. In this research UV assisted chemical modification of PET fabric was used to increase its bonding to nitrile rubber (NBR). NBR is perfect selection to produce fuel and oil resistant rubber parts but it has weak bonding to fabrics. For this purpose at first, the PET fabric was carboxylated under UV irradiation and then methylenediphenyl diisocyanate (MDI) was reacted and grafted to carboxylated PET. T-peel test was used to evaluate PET fabric to NBR bonding strength. Attenuated total reflectance-Fourier transform infrared spectroscopy (FTIR-AT) was used to assess surface modifications of the PET fabrics. The chemical composition of the PET surfaces before and after carboxylation and MDI grafting was investigated by X-ray photoelectron spectroscopy (XPS). It was found that at vulcanizing temperature of 150 °C, carboxylation in contrary to MDI grafting, improved considerably PET to NBR adhesion. Finally effect of curing temperature on PET to NBR bonding strength was determined. It was found that increasing vulcanizing temperature to 170 °C caused considerable improvement (about 134%) in bonding strength.
Keywords: Nitrile rubber (NBR); Adhesion; UV irradiation; Surface modification; PET fabric; MDI;