Applied Surface Science (v.366, #C)

Preparation of Ag2O/Ag2CO3/MWNTs composite photocatalysts for enhancement of ciprofloxacin degradation by Huiqin Wang; Jinze Li; Pengwei Huo; Yongsheng Yan; Qingfeng Guan (1-8).
The Ag2O/Ag2CO3/multi-walled carbon nanotube (MWNTs) composite photocatalysts were prepared by calcination of the obtained precipitate. The structures and morphology of as-prepared composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS). The Ag2O/Ag2CO3/MWNTs composite photocatalysts exhibit higher degradation rate of ciprofloxacin (CIP) than the pure Ag2CO3, Ag2O/Ag2CO3 and Ag2CO3/MWNTs under visible light irradiation. The amount of loaded Ag2CO3 onto MWNTs and calcined time for Ag2CO3/MWNTs were systematically investigated, and the optimal amount of loaded Ag2CO3 and calcined time of Ag2CO3/MWNTs are 150 wt% and 10 min, respectively. The highest photocatalytic degradation rate of CIP could reach 76% under optimal conditions. The active species trapping experiments were also analyzed, the results show that the holes are main contributor for the degradation processes of CIP, furthermore the electrons, •O2 and •OH are also crucially influenced the photocatalytic degradation processes of CIP. The possible photocatalytic processes of CIP with Ag2O/Ag2CO3/MWNTs composite photocatalyst are also proposed.
Keywords: Ag2O/Ag2CO3; MWNTs; Synergistic effect; Photocatalytic degradation; CIP;

In this paper, we introduce a circle detection technique named Hough transform to automatically recognize the corrosion pits in microscopic images. All the points in the input image are transformed into a parameter space, which is represented by a two-dimensional accumulative array with the same size of the original image. Local extreme values in the accumulative array, which represent the candidates of corrosion pits, are located using a maxima searching algorithm. The accuracy of detecting the number, radius and coordinate of pits from simulated images was examined. The results show that more than 95% of pits were successfully detected and the average errors of radius and coordinate are less than 10%, while these errors have negligible effect on the pit size distribution. The introduced method can also differentiate pits from scratches or inclusions, as indicated by the 100% accuracy of pit detection, from the simulated images presented in this study. Therefore, it is believed that the gradient-based Hough transform is a powerful method for the recognition of corrosion pits in microscopic images, making the statistical analysis of pit size and pit locations easier and more efficient.
Keywords: Pitting corrosion; Image recognition; Hough transform; Statistics;

The novel polyvinyl alcohol/titanium oxide/zinc oxide (PVA/TiO2/ZnO) nanofiber adsorbent functionalized with 3-mercaptopropyltrimethoxysilane (TMPTMS) was prepared by electrospinning method and its potential was investigated for the adsorption of thorium from single and multi-metal aqueous solutions. The prepared adsorbent was characterized by FTIR, SEM and BET analysis. The influences of different operational parameters such as pH, ionic strength, equilibrium time, initial concentration and temperature were studied in batch mode. Investigation of ionic strength effect showed that the addition of NaNO3 to metal solution has a slight effect on the thorium adsorption, whereas pH value has a serious effect on the thorium adsorption at pH values lower than 4. The double-exponential model described the adsorption of Th(IV) ions much better than other kinetic models within both the single and multi-component systems. Among various isotherm models used, the equilibrium data of Th(IV) conformed the Langmuir isotherm in the single system, while those were best fitted by Dubinin–Radushkevich (D-R) isotherm in multi-component system. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° indicated that the nature of adsorption process was spontaneous, endothermic and thermodynamically favored. The inhibitory effect of other metal ions on the adsorption capacity of Th(IV) was in order of Al(III) > Cu(II) > Cd(II) > Ni(II) > U(VI) > Fe(II).
Keywords: Electrospinning; PVA/TiO2/ZnO/TMPTMS; Nanofiber adsorbent; Thorium(IV); Multi-component system; Adsorption;

Solvothermal synthesis of carbon nanotube-AgBiS2 hybrids and their optical limiting properties by Dandan Liu; Dongdong Cai; Yan Yang; Huiye Zhong; Yiwen Zhao; Yinglin Song; Shiping Yang; Huixia Wu (30-37).
AgBiS2 nanoparticles (NPs) have been loaded on multiwalled carbon nanotubes (MWCNTs) by the solvothermal treatment on a mixture of MWCNTs, AgNO3, Bi(NO3)3·5H2O and thiosemicarbazide in a mixed polyol solvent. The resulting MWCNT-AgBiS2 hybrid samples have been extensively characterized by a variety of microscopic and spectroscopic techniques. The AgBiS2 NPs can be uniformly deposited on the sidewalls of MWCNTs by appropriately regulating the reaction conditions including reaction temperature and reaction time. Optical limiting (OL) studies have been performed on typical MWCNT-AgBiS2 samples using the Z-scan and OL measurements at the laser wavelength of 532 nm. The MWCNT-AgBiS2 hybrids with AgBiS2 NPs of ∼16 nm in size uniformly coated on the nanotubes show a significantly enhanced OL effect in comparison to the purified MWCNTs.
Keywords: Carbon nanotubes; AgBiS2 nanoparticles; Solvothermal method; Optical limiting;

Annealing-induced alloy formation in Pd/Fe bilayers on Si(1 1 1) for hydrogen sensing by Venkata Ramana Mudinepalli; Cheng-Jui Tsai; Ying-Chin Chuang; Po-Chun Chang; N. Plusnin; Wen-Chin Lin (38-45).
Display OmittedThe bilayers of Pd and Fe with different thickness and relative positions were grown on Si(1 1 1)-7 × 7 surface at room temperature. For the investigation of the thermal annealing induced inter-diffusion and the corresponding magnetic behavior, Auger electron spectroscopy (AES) measurement was carried out after various annealing processes, including the variation of annealing duration and temperature. With the annealing temperature of 300–500 K, the Pd/Fe bilayers were stable. Slight Si segregated into the thin film at around 700 K. Above 700 K, more serious Si segregation occurred and most of the Pd/Fe bilayer was mixed with Si, forming a silicide layer. 700–800 K annealing also induced change of Pd/Fe AES ratio, indicating the inter-diffusion between Pd and Fe layers. To overcome the unavoidable silicide formation induced magnetic dead layer, a relative thick Fe film of 20 ML capped with 1.5 ML Pd was chosen for the investigation of magnetism. The magnetic coercivity (H c ) increased by 2–3 times with the annealing temperature up to 740 K. Obvious hydrogenation effect was observed in 710 K-annealed sample; the in-plane H c increased by more than 10% when the hydrogen pressure was above 200 mbar. After further annealing at 740–800 K, the hydrogenation effect on H c became nearly unobservable. The annealing induced Pd-rich magnetic interface is supposed to dominate the hydrogenation effect on magnetism.
Keywords: Ultrathin film; Surface magnetism; Hydrogenation;

Facile synthesis of porous graphene as binder-free electrode for supercapacitor application by Guangsheng Luo; Haifu Huang; Chenglong Lei; Zhenzhi Cheng; Xiaoshan Wu; Shaolong Tang; Youwei Du (46-52).
Here, porous grapheme oxide (GO) gel deposited on nickel foam was prepared by using polystyrene (PS) colloidal particles as spacers for use as electrodes in high rate supercapacitors, then reduced by Vitamin C aqueous solution in ambient condition. The PS particles were surrounded by reduced graphene oxide (rGO) sheets, forming crinkles and rough textures. When PS particles were selectively removed, rGO gel coated on the skeleton of Ni foam can formed an open porous structure, which prevents elf-aggregation and restacking of graphene sheets. The porous rGO-based supercapacitors exhibit excellent electrochemical performances such as a specific capacitance of 152 F g−1 at 1 A g−1, high rate capability of 53% capacitance retention upon a current increase to 100 A g−1 and good cycle stability, due to effective rapid and short pathways for ionic and electronic transport provided by the sub-micrometer structure of rGO gel and 3D interconnected network of Ni foam.
Keywords: Graphene; Porous; Ni foam; Hydrothermal; Supercapacitor;

Room temperature deposited aluminium-doped zinc oxide thin films on glass substrate, using pulsed-DC magnetron sputtering, have shown high optical transmittance and low electrical resistivity with high uniformity of its spatial distribution after they were exposed to a rapid thermal annealing process at 400 °C under N2H2 atmosphere. It is particularly interesting to note that such an annealing process of AZO thin films for only 30 s was sufficient, on one hand to improve their optical transmittance from 73% to 86%, on the other hand to both decrease their resistivity from 1.7 × 10−3  Ω cm to 5.1 × 10−4  Ω cm and achieve the highest uniformity spatial distribution. To understand the mechanisms behind such improvements of the optoelectronic properties, electrical, optical, structural and morphological changes as a function of annealing time have been investigated by using hall measurement, UV–visible spectrometry, X-ray diffraction and scanning electron microscope imaging, respectively.
Keywords: AZO thin films; Pulsed-DC magnetron sputtering; Rapid thermal annealing; Spatial resistivity distribution; CIGS solar cells;

The proper adsorption sites of Rh B depending on the phases of composites significantly enhance photodegradation activity under visible light.A kind of novel composite ZnS/In(OH)3/In2S3 is synthesized using zinc oxide nanoplates as zinc raw material during hydrothermal process. Although the obtained samples are composited of ZnS and In(OH)3 and In2S3 phase, the samples possess different structure, morphology and optical absorption property depending on molar ratio of raw materials. Zeta potential analysis indicates different surface electrical property since various content and particle size of the phases. The equilibrium adsorption study confirms the composite ZnS/In(OH)3/In2S3 with surface negative charge is good adsorbent for Rhodamine B (Rh B) dye. In addition, the degradation of Rh B over the samples with surface negative charge under visible light (λ  ≥ 420 nm) is more effective than the samples with surface positive charge. The samples before and after adsorbing Rh B molecule are examined by FTIR spectra and Zetasizer. It is found that the three function groups of Rh B molecule, especially carboxyl group anchors to surface of the sample through electrostatic adsorption, coordination and hydrogen-bond. It contributes to rapid transformation of photogenerated electron to conduction band of In(OH)3 and suppresses the recombination of photogenerated carrier. The possible adsorption modes of Rh B are discussed on the basis of the experiment results.
Keywords: Photocatalyst; Rh B; Adsorption; Waste water; Dye; Degradation;

A self-assembled magnetite core/zirconia shell (Fe3O4@ZrO2) nanoparticle material was fabricated by the one-step co-precipitation method to capture phosphate from water. Fe3O4@ZrO2 with different Fe/Zr molar ratios were obtained and characterized by XRD, TEM, BET surface area and magnetization. It was shown that, with the decreasing of Fe/Zr molar ratio, magnetization decreased whereas surface area and adsorption capacity of phosphate increased. Fe3O4@ZrO2 with the ratio of higher than 4:1 had satisfactory magnetization property (>23.65 emu/g), enabling rapid magnetic separation from water and recycle of the spent adsorbent. The Langmuir adsorption capacity of Fe3O4@ZrO2 reached 27.93–69.44 mg/g, and the adsorption was fast (90% of phosphate removal within 20 min). The adsorption decreases with increasing pH, and higher ionic strength caused slight increase in adsorption at pH > about 5.5. The presence of chloride, nitrate and sulfate anions did not bring about significant changes in adsorption. As a result, Fe3O4@ZrO2 performed well to remove phosphate from real wastewater. These results were interpreted by the ligand exchange mechanism, i.e., the direct coordination of phosphate onto zirconium by replacement of hydroxyl groups. Results suggested that phosphate reacted mainly with surface hydroxyl groups but diffusion into interior of zirconia phase also contributed to adsorption. The adsorbed phosphate could be desorbed with a NaOH treatment and the regenerated Fe3O4@ZrO2 could be repeatedly used.
Keywords: Magnetite; Zirconia; Phosphate; Removal; Mechanism; Nanoparticles;

Stability of few layer graphene films doped with gold (III) chloride by Mir Abdullah-Al-Galib; Bo Hou; Tahmeed Shahriad; Sandra Zivanovic; Adarsh D. Radadia (78-84).
In this paper we study the stability of few layer graphene (5–7 layers) doped with gold nanoparticles through spin coating of a gold (III) chloride solution. Specifically sheet resistance, optical transmittance and surface morphology were monitored over a period of four weeks. Through scanning electron microscopy we observed that the gold nanoparticles of 29.1 ± 1.3 nm diameters, which were formed on surfaces freshly doped with a 20 mM solution, agglomerate and fuse over the period of four weeks into larger particles of 50–110 nm diameters. At the end of four weeks of aging, regardless in air or vacuum, the optical transmittance at 550 nm for the doped samples resumed a value close to that of undoped samples. During these four weeks, the sheet resistances of the samples doped with 20 mM gold chloride also increased from 130 ohm/sq to 300 ohm/sq, but stayed comparable to indium tin oxide. In summary, despite the instability of doped FLG surfaces obtained using gold (III) chloride solutions, this study warrants the use of doped FLG films for building the next generation photovoltaics.
Keywords: Few layer graphene; Gold chloride doping; Gold nanoparticles; Graphene photovoltaics;

Initial stages of oxidation for Cu-based catalysts using density functional theory by Zhi-Jun Zuo; Na Li; Shi-Zhong Liu; Pei-De Han; Wei Huang (85-94).
The adsorption, dissociation, and desorption of O2 on Cu(111), Cu(110), and Cu(100) surfaces at different coverages were studied at the molecular level. The dissociation energies of O2 molecules increase with the increase in coverage of adsorbed O2. The saturated coverage of O atoms from dissociation of O2 molecules on Cu(111), Cu(110), and Cu(100) surfaces are 0.25, 0.75, and 0.375 ML, respectively. Based on the computed Gibbs free energies, the relationships between O atoms/O2 molecules and temperature, as well as O2 partial pressure, on these surfaces are established. Cu(111), Cu(110), and Cu(100) surfaces are covered by O atoms under ultra-high vacuum at 298 K, with O atom coverage of 0.25, 0.625, and 0.375 ML, respectively. Phase diagrams provide useful information on phase transition from Cu to Cu2O in terms of temperature and O2 partial pressure. Results of this study may provide guidance in investigating the interaction between O2 and transition metals.
Keywords: Adsorption; Dissociation; Desorption; Coverage; Phase diagram;

In this work, the early-stage corrosion of a carbon steel with various surface roughness, which was created by different levels of surface finishing treatment, was characterized by an atomic force microscope and electrochemical measurements. It is found that the resulting surface roughness is at nano-meter scale. As the surface roughness increases, the corrosion activity of the steel is increased. The early-stage corrosion of the steel is featured with two stages of dissolution. While the first stage involves a rapid dissolution and increasing surface roughness of the steel, stage two is in an equilibrium state to have an approximately constant corrosion rate and surface roughness. Generally, the corrosion rate of the steel decreases when the surface finish of the specimen becomes finer. Local preferential corrosion occurs at surface irregularities, resulting in the deepening and widening of the features such as scratches with time.
Keywords: Early-stage corrosion; Surface roughness; Carbon steel; Atomic force microscope; Electrochemical measurements;

Parametric investigations on the influence of nano-second Nd3+:YAG laser wavelength and fluence in synthesizing NiTi nano-particles using liquid assisted laser ablation technique by Nandini Patra; K. Akash; S. Shiva; Rohit Gagrani; H. Sai Pranesh Rao; V.R. Anirudh; I.A. Palani; Vipul Singh (104-111).
This paper investigates the influence of laser wavelengths and laser fluences on the size and quality of the NiTi nanoparticles, generated through underwater solid state Nd:YAG laser ablation technique. The experiments were performed on Ni55%–Ti45% sheet to synthesize NiTi nano-particles at three different wavelengths (1064 nm, 532 nm and 355 nm) with varying laser fluences ranging from 20 to 40 J/cm2. Synthesized NiTi nano-particles were characterized through SEM, DLS, XRD, FT-IR, TEM and UV–vis spectrum. It was observed that, maximum particle size of 140 nm and minimum particle size of 10 nm were generated at varying laser wavelengths. The crystallinity and lattice spacing of NiTi alloy nanoparticles were confirmed from the XRD analysis and TEM images, respectively.
Keywords: NiTi nanoparticle; Under water laser ablation; Nd:YAG laser; Laser wavelength; Structural analysis; Formation efficiency;

Effects of copper-plasma deposition on weathering properties of wood surfaces by P. Gascón-Garrido; N. Mainusch; H. Militz; W. Viöl; C. Mai (112-119).
Thin layers of copper micro-particles were deposited on the surfaces of Scots pine (Pinus sylvestris L.) micro-veneers using atmospheric pressure plasma to improve the resistance of the surfaces to weathering. Three different loadings of copper were established. Micro-veneers were exposed to artificial weathering in a QUV weathering tester for 0, 24, 48, 96 and 144 h following the standard EN 927-6 . Mass losses after each exposure showed significant differences between copper coated and untreated micro-veneers. Tensile strength was assessed at zero span (z-strength) and finite span (f-strength) under dry conditions (20 °C, 65% RH). During 48 h, micro-veneers lost their z-strength progressively. In contrast, copper coating at highest loading imparts a photo-protective effect to wood micro-veneers during 144 h exhibiting z-strength retention of 95%. F-strength losses were similar in all copper treated and untreated micro-veneers up to 96 h. However, after 144 h, copper coated micro-veneers at highest loading showed significantly greater strength retention of 56%, while untreated micro-veneers exhibited only 38%. Infrared spectroscopy suggested that copper coating does not stabilize lignin. Inductively Coupled Plasma revealed that micro-veneers coated with the highest loading exhibited the lowest percentage of copper loss. Blue stain resistance of copper coated Scots pine following the guidelines of EN 152 was performed. Additional test with different position of the coated surface was also assessed. Copper coating reduced fungal growth when coated surface is exposed in contact with vermiculite. Spores of Aureobasidium pullulans were not able to germinate on the copper coated surface positioned uppermost.
Keywords: Artificial weathering; UV degradation; Copper; Plasma; Blue stain; Tensile strength;

Surface plasmon resonance enhanced visible-light-driven photocatalytic activity in Cu nanoparticles covered Cu2O microspheres for degrading organic pollutants by Yahui Cheng; Yuanjing Lin; Jianping Xu; Jie He; Tianzhao Wang; Guojun Yu; Dawei Shao; Wei-Hua Wang; Feng Lu; Lan Li; Xiwen Du; Weichao Wang; Hui Liu; Rongkun Zheng (120-128).
Micron-sized Cu2O with different coverage of Cu nanoparticles (NPs) on the sphere has been synthesized by a redox procedure. The absorption spectra show that Cu NPs induce the surface plasmon resonance (SPR) at the wavelength of ∼565 nm. Methylene blue (MB) photodegrading experiments under visible-light display that the Cu2O–Cu–H2O2 system exhibits a superior photocatalytic activity to Cu2O–H2O2 or pure H2O2 with an evident dependency on Cu coverage. The maximum photodegradation rate is 88% after visible-light irradiating for 60 min. The role of the Cu NPs is clarified through photodegradation experiments under 420 nm light irradiation, which is different from the SPR wavelength of Cu NPs (∼565 nm). By excluding the SPR effect, it proves that Cu SPR plays a key role in the photodegradation. Besides, a dark catalytic activity is observed stemming from the Fenton-like reaction with the aid of H2O2. The radical quenching experiments indicate that both •O2 and •OH radicals contribute to the photocatalysis, while the dark catalysis is only governed by the •OH radicals, leading to a lower activity comparing with the photocatalysis. Therefore, with introducing Cu NPs and H2O2, the Cu2O-based photocatalytic activity could be significantly improved due to the SPR effect and dark catalysis.
Keywords: Photocatalysis; Surface plasmon resonance; Cu2O; Visible-light-driven;

Dumbbell-like ZnO nanoparticles-CeO2 nanorods composite by one-pot hydrothermal route and their electrochemical charge storage by Geping He; Huiqing Fan; Longtao Ma; Kaige Wang; Chao Liu; Donghai Ding; Li Chen (129-138).
Dumbbell-like ZnO nanoparticles-CeO2 nanorods (ZnONPs-CeO2NRs) composite with superior electrochemical performance was fabricated by one-pot hydrothermal process. Charge storage of the ZnONPs-CeO2NRs composite was more 12 times than its precursor CeO2NRs.Dumbbell-like ZnO nanoparticles-CeO2 nanorods (ZnONPs-CeO2NRs) composites with superior electrochemical performance were fabricated by one-pot hydrothermal process and characterized by X-ray diffraction, an energy dispersive spectrum, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and nitrogen adsorption–desorption isotherms. The ZnONPs-CeO2NRs nanostructure possessed larger Brunauer–Emmett–Teller (BET) surface, crystallinity, lower resistance. The specific capacitance of ZnONPs-CeO2NRs composite (162.08 mF g−1) was higher than that of precursor CeO2NRs (151.43 mF g−1) in galvanostatic charge/discharge, and the super-capacitor charge storage of ZnONPs-CeO2NRs (581.39 F g−1) was more 12 times than the precursor (46.63 F g−1). The improved electrochemical performances could be ascribed to the import of ZnONPs, which induced variations in the structure, conductivity and surface morphology.
Keywords: Nanocomposite; Dumbbell-like nanostructure; Hydrothermal process; Super-capacitor charge storage;

To mitigate the threat of NO x on the environment, MnO x nanowires were fabricated on activated semi-coke (MnO x NW/ASC) for the first time. The prepared MnO x NW/ASC was used for the low temperature selective catalytic reduction (SCR) of NO x with NH3, which achieved an efficiency of over 90% with a low loading content of 1.64 wt% at 150–210 °C. This high performance could be ascribed to synergistic effect between MnO x and ASC. Specifically, the large specific surface area and reducible property of ASC facilitated the dispersion of MnO x and the formation of Mn3+, respectively. Meanwhile, MnO x nanowires provided more redox sites and lattice oxygen species due to the coexistence of Mn3+ and Mn4+, which accelerated the catalytic cycle. The in situ DRIFTS studies revealed that ASC was conducive to the adsorption of NO and NH3. Most importantly, the existence of Mn3+ favored the formation of amide species and the subsequent reduction reaction. Furthermore, the Langmuir–Hinshelwood (L–H) route between coordinated NH3 and bidentate nitrate was predominating in the SCR process and responsible for the high catalytic activity at low temperature.
Keywords: MnO x nanowires; Activated semi-coke; NO x ; SCR; In situ DRIFTS;

The mild steel surface has been modified to impart anticorrosion and antibacterial properties through a dip coating method followed by thermal curing of a mixture containing amine terminated cyclotriphosphazene and functionalized titanium dioxide nanoparticles reinforced benzoxazine based cyanate ester composite (ATCP/FTiO2/Bz-CE). The corrosion resistance behavior of coating material has been investigated by electrochemical and antibacterial studies by disc diffusion method. The nanocomposites coated mild steels have displayed a good chemical stability over long immersion in a corrosive environment. The protection efficiency has found to be high for ATCP/FTiO2/Bz-CE composites, which can be used in microelectronics and marine applications.
Keywords: Corrosion resistance; Cyanate ester; Benzoxazine; TiO2; Dip coating; Antibacterial;

Preparing a stable suspension is a main step towards the electrophoretically depositing of homogeneous and dense composite coatings on NiTi for its biomedical application. In the present study, different composite suspensions of hydroxyapatite, silicon and multi-walled carbon nano-tubes were prepared using n-butanol and triethanolamine as media and dispersing agent, respectively. Multi-walled carbon nanotubes were first functionalized in the nitric acid vapor for 15 h at 175 °C, and then mixed into suspensions. Thermal desorption spectroscopy profiles indicate the formation of functional groups on multi-walled carbon nano-tubes. An excellent suspension stability can be achieved for different amounts of triethanolamine. The amount of triethanolamine can be increased by adding a second component to a stable hydroxyapatite suspension due to an electrostatic interaction between components in suspension. The stability of composite suspension is less than that of the hydroxyapatite suspension, due to density differences, which under the gravitational force promote the demixing. The scanning electron microscopy images of the coatings surface show that more dense coatings are developed on NiTi substrate using electrophoretic deposition and sintering at 850 °C in the simultaneous presence of silicon and multi-walled carbon nanotubes in the hydroxyapatite coatings. The atomic force microscopy results of the coatings surface represent that composite coatings of hydroxyapatite-20 wt.% silicon and hydroxyapatite-20 wt.% silicon-1 wt.% multi-walled carbon nano-tubes with low zeta potential have rougher surfaces.
Keywords: Hydroxyapatite; Composite coating; Electrophoretic deposition; Suspensions; Carbon nanotubes; Surface morphology;

The dissociation of a hydrogen molecule on perfect MgO(0 0 1) films deposited on Mo(0 0 1) surface is investigated systematically using periodic density-functional theory (DFT) method. The unusual adsorption behavior of heterolytic dissociative hydrogen molecule at neighboring surface oxygen and surface magnesium, is clarified here. To our knowledge, this heterolytic dissociative state has never been found before on bulk MgO(0 0 1) or metal supported perfect MgO(0 0 1) surfaces (without low coordination sites). The results confirm that, in all cases, the heterolytic dissociation is much more favorable that homolytic dissociation both energetically and kinetically. The energy differences between two dissociative states are very large, in the range of 1.1 eV–1.5 eV for Mo supported 1 ML–3 ML oxide films, which inhibits, to a great extent, the homolytic dissociation in the respect of reaction thermodynamics. The energy barriers of heterolytic dissociation are about 0.5 eV, much lower that the barrier of homolytic dissociation. The transformation reaction on thick films will be more endothermic. Passing through heterolytic dissociation state has significantly lowered the reaction heat and the energy barrier for obtaining homolytic dissociative structure, which makes the homolytic splitting of H2 easier on 2 ML oxide films. The results provide a useful strategy for enhancing the reactivity of the nonreducible metal oxide.
Keywords: H2; MgO; Heterolytic dissociation; Homolytic dissociation; Density functional theory; Reaction pathway;

In this paper, in order to expand the light response range of TiO2, Ag3VO4/TiO2 nanorods photocatalysts were fabricated by a simple sol–gel method with microwave and hydrothermal method. The as-prepared samples were characterized by XRD, SEM, DRS, XPS and N2 adsorption–desorption. Meanwhile, their photocatalytic properties were investigated by the degradation of toluene under visible light irradiation. The degradation conversation of toluene had gotten to about 70% in 1% Ag3VO4/TiO2 nanorods after reaction 4 h. The predominant photocatalytic activity can be attributed to its strong absorption in visible light region and excellent charge separation characteristics. By using in situ FTIR, benzyl alcohol and benzaldehyde species could be observed during the reaction and the formed intermediates would be partially oxidized into CO2 and H2O. Electron spin resonance confirmed that OH• and O2 were involved in the photocatalytic degradation of toluene.
Keywords: Ag3VO4/TiO2 nanorods; Photocatalytic oxidation; Toluene; FTIR;

It is reported that the use of gold nanodumbbells as surface-enhanced Raman spectroscopy (SERS) substrates for the detection of ultra-low levels of four different food colorants: sunset yellow, lemon yellow, orange II and chrysoidin. Gold nanodumbbells are suitable to on-site detection because which have a λ max of 785 nm that tune the surface plasmon resonance of the nanoparticles to the laser excitation wavelength of the Raman spectrometer equipped with a 785 nm diode laser. In order to investigate the on-site application of the gold nanodumbbells substrate, four pigments in the orange juice and coke were detected by the portable Raman instrument. The results showed that this novel SERS platform can be used as an effective method in detecting prohibited additive colorants in food. This SERS platform provides valuable and powerful analytical tool in real-world applications in food analysis.
Keywords: Gold nanodumbbells; Surface-enhanced Raman spectroscopy; Prohibited colorants; Portable Raman spectrometer;

Numerical analysis of particle impacting and bonding processes during high velocity oxygen fuel spraying process by Jiajing Pan; Shengsun Hu; Anning Niu; Kunying Ding; Lijun Yang (187-192).
In this paper, the dynamic impact behavior of a particle and a substrate under different particle temperatures and velocities as well as using different materials for the particle and substrate were systematically studied. We found that the highest temperature occurred at the side edge of the particle after the collision, which is consistent with the distribution of equivalent plastic strain. The deformation of the particle and substrate was very severe at the first 40 ns, slowed down after 40 ns and remained almost unchanged after 80 ns. With the increase in the particle velocity, the effective combination area became larger, the equivalent plastic strain of the substrate is increased, and the equivalent plastic strain of the particle is decreased. As the initial temperature of particles increased, the effective combination area between the particle and substrate increased, and higher temperature and larger equivalent plastic strain of the particle could be obtained. With the increase in the substrate strength, the temperature and the equivalent plastic strain of the particle is increased, whereas the plastic deformation of the substrate is decreased.
Keywords: Numerical analysis; HVOF; Thermal spray; Particle impacting;

Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.
Keywords: Surface modification; Halloysite nanotubes; Interfacial enhancement; Rubber nanocomposites;

The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).
Keywords: Langmuir-Blodgett films; Glucose oxidase; Gold nanoparticles; Composite film; Architecture effect;

Microwave absorption properties of polyaniline-Fe3O4/ZnO-polyester nanocomposite: Preparation and optimization by M.S. Seyed Dorraji; M.H. Rasoulifard; M.H. Khodabandeloo; M. Rastgouy-Houjaghan; H. Karimi Zarajabad (210-218).
New nanocomposites have been successfully prepared based on polyester resin, including various metal oxides (ZnO nanorod bundles, Fe3O4 nanoparticles, and nano Fe3O4/ZnO) and Polyaniline (PANI) synthesized with different dopants. The microwave absorption properties of nanocomposites were investigated in X-band range. The Taguchi experimental design was used to study the effects of the type of metal oxide and that of PANI (doped with various acids) and the weight percent of metal oxide in PANI and that of filler (metal oxide and PANI) in polyester matrix on the microwave absorption properties with the absorber thickness of only 2 mm. The weight percent of metal oxide in PANI was found to be the most significant parameter, accounting for 45.611% of the total contribution of the four selected parameters. Fe3O4/ZnO as inorganic oxide, PTSA as dopant of PANI, 25  wt.% for inorganic oxide in PANI, and filler in the polyester matrix were selected as optimum conditions by Taguchi method. The sample prepared in optimal conditions had reflection loss of less than −10 dB (absorption >90%) and covering a frequency range of 8.4–11.6 GHz.
Keywords: Conducting polymer; Microwave absorption; Magnetite; Nanocomposites; Zinc oxide;

Although many studies have reported the chemical vapor deposition (CVD) growth of large-area monolayer graphene from methane, synthesis of graphene using acetylene as the source gas has not been fully explored. In this study, the low-pressure CVD (LPCVD) growth of graphene from acetylene was systematically investigated. We succeeded in regulating the domain size, defects density, layer number and the sheet resistance of graphene by changing the acetylene flow rates. Scanning electron microscopy and Raman spectroscopy were employed to confirm the layer number, uniformity and quality of the graphene films. It is found that a low flow rate of acetylene (0.28 sccm) is required to form high-quality monolayer graphene in our system. On the other hand, the high acetylene flow rate (7 sccm) will induce the growth of the bilayer graphene domains with high defects density. On the basis of selected area electron diffraction (SAED) pattern, the as-grown monolayer graphene domains were analyzed to be polycrystal. We also discussed the relation between the sheet resistacne and defects density in graphene. Our results provide great insights into the understanding of the CVD growth of monolayer and bilayer graphene from acetylene.
Keywords: Monolayer graphene; Acetylene; Rapid growth; LPCVD;

How to fabricate conductive patterns on ceramic boards with higher resolution is a challenge in the past years. The fabrication of copper patterns on alumina substrate by laser direct writing and electroless copper plating is a low cost and high efficiency method. Nevertheless, the lower resolution limits its further industrial applications in many fields. In this report, the mechanisms of laser direct writing and electroless copper plating were studied. The results indicated that as the decomposed products of precursor PdCl2 have different chemical states respectively in laser-irradiated zone (LIZ) and laser-affected zone (LAZ). This phenomenon was utilized and a special chemical cleaning method with aqua regia solution was taken to selectively remove the metallic Pd in LAZ, while kept the PdO in LIZ as the only active seeds. As a result, the resolution of subsequent copper patterns was improved significantly. This technique has a great significance to develop the microelectronics devices.
Keywords: Laser direct writing; Selective metallization; Chemical cleaning; Electroless copper plating;

Structural properties and stability characteristics of single- and double-walled boron-nitride nanotubes functionalized with Flavin mononucleotide (FMN) in aqueous environment are investigated employing molecular dynamics simulations.The non-cytotoxic properties of Boron-nitride nanotubes (BNNTs) and the ability of stable interaction with biomolecules make them so promising for biological applications. In this research, molecular dynamics (MD) simulations are performed to investigate the structural properties and stability characteristics of single- and double-walled BNNTs under physical adsorption of Flavin mononucleotide (FMN) in vacuum and aqueous environments. According to the simulation results, gyration radius increases by rising the weight percentage of FMN. Also, the results demonstrate that critical buckling force of functionalized BNNTs increases in vacuum. Moreover, it is observed that by increasing the weight percentage of FMN, critical force of functionalized BNNTs rises. By contrast, critical strain reduces by functionalization of BNNTs in vacuum. Considering the aqueous environment, it is observed that gyration radius and critical buckling force of functionalized BNNTs increase more considerably than those of functionalized BNNTs in vacuum, whereas the critical strains approximately remain unchanged.
Keywords: Boron-nitride nanotube; Non-covalent functionalization; Flavin mononucleotide (FMN); Buckling; Molecular dynamics simulations;

The effect of yttrium addition on oxidation of a sputtered nanocrystalline coating with moderate amount of tantalum in composition by Jinlong Wang; Minghui Chen; Lanlan Yang; Li Liu; Shenglong Zhu; Fuhui Wang; Guozhe Meng (245-253).
The effect of yttrium addition on isothermal oxidation at 1050 °C of a sputtered nanocrystalline coating with moderate amount of tantalum in composition was investigated. Results indicate that yttrium addition delays transformation of metastable θ-Al2O3 to equilibrium α-Al2O3 grown on the nanocrystalline coatings. It prevents scale rumpling and promotes the formation of oxide pegs at interface between the oxide scale and the underlying coating. Besides, yttrium prefers to segregate at grain boundaries of the nanocrystalline coating and retards the outward transportation of tantalum from coating to oxide scale, thus reducing the excessive oxidation of tantalum.
Keywords: Single-crystal superalloys; Nanocrystalline coating; High-temperature oxidation; Reactive element effect;

Probing stem cell differentiation using atomic force microscopy by Xiaobin Liang; Xuetao Shi; Serge Ostrovidov; Hongkai Wu; Ken Nakajima (254-259).
A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.
Keywords: Atomic force microscopy; Stem cell differentiation; Cell mechanical property; Extracellular matrix;

Friction and wear behaviour of Mo–W doped carbon-based coating during boundary lubricated sliding by Papken Eh. Hovsepian; Paranjayee Mandal; Arutiun P. Ehiasarian; G. Sáfrán; R. Tietema; D. Doerwald (260-274).
A molybdenum and tungsten doped carbon-based coating (Mo–W–C) was developed in order to provide low friction in boundary lubricated sliding condition at ambient and at high temperature. The Mo–W–C coating showed the lowest friction coefficient among a number of commercially available state-of-the-art DLC coatings at ambient temperature. At elevated temperature (200 °C), Mo–W–C coating showed a significant reduction in friction coefficient with sliding distance in contrast to DLC coatings. Raman spectroscopy revealed the importance of combined Mo and W doping for achieving low friction at both ambient and high temperature. The significant decrease in friction and wear rate was attributed to the presence of graphitic carbon debris (from coating) and ‘in situ’ formed metal sulphides (WS2 and MoS2, where metals were supplied from coating and sulphur from engine oil) in the transfer layer.
Keywords: Sliding friction; Tribochemical reaction; Wear; Raman spectroscopy;

The development of eco-friendly and cost-effective synthetic protocol for the preparation of nanomaterials, especially metal nanoparticles is an emerging area of research in nanotechnology. These metal nanoparticles, especially silver can play a crucial role in various catalytic reactions. The biosynthesized silver nanoparticles described here was very stable up to 6 months and can be further exploited as an effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. The silver nanoparticles were utilized as an efficient surface-enhanced Raman scattering (SERS) active substrate using Rhodamine 6G as Raman probe molecule. We have also carried out systematic comparative studies on the catalytic efficiency of both silver and gold nanoparticles using UV–vis spectra to monitor the above reaction spectrophotometrically. We find that the reaction follows pseudo-first order kinetics and the catalytic activity can be explained by a simple model based on Langmuir–Hinshelwood mechanism for heterogeneous catalysis. We also find that silver nanoparticles are more efficient as a catalyst compare to gold nanoparticles in the reduction of 4-nitrophenol to 4-aminophenol, which can be explained by the morphology of the nanoparticles as determined by transmission electron microscopy.
Keywords: Nanoparticles; Surface morphology; 4-Nitrophenol; Catalytic activity; Pseudo-first order reaction; Surface-enhanced Raman scattering;

Surface wetting properties of implants are one of the most critical parameter, which determine the interaction of proteins and cells with the implant surface. In this regards, acid etching and sand blasting are the mostly used methods at surface modification of Titanium (Ti) for enhanced surface wettability. Besides, these kinds of modifications may cause a conflict whether the surface wettability is influenced by the process related surface contaminations or by the surface roughness. In contrast, lasers might be an option for the alteration of surface wetting properties via supporting micro and/or nano surface topographies while preventing surface chemical contaminations. In this work, we focused on two steps of surface processing approaches of Ti surface: physical and chemical modifications. Herein, we hierarchically structured Ti surfaces by using microsecond modulated pulsed fiber laser. Subsequently, laser structured and non-structured Ti surfaces were further modified with novel histidine and leucine Amino Acid conjugated Self-Assembled Molecules (His1-SAMs2 and Leu3-SAMs) to alter the surface wettability by introducing biologically hydrophilic and hydrophobic groups. Modification of Ti surfaces with His-SAMs and Leu-SAMs ended up with stable wetting properties when compared to non-modified surfaces after 7 days which may enhances the cell–surface interaction.
Keywords: Titanium; Laser; Self-assembled molecules (SAMs); Histidine; Leucine; Wettability;

Au/TS-1 catalysts with different Au nanoparticles (NPs) sizes ranging from 3.1 to 8.4 nm but the same Au loading of 0.5 wt% were prepared through changing the concentration of Cinnamomum camphora leaves extract. Smaller Au NPs are the dominant active sites. There is no decreasing in both the activity and the PO selectivity for the Au/TS-1 catalysts after reaction of 100 h.The Au/TS-1 catalysts with different Au nanoparticles (NPs) sizes ranging from 3.1 to 8.4 nm but the same Au loading of 0.5 wt% were prepared by Cinnamomum camphora (CC) extract, and were used for propylene epoxidation. The results showed that the interaction between Au and TS-1 support surface is important for propylene epoxidation and much smaller Au NPs (<3 nm) are the dominant active sites. After reaction of 100 h, there is no decreasing in both the activity and the PO selectivity for the Au/TS-1 catalysts, and only 1.8 wt% of the carbonaceous deposits on the surface of the catalyst after reaction, suggesting that the desorption of the product from the modified catalysts surface by residual biomolecules is much easier.
Keywords: Propylene epoxidation; Au/TS-1 catalyst; Au nanoparticles size; Catalytic stability;

Effect of profile and size of isolation trench on the optical and electrical performance of GaN-based high-voltage LEDs by Shengjun Zhou; Chenju Zheng; Jiajiang Lv; Yingce Liu; Shu Yuan; Sheng Liu; Han Ding (299-303).
Four types of HV-LEDs with different isolation trench width were presented. The isolation trench with an oblique angle of 45.6° was obtained using a combination of Cl2/BCl3 plasma chemistry and a thermally reflowed photoresist mask layer, enabling conformal metal lines coverage across the isolation trench. The effect of isolation trench width on the optical and electrical characteristics of HV LEDs was also investigated. A quantitative model was developed to analyze light coupling propagation phenomenon occurring within HV LEDs. The suppression of light coupling propagation among adjacent LED cells was achieved by extending isolation trench width from 3.81 μm to 12.30 μm, which improved light extraction efficiency and thus increased light output power of HV LEDs. However, the significantly increasing loss of MQW active region area, which was caused by further extending isolation trench width from 12.30 μm to 40.49 μm, decreased light output power of HV LEDs.
Keywords: High voltage LEDs; Tapered GaN isolation trench; GaN etching; Light coupling propagation;

Plasma etching behavior of Y2O3 ceramics: Comparative study with Al2O3 by Yu-Chao Cao; Lei Zhao; Jin Luo; Ke Wang; Bo-Ping Zhang; Hiroki Yokota; Yoshiyasu Ito; Jing-Feng Li (304-309).
The resistance mechanism against plasma etching has been studied mainly by XPS experiments, which revealed the formation of YF3 layer on the surface of Y2O3 coating exposed to CF4 plasma, as evidenced by the existence of 3d XPS peaks of Y―F bonding and the concentration of F element at outmost surface.The plasma etching behavior of Y2O3 coating was investigated and compared with that of Al2O3 coating under various conditions, including chemical etching, mixing etching and physical etching. The etching rate of Al2O3 coating declined with decreasing CF4 content under mixing etching, while that of Y2O3 coating first increased and then decreased. In addition, the Y2O3 coating demonstrated higher erosion-resistance than Al2O3 coating after exposing to fluorocarbon plasma. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formations of YF3 and AlF3 on the Y2O3 and Al2O3 coatings, respectively, which acted as the protective layer to prevent the surface from further erosion with fluorocarbon plasma. It was revealed that the etching behavior of Y2O3 depended not only on the surface fluorination but also on the removal of fluoride layer. To analyze the effect of porosity, Y2O3 bulk samples with high density were prepared by spark plasma sintering, and they demonstrated higher erosion-resistances compared with Y2O3 coating.
Keywords: Fluorocarbon plasma; Etching; Yttrium oxide; Thermal spray; Spark plasma sintering;

Characterization of photo-induced anomalous Hall effect in the two-dimensional MoS2 by Yingzi Peng; Ji Chen; Yang Song; Yuan Li (310-316).
We report the observation of a small but finite valley Hall effect (VHE) signal in two-dimensional MoS2 channels which is grown on SiO2/Si substrates under the circularly polarized light. And the angular dependence of VHE in two-dimensional MoS2 is studied. The VHE signal is a periodic function (period π) but with a phase shift, which confirms the presence of strong coupling between spin and valley. Furthermore, using a weak measurement under the condition of the optical circular dichroism, we find resembling beating phenomena, which suggests that a static electric field can induce oscillations. It is interesting that the interval time of the peak starts from an certain value, which is related to carrier densities. We suppose that this certain value is explained by a quasi-two-dimensional electron gas model, which is based on the Hall conductance quantized value of e 2 /h. To our knowledge, it is the first experiment that realizes such quantized values.
Keywords: 2D-MoS2; Anomalous Hall effects; Beating phenomena; Quantized value e 2/h;

Corrosion investigation of fire-gilded bronze involving high surface resolution spectroscopic imaging by G. Masi; C. Chiavari; J. Avila; J. Esvan; S. Raffo; M.C. Bignozzi; M.C. Asensio; L. Robbiola; C. Martini (317-327).
Gilded bronzes are often affected by severe corrosion, due to defects in the Au layer and Au/Cu alloy galvanic coupling, stimulated by large cathodic area of the gilded layer. Galvanic corrosion, triggered by gilding defects, leads to products growth at the Au/bronze interface, inducing blistering or break-up of the Au layer. In this context, fire-gilded bronze replicas prepared by ancient methods (use of spreadable Au–Hg paste) was specifically characterised by compiling complementary spectroscopic and imaging information before/after accelerated ageing with synthetic rain. Fire-gilded bronze samples were chemically imaged in cross-section at nano-metric scale (<200 nm) using high energy and lateral resolution synchrotron radiation photoemission (HR-SRPES) of core levels and valence band after conventional characterisation of the samples by Glow Discharge optical Emission Spectroscopy (GD-OES) and conventional X-ray photoelectron spectroscopy (XPS). We have found a net surface enrichment in Zn and Sn after fire-gilding and presence of metallic Hg, Pb and Cu within the Au layer. Moreover, the composition distribution of the elements together with their oxidation has been determined. It was also revealed that metallic phases including Hg and Pb remain in the gilding after corrosion. Moreover, selective dissolution of Zn and Cu occurs in the crater due to galvanic coupling, which locally induces relative Sn species enrichment (decuprification). The feasibility advantages and disadvantages of chemical imaging using HR-SRPES to study artworks have been investigated on representative replicas.
Keywords: Fire gilded bronze; Corrosion; Chemical imaging; Synchrotron radiation; Photoemission; Artworks; XPS; Decuprification;

Red-blood-cell-like BSA/Zn3(PO4)2 hybrid particles: Preparation and application to adsorption of heavy metal ions by Baoliang Zhang; Peitao Li; Hepeng Zhang; Xiangjie Li; Lei Tian; Hai Wang; Xin Chen; Nisar Ali; Zafar Ali; Qiuyu Zhang (328-338).
A novel kind of red-blood-cell-like bovine serum albumin (BSA)/Zn3(PO4)2 hybrid particle is prepared at room temperature by a facile and rapid one-step method based on coordination between BSA and zinc ion. The morphology of the monodisperse hybrid particle shows oblate spheroidal type with a one sided single hole on the surface. The hybrid particle is constructed with BSA/Zn3(PO4)2 nanoplates of 35 nm thick. The average particle size of hybrid particle is 2.3 μm, and its BET specific surface area is 146.64 cm2/g. To clarify the evolution of BSA/Zn3(PO4)2 hybrid particle, SEM and elemental analysis as a function of particle growth time are investigated. The formation mechanism of BSA/Zn3(PO4)2 hybrid particle, which can be described as crystallization, coordination and self-assembly process, is illustrated in detail. The as-prepared BSA/Zn3(PO4)2 hybrid particle is used for adsorption of Cu2+. The hybrid particle displayed excellent adsorption properties on Cu2+. The adsorption efficiency of BSA/Zn3(PO4)2 hybrid particles at 5 min and 30 min are 86.33% and 98.9%, respectively. The maximum adsorption capacity is 6.85 mg/g. Thus, this kind of novel adsorbent shows potential application value in ultra-fast and highly efficient removal of Cu2+.
Keywords: Hybrid particle; BSA; Zn3(PO4)2; Adsorption; Heavy metal ions;

The effect of surface pre-conditioning treatments on the local composition of Zr-based conversion coatings formed on aluminium alloys by J. Cerezo; I. Vandendael; R. Posner; J.H.W. de Wit; J.M.C. Mol; H. Terryn (339-347).
This study investigates the effect of different alkaline, acidic and thermal pre-conditioning treatments applied to different Al alloy surfaces. The obtained results are compared to the characteristics of Zr-based conversion coatings that were subsequently generated on top of these substrates. Focus is laid on typical elemental distributions on the sample surfaces, in particular on the amount of precipitated functional additives such as Cu species that are present in the substrate matrix as well as in the conversion bath solutions. To this aim, Field Emission Auger Electron spectra, depth profiles and surface maps with superior local resolution were acquired and compared to scanning electron microscopy images of the sample. The results show how de-alloying processes, which occur at and around intermetallic particles in the Al matrix during typical industrial alkaline or acidic cleaning procedures, provide a significant source of crystallization cores for any following coating processes. This is in particular due for Cu-species, as the resulting local Cu structures on the surface strongly affect the film formation and compositions of state-of-the-art Zr-based films. The findings are highly relevant for industrial treatments of aluminium surfaces, especially for those that undergo corrosion protection and painting process steps prior to usage.
Keywords: Zr-based conversion coatings; Aluminium alloys; FE-AES; Surface treatments; Copper enrichment;

Rectifying properties of ZnO thin films deposited on FTO by electrodeposition technique by Jianguo Lv; Yue Sun; Min Zhao; Li Cao; Jiayuan Xu; Gang He; Miao Zhang; Zhaoqi Sun (348-352).
ZnO thin films were successfully grown on fluorine-doped tin oxide glass by electrodeposition technique. The crystal structure, surface morphology and optical properties of the thin films were investigated. The average crystallite size and intensity of A1(LO) mode increase with improving the absolute value of deposition potential. The best preferential orientation along c-axis and the richest oxygen interstitial defects have been observed in the sample deposited at −0.8 V. A heterojunction device consisting of ZnO thin film and n-type fluorine-doped tin oxide was fabricated. The current–voltage (IV) characteristic of the p–n heterojunction device deposited at −0.8 V shows the best rectifying diode behavior. The p-type conductivity of the ZnO thin film could be attributed to complex defect of unintentional impurity and interstitial oxygen.
Keywords: ZnO thin films; Electrodeposition; Photoluminescence; Heterojunction; Rectifying properties;

The nickel, nickel-molybdenum alloy, nickel-graphite and nickel-reduced graphene oxide composite coatings were obtained by the electrodeposition technique from a nickel sulfate bath. Nanocrystalline molybdenum, graphite and reduced graphene oxide in nickel coatings promoted hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. However, the nickel-reduced graphene oxide composite coating exhibited the highest electrocatalytic activity for the hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. A large number of gaps between ‘cauliflower’ like grains could decrease effective area for hydrogen evolution reaction in slight amorphous nickel-molybdenum alloy. The synergistic effect between nickel and reduced graphene oxide promoted hydrogen evolution, moreover, refined grain in nickel-reduced graphene oxide composite coating and large specific surface of reduced graphene oxide also facilitated hydrogen evolution reaction.
Keywords: Alloy; Hydrogen evolution; Electrodeposition; Surface morphology; Graphene;

In this study, we have synthesized TiO2 nanorods (NRs) on silicon and porous silicon (PS) substrates by hydrothermal method. The PS substrates with different porosities were fabricated by electrochemical anodization on silicon. According to the field emission electron microscopy images, TiO2 NRs grown on PS substrates have a better growth compared to those grown on silicon. Also increasing substrate porosity leads to an increase in density of the NRs. Atomic force microscopy observation demonstrates that porous layer formation due to etching of silicon surface leads to an increase of its roughness. Results indicate surface roughness evolution with porosity increasing enhances TiO2 nucleation on substrate and thus increases TiO2 NRs density. We propose a growth mechanism to explain how we can control the local surface chemical potential and thus the nucleation and alignment of TiO2 NRs by surface roughness variation. Also, photoluminescence studies show a red-shift in band gap energy of NRs compared to that of common bulk TiO2.
Keywords: Porous silicon; TiO2 nanorods; Hydrothermal method; Surface roughness;

Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure by M.S. Rubina; E.E. Kamitov; Ya. V. Zubavichus; G.S. Peters; A.V. Naumkin; S. Suzer; A.Yu. Vasil’kov (365-371).
Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-СollСh) and Ag-Сollagen-Сhitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.
Keywords: Collagen-chitosan scaffolds; Metal-vapor synthesis; Nanoparticles; XPS; XRD; SAXS; XANES/EXAFS;

Investigation into the morphology, composition, structure and dry tribological behavior of rice husk ceramic particles by Enzhu Hu; Kunhong Hu; Zeyin Xu; Xianguo Hu; Karl David Dearn; Yong Xu; Yufu Xu; Le Xu (372-382).
To expand the application of rice husk (RH) resource, this study developed carbon-based RH ceramic (RHC) particles using a common high-temperature carbonization method. The morphology, composition, and structure of the RHC particles were characterized with a series of modern analysis technologies and were then compared with those of the initial RH powder and carbonized RH (CRH) particles. The dry tribological behavior of RHC particle adobes (RHAs) was also investigated. Results showed the sheet-shaped morphology of the RHC particles. The graphitization degree of the RHC particles was lower than that of the CRH particles possibly because the phenolic resin (PR) filled the micro-pores of the RH particles, thereby prompting the formation of amorphous carbon in the RHC particles as a result of high-temperature carbonization. The appearance of a hydroxy function group (―OH) on the surface of the RHC particles was ascribed to the decomposition of PR at 900 °C. The friction coefficients and mass loss rates of the RHAs almost increased with the rise in load and velocity. In addition, the friction coefficients of the RHAs decreased at high load (5 N) and velocity (0.261 m/s) conditions. Such outcome indicated that the variation of contact area between steel ball and RHA at high load and velocity conditions resulted in the abrasive wear or catastrophic wear.
Keywords: Rice husk ceramic particles; Morphology; Composition and structure; Dry friction;

Structural, morphological and electrical characteristics of electrodeposited Cu2O: Effect of deposition time by O. Messaoudi; I. Ben assaker; M. Gannouni; A. Souissi; H. Makhlouf; A. Bardaoui; R. Chtourou (383-388).
In this work, a new contribution to the knowledge of thickness (or deposition time) dependence of structural, morphological and optical properties is reported, as well as the electrochemical behavior of the Cu2O electrode/(NaOH) electrolyte solution interface. According to these studies, X-ray diffraction revealed that all films are mainly crystallized in Cu2O cubic phase characterized by the preferential orientation along (1 1 1) plane. Optical measurements show that both values of reflectance and film thickness increase when increasing the deposition time, unlike the band gap energy which decreases with time. Using the electrochemical impedance spectroscopy data, the interface was modeled as an equivalent circuit approach. From the Mott–Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 0.949 × 1017  cm−3 and 6 × 1017  cm−3.
Keywords: Cu2O; Electrodeposition; Electrochemical impedance spectroscopy; Deposition time;

Laser-induced forward transfer of high-viscosity silver pastes by D. Munoz-Martin; C.F. Brasz; Y. Chen; M. Morales; C.B. Arnold; C. Molpeceres (389-396).
In this work, a study of the morphology of individual dots of silver paste deposited by laser-induced forward transfer (LIFT) is performed using a ns-pulsed laser at 532 nm. The LIFT process is characterized by scanning confocal microscopy on the deposited material and in-situ time-resolved imaging during the transfer in order to illuminate the flow dynamics in relation to the pulse energy and paste thickness. The influence of process parameters on the structure of transferred dots is explained both phenomenologically and analytically.Depending on the experimental conditions, different transfer regimes were observed. These regimes have similarities to those reported for LIFT of Newtonian fluids and nanopastes, but the multiphase and non-Newtonian rheology and thicker films used lead to noticeable differences, such as the formation of a continuous and stable pillar connecting donor and acceptor substrates when the paste film is thick enough and the energy is optimum. This process regime allows transfer of dots with high aspect ratios, which is desirable for the printing of contacts on solar cells.
Keywords: Laser-induced forward transfer; Laser direct-write; Printing; Metallization;

Angle-resolved photoemission studies of the valence bands of ZrS x Se2−x by Mohamed Moustafa; Alexander Paulheim; Mansour Mohamed; Christoph Janowitz; Recardo Manzke (397-403).
The obtained experimental valence band structures of the ZrSe2 (above) and ZrS2 (below). The agreement between the obtained experimental and the calculated band structure (solid lines) in generally very good for the parallel directions of the BZ.The electronic structure of the ternary layered transition metal dichalcogenide compounds of ZrS x Se2−x , where 0 ≤  x  ≤ 2, has been studied by means of high resolution angle-resolved photoemission spectroscopy (ARPES) used in conjunction with synchrotron radiation facilities. The crystals were grown by the chemical vapor transport technique using iodine as a transport agent. They are found to be degenerate extrinsic n-type semiconductors with an indirect bandgap character. The experimental valence band structure of the complete series of ZrS x Se2−x is reported along the major symmetry azimuthal directions in the Brillouin zone parallel to the layers. The results show that the binding energies of the topmost valence band shift almost linearly with the composition parameter x. Further, an emission from the conduction band minimum observed just below the Fermi edge enabled us to estimate the energy gap values. The electronic structure deduced from the photoemission measurements are discussed and compared to band structure calculations.
Keywords: The electronic structure; ARPES; Metal dichalcogenide compounds;

The modified nanocrystalline cellulose for hydrophobic drug delivery by Weixia Qing; Yong Wang; Youyou Wang; Dongbao Zhao; Xiuhua Liu; Jinhua Zhu (404-409).
In this work, torispherical nanocrystalline cellulose (NCC) was synthesized, and firstly modified with a cationic surfactant cetyltrimethylammonium bromide (CTMAB). It was proved that the kinetics of NCC adsorbing CTMAB followed the pseudo-second-order kinetics equation, and the adsorption isotherm model followed Freundlich which was multi molecular layer adsorption model. The morphology and structure of NCC and CTMAB-coated NCC were characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Stabilities of NCC and CTMAB-coated NCC were assayed by zeta potential. The results showed that NCC in CTMAB solution was well-dispersed and stable. Moreover, the drug loading and release performance of CTMAB-coated NCC were studied using luteolin (LUT) and luteoloside (LUS) as model drugs.
Keywords: Nanocrystalline cellulose (NCC); Cationic surfactant cetyltrimethylammonium bromide (CTMAB); Luteolin (LUT); Luteoloside (LUS); Drug delivery;

Nature and morphology of fumed oxides and features of interfacial phenomena by V.M. Gun’ko; V.I. Zarko; O.V. Goncharuk; A.K. Matkovsky; O.S. Remez; J. Skubiszewska-Zięba; G. Wojcik; B. Walusiak; J.P. Blitz (410-423).
Individual and complex fumed nanooxides were studied using high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet-visible (UV–vis) spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, adsorption, desorption (evaporation), and quantum chemical methods. For mixed nanooxides in contrast to simple and small nanoparticles of individual silica or titania, complex core–shell nanoparticles (50–200 nm in size) with titania or alumina cores and silica or alumina shells can be destroyed under high-pressure cryogelation (HPCG), mechnochemical activation (MCA) that also affect the structure of aggregates of nanoparticles and agglomerates of aggregates becoming more compacted. This is accompanied by changes in color from white to beige of different tints and changes in the UV–vis spectra in the 300–600 nm range, as well as changes in crystalline structure of alumina. Any treatment of ‘soft’ nanooxides affects the interfacial behavior of polar and nonpolar adsorbates. For some of them, the hysteresis loops become strongly open. Rearrangement of secondary particles affects the freezing-melting point depression. Clusterization of adsorbates bound in pores causes diminution of heat effects during phase transition (freezing, fusion). Freezing point depression and increasing melting point cause significant hysteresis freezing-melting effects for adsorbates bound to oxide nanoparticles. The study shows that complex nanooxides can be more sensitive to external actions than simple nanooxides such as silica.
Keywords: Nanosilica; Mixed fumed oxides; High-pressure cryogelation; Interfacial phenomena; Adsorption; Evaporation;

Effect of fiber orientations on surface grinding process of unidirectional C/SiC composites by Lifeng Zhang; Chengzu Ren; Chunhui Ji; Zhiqiang Wang; Guang Chen (424-431).
In this work, a new model material consisting of unidirectional CVI-C/SiC was prepared and ground to investigate the grinding mechanism of the woven ceramic matrix composites. The composite was ground in three typical directions and the experimental investigation of the surface grinding process is described. In addition, the micro structural characteristics and grinding mechanism of the composite were analyzed. Finally, the effect of fiber orientations on surface grinding process of unidirectional C/SiC composites was obtained. In addition, the grinding mechanism of C/SiC was revealed.The machining mechanism of woven ceramic matrix composites is one of the most challenging problems in composite application. To elucidate the grinding mechanism of the woven ceramic matrix composites, a new model material consisting of unidirectional CVI-C/SiC was prepared and ground. The composite was ground in three typical directions and the experimental investigation of the surface grinding process for this composite is described. In addition, the micro structural characteristics and grinding mechanism of the composite were analyzed. The result shows that brittle fracture is the dominant removal mechanism for grinding of the C/SiC composites, and the destroy form of the composites is mainly the syntheses of the matrix cracking, fiber fracture, and interfacial debonding. The grinding force follows the order: Normal > Longitudinal > Transverse, and the surface roughness follows: Longitudinal > Normal > Transverse. The grinding parameters (feed speed, cut depth, grinding speed) have great influence on the grinding force and surface roughness. Based on the findings, the grinding force and surface integrity of the woven ceramic matrix composites can be predicted. Furthermore, it is expected to provide a useful guideline for the design, evaluation and optimal application of the C/SiC composites.
Keywords: Grinding; Ceramic matrix composites; Carbon fibers; Surface roughness; Grinding forces;

Formation process of in situ oxide coatings with high porosity using one-step plasma electrolytic oxidation by Xiwen Yu; Li Chen; Honglei Qin; Mingyue Wu; Zongcheng Yan (432-438).
Porous oxide films prepared via plasma electrolytic oxidation are ideal in situ catalysts. However, such films have low porosity. To overcome this limitation, we proposed a promising approach that controls discharge events. The treatments were performed in two kinds of alkaline-silicate solutions namely KOH-enriched solution and Na2SiO3-enriched solution. The coatings prepared in the former electrolyte exhibited superior growth behaviors and catalytic structures. Due to the strong corrosive of KOH-enriched electrolyte, the growth of the film was suppressed, and the sparks were maintained small and evenly distributed throughout the process. Such layers showed high porosity and were evenly covered by nanoparticles. The coating porosity increased with increasing time, and the film treated for 60 min exhibited a high porosity of 33.3 ± 1.7%. Moreover, an oxide film with an outer dendritic and inner porous structure was formed within 120 min. The energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy characterizations indicated that the coatings were mainly composed of aluminum oxide and that the doped iron oxide was enriched on the top surface of the coating. Finally, the formation mechanisms of the coating and nanoparticles were discussed with consideration of the dynamic equilibrium theory.
Keywords: Plasma electrolytic oxidation; Oxide film; High porosity; Nanoparticles; Formation mechanism;

Size-dependent magnetic and electrocatalytic properties of nickel phosphide nanoparticles by Yuan Pan; Yan Lin; Yunqi Liu; Chenguang Liu (439-447).
Nickel phosphide (Ni2P) nanoparticles (NPs) with different sizes were synthesized via thermal decomposition of bis(triphenylphosphine)nickel dichloride precursor in the presence of oleylamine. The size of the as-synthesized Ni2P NPs could easily be controlled by increasing the reaction temperature from 300 to 340 °C. The structure and morphology were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption and X-ray photoelectron spectroscopy (XPS). Then the influences of the size of the Ni2P NPs on the magnetic and electrocatalytic properties were investigated systematically. The results indicate that the as-synthesized Ni2P NPs exhibit ferromagnetic characteristic at 5 K. The Ni2P NPs with small size exhibit superparamagnetism and the larger size exhibit ferromagnetic characteristic at 300 K. The blocking temperature, saturation magnetization, remanent magnetization and coercivity increased significantly with the increase of size of Ni2P NPs, indicating the strong size effect of Ni2P NPs for magnetic properties. Electrochemical tests indicate that the catalytic activity can be enhanced by decreasing the size of Ni2P NPs. Due to the larger electrochemical active surface area and higher electrical conductivity, the Ni2P NPs with small size exhibit higher electrocatalytic activity. This work suggests that the size of Ni2P NPs is an important factor to affect the magnetic and electrocatalytic properties.
Keywords: Nickel phosphide; Size-dependent; Magnetic; Electrocatalytic;

Field emission characteristics found in reduced graphene oxide (RGO) and RGO based composite systems have always been an area of research interest mainly due to presence of prolific quasi aligned edges working as emitter sites. However, the specific role and extent of edge curvature geometry in RGO systems in regards to the enhancement of field emission has not discussed thoroughly prior to this work. In this work we demonstrate enhanced axial field emission due to top assembly of thin RGO layer over a quasi-vertically aligned carbon nanofiber thin film supported on a tungsten wire substrate. Furthermore, simulation analysis for our RGO based hybrid system using finite element modeling showed that two-stage local field amplification in RGO is responsible for the overall improvement of field emission characteristics. In support of our findings, a tentative explanation has been proposed based on the additional emission from RGO edges in between the CNF network resulting to the enhancement of axial field emission in the nanocomposite superstructure.
Keywords: Carbon nanofiber; Composite materials; Reduced graphene oxide; Nanostructured materials; Field emission;

Sulfur passivation for the formation of Si-terminated Al2O3/SiGe(0 0 1) interfaces by Kasra Sardashti; Kai-Ting Hu; Kechao Tang; Sangwook Park; Hyonwoong Kim; Shailesh Madisetti; Paul McIntyre; Serge Oktyabrsky; Shariq Siddiqui; Bhagawan Sahu; Noami Yoshida; Jessica Kachian; Andrew Kummel (455-463).
Sulfur passivation is used to electrically and chemically passivate the silicon–germanium (SiGe) surfaces before and during the atomic layer deposition (ALD) of aluminum oxide (Al2O3). The electrical properties of the interfaces were examined by variable frequency capacitance–voltage (CV) spectroscopy. Interface compositions were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The sulfur adsorbs to a large fraction of surface sites on the SiGe(0 0 1) surface, protecting the surface from deleterious surface reactions during processing. Sulfur passivation (a) improved the air stability of the cleaned surfaces prior to ALD, (b) increased the stability of the surface during high-temperature deposition, and (c) increased the Al2O3 ALD nucleation density on SiGe, thereby lowering the leakage current. S passivation suppressed formation of Ge―O bonds at the interface, leaving the majority of the Al2O3–SiGe interface terminated with direct Si―O―Al bonding.
Keywords: Silicon–germanium; Sulfur passivation; Atomic layer deposition; Aluminum oxide;

The present work evaluates different materials and surface finish in the presence of newly designed, hydrophobic halogen-free room temperature ionic liquids (RTILs) as lubricants. A reciprocating tribo-tester was employed with steel-ceramic and steel-thermosetting epoxy resin contacts under boundary lubrication conditions. Four different tetraalkylphosphonium organosilanesulfonate RTILs provided excellent lubricating performance, with friction coefficients as low as 0.057, and non-measurable wear for the higher roughness machine-finish stainless steel flat against sapphire balls, in the case of the lubricants containing the 2-trimethylsilylethanesulfonate anion. Higher friction coefficients of the order of 0.1 and wear volumes of the order of 10−4  mm3 were observed for the lower roughness fine-finished flat stainless steel surface. All RTILs prevent wear of epoxy resin against stainless steel balls, with friction coefficients in the range of 0.03−0.06. EDX analysis shows the presence of RTILs on the stainless steel surfaces after the tribological tests. Under the experimental conditions, no corrosive processes were observed.
Keywords: Halogen-free ionic liquids; Boundary lubrication; Surface roughness; Steel; Ceramic; Epoxy resin;

XPS determination of Mn oxidation states in Mn (hydr)oxides by Eugene S. Ilton; Jeffrey E. Post; Peter J. Heaney; Florence T. Ling; Sebastien N. Kerisit (475-485).
Hydrous manganese oxides are an important class of minerals that help regulate the geochemical redox cycle in near-surface environments and are also considered to be promising catalysts for energy applications such as the oxidation of water. A complete characterization of these minerals is required to better understand their catalytic and redox activity. In this contribution an empirical methodology using X-ray photoelectron spectroscopy (XPS) is developed to quantify the oxidation state of hydrous multivalent manganese oxides with an emphasis on birnessite, a layered structure that occurs commonly in soils but is also the oxidized endmember in biomimetic water-oxidation catalysts. The Mn2p 3/2 , Mn3p, and Mn3s lines of near monovalent Mn(II), Mn(III), and Mn(IV) oxides were fit with component peaks; after the best fit was obtained the relative widths, heights and binding energies of the components were fixed. Unknown multivalent samples were fit such that binding energies, intensities, and peak-widths of each oxidation state, composed of a packet of correlated component peaks, were allowed to vary. Peak-widths were constrained to maintain the difference between the standards. Both average and individual mole fraction oxidation states for all three energy levels were strongly correlated, with close agreement between Mn3s and Mn3p analyses, whereas calculations based on the Mn2p 3/2 spectra gave systematically more reduced results. Limited stoichiometric analyses were consistent with Mn3p and Mn3s. Further, evidence indicates the shape of the Mn3p line was less sensitive to the bonding environment than that for Mn2p. Consequently, fitting the Mn3p and Mn3s lines yielded robust quantification of oxidation states over a range of Mn (hydr)oxide phases. In contrast, a common method for determining oxidation states that utilizes the multiplet splitting of the Mn3s line was found to be not appropriate for birnessites.
Keywords: XPS; Manganese; Valence; Birnessite; Catalysis; Oxidation;

One-step synthesis of novel PANI–Fe3O4@ZnO core–shell microspheres: An efficient photocatalyst under visible light irradiation by Xiaoyuan Zhang; Jianning Wu; Guihua Meng; Xuhong Guo; Chang Liu; Zhiyong Liu (486-493).
PANI–Fe3O4@ZnO core–shell composite with ZnO shell and PANI core, Fe3O4-OA was embedded in PANI, has enhanced photocatalytic activity under visible light irradiation and can be separated using an external magnet.For the first time, novel multifunctional superparamagnetic PANI–Fe3O4@ZnO core–shell composite photocatalysts with different PANI: ZnO ratios were synthesized by Pickering emulsion route in one step in the presence of ZnO nanoparticles. PANI–Fe3O4@ZnO core–shell microspheres consist of PANI core which embedded with Fe3O4-OA (oleic acid modified Fe3O4) nanoparticles and tunable ZnO shell thickness. The resulting samples were thoroughly studied by using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The catalytic activity of the as-prepared PANI–Fe3O4@ZnO core–shell microspheres is investigated by the degradation of MB under visible light irradiation. As expected, the as prepared PANI–Fe3O4@ZnO photocatalysts exhibit highly enhanced photocatalytic activities in the degradation of MB under visible light irradiation owing to fast separation of photo-generated electron-hole pairs. Significantly, the PANI–Fe3O4@ZnO catalysts can be separated from the reaction media by applying an external magnet, and can be reused for seven cycles without change in stability and degradation efficiency.
Keywords: Pickering emulsion; ZnO; PANI; Photocatalytic; Magnetic separation;

Ultrathin flexible planar crystalline-silicon/polymer hybrid solar cell with 5.68% efficiency by effective passivation by Yingfeng Li; Pengfei Fu; Ruike Li; Meicheng Li; Younan Luo; Dandan Song (494-498).
Ultrathin silicon based solar cells provide a viable way to reduce the material usage and diversify their applications. However, complex light-trapping structures are always needed to be fabricated to enhance light absorption, which will lead to exacerbation of carrier collection and expensive fabrication cost. Here, we report very simple planar flexible crystalline silicon-polymer hybrid solar cell with thickness about 18 μm, whose power conversion efficiency (PCE) reaches 5.68%. By introducing the amorphous silicon layer to passivate the Silicon/Polymer interface in our device, with accuracy control of the thickness of 2 nm to balance the passivation effect and the deterioration of internal electric field, the short current density reaches 83.0% of the theoretical limit. Additionally, we found that the average PCE of solar cells passivated by such technology is 5.8% and 7.1% enhanced compared with those without passivation (H-terminated) and passivated by native oxide approaches. The simple device structure provided in this study has great practicability, and the passivation processes can be duplicated for other silicon based photovoltaic devices.
Keywords: Ultrathin; Planar; Silicon; Hybrid solar cell; Passivation;

Effects of rf power on chemical composition and surface roughness of glow discharge polymer films by Ling Zhang; Xiaoshan He; Guo Chen; Tao Wang; Yongjian Tang; Zhibing He (499-505).
The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no “void” defect was observed.
Keywords: Glow discharge polymer films; Chemical composition; Surface morphology; Surface roughness;

ZnO flower: Self-assembly growth from nanosheets with exposed { 1 1 ¯ 0 0 } facet, white emission, and enhanced photocatalysis by Ruixia Shi; Ping Yang; Xueling Song; Junpeng Wang; Quande Che; Aiyu Zhang (506-513).
ZnO flowers consisting of single crystal nanosheets with exposed { 1 1 ¯ 0 0 } facets were fabricated from trisodium citrate via hydrothermal at 180 °C. The single crystal nanosheet has the thickness of about 70 nm and a well-crystalline structure with dominant surfaces as { 1 1 ¯ 0 0 } planes. The site-specific nucleation-growth process contributes to the formation of hierarchical flower-like ZnO structures. The ZnO flowers exhibited white emission. The visible emission gradually decreased with time and the UV emission suggests that the recombined rate of photogenerated electrons and holes of samples varied with the synthesis parameters. The ZnO flowers displayed an enhanced photocatalytic performance compared with ZnO microspheres. The maximized exposure of the reactive { 1 1 ¯ 0 0 } facets also favors the enhanced photocatalytic performance. Additionally, the special loose structural feature with an open microstructure has more important influences on the photocatalytic activity than specific surface area.
Keywords: Hierarchical ZnO; Self-assembly; Nanosheets; Photocatalysis; White emission;

Display OmittedThe kinetically active two dimensional surface of graphene oxide (GrO) plays an important role in understanding the chemistry of graphene. The GrO is comprises of carbon and oxygen while the f-(6-AIND) GrO contains nitrogen along with carbon and oxygen. The prominent thermal instability of GrO is widely explored. However, due to the synergistic impact of their constituting elements, the thermal and electrochemical stability of f-(6-AIND) GrO enhances after N-doping with nitrogen containing heterocycles like 6-Aminoindazole. Hence it is essential to probe the mutual impact of various functionalities present over the surface of GrO, to understand the mechanism of direct functionalization of GrO with thermal and electrochemical stabilities. Therefore, the decomposition kinetics of discrete atomic domains and their effect on thermal stability of f-(6-AIND) GrO was revealed with spectroscopic analysis and thermal assessment. Additionally, the mechanism of thermal transformation is precisely developed to demonstrate the impact of heat on weight loss due to the mass transfer. Likewise, the electrochemical properties can be well understood with the help of mechanism of electrochemical activity and cyclic voltammetry experiments. Also, the f-(6-AIND) GrO is confirmed with the help of various surface analysis techniques like FTIR, EDS, HR-XPS, HR-TEM, CV, SAED, TGA, DSC and UV-vis.
Keywords: Graphene oxide; Functional behaviour; Structure properties relationship; Kinetics of thermal transformations; Electrochemical behaviour;

Proposed molecular orientation of AMP intercalated in the Li−Al LDH.A Li–Al layered double hydroxide intercalated with amino tris(methylene phosphonic acid) (AMP·Li–Al LDH) was synthesized by the drop-wise addition of an Al-containing solution to a Li-AMP solution at a constant pH of 8.0. The AMP·Li–Al LDH was found to take up Nd3+ and Sr2+ ions from aqueous solutions; this phenomenon was attributable to the metal-chelating functionality of the AMP ions in the interlayers of the AMP·Li–Al LDH. Further, the AMP·Li–Al LDH was found to take up Nd3+ ions preferentially than Sr2+ ions. This was attributable to the stability of the Nd-AMP complex being higher than that of the Sr-AMP complex. The mass-transfer-controlled shrinking-core model could describe the uptake behavior better than the surface-reaction-control model. The AMP ions in the AMP·Li–Al LDH interlayers rapidly formed chelate complexes with the Nd3+ or Sr2+ ions. As a result, the transfer of Nd3+ and Sr2+ ions through the product layer was the rate-limiting step. Furthermore, this reaction could be explained by a Langmuir-type adsorption mechanism, indicating that it involved chemical adsorption; this was consistent with the formation of chelate complexes between Nd3+ and Sr2+ ions and the AMP ions in the interlayers of the AMP·Li–Al LDH.
Keywords: Li–Al layered double hydroxide; Amino tris(methylene phosphonic acid); Uptake; Kinetic; Equilibrium;

A polypropylene cartridge filter with hematite nanoparticles for solid particles retention and arsenic removal by Justyna Tomaszewska; Szymon Jakubiak; Jakub Michalski; Wouter Pronk; Stephan J. Hug; Krzysztof J. Kurzydłowski (529-534).
In this article, we report a processing route for deposition of hematite (α-Fe2O3) nanoparticles into a cartridge filter composed of polypropylene (PP) non-woven fabric by a dip-coating method. During the process, a plasma activated non-woven fabric was immersed in an electrostatically stabilized aqueous hematite suspension under low vacuum conditions. Oxygen groups introduced onto the surface of the polymer provide a strong attachment of hematite nanoparticles to the polypropylene surface, confirmed under conditions of ultrasound. Preliminary tests demonstrated the efficiency of the cartridge in treating spring water with moderate arsenic concentrations, with kinetics and extent of adsorption showing a good correlation to a Langmuir adsorption model.
Keywords: Hematite; Nanoparticles; Dip-coating; Non-woven fabric; Electrostatic stabilization; As adsorption;

Graded Ti/C composite films with carbon topcoats are prepared on bendable stainless steel foils by hybrid cathodic arc / glow discharge plasma-assisted chemical vapor deposition to simulate cardiovascular stents. Strong adhesion between the stainless steel substrate and carbon topcoat is achieved due to the graded Ti/C interface and it is further improved by increasing the pulse voltage. Moreover, the graded coating is more hydrophilic than the stainless steel substrate.
Keywords: A. Stainless steel; B. SEM; B. XPS; C. Amorphous structures;

Theoretical evaluation of a double–functional heterogeneous nano-sensor by Fatemeh Fallahpour; Milad Nouraliei; Sara Soleimani Gorgani (545-551).
Given the special importance of nitric oxide (NO) in the areas of biology, particularly cancer–related incidents and also its diagnosis as a strong environmental pollutant, utilizing efficient ways for detection and monitoring NO molecule is a critical and essential issue. In order to achieve this goal, in this work, a heterogeneous C16Zn8O8 nano-cage was selected as a novel sensor to investigate the adsorption of nitric oxide (NO) molecule using density functional theory (DFT) calculations. It was explored that heterogeneous C16Zn8O8 nanoclusters could perform two adsorption performances: NO molecule was adsorbed from its O head on the ZnO surface of the cluster, where the positive Zn atom existed. On the other hand, the NO molecule was adsorbed from its N head on the carbon surface of the nano-cage, where a negative C atom was located. The analysis of energy, geometry, and electronic structure of various NO adsorptions on the both ZnO and carbon surface of the cluster were performed. The results indicated that, the NO adsorption processes in both sites significantly changed the electronic properties of the cluster by decreasing the HOMO/LUMO energy gap. The C16Zn8O8 was transformed to a stronger semi–conductor substance upon the NO adsorption. We believe that this research work may open a new gate to explore novel nanostructured materials for investigating in the field of sensor and catalyst applications for biological and environmental issues.
Keywords: Heterogeneous C16Zn8O8; Adsorption; Density functional theory; Electrical conductivity; Sensor;

A new nanocomposite was synthesized via deposition of MnO2 on Nitrogen-doped reduced graphene (MnO2/NRGO) by sonochemical method, in which, the particles of manganese oxide were uniformly distributed on NRGO sheets. The structure and morphology of MnO2/NRGO nanocomposites are characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical supercapacitive performance of the nanocomposite was investigated by cyclic voltammetry (CV), continuous cyclic voltammetry (CCV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) methods. The MnO2/NRGO nanocomposite shows enhanced specific capacitance of 522 F g−1 at 2 mV s−1 and its high synergistic effect was compared with MnO2/RGO. The high specific capacitance and exceptionally high cyclic stability of MnO2/NRGO attributes to the doping of nitrogen and uniform dispersion of MnO2 particles on NRGO. The CCV showed that the capacity retention for MnO2/NRGO and MnO2/RGO still maintained at 96.3% and 93% after 4000 CVs. The improved supercapacitive performance enables this nanocomposite as efficient electrode material for supercapacitor electrodes.
Keywords: Supercapacitor; Nanocomposite; N-doped graphene; MnO2 nanoparticles; Sonochemistry;

Beneficial surface passivation of hydrothermally grown TiO2 nanowires for solar water oxidation by Gun Yun; Gwang Yeom Song; Bo-Eun Ahn; Sang-Kwon Lee; Jaeyeong Heo; Kwang-Soon Ahn; Soon Hyung Kang (561-566).
Rutile TiO2 nanowires (TONWs) with a length of 2.0 μm were synthesized using a facile hydrothermal method in a strong acid solution. To investigate the effect of surface passivation of TONW arrays, a TiO2 layer with a thickness varying from 5 to 20 nm on TONW arrays was applied by atomic layer deposition (ALD). No distinct morphological modification was observed in all prepared TONW arrays in the environment where the diameter of the TONW arrays was systematically increased from 10 to 40 nm. In this study, Mott-Schottky analysis revealed that 10 nm TiO2-coated TONW (denoted as TiO2(10 nm)/TONW) arrays showed the highest electronic conductivity, followed by the 5 nm, 20 nm, and 0 nm TiO2/TONW arrays. The photoelectrochemical (PEC) performance was assessed in 0.1 M KOH, which revealed that TiO2(10 nm)/TONW arrays displayed a photocurrent density (3.92 mA/cm2 at 0.5 VNHE) higher than that (2.72 mA/cm2) of TONW arrays. This may be ascribed to the surface passivation of trap or defect sites by the thin TiO2 surface coating, leading to the increased electron densities and improving the PEC performance. For a more definitive examination, photovoltage decay measurement was performed to calculate the decay lifetime, which is closely correlated to the electron-hole recombination reaction. In this study, TiO2(10 nm)/TONW arrays exhibited a decay lifetime (0.7 s) shorter than that (1.1 s) of TONW arrays, proving the suppressed charge recombination in the thin TiO2/TONW arrays.
Keywords: Photoelectrochemical water splitting; Surface passivation; TiO2 nanowire; Photovoltage decay measurement;