Applied Surface Science (v.257, #20)
Synthesis and characterization of TiO2/Ag/polymer ternary nanoparticles via surface-initiated atom transfer radical polymerization by Jung Tae Park; Joo Hwan Koh; Jin Ah Seo; Yong Soo Cho; Jong Hak Kim (8301-8306).
► Ternary hybrid materials consisting of semiconductor, metal and polymer were developed. ► A hydrophilic polymer (POEM) was grafted from TiO2 nanoparticles via atom transfer radical polymerization (ATRP). ► The TiO2–POEM brush nanoparticles were templated for the formation of Ag nanoparticles.We report on the novel ternary hybrid materials consisting of semiconductor (TiO2), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO2–POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF3SO3 precursor and a NaBH4 aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO2 nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV–vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the C＝O groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic–organic nanomaterials.
Keywords: Titanium oxide (TiO2); Graft copolymer; Atom transfer radical polymerization (ATRP); Silver; Nanoparticles;
Influence of inserting AlN between AlSiON and 4H–SiC interface for the MIS structure by Naoyoshi Komatsu; Tomohisa Satoh; Masatomo Honjo; Takashi Futatuki; Keiko Masumoto; Chiharu Kimura; Hidemitsu Aoki (8307-8310).
► AlSiON/4H–SiC and conventional thermal oxidized SiO x /SiC have interfacial roughness. ► Inserting AlN film between AlSiON and SiC decreases the roughness of SiC surface. ► The roughness of AlN/SiC interface is less than that of half of the SiO x /SiC. ► C–V characteristics on AlSiON/AlN/SiC are improved by depositing temperature of AlN. ► AlSiON/AlN/SiC structure is one of attractive MIS structures for SiC devices.A control of interface between gate insulating film and semiconductor is required to achieve high-power field effect transistors (FET) using SiC. To improve the interface between the high-k layer and SiC, we propose inserting an AlN layer as an interfacial layer. The reason for selecting AlN film is that it has a wide bandgap, as well as almost the same lattice constant as that of 4H–SiC. The insertion of AlN film between 4H–SiC and the insulating film effectively reduces the interfacial roughness. The roughness of the interface between AlN and SiC can be suppressed compared with that of the thermal oxidized SiC. Moreover, the AlSiON film was deposited on the AlN layer as a high dielectric gate insulating film with low leakage current at high temperature and low space charge. The C–V characteristics of the AlSiON/AlN/SiC MIS structure with an AlN buffer layer are improved by increasing the deposition temperature of the AlN film. This demonstrates that AlSiON/AlN/SiC is one of attractive MIS structures for SiC devices.
Keywords: AlN; Buffer layer; AlSiON; Wide bandgap; High temperature; Power device; MOSFET;
Electrodeposition of nanocrystalline Zn–Ni alloy from alkaline glycinate bath containing saccharin as additive by S.H. Mosavat; M.E. Bahrololoom; M.H. Shariat (8311-8316).
► Nanocrystalline Zn–Ni alloy was electrodeposited from alkaline bath in this research. ► The nanocrystalline deposit was synthesized with direct current only by modification of the bath. ► In addition to buffering and complexing, glycine added to the bath acted as a grain refiner. ► The microhardness of coatings did not depend on crystallite size via Hall–Petch equation.Nanocrystalline Zn–Ni (crystallite sizes 13–68 nm) alloy coatings were produced from an alkaline glycinate bath containing saccharin as additive. X-ray diffraction (XRD) was used to determine the phase composition and average crystallite size of nanocrystalline Zn–Ni alloy coatings. The average grain size of a deposit was also studied by transmission electron microscopy (TEM). The effects of saccharin concentration and current density on the crystallite size and surface roughness of the coatings were studied. Crystallite size and average surface roughness were diminished as a result of increasing saccharin concentration. Scanning electron microscopy (SEM) examination showed that coatings had a colony-like morphology and the colony size was increased with increasing current density. Microhardness testing was carried out in order to determine the degree of dependence of this mechanical property on the crystallite size. It was found that microhardness did not depend on crystallite size (Hall–Petch).
Keywords: Nanocrystalline Zn–Ni alloy; Alkaline glycinate bath; Saccharin; Crystallite size;
Synthesis and characterization of polypyrrole/Sn-doped TiO2 nanocomposites (NCs) as a protective pigment by M.R. Mahmoudian; W.J. Basirun; Y. Alias; M. Ebadi (8317-8325).
► The dispersion of synthesized PPy in the presence of Sn-doped TiO2 NPs is more than TiO2 NPs. ► The increase of PPy dispersion can increase the efficiency of PPy in corrosion control. ► The band gap of TiO2 NPs increases with doped of Sn in lattice of TiO2. ► The increase of the band gap can decrease the charge transfer through the coating.We have chemically polymerized pyrrole in the presence of Sn-doped TiO2 nanoparticles (NPs) and TiO2 (NPs) which act as a protective pigment. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results show a core–shell structure of pigments in which TiO2 and Sn-doped TiO2 NPs have a nucleus effect and caused a homogenous PPy core–shell type morphology leading to coverage of the TiO2 and Sn-doped TiO2 NPs by PPy deposit. The XRD results indicate that the crystalline size of polypyrrole/TiO2 NCs and polypyrrole/Sn-doped TiO2 NCs were approximately 93.46 ± 0.06 and 23.36 ± 0.06 nm respectively. The electrochemical impedance spectroscopy (EIS) results show that the performance of polypyrrole/Sn-doped TiO2 NCs is better than polypyrrole/TiO2 NCs. The results indicate that increasing the area of synthesized polypyrrole in the presence of Sn-doped TiO2 NPs can increase its ability to interact with the ions liberated during the corrosion reaction of steel in the presence of NaCl. The UV–vis results show that the band gap of TiO2 NPs increases with doped of Sn in lattice of TiO2. The increase of the band gap of TiO2 with doping of Sn can decrease the charge transfer through the coating.
Keywords: Titanium dioxide; Nanocomposite; Polypyrrole; Corrosion; Coating;
Effect of structure variation on thermal conductivity of hydrogenated silicon film by Shibin Li; Yadong Jiang; Zhiming Wu; Jiang Wu; Zhihua Ying; Zhiming Wang; Wei Li; Gregory J. Salamo (8326-8329).
► The thermal conductivity of silicon film is measured using platinum as electrode. ► The thermal conductivity is proportional to crystalline volume fraction of silicon. ► There is crystalline and thermal conductive gradient in the microcrystalline film.Hydrogenated silicon film was fabricated by using plasma enhanced chemical vapor deposition method. The influence of crystalline volume fraction variation on the thermal conductivity was investigated. The relation between crystalline volume and film thickness was characterized by using spectroscopic ellipsometry with Bruggeman effective medium (BEMA) model. The thermal conductivity of silicon film was measured based on Fourier thermal transmitting law using sputtering platinum as electrode. The results demonstrate that the thermal conductivity of silicon film is proportional to the volume fraction of crystalline silicon, and there is crystalline and thermal conductive gradient between surface and bottom in the microcrystalline film.
Keywords: Thermal conductivity; Microcrystalline; Silicon film; Gradient;
Optical properties of p-type CuAlO2 thin film grown by rf magnetron sputtering by Min Fang; Haiping He; Bin Lu; Weiguang Zhang; Binghui Zhao; Zhizhen Ye; Jingyun Huang (8330-8333).
► This paper focus on the preparation and characterization of CuAlO2 thin film. ► Absorption exhibit the defect absorption according to the Urbach tailing energy. ► The photoluminescence show the near-band-edge (NBE) emission and defect emission.We report the structural and optical properties of copper aluminium oxide (CuAlO2) thin films, which were prepared on c-plane sapphire substrates by the radio frequency magnetron sputtering method. X-ray photoelectron spectroscopy (XPS) along with X-ray diffraction (XRD) analysis confirms that the films consist of delafossite CuAlO2 phase only. The optical absorption studies show the indirect and direct bandgap is 1.8 eV and 3.45 eV, respectively. Room temperature photoluminescence (PL) measurements show three emission peaks at 360 nm (3.45 eV), 470 nm (2.63 eV) and 590 nm (2.1 eV). The first one is near band edge emission while the other two are originated from defects.
Keywords: Rf magnetron sputtering; CuAlO2 thin films; Photoluminescence;
On single doping and co-doping of spray pyrolysed ZnO films: Structural, electrical and optical characterisation by T.V. Vimalkumar; N. Poornima; K.B. Jinesh; C. Sudha Kartha; K.P. Vijayakumar (8334-8340).
► Single doping ZnO using indium and co-doping using indium and fluorine were done. ► Ex-situ doping using Indium resulted in preferred (0 0 2) plane orientation, in-situ doping caused preferred orientation along (1 0 0), (0 0 2), (1 0 1) planes. The co-doped films had (0 0 2) and (1 0 1) planes. ► Lowest resistivity (2 × 10−3 Ω cm) was achieved for 1% Indium through in-situ method. ► Ex-situ doped and co-doped ZnO films showed two PL peaks; near band edge emission and blue–green emission. In-situ doped ZnO exhibited only the near band edge emission.In this paper we present studies on ZnO thin films (prepared using Chemical Spray pyrolysis (CSP) technique) doped in two different ways; in one set, ‘single doping’ using indium was done while in the second set, ‘co-doping’ using indium and fluorine was adopted. In the former case, effect of in-situ as well as ex-situ doping using In was analyzed. Structural (XRD studies), electrical (I–V measurements) and optical characterizations (through absorption, transmission and photoluminescence studies) of the films were done. XRD analysis showed that, for spray-deposited ZnO films, ex-situ doping using Indium resulted in preferred (0 0 2) plane orientation, while in-situ doping caused preferred orientation along (1 0 0), (0 0 2), (1 0 1) planes; however for higher percentage of in-situ doping, orientation of grains changed from (0 0 2) plane to (1 0 1) plane. The co-doped films had (0 0 2) and (1 0 1) planes. Lowest resistivity (2 × 10−3 Ω cm) was achieved for the films, doped with 1% Indium through in-situ method. Photoluminescence (PL) emissions of ex-situ doped and co-doped samples had two peaks; one was the ‘near band edge’ emission (NBE) and the other was the ‘blue–green’ emission. But interestingly the PL emission of in-situ doped samples exhibited only the ‘near band edge’ emission. Optical band gap of the films increased with doping percentage, in all cases of doping.
Keywords: - ZnO; Spray pyrolysis; In-situ doping; Ex-situ doping; Co-doping; Photoluminescence;
Investigating the effect of different asphaltene structures on surface topography and wettability alteration by J. Sayyad Amin; E.Nikooee; M.H. Ghatee; Sh. Ayatollahi; A. Alamdari; T. Sedghamiz (8341-8349).
► We investigate the effect of asphaltene structure on wettability alteration of heterogeneous surface. ► The effect of asphaltene structure is more pronounced for precipitation at higher pressure. ► Asphaltne particle with larger poly-aromatic rings tend to be detached easier at higher pressure than those with poly-aromatic rings.This paper aims at investigation of the effect of asphaltene structure on wettability and topography alteration of a glass surface as a result of asphaltene precipitation. In order to provide a better insight into the topography alteration, a bi-fractal approach was employed. Such an approach is capable of discriminating topography alteration in two different surface types, namely, macro-asperities and micro-asperities. The observed variation of the fractal dimension in the two surface types could be considered as the consequence of different asphaltene sources. Therefore, the structure of different asphaltene sources was carefully examined. The effect of asphaltene structure is more pronounced for asphaltene precipitation at higher pressure. It was revealed that asphaltene particles of high complexity and with larger poly-aromatic rings tend to be detached easier at higher pressure than those with smaller poly-aromatic rings. Another evidence to emphasize the significance of asphaltene structure was given through wettability alteration. It was found that asphaltene particles with larger poly-aromatic rings turn the surface less oil wet at higher pressure. It seems that the difference in wetting condition and surface topography alteration of different asphaltene sources roots in their different structures.
Keywords: Bi-fractal; Surface topography; Asphaltene structure; Wettability alteration;
The microstructure and optical properties of crystallized hydrogenated silicon films prepared by very high frequency glow discharge by Desheng Wang; Zhibo Yang; Fei Li; Deyan He (8350-8354).
► Hydrogenated nanocrystalline Si films were prepared by PECVD with an excitation frequency of 81.36 MHz. ► A modified four-layer-medium transmission model based on the envelope method was employed to determine optical constants of the obtained films. ► The samples prepared by very high frequency glow discharge have higher absorption coefficients due to their better compactness and lower defect density.A series of nc-Si:H films with different crystalline volume fractions have been deposited by very high frequency glow discharge in a plasma with a silane concentration [SiH4]/([SiH4] + [H2]) varying from 2% to 10%. The nc-Si:H films have been characterized by Raman spectroscopy, XRD diffraction, and UV–vis–near infrared spectrophotometer. The deposition rate increases nearly linear with increasing the silane concentration while the crystalline volume fraction decrease from 58% to 12%. The refractive index and the absorption of the samples were obtained through a modified four-layer-medium transmission model based on the envelope method. It was found that the refractive indices and absorption coefficient increase with increasing silane concentration. Compared to the films deposited using conventional RF-PECVD with excitation frequency of 13.56 MHz, the samples prepared by very high frequency glow discharge have higher absorption coefficients, which is due to its better compactness and lower defect density.
Keywords: Nanocrystalline silicon; Thin film; Optical property;
Yellow phosphors coated with TiO2 for the enhancement of photoluminescence and thermal stability by Hyeong Seok Lee; Jung Whan Yoo (8355-8359).
► In order to improve the phosphor efficiency and thermal stability, the Ba2+ Mg2+ co-doped Sr2SiO4:Eu phosphors were synthesized and were coated with thin and uniform TiO2. ► The TiO2 layer with 20 nm was uniformly coated over the phosphor surface. ► The temperature dependence of photoluminescence was measured from 25 to 150 °C. ► The TiO2-coated phosphors showed high thermal quenching property compared to pristine phosphors.In order to improve the phosphor efficiency of yellow emission of the phosphor-converted white light emitting diode (pcW-LED), the Ba2+ Mg2+ co-doped Sr2SiO4:Eu phosphors were synthesized and were coated with thin and uniform TiO2. The TiO2 layer with 20 nm was uniformly coated over the phosphor surface. The photoluminescence (PL) properties of the TiO2-coated phosphors showed improved yellow-emission intensity compared to the pristine phosphors. The temperature dependence of photoluminescence was measured from 25 to 150 °C. The TiO2-coated phosphors showed superior thermal quenching property compared to pristine phosphors. We concluded that the TiO2-coated surface of the phosphor is an effective way to improve the phosphor efficiency and enhance the thermal quenching stability.
Keywords: Phosphor; TiO2 coating; Thermal stability; Surface modification;
Effects of Cu/In ratio of electrodeposited precursor on post-sulfurization process in fabricating quaternary CuIn(S,Se)2 thin films by Yanqing Lai; Sanshuang Kuang; Fangyang Liu; Zhixue Yuan; Zhian Zhang; Yi Li; Jun Liu; Bo Wang; Ding Tang; Jie Li; Yexiang Liu (8360-8365).
► This paper describes an interesting analysis of the dependence of the incorporation of S during the sulphurization step of electrodeposited CuInSe2 precursors on the Cu/In ratio, proposing a mechanism related to the presence of Cu–(Se,S) phases in the layers during the process. ► The data are of interest, as they contribute to deepen in the understanding of these processes that are relevant for the synthesis of CuIn(S,Se)2 alloys with controlled composition. ► These results should contribute to the progress in band gap engineering of absorber CuInSe2 film by adding S and hence to improve conversation efficiency of such solar cells.This paper reports the analysis of S diffusion into electrodeposited CuInSe2 (CISe) precursors during post-sulfurization treatment at 500 °C in an Ar/H2S ambient. The characterizations of the sulfurized films by X-ray diffraction, grazing-incidence X-ray diffraction, Auger electron spectroscopy and micro-Raman spectroscopy allow the observation of the strong dependence of S incorporation into these films on the Cu/In ratio of the precursor. AES profiles reveal higher S content along the depth of Cu-rich film than Cu-poor film after sulfurization. Raman Scattering shows that copper sulfoselenides Cu–(Se,S) are only detected in Cu-rich samples. The re-crystallization of films during sulfurization was analyzed and it is presumed that quasi-liquid Cu–Se phases, which are related to Cu/In ratio of precursor, promote continuous incorporation of S into these films.
Keywords: Electrodeposition; CuIn(S,Se)2 thin film; Post-sulfurization; Copper sulfoselenide Cu–(Se,S); Secondary phases;
Synthesis of Cu–ZnO and C–ZnO nanoneedle arrays on zinc foil by low temperature oxidation route: Effect of buffer layers on growth, optical and field emission properties by Farid Jamali-Sheini; K.R. Patil; Dilip S. Joag; Mahendra A. More (8366-8372).
► The effect of different buffer layers has been studied on the optical and field emission properties. ► The buffer layer plays an important factor to control the growth process of the ZnO nanoneedles. ► The morphological studies show different density of ZnO nanoneedles.Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 °C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of ∼100 μA/cm2, is observed to be 2.25 V/μm and 1.57 V/μm for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of ∼100 μA over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications.
Keywords: Field emission; ZnO; Nanoneedle; Buffer layer; Copper; Carbon;
Trapping and release of citrate-capped gold nanoparticles by Darwin R. Reyes; Geraldine I. Mijares; Brian Nablo; Kimberly A. Briggman; Michael Gaitan (8373-8377).
► Gold nanoparticles are attracted to the surface of aminoalkanethiolated gold electrodes and electrostatic interactions hold them in place. ► Impedance spectroscopy, cyclic voltammetry and UV–Vis spectroscopy measurements confirm the presence on the surface of the electrodes. ► Release of the surface-bound gold nanoparticles is exerted when a negative bias is applied. ► Partial release of gold nanoparticles is attained and monitored using cyclic voltammetry in situ, UV–Vis spectroscopy and atomic force microscopy.An electrical method to trap and release charged gold nanoparticles onto and from the surface of gold electrodes modified by an alkanethiol self-assembled monolayer (SAM) is presented. To form electrodes coated with gold nanoparticles (GNPs), amine-terminated SAMs on gold electrodes were immersed in a solution of negatively charged citrate-capped GNPs. Accumulation of GNPs on the electrode surface was monitored by a decrease in the impedance of the SAM-modified electrode and by an increase in the electrochemical activity at the electrode as shown through cyclic voltammetry (CV). Electrostatic interactions between the GNPs and the amine-terminated SAM trap the GNPs on the electrode surface. Application of a subsequent negative bias to the electrode initiated a partial release of the GNPs from the electrode surface. Impedance spectroscopy, cyclic voltammetry, ultraviolet–visible (UV–Vis) spectroscopy and atomic force microscopy (AFM) were used to monitor and confirm the attraction of GNPs to and release from the aminealkanethiolated gold electrodes. This work describes a method of trapping and release for citrate-capped GNPs that could be used for on-demand nanoparticle delivery applications such as in assessing and modeling nanoparticle toxicology, as well as for monitoring the functionalization of gold nanoparticles.
Keywords: Gold nanoparticles; Trapping and release; Impedance spectroscopy; Self-assembled monolayers; Electrical manipulation; Cyclic voltammetry;
Surface modification of PDMS using atmospheric glow discharge polymerization of tetrafluoroethane for immobilization of biomolecules by V. Anand; S. Ghosh; M. Ghosh; G.M. Rao; R. Railkar; R.R. Dighe (8378-8384).
► Thin film was deposited on PDMS with fluorocarbon plasma at atmospheric pressure. ► All coated surfaces were treated with proteins. ► Amount of protein adsorbed oscillated with increasing plasma exposure time. ► Stranski–Krastanov mode of thin film growth was explained for the irregularity.In this study an atmospheric glow discharge with a fluorocarbon gas as precursor was used to modify the surface of polydimethyl siloxane (PDMS –[(CH3)2SiO] n –). The variation in protein immobilizing capability of PDMS was studied for different times of exposure. It was observed that the concentration of proteins adsorbed on the surface varied in an irregular manner with treatment time. The fluorination results in the formation of a thin film of fluorocarbon on the PDMS surface. The AFM and XPS data suggest that the film cracks due to stress and regains its uniformity thereafter. This Stranski–Krastanov growth model of the film was due to the high growth rate offered by atmospheric glow discharge.
Keywords: APGD; PDMS; Protein; Surface modification; Wettability;
Microstructure: Surface and cross-sectional studies of hydroxyapatite formation on the surface of white Portland cement paste in vitro by Arnon Chaipanich; Pincha Torkittikul (8385-8390).
► In this work, the surface and cross-sectional area of the cement paste placed in simulated body fluid (SBF) was examined using both SEM and line scanning techniques. ► The cross-section of the samples was investigated using line scanning technique for the first time and was used to determine the hydroxyapatite layer. ► A strong spectrum of phosphorus spectrum is detected up to 6–8 μm depth for samples after 4, 7 and 10 days immersion in simulated body fluid when compared to weak spectrum detected before immersion. ► The increase in the phosphorus spectrum corresponds to the hydroxyapatite formation on the surface of the samples after the samples were placed in simulated body fluid.The formation of hydroxyapatite was investigated at the surface and at the cross-section of white Portland cement paste samples before and after immersion in simulated body fluid. Scanning electron microscope images showed that hydroxyapatite were found at the surface of white Portland cement after immersion in simulated body fluid. Hydroxyapatite grains of mostly ≈1 μm size with some grain size of ≈2–3 μm were seen after 4 days immersion period. More estabilshed hydroxyapatite grain size of ≈3 μm grains were observed at longer period of immersion at 7 and 10 days. The cross-section of the samples was investigated using line scanning technique and was used to determine the hydroxyapatite layer. A strong spectrum of phosphorus is detected up to 6–8 μm depth for samples after 4, 7 and 10 days immersion in simulated body fluid when compared to weak spectrum detected before immersion. The increase in the phosphorus spectrum corresponds to the hydroxyapatite formation on the surface of the samples after the samples were placed in simulated body fluid.
Keywords: Hydroxyapatite; Surface; Microstructure; Bioactivity; Cement;
Effect of calcination temperature on porous titania prepared from industrial titanyl sulfate solution by Cong-Xue Tian; Ying Yang; Hong Pu (8391-8395).
► Industrial titanyl sulfate solution as hydrolysis precursor. ► The thermal stability of the porous structure higher than 550 °C. ► Calcinaton enables crystallization of anatase phase. ► Calcination temperature at 550 °C is the optimum calcination condition.Porous titania with anatase phase was prepared via thermal hydrolysis of industrial titanyl sulfate solution, and subsequent calcination at different temperature. The as-prepared powders were characterized by TG, DSC, XRD, particle size distribution test, N2 adsorption–desorption isotherm and SEM. Raising calcination temperature could accelerate the crystal growth, enlarge its specific surface area, pore diameter, and improve its photocatalytic activity. While too high temperature could destroy the pore structure even collapse. The optimal calcination temperature is 550 °C, and the obtained sample showed good thermal stability and high photocatalytic activity, with specific surface area of 189.3 m2/g and higher degree of crystallinity, and its photocatalytic degradation rate of methylene blue was of 95.76%.
Keywords: Porous titania; Thermal hydrolysis; Calcination; Photocatalysis;
ZnO nanoparticles produced by reactive laser ablation by V.V. Gafiychuk; B.K. Ostafiychuk; D.I. Popovych; I.D. Popovych; A.S. Serednytski (8396-8401).
► Mechanism of ZnO nanopowders formation by means of laser reactive ablation. ► Crater formation is accompanied drops ablation from his edges. ► Particles formed on processes ablation, coagulation and cluster coalescence in plume. ► Qualitative and quantitative characteristics of disperse and chemical compositions. ► Structural characteristics of nanopowders depending on parameters of production.The paper presents the results of theoretical and experimental researches of the analysis of nanopowder ZnO and ZnO-based structures formation mechanisms by means of pulse laser reactive technology (λ = 1.06 μm, τ = 10−7 to 10−5 s). The developed 2D model combines non-stationary heat transfer and fluid motion along with the calculated profile of surface deformation. The characteristics of the dispersive and chemical compositions and structural parameters of the synthesized nanopowder together with the influence of the energy of laser impulse evaporation, its duration and gas pressure in the reaction chamber have been studied using X-ray diffractrometry (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM). Particle size distribution analysis of ZnO has shown that the majority of them range from 5 to 60 nm in size. The photoluminescence emission spectra of the initial ZnO nanopowder at room temperature have been identified.
Keywords: Nanopowders oxides; Cluster formation; Luminescence; Laser annealing; Gas sensors;
Oxygen adsorption on anatase surfaces and edges by Li Zhang; Hefei Ji; Yinkai Lei; Wei Xiao (8402-8408).
► After adsorption, an O 2 − forms on (1 0 1) and (1 0 0) surfaces and facets related edges, while a Ti–O–O–O–Ti bridge forms on the (0 0 1) surface or (0 0 1) surface related edges. ► Electrons transfer from the anatase to the adsorbed oxygen molecules which can be used to hinder the electron hole recombination during the photo-catalytic processes. ► Oxygen adsorption on (0 0 1) surfaces and (0 0 1) facets related edges are more energetic favorable than the adsorption on (1 0 1) and (1 0 0) facets or related edges. ► For the adsorptions on (1 0 1), (1 0 0) surfaces and the edges related with those two facets, edge adsorptions are more energetic favorable than the surface adsorptions. We do not see this edge effect on the (0 0 1) surface.Oxygen adsorptions on anatase surfaces and edges are investigated with semi-empirical method MSINDO. After adsorption, an O 2 − forms on (1 0 1) and (1 0 0) surfaces and facets related edges, while a Ti–O–O–O–Ti bridge forms on the (0 0 1) surface or (0 0 1) surface related edges. Electrons transfer from the anatase to the adsorbed oxygen molecules which can be used to hinder the electron hole recombination during the photo-catalytic processes. Oxygen adsorption on (0 0 1) surfaces and (0 0 1) facets related edges are more energetic favorable than the adsorption on (1 0 1) and (1 0 0) facets or related edges. For the adsorptions on (1 0 1), (1 0 0) surfaces and the edges related with those two facets, edge adsorptions are more energetic favorable than the surface adsorptions. We do not see this edge effect on the (0 0 1) surface. Small size particles with more edges or particles with more (0 0 1) facets can adsorb more oxygen molecules and hinder the electron hole recombination more efficiently, and those adsorbed oxygen molecules may also oxidize other absorbed small toxic gas molecules.
Keywords: Oxygen; Adsorption; Anatase; Edge; Semi-empirical method;
Tuning photoresponse through size distribution control of silicon quantum dots by C. Xu; Z.P. Li; W. Pan; W.Z. Shen (8409-8412).
► We present a novel strategy to maximize the photoresponse through size distribution control of the Si quantum dots. ► We take advantage of the inherent size distribution to provide a marked improvement of light harvest for the potential application in quantum dot rainbow solar cells. ► We show that there is a tradeoff between the absorption enhancement and tunneling loss for the photocurrent intensity in Si quantum dots. ► We develop a new approach for maximizing light energy conversion with relative simple and low cost manufacturing process.We report a detailed experimental and theoretical investigation on the photocurrent characteristics of nanocrystalline Si thin films, with the emphasis on the effect of Si dot size distribution. Broader photocurrent response has been observed in Si quantum dots with larger size dispersion due to the improvement of light harvest. As a result of tunneling loss in the expanded energy distribution, we have demonstrated that there is a tradeoff between the absorption enhancement and reduced transport for the photocurrent intensity. The present work opens new strategy to maximize the photoresponse through size distribution control for quantum dot solar cell application.
Keywords: Photoresponse; Size distribution; Quantum dots; Silicon;
UV lithography-based protein patterning on silicon: Towards the integration of bioactive surfaces and CMOS electronics by S. Lenci; L. Tedeschi; F. Pieri; C. Domenici (8413-8419).
► Within the framework of our research activity on biosensors, we developed a methodology for obtaining CMOS-compatible biomolecule immobilization. ► We would like to point at the importance of studying the compatibility of bioactive surfaces with CMOS electronics. Such multidisciplinary investigation, involving the study of biochemical processes and electronic technologies, paves the way to the development of highly sensitive and compact biosensors. ► The purpose of our work is to give insights into the bidirectional interaction biosurface-chip: the effect of functionalization chemicals onto the CMOS backend is investigated and, at the same time, the influence of adhesion promoter (commonly used in CMOS technology) on the silane deposition is shown. ► This work is a first step towards complete CMOS-compatibility: biomolecule immobilization and washing techniques without ions dangerous for the CMOS are under investigation.A simple and fast methodology for protein patterning on silicon substrates is presented, providing an insight into possible issues related to the interaction between biological and microelectronic technologies. The method makes use of standard photoresist lithography and is oriented towards the implementation of biosensors containing Complementary Metal-Oxide-Semiconductor (CMOS) conditioning circuitry. Silicon surfaces with photoresist patterns were prepared and hydroxylated by means of resist- and CMOS backend-compatible solutions. Subsequent aminosilane deposition and resist lift-off in organic solvents resulted into well-controlled amino-terminated geometries. The discussion is focused on resist- and CMOS-compatibility problems related to the used chemicals. Some samples underwent gold nanoparticle (Au NP) labeling and Scanning Electron Microscopy (SEM) observation, in order to investigate the quality of the silane layer. Antibodies were immobilized on other samples, which were subsequently exposed to a fluorescently labeled antigen. Fluorescence microscopy observation showed that this method provides spatially selective immobilization of protein layers onto APTES-patterned silicon samples, while preserving protein reactivity inside the desired areas and low non-specific adsorption elsewhere. Strong covalent biomolecule binding was achieved, giving stable protein layers, which allows stringent binding conditions and a good binding specificity, really useful for biosensing.
Keywords: Biosensors; CMOS; Protein patterning; UV lithography; Silanization; APTES;
Surface morphology, growth rate and quality of diamond films synthesized in hot filament CVD system under various methane concentrations by M. Ali; M. Ürgen (8420-8426).
► Surface morphology/interface studies of diamond films at various vol.% of methane. ► Well-faceted cubes with step growth are rarely observed in HFCVD films. ► Growth rate of diamond films varies from ∼0.25 to ∼2.0μm/h.Hot filament chemical vapor deposition (CVD) technique has been used to deposit diamond films on silicon substrate. In the present study, diamond films were grown at various vol.% CH4 in H2 from 0.5% to 3.5%, at substrate temperature and pressure of 850 °C and 80 torr, respectively. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were employed to analyze the properties of deposited films. The formation of methyl radicals as a function of vol.% CH4 not only changes film morphology but also increase film growth rate. At low, intermediate and high vol.% CH4, cluster, faceted cubes and pyramidal features growth, were dominant. By increasing vol.% CH4 from 0.5% to 3.5%, as the growth rate improved from ∼0.25 μm/h to ∼2.0 μm/h. Raman studies features revealed high purity diamond films at intermediate range of vol.% CH4 and grain density increased by increasing CH4 concentration. The present study represents experimentally surface morphology, growth rate and quality of diamond films grown in hot filament CVD system at various CH4 concentrations.
Keywords: Chemical vapor deposition; Thin films; Crystal structure; Grain growth; Cubic morphology;
Fabrication of <1 1 0> oriented tungsten nano-tips by field-assisted water etching by Jo Onoda; Seigi Mizuno (8427-8432).
► Sharpening procedure of polycrystalline tungsten tips by field-assisted H2O etching. ► Highly collimated and stable field emission. ► Nano-tip composed of a nano-protrusion and a large base resulting high lens effect.We report the field-assisted H2O etching that enabled us to fabricate nano-tips from polycrystalline <1 1 0> oriented tungsten wires at room temperature. We optimized the sharpening procedure in order to obtain field emissions (FEs) with high collimation. The typical tip apex was composed of a large base and a nano-protrusion with a radius of curvature less than 3.5 Å. The narrowest opening angle (full width at half maximum) of the FE was 4.3° at 150 pA. We prepared two types of tips using two different applied bias voltages during the H2O etching. The electron microscope images and the analysis of Fowler-Nordheim (FN) plots revealed that the sizes of the individual bases depended on the fixed bias voltages during the H2O etching and affected their FE properties. In addition, we could confirm that the FE current from the nano-tip was more stable than that of the normal tip.
Keywords: Field-assisted water etching; <1 1 0> oriented polycrystalline tungsten tip; Nano-tip; Field emission (FE); Field ion microscopy (FIM); Fowler-Nordheim (FN) plot;
Study of methanol oxidation of hydrothermally synthesized PtRuMo on multi wall carbon nanotubes by Nitul Kakati; Jatindranath Maiti; Jun Young Oh; Young Soo Yoon (8433-8437).
► Methanol oxidation study on PtRuMo/MWCNTs synthesized by hydrothermal method showed well performance. ► PtRuMo/MWCNTs catalyst shows an electrochemically active surface area of 138 m 2 g Pt − 1 and a mass activity of 15 A cm − 2 m g Pt − 1 . ► Hydrothermal synthesis offers small particle size as well as well dispersion of the catalyst nanoparticles.PtRuMo on multi wall carbon nanotubes (PtRuMo/MWCNTs) as anode catalyst for direct methanol fuel cell (DMFC) was prepared by hydrothermal synthesis method. The results were compared with a PtRu/MWCNTs catalyst prepared using the same synthesis method. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). PtRuMo nanoparticles were uniformly dispersed on MWCNTs with a mean diameter of about 2.06 nm. The electrocatalytic activities of the synthesized catalysts were measured by cyclic voltammetry, chrono-amperometry and impedance spectroscopy in 0.5 M H2SO4 solution containing 1.0 M CH3OH. PtRuMo/MWCNTs catalyst shows an electrochemically active surface area of 138 m 2 g Pt − 1 and a mass activity of 15 A cm − 2 m g Pt − 1 . The results showed that the PtRuMo/MWCNTs catalysts have a higher electrocatalytic activity toward methanol oxidation than that of PtRu/MWCNTs synthesized by the same hydrothermal method.
Keywords: PtRuMo/multiwall carbon nanotubes; Methanol oxidation; Hydrothermal synthesis; Direct methanol fuel cell; Mass activity;
Extreme wettability due to dendritic copper nanostructure via electrodeposition by Peng Wang; Dun Zhang; Ri Qiu (8438-8442).
► Dendritic copper crystal is prepared on metal surface via electrodeposition. ► The formation mechanism of dendritic copper is elucidated. ► The film can convert from super-hydrophilicity to super-hydrophobicity via modification. ► The conversion of extreme wettability is explained with theoretical description.Dendritic copper film with convertible extreme wettability is prepared on metal surface via electrodeposition. With field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and electrochemical measurement, the morphology, composition and formation mechanism of dendritic copper film were studied. It is found that the film is mainly composed of metallic copper. Also some residual cuprous oxide and chloride exist in the deposit. The single micron-sized dendrite consists of a main stem with side branches, on which the higher-order branches with the dimension of tens of nanometers grow. A hydrophobic modification can induce the conversion of the apparent wettability of film from super-hydrophilicity (with apparent water contact angle of 5 ± 3°) to super-hydrophobicity (with apparent water contact angle of 154.1 ± 3°), which is due to the capillary effect. The method proposed in this paper is time-saving and facile to operate, and it offers a promising technique to prepare metallic surface with a high wettability contrast for water.
Keywords: Electrodeposition; Super-hydrophobicity; Super-hydrophilicity; Dendritic copper;
Preparation of polybutylene terephthalate/silica nanocomposites by melt compounding: Evaluation of surface properties by Roozbeh Hajiraissi; Mazeyar Parvinzadeh (8443-8450).
► Incorporation of nanosilica into PBT matrix to study various surface properties. ► Study of wetting properties of the PBT/silica nanocomposite. ► Higher reflection of light for PBT/silica nanocomposite compared with pure PBT.Influence of nanosilica on surface properties of poly(butylene terephthalate) was investigated by the use of Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). FTIR results indicated that surface groups of silica have some interfacial interactions and bonding with carboxyl or hydroxyl end groups of PBT chains. AFM and SEM figures of the resultant nanocomposites illustrated increased surface roughness compared to pure PBT. Optical properties of nanocomposite films were finally determined by the aid of reflectance spectrophotometer.
Keywords: Nanosilica; Polyester; AFM; Reflectance;
Cotton fabric coated with nano TiO2-acrylate copolymer for photocatalytic self-cleaning by in-situ suspension polymerization by Xue Jiang; Xiuzhi Tian; Jian Gu; Dan Huang; Yiqi Yang (8451-8456).
The cotton fabrics that was coated by a certain quantity of TBM-w3 prepared by novel in-situ suspension polymerization has the best self-cleaning property (the green curve).Display Omitted► In-situ suspension polymerization of acrylates and modifying of nano-TiO2 have been carried on. ► The modified nanoparticles were coated on cotton fabrics. ► The coated fabrics’ self-cleaning property was tested. ► A novel preparation of self-cleaning materials has been proposed.Two kinds of nano TiO2-polyacrylate hybrid dispersions, TBM-w and TBM-e were synthesized by in-situ suspension polymerization and solution polymerization respectively, in order to fix the nano TiO2 on fabrics. The photocatalytic self-cleaning fabrics have received much attention in recent years for its water-saving and environment-protection advantages. However, the fixation of the photocatalyst on fabrics is still a key problem that inhibits industrialization of these eco-friendly fabrics. The cotton fabric was treated by the two hybrid dispersions. The photocatalytic self-cleaning property was characterized. Infrared spectroscopy, burning loss test and thermogravimetry showed that some copolymer chains entangled with the nano TiO2. Transmission electron microscope illustrated that there was a polymeric layer on the surface of nano TiO2. The average diameter of TBM-w was smaller than that of TBM-e based on size analysis. The photocatalytic decoloration of the grape syrup indicated that the fabric with TiO2-polymer hybrid had excellent self-cleaning property.
Keywords: Nano TiO2-polyacrylate hybrid; Dispersion; Polymer content; Cotton fabric; Photocatalytic self-cleaning; Suspension polymerization;
Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion by Zhishuang Dai; Baoyan Zhang; Fenghui Shi; Min Li; Zuoguang Zhang; Yizhuo Gu (8457-8461).
► The carbon fiber surface properties and fiber/epoxy interfacial adhesion have great changes during heat treatment. ► This research has concluded that the wettability depends not only by the surface energy values of carbon fiber and resin, but also on the polarity match of surface energy. ► Close correlation can be found between IFSS and the concentration of reactive groups in interface region including hydroxyl group and epoxy group. ► The results can be theoretical guidance for improving performances of carbon fiber and carbon fiber reinforced resin matrix composite.Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γ S d increases and the polar surface energy γ S sp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.
Keywords: Carbon fiber; Heat treatment; Surface energy; Wettability; Interfacial shear strength;
Effects of rubrene mixing on the electronic structures of donor/acceptor interface in organic photovoltaic device by Zengtao Liu; Haibo Wang; Qingdan Yang; T.W. Ng; M.F. Lo; N.B. Wong; S.T. Lee; C.S. Lee (8462-8464).
Rubrene mixing has been shown to be an effect mean for enhancing both the open circuit voltage (Voc) and the short-circuit current (Jsc) of copper-phthalocyanine (CuPc)/fullerene (C60) based solar cell. While the increase in Jsc can be readily explained by the additional rubrene absorption and the introduction of a bulk heterojunction; causes for Voc increase are still not clear. The energy offset between the highest occupied molecular orbital (HOMO) level of donor and the lowest unoccupied molecular orbital (LUMO) level of acceptor (HOMOD–LUMOA) at the CuPc/C60 interface was found to increase substantially upon rubrene mixing in either side of the interface. As the HOMOD–LUMOA is generally considered to limit the Voc, its increase agrees well with the device results. Energy level bending and associated built-in electric fields were also observed and their possible implications to device performance are discussed.
Keywords: Organic photovoltaic; UPS; Open circuit voltage;
Enhancement of saturation magnetization in Cr-ion implanted silicon by high temperature annealing by Shuang Yang; Wenyong Zhang; Jihong Chen; Zhongpo Zhou; Zhiwei Ai; Liping Guo; Congxiao Liu; Honglin Du (8465-8468).
► We observed a significant enhancement of saturation magnetization of Cr ion implanted silicon after annealing at 900 °C. ► We proposed a mechanism to explain the enhancement of magnetism. ► Cr implantation dosage can affect the magnetic properties.Magnetic properties and microstructure of Cr-implanted Si have been investigated by alternating gradient magnetometer (AGM), superconducting quantum interference device (SQUID) magnetometer, and transmission electron microscopy (TEM). p-Type (1 0 0) Si wafers were implanted at 200 keV at room temperature with a dosage of 1 × 1016 cm−2 Cr ions and then annealed at 600–900 °C for 5 min. The effect of annealing on the structure and magnetic properties of Cr-implanted Si is studied. The as-implanted sample shows a square M–H loop at low temperature. Magnetic signal becomes weaker after short time annealing of the as-implanted sample at 600 °C, 700 °C, and 800 °C. However, the 900 °C annealed sample exhibits large saturation magnetization at room temperature. TEM images reveal that the implanting process caused amorphization of Si, while annealing at 900 °C led to partial recovery of the crystal. The enhancement of saturation magnetization can be explained by the redistribution and accumulation of Cr atoms in the vacancy-rich region of Si during annealing.
Keywords: Diluted magnetic semiconductors; Ion implantation; Silicon; Chromium;
RF-PACVD of water repellent and protective HMDSO coatings on bell metal surfaces: Correlation between discharge parameters and film properties by A.J. Choudhury; S.A. Barve; Joyanti Chutia; A.R. Pal; R. Kishore; Jagannath; M. Pande; D.S. Patil (8469-8477).
► Hexamethyldisiloxane (HMDSO) coatings on bell metal using RF-PACVD technique. ► Investigations of the films properties as a function of DC self-bias voltage. ► Impinging ion energy affects water repellency and protective behavior of the films. ► Correlation between impinging ion energy and deposited HMDSO film properties. ► Efficient use of HMDSO films for surface protection of bell metal using RF-PACVD.Hexamethyldisiloxane (HMDSO) films have been deposited on bell metal using radiofrequency plasma assisted chemical vapor deposition (RF-PACVD) technique. The protective performances of the HMDSO films and their water repellency have been investigated as a function of DC self-bias voltage on the substrates during deposition. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. Optical emission spectroscopy (OES) analyses of the plasma during deposition reveal no significant change in the plasma composition within the DC self-bias voltage range of −40 V to −160 V that is used. Raman and X-ray photoelectron spectroscopy (XPS) studies are carried out for film chemistry analysis and indicate that the impinging ion energy on the substrates influences the physio-chemical properties of the HMDSO films. At critical ion energy of 113 qV (corresponding to DC self-bias voltage of −100 V), the deposited HMDSO film exhibits least defective Si–O–Si chemical structure and highest inorganic character and this contributes to its best corrosion resistance behavior. The hardness and elastic modulus of the films are found to be bias dependent and are 1.27 GPa and 5.36 GPa for films deposited at −100 V. The critical load for delamination is also bias dependent and is 11 mN for this film. The water repellency of the HMDSO films is observed to be dependent on the variation in surface roughness. The results of the investigations suggest that HMDSO films deposited by RF-PACVD can be used as protective coatings on bell metal surfaces.
Keywords: RF plasma; PACVD; Hexamethyldisiloxane (HMDSO); Plasma diagnostics; Corrosion protective coatings; Hydrophobic coatings;
Application of ultrasonic wave to clean the surface of the TiO2 nanotubes prepared by the electrochemical anodization by Hao Xu; Qian Zhang; Chunli Zheng; Wei Yan; Wei Chu (8478-8480).
► The ultrasonic wave was used to remove the precipitates from the surface of TiO2 nanotubes prepared by electrochemical anodization. ► The top surface of TiO2 nanotubes was cleaned effectively after 9 min of ultrasonic treatment (80W and 40 kHz) and the well-aligned and uniform TiO2 nanotubes appeared. ► When the treating time was extended to 40 min a small part of nanotubes broken and no nanotubes were left on the titanium base if the sonication further increased to 60 min.In this study, the TiO2 nanotubes were fabricated by electrochemical anodization in a NH4F/Na2SO4/PEG400/H2O electrolyte system. Ultrasonic wave (80 W, 40 kHz) was used to clean the surface of TiO2 nanotube arrays in the medium of water after the completion of the anodization. Surface morphology (FESEM) and X-ray diffraction spectrum of the nanotubes treated by sonication at 0 min, 9 min, 40 min and 60 min were compared. The experimental results showed that the precipitate on the surface of the nanotube arrays could be removed by the ultrasonic wave. The treating time had an influence on the precipitate removal and 9 min (corresponding to 12 Wh) is the suitable time for surface cleaning of the TiO2 nanotubes on this experimental condition.
Keywords: TiO2 nanotubes; Electrochemical anodization; Ultrasonic wave; Surfaces; Microstructure;
Fabrication and surface characterization of biomimic superhydrophobic copper surface by solution-immersion and self-assembly by Shiheng Yin; Dongxiao Wu; Ji Yang; Shumei Lei; Tongchun Kuang; Bin Zhu (8481-8485).
► Copper plate. ► Sodium hydroxide and potassium persulfate solution treatment. ► Crystallized Cu(OH)2 nanoneedles formed. ► Surface self-assembly with dodecanoic acid. ► Superhydrophobic with water contact angle 153̊.Biomimic superhydrophobic surfaces with contact angle greater than 150° and low sliding angle on copper substrate were fabricated by means of a facile solution immersion and surface self-assembly method. The scanning electron microscopy showed a nanoneedle structure copper surface with sporadic flower-like aggregates after treatment with sodium hydroxide and potassium persulfate solution. X-ray photoelectron spectroscopy and X-ray diffraction results confirmed that the formed nanoneedles were crystallized Cu(OH)2. And the hydrophilic Cu(OH)2 surface can be further modified into superhydrophobic through surface self-assembly with dodecanoic acid.
Keywords: Superhydrophobic; Nanoneedle; Copper; Solution immersion; Self-assembly;
The transparence comparison of Ga- and Al-doped ZnO thin films by Zheng-Zheng Li; Zhi-Zhan Chen; Wei Huang; Shao-Hui Chang; Xue-Ming Ma (8486-8489).
► Ga- and Al-doped ZnO thin films (GZO and AZO) were grown on quartz glass by pulsed laser deposition. ► The transmittance of GZO and AZO were varied in according with the change of crystallization quality respectively. ► The higher transmittance of GZO than AZO was not dominated by the doping impurity ions. ► GZO surfaces were smoother than that of AZO was due to Ga acting as the surfactant.The Ga-doped ZnO (GZO) and Al-doped ZnO (AZO) thin films were grown on quartz glass substrates by pulsed laser deposition under different oxygen partial pressures ( P O 2 ) . The transparent performances of films versus properties of structure and conductivity were discussed. With the increase of P O 2 , the transmittance of both GZO films and AZO films increased to maximum and then decreased which were in according with the change of crystallization quality. The transmittance of GZO films was higher than that of AZO films, which were not dominated by the impurity ions induced by doping. AFM images and surface roughness mean square coefficients showed that the surfaces of GZO films were smoother than that of AZO films, which were due to the dopant Ga acting as the surfactant and smoothed the GZO films surface.
Keywords: Ga- and Al-doped ZnO; ZnO thin films; TCO electrode;
Cu2ZnSnSe4 thin films prepared by selenization of co-electroplated Cu–Zn–Sn precursors by Zhesheng Chen; Lei Han; Lei Wan; Chunhui Zhang; Haihong Niu; Jinzhang Xu (8490-8492).
► Cu2ZnSnSe4 thin films were prepared by selenizing co-electroplated Cu–Zn–Sn precursors. ► The selenization temperatures of substrate and selenium particles were controlled separately. ► Impurity phases were not detected from XRD and Raman spectrum. ► Stannite structure of Cu2ZnSnSe4 thin film was confirmed.A novel technique for growth of high quality Cu2ZnSnSe4 (CZTSe) thin films is reported in our work. The CZTSe thin films were fabricated onto Mo layers by co-electroplating Cu–Zn–Sn precursors followed by annealing in the selenium vapors at the substrate temperature of 550 °C. The morphology and structure of CZTSe thin films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum, respectively. The results revealed that the single phase was in the CZTSe thin films, and the other impurities such as ZnSe and Cu2SnSe3 were not existed though they were difficult to distinguish both from EDS and XRD.
Keywords: Cu2ZnSnSe4; Electrodeposition; Selenization; Thin films; Solar energy materials;
Improvement of corrosion resistance of NiTi sputtered thin films by anodization by N. Bayat; S. Sanjabi; Z.H. Barber (8493-8499).
► Nanometeric barrier layer was formed on the surface of NiTi thin film after anodization in 1 M acetic acid. The thickness of nanometer oxide layer was depended upon the anodization time. ► Increasing the voltages from 2 to 10 V had a significant influence on the corrosion behavior of NiTi thin films. The corrosion resistance of anodized NiTi film at 6 V was about 10 times greater than untreated NiTi. ► By anodization of annealed austenitic NiTi film, the corrosion resistance was improved.Anodization of sputtered NiTi thin films has been studied in 1 M acetic acid at 23 °C for different voltages from 2 to 10 V. The morphology and cross-sectional structures of the untreated and anodized surfaces were investigated by field emission scanning electron microscopy (FE-SEM). The results show that increasing anodization voltage leads to film surface roughening and unevenness. It can be seen that the thickness of the anodized layer formed on the NiTi surface is in the nanometer range. The corrosion resistance of anodized thin films was studied by potentiodynamic scan (PDS) and impedance spectroscopy (EIS) techniques in Hank's solution at 310 K (37 °C). It was shown that the corrosion resistance of the anodized film surface improved with increasing voltage to 6 V. Anodization of austenitic sputtered NiTi thin films has also been studied, in the same anodizing conditions, at 4 V. Comparison of anodized sputtered NiTi thin films with anodized austenitic shape memory films illustrate that the former are more corrosion resistant than the latter after 1 h immersion in Hank's solution, which is attributed to the higher grain boundary density to quickly form a stable and protective passive ﬁlm.
Keywords: Anodizing; NiTi thin film; Corrosion resistance; Morphology;
Effect of dispersing media on microstructure of electrophoretically deposited TiO2 nanoparticles in dye-sensitized solar cells by S.M.A. Fateminia; R. Yazdani-Rad; T. Ebadzadeh; S. Ghashghai (8500-8505).
► Electrophoretic deposition of TiO2 nanoparticles avoiding crack formation. ► Microstructure studying of deposited layers in acetone and isopropanol using AFM & SEM. ► Fabrication of DSSCs whose photoelectrodes were deposited in acetone & isopropanol. ► Investigating the effect of microstructure on solar cells performance.In the present study, dye-sensitized solar cells were fabricated using electrophoretically deposited layers of titanium dioxide nanoparticles from two common organic media, acetone and isopropanol. Characterization of the obtained layers by scanning electron microscope and atomic force microscope showed that a non-uniform porous layer was obtained in acetone; however, deposition from the titanium dioxide/isopropanol cell resulted in the formation of a relatively uniform microstructure. Ultraviolet–visible (UV–vis) spectra of adsorbed dye on the two layers show that more dye is loaded on the layer deposited in acetone. Current–voltage characteristics of the cells indicate that for the case of the cells made by the layer formed in acetone, the internal resistance of the cell is more than that of isopropanol medium which would decrease the efficiency of the cell. This difference was attributed to the reduction of effective surface area and also the loss of particles interconnection as a result of the presence of aggregates within the layer obtained in acetone.
Keywords: Electrophoretic deposition; Acetone; Isopropanol; Dye-sensitized solar cell;
Influence of oxygen partial pressure on the properties of pulsed laser deposited nanocrystalline zirconia thin films by G. Balakrishnan; T.N. Sairam; P. Kuppusami; R. Thiumurugesan; E. Mohandas; V. Ganesan; D. Sastikumar (8506-8510).
► Optical properties of zirconia films versus oxygen partial pressure. ► Band gap in the range 5.15-5.20 eV for tetragonal phase, and 5.57-5.65 eV for monoclinic phase. ► The refractive index decreases, while the transmittance increases with the oxygen partial pressure.ZrO2 thin films were deposited at various oxygen partial pressures (2.0 × 10−5–3.5 × 10−1 mbar) at 973 K on (1 0 0) silicon and quartz substrates by pulsed laser deposition. The influence of oxygen partial pressure on structure, surface morphology and optical properties of the films were investigated. X-ray diffraction results indicated that the films are polycrystalline containing both monoclinic and tetragonal phases. The films prepared in the oxygen partial pressures range 2.0 × 10−5–3.5 × 10−1 mbar contain nanocrystals of sizes in the range 54–31 nm for tetragonal phase. The peak intensity of the tetragonal phase decreases with the increase of oxygen partial pressures. Surface morphology of the films examined by AFM shows the formation of nanostructures. The RMS surface roughness of the film prepared at 2.0 × 10−5 mbar is 1.3 nm while it is 3.2 nm at 3.5 × 10−1 mbar. The optical properties of the films were investigated using UV–visible spectroscopy technique in the wavelength range of 200–800 nm. The refractive index is found to decrease from 2.26 to 1.87 as the oxygen partial pressure increases from 2.0 × 10−5 to 3.5 × 10−1 mbar. The optical studies show two different absorption edges corresponding to monoclinic and tetragonal phases.
Keywords: Thin films; Zirconia; Pulsed laser deposition; X-ray diffraction; UV–visible spectroscopy;
Effects of Nd:YAG laser irradiation on structural, morphological, cation distribution and magnetic properties of nanocrystalline CoFe2O4 by Maheshkumar L. Mane; Vinod N. Dhage; R. Sundar; K. Ranganathan; S.M. Oak; D.R. Shengule; K.M. Jadhav (8511-8517).
► Synthesis of nanocrystalline CoFe2O4 by sol–gel auto-combustion method. ► Laser irradiation effect on spinel ferrite. ► Structural and cation distribution. ► Morphological study. ► Magnetic measurements.The cobalt ferrite nanoparticles of 20 nm size were synthesized by sol–gel auto-combustion technique. The samples were irradiated with Nd:YAG laser to understand the effects of irradiation on structural, cation distribution and magnetic properties. The virgin and irradiated samples were characterized by X-ray diffraction technique. The X-ray diffraction studies at room temperature shows that defects were created in the lattice after irradiation which causes effects on structural, cation distribution and magnetic properties. The energy dispersive analysis of X-rays (EDAX) showed the chemical composition is as per the expected stichiometry. The lattice constant observed from XRD data for virgin and irradiated samples shows increasing trend after irradiation. Cation distribution was investigated by using X-ray diffraction method. We observe decrease in magnetization of the samples after irradiation. The observed reduction in the saturation magnetization after irradiation can be understood on the basis of the partial formation of paramagnetic centers and rearrangement of cations in the lattice.
Keywords: Laser irradiation; Structural; Defect; Magnetization;
Influence of adhesion of silica and ceria abrasive nanoparticles on Chemical–Mechanical Planarization of silica surfaces by D.O. Volkov; P.R Veera Dandu; H. Goodman; B. Santora; I. Sokolov (8518-8524).
.Display Omitted► New AFM method to measure adhesion between nanoparticles and surfaces developed. ► Adhesion between abrasive nanoparticles of irregular shape and silica surface measured. ► The method is applied to the process of Chemical–Mechanical Planarization (CMP). ► Correlations between adhesion and CMP removal rate and defectivity are analyzed.We report on a direct measurement of adhesion between abrasive nanoparticles of irregular shape, which are used in semiconductor industry in the process of Chemical–Mechanical Planarization (CMP), and silica surface. The adhesion of ceria and silica nanoparticles to silica surface is measured in multiple chemistries of different CMP slurries using a specially developed atomic force microscopy (AFM) method. Using this method, we study the influence of adhesion on the main parameters of CMP, removal rate and defectivity, scratches. While being plausible to expect correlation between these parameters and adhesion, it has not been systematically studied as of yet. We observed direct correlation between adhesion and removal rate. Comparing the measured defectivity and adhesion, we observe the presence of some correlation between these parameters. We conclude that both adhesion and shape of abrasive particles influence defectivity, micro-scratches. Direct measurements of the adhesion between abrasive nano-particles and surface can be used in the screening of new slurries as well as various modeling related to wearing of the surfaces.
Keywords: Atomic Force microscopy (AFM); Adhesion; Ceria nanoparticles; Silica nanoparticles; Chemical–Mechanical Planarization (CMP); Removal rate; Defectivity; Micro-scratches;
Development of novel titanium nitride-based decorative coatings by calcium addition by A. Hodroj; J.F. Pierson (8525-8528).
► Calcium was added into arc evaporated titanium nitride films. ► Calcium atoms can substitute titanium ones in the TiN lattice. ► Addition of calcium induced modification of the film colour. ► Coppery or violet coatings may be suitable for decorative applications.Calcium was added into titanium nitride coatings deposited using a hybrid magnetron sputtering–arc evaporation process. The calcium content in the films was adjusted by the variation of the pulsed DC current applied to the Ca sputtering target. X-ray diffraction analyses suggested that the increase of the calcium content induced the partial substitution of titanium atoms by calcium ones in the TiN lattice and a refinement of the grain size. Optical reflectance investigations showed that the absorption band of TiN was shifted towards higher wavelengths and that (Ti,Ca)N coatings may be suitable for decorative applications. Finally, the decrease of the film reflectivity was interpreted as a consequence of a free electron concentration decrease as confirmed from electrical resistivity measurements.
Keywords: Decorative coatings; Structure; Arc evaporation; Reactive sputtering;
Investigations on co-evaporated Cu2SnSe3 and Cu2SnSe3–ZnSe thin films by P. Uday Bhaskar; G. Suresh Babu; Y.B. Kishore Kumar; V. Sundara Raja (8529-8534).
► Cu2SnSe3 (CTSe) is an important precursor material for the growth of Cu2ZnSnSe4, a novel solar cell absorber material. ► Cu2SnSe3–ZnSe (20%) growth and characterization helps us to understand the influence of ZnSe on CTSe. ► The films were deposited using co-evaporation method.Cu2SnSe3 is an important precursor material for the growth of Cu2ZnSnSe4, an emerging solar cell absorber layer via solid state reaction of Cu2SnSe3 and ZnSe. In this study, we have grown Cu2SnSe3 (CTSe) and Cu2SnSe3–ZnSe (20%) films onto soda-lime glass substrates held at 573 K by co-evaporation technique. The effect of annealing of these films at 723 K for an hour in selenium atmosphere is also investigated. XRD studies of as-deposited Cu2SnSe3 and Cu2SnSe3–ZnSe films indicated SnSe as secondary phase which disappeared on annealing. The direct optical band gap of annealed Cu2SnSe3 and Cu2SnSe3–ZnSe films were found to be 0.90 eV and 0.94 eV respectively. Raman spectroscopy studies were used to understand the effect of ZnSe on the properties of Cu2SnSe3.
Keywords: Cu2SnSe3; Cu2SnSe3–ZnSe; Co-evaporation; X-Ray Diffraction; Raman studies; Optical studies;
Effects of O2 and N2/H2 plasma treatments on the neuronal cell growth on single-walled carbon nanotube paper scaffolds by Ok Ja Yoon; Hyun Jung Lee; Yeong Mi Jang; Hyun Woo Kim; Won Bok Lee; Sung Su Kim; Nae-Eung Lee (8535-8541).
Display Omitted► The O2 and N2/H2 plasma-chemical functionalization caused changes in the surface charge states with functional groups with positive and negative charges, respectively. ► The chemical functionalization and the increased surface roughness enhanced neuronal cell adhesion, mitochondrial membrane potential, and the level of neurotransmitter in vitro. ► The cell adhesion and mitochondrial membrane potential on the negatively charged SWCNT papers were improved more than on the positively charged SWCNT papers. ► An enhanced acetylcholine level on the negatively charged SWCNT papers was observed compared to the positively charged SWCNT papers.The O2 and N2/H2 plasma treatments of single-walled carbon nanotube (SWCNT) papers as scaffolds for enhanced neuronal cell growth were conducted to functionalize their surfaces with different functional groups and to roughen their surfaces. To evaluate the effects of the surface roughness and functionalization modifications of the SWCNT papers, we investigated the neuronal morphology, mitochondrial membrane potential, and acetylcholine/acetylcholinesterase levels of human neuroblastoma during SH-SY5Y cell growth on the treated SWCNT papers. Our results demonstrated that the plasma-chemical functionalization caused changes in the surface charge states with functional groups with negative and positive charges and then the increased surface roughness enhanced neuronal cell adhesion, mitochondrial membrane potential, and the level of neurotransmitter in vitro. The cell adhesion and mitochondrial membrane potential on the negatively charged SWCNT papers were improved more than on the positively charged SWCNT papers. Also, measurements of the neurotransmitter level showed an enhanced acetylcholine level on the negatively charged SWCNT papers compared to the positively charged SWCNT papers.
Keywords: Single-walled carbon nanotube; O2 and N2/H2 plasma treatments; Mitochondrial membrane potential; Neurotransmitter; Scaffolds; Neuronal activity;
Investigation of oxygen states and reactivities on a nanostructured cupric oxide surface by D.A. Svintsitskiy; A.I. Stadnichenko; D.V. Demidov; S.V. Koscheev; A.I. Boronin (8542-8549).
► Nanostructured copper (II) oxide was formed using RF discharge activated oxygen. ► The non-lattice oxygen states were observed by XPS. ► These species provide high catalytic activity in CO oxidation at low temperatures.Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10–20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100 °C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu2O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80 °C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 × 10−5 and was steadily reduced down to 5 × 10−9 as the exposure was increased. O1s spectral analysis allowed us to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. We established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O2 restored the highly reactive oxygen form on the surface. These results allowed us to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.
Keywords: Oxygen species; Copper (II) oxide; Nanoparticles; RF discharge; XPS; STM; CO oxidation;
Influence of Ti/TiAlN-multilayer designs on their residual stresses and mechanical properties by E. Vogli; W. Tillmann; U. Selvadurai-Lassl; G. Fischer; J. Herper (8550-8557).
► In this we studied three different TiAlN-based multilayers deposited on differently etched steel substrates. ► Multilayer with the thickest ceramic layers has the highest hardness and lowest wear coefficients as well as the lowest compressive stress in the ceramic layers. ► Owing to the etching process prior coating, high adhesion of multilayers was achieved by applying a combination of MF-pulsed sputter etching followed by ion sputter etching. ► Compressive stresses were found in the coating-near substrate region, which support and fit on the subsequent deposited multilayers.In this research work, Ti/TiAlN multilayers of various designs were deposited onto substrates pretreated by different etching procedures. The influence of multilayer design and substrate pretreatment on multilayers adhesion, hardness, wear and friction coefficients was systematically analyzed and correlated with residual stresses of these multilayers as well as with residual stresses on the coating-near substrate region, which were analyzed by synchrotron X-ray diffraction at HZB-BESSYII. These investigations show that the adhesion can be improved by a specific etching procedure, which cause increased compressive stress in the coating-near the substrate region. Additionally, it was found, that the multilayer with the thickest ceramic layers has the highest hardness and the lowest wear coefficients as well as the lowest compressive residual stress within studied multilayers.
Keywords: Multilayers; Ti/TiAlN; Etching; Hardness; Residual stresses; Physical vapor deposition (PVD);
Effect of the chemistry and structure of the native oxide surface film on the corrosion properties of commercial AZ31 and AZ61 alloys by Sebastián Feliu; C. Maffiotte; A. Samaniego; Juan Carlos Galván; Violeta Barranco (8558-8568).
► The native oxide surface film formed on magnesium alloys seems to be protective. ► The corrosion resistance depends on the thickness and uniformity of this thin film. ► The thickness of the native oxide layer depend of the alloy composition. ► Additional layer of mixtures of spinel and MgO is observed in as received alloys. ► The amount of spinel depends of the alloy composition.The purpose of this study has been to advance in knowledge of the chemical composition, structure and thickness of the thin native oxide film formed spontaneously in contact with the laboratory atmosphere on the surface of freshly polished commercial AZ31 and AZ61 alloys with a view to furthering the understanding of protection mechanisms. For comparative purposes, and to more fully describe the behaviour of the native oxide film, the external oxide films formed as a result of the manufacturing process (as-received condition) have been characterised. The technique applied in this research to study the thin oxide films (thickness of just a few nanometres) present on the surface of the alloys has basically been XPS (X-ray photoelectron spectroscopy) in combination with ion sputtering. Corrosion properties of the alloys were studied in 0.6 M NaCl by measuring charge transfer resistance values, which are deduced from EIS (electrochemical impedance spectroscopy) measurements after 1 h of exposure. Alloy AZ61 generally showed better corrosion resistance than AZ31, and the freshly polished alloys showed better corrosion resistance than the alloys in as-received condition. This is attributed to a combination of (1) higher thickness of the native oxide film on the AZ61 alloy and (2) greater uniformity of the oxide film in the polished condition. The formation of an additional oxide layer composed by a mixture of spinel (MgAl2O4) and MgO seems to diminish the protective properties of the passive layer on the surface of the alloys in as-received condition.
Keywords: Magnesium alloys; Native oxide film; Chemistry and structure; Corrosion properties; XPS;
Fabrication of superhydrophobic surfaces based on ZnO–PDMS nanocomposite coatings and study of its wetting behaviour by R.P.S. Chakradhar; V. Dinesh Kumar; J.L. Rao; Bharathibai J. Basu (8569-8575).
► Superhydrophobic (SH) surfaces based on ZnO–PDMS nanocomposite coatings are demonstrated by wet chemical method. ZnO coating exhibits wetting behaviour with WCA of ∼108°, on modification with PDMS, it transforms to superhydrophobic surface ∼155°. ► FESEM micrographs reveal that nanoparticles are connected to each other to make large network systems consisting of hierarchical structure. ► EPR studies on SH coatings revealed that the surface defects play a major role on the wetting behaviour. Advantages of the present method include the cheap and fluorine-free raw materials, environmentally benign solvents, and feasibility for applying on large area of different substrates.Superhydrophobic surfaces based on ZnO–PDMS nanocomposite coatings are demonstrated by a simple, facile, time-saving, wet chemical route. ZnO nanopowders with average particle size of 14 nm were synthesized by a low temperature solution combustion method. Powder X-ray diffraction results confirm that the nanopowders exhibit hexagonal wurtzite structure and belong to space group P63mc. Field emission scanning electron micrographs reveal that the nanoparticles are connected to each other to make large network systems consisting of hierarchical structure. The as formed ZnO coating exhibits wetting behaviour with Water Contact Angle (WCA) of ∼108°, however on modification with polydimethylsiloxane (PDMS), it transforms to superhydrophobic surface with measured contact and sliding angles for water at 155° and less than 5° respectively. The surface properties such as surface free energy (γ p), interfacial free energy (γ pw), and the adhesive work (W pw) were evaluated. Electron paramagnetic resonance (EPR) studies on superhydrophobic coatings revealed that the surface defects play a major role on the wetting behaviour. Advantages of the present method include the cheap and fluorine-free raw materials, environmentally benign solvents, and feasibility for applying on large area of different substrates.
Keywords: ZnO–PDMS nanocomposite coating; Superhydrophobic; XRD; FESEM; FTIR; Water contact angle (WCA); Sliding angle (SA); Electron paramagnetic resonance (EPR);
Temperature-dependent linear or nonlinear gas sensing characteristics of In2O3 mixed α-Fe2O3 nanorods with high sensitivity by Li-Li Xing; Chun-Hua Ma; Zhao-Hui Chen; Xin-Yu Xue (8576-8580).
► In2O3 mixed α-Fe2O3 nanorods have been firstly synthesized by a simple two-step method. The crystal phase and morphology of the products were characterized by XRD and SEM which confirm that α-Fe2O3 and In2O3 crystals have relatively pure phases. ► Highly sensitive gas sensors are realized from In2O3 mixed α-Fe2O3 nanorods. At 200 °C, the sensitivity of the sensors upon exposure to 200 ppm ethanol is 31.3, and the sensors exhibit linear dependence of the sensitivity on the ethanol concentration. ► The relationship between sensitivity and ethanol concentration is discussed by using the conduction model, and the experimental data are in good agreement with the obtained equations.Highly sensitive gas sensors are realized from In2O3 mixed α-Fe2O3 nanorods. At 200 °C, the sensitivity of the sensors upon exposure to 200 ppm ethanol is 31.3, and the sensors exhibit linear dependence of the sensitivity on the ethanol concentration at 100 °C and 200 °C. In contrast, nonlinear gas sensing characteristics are observed at 300 °C and 400 °C. The relationship between sensitivity and ethanol concentration is discussed by using the conduction model, and the experimental data are in good agreement with the obtained equations. Our results imply that In2O3 mixed α-Fe2O3 nanorods are good candidates for nano-scale gas sensors and the relationship between sensitivity and ethanol concentration is significantly influenced by temperatures.
Keywords: Nanomaterials; Gas sensing; Sensitivity;
A novel method for the synthesis of polystyrene-graft-silica particles using random copolymers based on styrene and triethoxyvinylsilane by Natalia A. Agudelo; Leon D. Perez; Betty L. Lopez (8581-8586).
Display Omitted► Silica particles were grafted with poly(styrene-co-triethoxyvinylsilane). ► PS-g-silica particles presents high dispersability in organic solvents. ► We investigated the effect of the copolymers weight on the grafting density.In the present research, random copolymers based on triethoxyvinylsilane (TEVS) and styrene (St) are synthesized and structurally characterized. According to the reactivity ratios of the monomers determined by infrared analysis; St tends to form blocks whilst TEVS is expected to be incorporated as isolated units. A sample of poly(styrene-co-triethoxyvinylsilane) synthesized at low conversion using a monomer feeding ratio St:TEVS of 2:3 was used as macrosilane in the synthesis of polystyrene-g-silica particles. The grafting reaction was confirmed by infrared spectroscopy, thermogravimetric analysis and by the evaluation of the morphological characteristics of the hybrid particles.
Keywords: Silica; Random copolymers; Hybrid materials; Polystyrene-grafted silica particles;
Enhancement of cells proliferation and control of bioactivity of strontium doped glass by H. Oudadesse; E. Dietrich; X.V. Bui; Y. Le Gal; P. Pellen; G. Cathelineau (8587-8593).
► NMR reveals: emergence of new components attributed to Q3(OH) after “in vitro” assays. ► Presence of Sr slowed down the kinetic of bioactivity of glasses after immersion in SBF. ► Introduction of Sr at 0.1 wt% induce an enhancement of cells at about 14.3%.Bioactivity and chemical reactivity of bioactive glass offer the ability to bond for soft and hard biological tissues. In this work, synthesis was carried out by using melting and rapid quenching. Strontium was introduced as trace element at different contents in the glass matrix, according to its concentration in the bone matrix. This chemical element presents a high interest in the bone metabolism activity. Investigations were conducted on the surface of biomaterials by using in vitro assay after immersion in SBF. Several physico-chemical methods such as SEM, FTIR, NMR, ICP-OES and MTT test were employed to highlight the effects of the Sr. The in vitro experiments showed that after soaking in SBF, the behaviour of pure glass is different compared to glass doped with Sr. NMR analyses showed in the 29Si MAS-NMR that glass matrix undergoes some changes after in vitro assays particularly the emergence of new components attributed to Q3(OH). The presence of Sr slowed down the bioactivity of glass after immersion in SBF. The non toxic character of compounds was confirmed. Introduction of Sr at 0.1 wt % induce an enhancement of cells at about 14.3%.
Keywords: Surface; Reactivity; Bioactivity; Strontium; Physico-chemical characterization; “In vitro” assays; Cells proliferation;
Characterization of the PEDOT:PSS/KDP mixture on a flexible substrates and the use in pressure sensing devices by F.A.R. Silva; M.J.A. Sales; R.S. Angélica; E.R. Maia; A.M. Ceschin (8594-8599).
► We studied the mixture PEDOT:PSS with KDP for a flexible pressure sensing device. ► Theoretical studies showed no chemical reaction within the components of the mixture. ► XRD studies indicated the growing of KDP structures when the mixture is dried. ► Stress experiments indicated that the studied material reacts to applied pressure.In this work, the mixture poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with monobasic potassium phosphate (KDP), a piezoelectric salt, was studied as a novel material in the fabrication of a low cost, easy-to-make, flexible pressure sensing device. Firstly a theoretical study was carried out, followed by an experimental study where the mixture PEDOT:PSS and KDP was deposited in a flexible polyester substrate and dried. Afterwards, XRD analysis and impulse voltage measures were performed. The results showed that the KDP does not react chemically with PEDOT:PSS and this mixture acts directly responding to the pressure applied on the sample.
Keywords: PEDOT:PSS; KDP; Pressure sensing devices; Conductive polymers; Piezoelectric materials; Molecular modeling;
Fabrication of tungsten oxide microfibers with photocatalytic activity by electrospunning from PVA/H3PW12O40 gel by Chunhong Sui; Jian Gong; Tiexin Cheng; Guangdong Zhou; Shunfu Dong (8600-8604).
► The ultra-fine fibers WO3 was prepared firstly by electrospinning technique. ► Heteropolyacids as well as being unconventional, is regarded as particular precursor. ► Higher photocatalytic activity of ultra-fine fibers WO3 was measured.Regarding gel poly (vinyl alcohol)/H3PW12O40 as precursor, the ultra-fine fibers tungsten oxide (WO3) was prepared by using electrospinning and calcinating techniques. Scanning electron microscope (SEM) shows that the average diameter of fibrous WO3 were changed from 200 nm to 600 nm after calcined PVA/H3PW12O40 fibers at 600 and 800 °C, respectively. X-ray diffraction (XRD) and Raman spectroscope revealed that the fibrous WO3 was monoclinic phase, and the band-gap energies were observed by UV–vis diffuse reflectance spectra. The small size WO3 exhibits excellent photocatalytcic activity in degradation of Rhodamine B at 365 nm wavelength.
Keywords: Electrospinning; Monoclinic; Tungsten oxide; Photocatalytic Activity;
Remarkable difference in catalytic performance of an organoamino-functionalized MCM-41–HPA composite with controlled site-isolation and site-aggregation by Xiaofeng Chu; Ying-Yi Le; Quanjing Zhu; Kangnian Fan; Wei-Lin Dai (8605-8609).
Display Omitted► Novel organoamino-functionalized MCM-41 silicas are successfully prepared. ► Different distribution patterns—site-isolation or site-aggregation was obtained. ► The solvents have remarkable effect on the loading and distribution of organic moieties. ► H3PW12O40 was successfully loaded on the NH2-functionalized MCM-41. ► Distinct performances in the catalytic oxidation of cycloocta-1,5-diene were obtained.The organoamino-functionalized mesoporous silicas with different distribution patterns—site-isolation or site-aggregation are prepared using post-grafting method. We have investigated the effects of the solvents and the catalytic reactivity of these catalysts. It is found that, using the polar ethanol as solvent, the catalytic center is site-isolated. Contrarily, the catalytic center is site-aggregated with the non-polar toluene. Characterization techniques, including transmission electron microscopy, nitrogen sorption experiments, thermogravimetric analysis, and ultraviolet–visible absorbance spectroscopy, demonstrate the most important dependencies of the distribution pattern on the polarity of solvent.
Keywords: Distribution pattern; Solvent effect; Site-isolation; Site-aggregation;
Preparation and characterization of hexadecyl functionalized magnetic silica nanoparticles and its application in Rhodamine 6G removal by Yan-Ping Chang; Cui-Ling Ren; Qing Yang; Zhen-Yang Zhang; Li-Jun Dong; Xing-Guo Chen; De-Sheng Xue (8610-8616).
► C16/Si–OH–Fe3O4 NPs were prepared by simultaneous hydrolysis of TEOS and HTMOS. ► Hydrophobic and electrostatic interaction both took effect, which favored adsorption. ► Facile synthetic conditions and magnetic separation enhanced operating efficiency. ► Bi-functional magnetic adsorbent have potential use in dyes removal.In this paper, a new adsorbent, hexadecyl functionalized magnetic silica nanoparticles (C16/SiO2–Fe3O4 NPs), was prepared by a facile method. The final product was characterized by X-ray diffractometer, transmission electron microscope, Fourier transform infrared spectrometer and vibration sample magnetometer. The preparation and adsorption conditions of the adsorbent were optimized. The adsorbent prepared maintaining volume ratio of tetraethylorthosilicate to hexadecyltrimethoxysilane at 1:0.5 and their total volume at 1100 μL exhibited high adsorption capacity. The optimum pH value for the adsorption experiments was 11.00. The adsorption behavior of Rhodamine 6G onto C16/SiO2–Fe3O4 NPs obeyed pseudo-second-order kinetic model and Langmuir isotherm. Thermodynamic data indicated that the adsorption process was spontaneous and exothermic. The adsorption capacity of the adsorbent could reach to 35.6 mg g−1, owing to the hydrophobic attraction and the enhanced electrostatic attraction. The saturation magnetization of the magnetic adsorbent was 35 emu g−1, which ensured the magnetic separation after adsorption.
Keywords: Hexadecyl functionalized magnetic silica nanoparticles; Hydrophobic attraction; Electrostatic attraction; Dyes removal;
Adsorption of Cathepsin B-sensitive peptide conjugated DOX on nanodiamonds by Shanshan Huang; Jianqun Shao; Lifang Gao; Yingzhe Qi; Ling Ye (8617-8622).
Cathepsin B-sensitive peptide Phe-Lys conjugated DOX (Phe-Lys-PABC-DOX) and HIV-1 trans-activating transcriptor (YGRKKRRQRRR, denoted as TAT) were adsorbed onto carboxylated nanodiamonds (NDs) sequentially via the electrostatic interactions. The adsorption equilibrium, adsorption kinetics and thermodynamics of Phe-Lys-PABC-DOX onto the NDs were investigated.Display Omitted► Phe-Lys-PABC-DOX (PD) and HIV-1 trans-activating transcriptor (TAT) peptide were sequentially adsorbed onto NDs. ► The adsorption characteristics of PD by NDs were determined and the electrostatic interaction between PD and NDs was verified. ► The present work provided a non-covalent adsorption method to construct ND based drug delivery system with multifunctionality in a layer by layer fashion.Drug delivery mediated by nanodiamonds (NDs) has shown great promise in controlled drug release field. In present study, dipeptide (Phe-Lys) conjugated antitumor drug doxorubicin hydrochloride (DOX) with self-immolative p-aminobenzylcarbonyl (PABC) spacer was non-covalently bound to carboxylated NDs via the electrostatic interactions. HIV-1 trans-activating transcriptor peptide (TAT) was additionally integrated to this ND-based delivery system in order to enhance the transmembrane efficiency. Fourier transforms infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and zeta potentials were applied to characterize the DOX and TAT loaded ND delivery platform. The adsorption equilibrium, kinetics and thermodynamics for the adsorption of peptide conjugated DOX onto NDs were investigated. It was found that the adsorption fitted well with the Freundlich model and conformed to pseudo-second order kinetics. It also showed that the adsorption was a spontaneous and exothermic process. Therefore, our work offered a facile way to formulate a ND-based drug delivery platform with multifunctionality in a layer by layer adsorption fashion.
Keywords: Adsorption kinetics; Adsorption thermodynamics; DOX; Nanodiamonds; TAT;
Room temperature growth of In x Ga1−x N thin films by mixed source modified activated reactive evaporation by S.R. Meher; Kuyyadi P. Biju; Mahaveer K. Jain (8623-8628).
► c-Axis oriented nano-crystalline InGaN films are grown by MARE technique. ► InGaN films were grown at room temperature on amorphous glass substrates. ► Promising technique to grow InGaN films on flexible substrates in the entire composition range.Polycrystalline In x Ga1−x N thin films were prepared by mixed source modified activated reactive evaporation (MARE) technique. The films were deposited at room temperature on glass substrates without any buffer layer. All the films crystallize in the hexagonal wurtzite structure. The indium concentration calculated from XRD peak shift using Vegard's law was found to be varying from 2% to 92%. The band gap varies from 1.72 eV to 3.2 eV for different indium compositions. The indium rich films have higher refractive indices as compared to the gallium rich films. The near infra-red absorption decreases with gallium incorporation into InN lattice which is mainly due to decrease in the free carrier concentration in the alloy system. This fact is further supported from Hall effect measurements. MARE turns out to be a promising technique to grow In x Ga1−x N films over the entire composition range at room temperature.
Keywords: Modified activated reactive evaporation; InGaN; Thin film; Band gap;
A SIMS study on Mg diffusion in Zn0.94Mg0.06O/ZnO heterostructures grown by metal organic chemical vapor deposition by L.L. Yang; Q.X. Zhao; G.Z. Xing; D.D. Wang; T. Wu; M. Willander; I. Ivanov; J.H. Yang (8629-8633).
► Mg diffusion coefficient in Zn0.94Mg0.06O was investigated by SIMS. ► A thick ZnO buffer layer is needed to reduce n-type background doping. ► 700 °C is the optimized temperature to grow ZnMgO/ZnO structures.Zn0.94Mg0.06O/ZnO heterostructures have been grown on 2 in. sapphire wafer using metal organic chemical vapor deposition (MOCVD). Photoluminescence (PL) mapping demonstrates that Mg distribution on the entire wafer is very uniform (standard deviation of Mg concentration/mean Mg concentration = 1.38%) with average concentration of ∼6%. The effect of annealing on the Mg diffusion in Zn0.94Mg0.06O/ZnO heterostructures has been investigated in detail by using secondary ion mass spectrometry (SIMS). All the Mg SIMS depth profiles have been fitted by three Gaussian distribution functions. The Mg diffusion coefficient in the as-grown Zn0.94Mg0.06O layer deposited at 700 °C is two orders of magnitude lower than that of annealed samples, which clearly indicates that the deposition temperature of 700 °C is much more beneficial to grow ZnMgO/ZnO heterostructures and quantum wells.
Keywords: Heterostructures; Diffusion coefficient; Secondary ion mass spectrometry;
Effect of temperature and pumping power on the photoluminescence properties of type-II CdTe/CdSe core-shell QDs by A.M. Saad; M.M. Bakr; I.M. Azzouz; Maram T.H. Abou Kana (8634-8639).
► CdTe/CdSe core-shell NCs have very large stock shift which lead to appearance of the emission of such system near IR-region. ► The tunability of band gap from visible to IR region depend upon the thickness of shell and the size of core of prepared samples. ► Also, some optical properties of CdTe/CdSe core-shell QDs depending upon the different pumping power (1–200 mW) of 488 nm Ar-laser and depending also on the effect of different temperatures (100–10 K) were studied. Lifetime measurement of prepared QDs was documented by using N2-laser. ► CdTe/CdSe core-shell NCs are good lasing materials with lifetime exceed 7 ns because of very large stock shift which prevents the reabsorption and increase quantum yield.CdTe/CdSe core-shell QDs type II was prepared by two steps synthetic process and embedded in polymer host. Emission in the NIR region was recorded. The effect of Ar laser excitation at different powers on the optical properties of the prepared QDs is studied at different temperatures (300–10 K). Amplified spontaneous emission is observed at room temperature and at 10 K. Also, lifetime measurement of prepared QDs was documented using N2-laser.
Keywords: CdTe-CdSe core-shell; Near IR-spectrum; Photoluminescence; Quantum dots; Lifetime;
Surface modification on a glass surface with a combination technique of sol–gel and air brushing processes by Meng-Yu Tsai; Chin-Chi Hsu; Ping-Hei Chen; Chao-Sung Lin; Alexander Chen (8640-8646).
► This study fabricated the large area and optically transparent superhydrophobic silica-based films on glass surface. ► Desired surface roughness was obtained by adjusting nano silica particles concentration of the precursors prepared by the sol–gel process. Silica suspension was coated onto the glass substrate by the air brushing methods. ► This method can deposit a uniform, transparent coating on the glass substrate efficiently.This study fabricated the large area and optically transparent superhydrophobic silica based films on glass surface with optimized hardness. A silane coupling agent, tetraethoxysilane (TEOS), effectively bonds silica particles onto the glass substrate. Desired surface roughness was obtained by adjusting nano silica particles concentration of the precursors prepared by the sol–gel process. Silica suspension was coated onto the glass substrate by the air brushing methods. This method can deposit a uniform, transparent coating on the glass substrate efficiently. Diluting the precursor by adding ethanol or a mixture of D.I. water and ethanol further improved the transmittance and superhydrophobicity efficiency. The results showed that as the silica particle concentration and the thickness of the coating were increased, the surface roughness was enhanced. Rougher surface displayed a higher superhydrophobicity and lower transmittance. Therefore, the concentration of silica particle, volume of coatings, and the ratio of ethanol and D.I. water are of great importance to deposit a transparent, superhydrophobic coating on glass.
Keywords: Superhydrophobic; Transparent; Glass; Sol–gel; Silica particle; Air brushing;
Density functional theory study on activity of α-Fe2O3 in chemical-looping combustion system by Changqing Dong; Shuhui Sheng; Wu Qin; Qiang Lu; Ying Zhao; Xiaoqiang Wang; Junjiao Zhang (8647-8652).
► Fe2O3 is a kind of the most important oxygen carriers used in the promising chemical-looping combustion (CLC) technology, the microscopic structure and physicochemical properties of CO–Fe2O3 interaction system have not been observed before. Here, we investigate the activity of α-Fe2O3 for CO oxidation in CLC process.The dominant growth planes (0 0 0 1) and (1 1 0 2) have been used to investigate the activity of the natural α-Fe2O3 in chemical-looping combustion system based on density functional theory (DFT) calculations. In the chemical-looping combustion system, CO is selected as the probe fuel gas to detect the activities of the different surfaces. CO interacts stronger to Fe2O3 (1 1 0 2) than Fe2O3 (0 0 0 1). CO can be oxidized into CO2 species directly on Fe2O3 (1 1 0 2) rather than Fe2O3 (0 0 0 1). The formation of CO2 accompanying with a transformation from hematite to magnetite acted as the key step for the reduction process of hematite.
Keywords: CO; α-Fe2O3; Chemical-looping combustion; Density functional theory;
Comparison of the coating properties and corrosion rates in electroless Ni–P/PTFE composites prepared by different types of surfactants by Iman R. Mafi; Changiz Dehghanian (8653-8658).
► Effects of different types of surfactants (cationic, anionic, non-ionic) on the surface morphology and deposition rate of electroless Ni–P/PTFE coatings were investigated. ► For CTAB and PVP, there is an optimum amount of surfactant at which the PTFE content in the electroless Ni–P coating is the highest. ► CTAB was the most effective surfactant for dispersing the PTFE particles in the Ni–P matrix. ► The addition of PTFE to the Ni–P matrix improved the corrosion properties. ► The Ni–P/PTFE specimen prepared by CTAB exhibited the highest corrosion resistance while SDS was found to be the least effective.The effects of the addition of three types of surfactants (cationic, anionic, non-ionic) at different concentrations in the plating bath on the deposition rate, PTFE content and surface morphology of electroless Ni–P/PTFE composite coatings were investigated. It was demonstrated that the cationic and non-ionic surfactants created a uniform distribution of PTFE particles in the coatings. The effects of the surfactant type and concentration on the corrosion properties of Ni–P/PTFE coatings were also studied. The corrosion resistance was increased by the incorporation of PTFE particles into the Ni–P matrix. The level of improvement depended largely on the type and concentration of the applied surfactants.
Keywords: Electroless deposition; Composite coating; PTFE; Corrosion resistance; Polarization; Impedance;
Formation of two ripple modes on Si by ion erosion with simultaneous Fe incorporation by Marina Cornejo; Bashkim Ziberi; Christoph Meinecke; Frank Frost (8659-8664).
► Near normal incidence ion erosion of Si results in two mode ripples. ► Ripples perpendicular to ion beam direction are inherently related to Fe addition. ► Ripples parallel to ion beam are less affected by Fe incorporation. ► Ripples parallel to ion beam become dominant at low ion energy (≤500 eV).This report focuses on the self organized nanostructure formation on Si (0 0 1) by erosion with low energy Kr+ ions with simultaneous incorporation of metallic atoms, in particular Fe. The incorporation of Fe is thought to play an important role in the formation of some features. In the experimental set-up used here the Fe atoms come from the sputtering of a cylindrical stainless steel target situated between the source and the sample holder. It is demonstrated how the Fe flux can be regulated by operational parameters of the ion source. It is shown that two different ripple modes, one perpendicular to the ion beam projection on the surface and the other parallel, were formed at near normal incidence (α = 20°) with ion energy between 300 eV and 2000 eV and a fluence of 6.7 × 1018 cm−2. The perpendicular mode ripples dominated the topography when E ion = 2000 eV, while the parallel mode ripples were the main features observed when E ion = 300 eV. The correlation of Fe concentration with ion sources parameters and resulting topography is analyzed. It is demonstrated that a certain Fe concentration is necessary for the formation of ripples that are oriented perpendicular to the ion beam and that the Fe concentration alone does not determine the evolving topography.
Keywords: Ion erosion; Self organization; Silicon; Nanostructures; Ripples;
Molecular dynamics study of interfacial bonding strength of self-assembled monolayer-coated Au-epoxy and Au–Au systems by Hsien-Chie Cheng; Yu-Chen Hsu; Chun-Hung Wu; Wen-Hwa Chen (8665-8674).
► A comparative study of Au substrate and SAMs on the bonding strength. ► SH(CH2) n NH2 consists of the highest elastic modulus, followed by the SH(CH2) n OH and the SH(CH2) n CH3. ► The maximal interfacial bonding strength in SH(CH2) n CH3 SAM-coated Au–Au joint is at the chain length n = 8. In SH(CH2) n CH3 SAM-coated Au-epoxy system, minimum is at n = 4 and maximum at n = 10. ► The Au(1 1 1) would outperform the Au(1 0 0) substrate in the interfacial bonding strength of the SAM-coated Au-epoxy system, but a totally opposite result for the SAM-coated Au–Au joint.Interfacial adhesion between metals and organic polymers plays a crucial role in the mechanical properties and reliability performance of multiplayer thin film structures. To improve their interfacial bonding strength and so the reliability, the self-assembled monolayer (SAM) method is considered as an effective means. The present study is devoted to studying the effects of SAM coating on the interfacial bonding strength of the Au-epoxy and the Au–Au bonding structures through molecular dynamics (MD) simulation. Three different types of functionalized alkanethiol SAMs (SH(CH2) n X, X = CH3, OH, NH2) chemisorbed onto two different Au crystal planes, i.e., (1 0 0) and (1 1 1), are considered. The study starts from the characterization of the interfacial bonding strength of both the SAM-coated Au-epoxy and Au–Au systems, followed by the investigation of the dependence of the interfacial bonding strength on the chain lengths and tail groups of the n-alkanethiolates. A comparative study of the effects of the crystal orientation of Au substrate on the bonding strength is reported, and the elastic moduli of these SAMs through uniaxial tensile simulation are also examined. The calculated results are compared with the published experimental data, and also with each other to identify the optimal SAM candidate.Results show that the interfacial bonding strength of the SAM-coated Au-epoxy and Au–Au systems exhibits a strong dependency on the crystal orientation of Au substrate and also on the chain length of the monolayer where it tends to increase with an increasing SAM chain length. In specific, the interfacial bonding strength of the SH(CH2) n CH3 SAM-coated Au–Au joint would reach a maximal value at the chain length n = 8 while that of the SAM/epoxy interface in the SH(CH2) n CH3 SAM-coated Au-epoxy system attains a minimal value at n = 4 and becomes the maximum at n = 10, regardless of the crystal orientation of the Au substrates. Besides, the Au substrate with (1 1 1) crystal orientation would outperform the Au(1 0 0) substrate in the SAM/epoxy interfacial bonding strength of the SAM-coated Au-epoxy system while there is a totally opposite result for that of the SAM-coated Au–Au joint.
Keywords: Self-assembled monolayer; Molecular dynamics simulation; Bonding strength; Au-epoxy bi-material structure; Au–Au joint;
Improving p-type contact characteristics by Ni-assisted annealing and effects on surface morphologic evolution of InGaN LED films grown on Si (1 1 1) by Guangxu Wang; Chuanbing Xiong; Junlin Liu; Fengyi Jiang (8675-8678).
► p-type specific contact resistivity can be reduced by Ni-assisted annealing. ► Ni-assisted annealing can promote interface reaction between GaN and Ni. ► Acid–hydrogen peroxide can be used to etch the interface defect-selectively. ► Pits formed on surface of p-GaN after etch in acid–hydrogen peroxide. ► Ni-assisted annealing can promote the forming and growth of pits.Ni thin layer was deposited to assist to activate p-GaN and then was removed. The process was named Ni-assisted annealing (NA). We investigate the surface morphology and p-type contact behaviors of InGaN LED films grown on Si (1 1 1) substrates. Compared with conventional thermal annealing (TA), NA can improve the p-type contact characteristic at lower anneal temperature and a smaller specific contact resistivity (ρ c = 6.1 × 10−5 Ω cm2) employing nonalloy Pt electrode was obtained. A wet etching method using acid–hydrogen peroxide was adopted to boil films surface after activation. We found that some nano-pits appeared on surfaces while original surface step structure was still clearly visible, which shows a defect-selective etching characteristic. Otherwise, we demonstrated that the surface morphology could be affected by NA while independent to TA. Some mechanisms for experimental phenomena were also discussed in the letter.
Keywords: Light emitting diode (LED); Ni-assisted annealing; p-type contact characteristic; Surface morphology;
Polishing behavior of PS/CeO2 hybrid microspheres with controlled shell thickness on silicon dioxide CMP by Yang Chen; Renwei Long (8679-8685).
► Organic–inorganic composite microspheres with PS as a core and CeO2 nanoparticles as a shell were synthesized by in situ chemical precipitation. ► The shell thickness of the composite microspheres could be turned. The whole process required neither surface treatment for PS microspheres nor additional surfactant or stabilizer. ► A possible mechanism for the formation of PS/CeO2 composite microspheres was discussed. ► The effects of CeO2 shell thickness of the PS/CeO2 composite abrasives on oxide CMP performance were investigated.Organic–inorganic composite microspheres with PS as a core and CeO2 nanoparticles as a shell were synthesized by in situ decomposition reaction of Ce(NO3)3 on the surfaces of PS microspheres prepared through soap-free emulsion polymerization. The shell thickness of the composite microspheres could be turned by varying the concentration of Ce(NO3)3 in the reaction solution. The whole process required neither surface treatment for PS microspheres nor additional surfactant or stabilizer. The as-synthesized PS/CeO2 composite microsphere samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Oxide chemical mechanical polishing (CMP) performance of the PS/CeO2 composite abrasives with different shell thickness was characterized by atomic force microscopy (AFM). The results indicated that the as-prepared core–shell structured composite microspheres (220–260 nm in diameter) possessed thin shell (10–30 nm) composed of CeO2 nanoparticles (particle diameter of 5–10 nm), and the final CeO2 contents of the composite microspheres ranged from 10 to 50 wt%. A possible mechanism for the formation of PS/CeO2 composite microspheres was discussed also. The CMP test results confirmed that the novel core–shell structured composite abrasives are useful to improve oxide CMP performance. In addition, there is an obvious effect of shell thickness of the composite abrasives on oxide CMP performance.
Keywords: PS/CeO2 composite abrasive; Core–shell structure; Shell thickness; Chemical mechanical polishing (CMP);
Simple approach to carboxyl-rich materials through low-temperature heat treatment of hydrothermal carbon in air by Zhen Chen; Lijian Ma; Shuqiong Li; Junxia Geng; Qiang Song; Jun Liu; Chunli Wang; Hang Wang; Juan Li; Zhi Qin; Shoujian Li (8686-8691).
Display Omitted► Carboxyl-rich hydrothermal carbon can be obtained by heat-treatment in air. ► Content of carboxyl groups on the heat-treated carbon can reach up to 3.70 mmol/g. ► Much higher sorption capacity for Pb and Cr is observed after heating the matrix. ► Mechanism for newly generating carboxyl groups during heat-treatment is supposed.It was found that a large number of oxygen-containing functional groups (OFGs) could be created on the surface of hydrothermal carbon (HTC) by simply heating at lower temperature in air during the course of our preliminary experiments which focused on oxidation pre-treatment of pristine HTC for the purpose of grafting functionalization. Especially carboxyl groups on HTC would increase significantly, from 0.53 to 3.70 mmol/g after heat treatment at 300 °C. So, effects of heat-treatment on the OFGs on the carbon microsphere were deeply studied to confirm and explain the findings. Experiments involving different materials (HTC, activated carbon and glucose) were performed under varying conditions (heating temperature and time, in air or in Ar atmosphere). A reaction mechanism for newly generating carboxyl groups on HTC surface during heat-treatment process was supposed based on the results from the sample characterization using Boehm titrations, infrared spectra, X-ray photoelectron spectroscopy, energy dispersive spectrometry and elemental analysis. In addition, the as heat-treated product has excellent sorption capability for Pb2+ and Cd2+ ions.
Keywords: Hydrothermal carbon; Oxidative functionalization; Heat treatment; Carboxyl groups; Adsorption;
Adsorption of formaldehyde on the Fe site of clean and M2+ (Ca2+, Sr2+ and Ba2+) doped LaFeO3 (0 1 0) surface by Lihui Sun; Jifan Hu; Feng Gao; Hongwei Qin (8692-8695).
The adsorption of formaldehyde (H2CO) on the Fe site of clean and M2+ (Ca2+, Sr2+ and Ba2+) doped LaFeO3 (0 1 0) surface have been investigated using the density functional theory (DFT) method. Calculation results show that the oxygen atom of the H2CO molecule prefers to be adsorbed on the Fe site of the clean LaFeO3 (0 1 0) surface. The adsorption of H2CO could change the electronic properties of the LaFeO3, indicating that the LaFeO3 could be used as gas sensing material to detect the H2CO gas. The analysis results of the DOS suggest that the bonding mechanism between the H2CO molecule and the Fe site is mainly from the interaction between the Fe 3d and H2CO 2p orbital. Comparing with the binding energy and the net charge-transfer, we find that the M2+ (Ca2+, Sr2+ and Ba2+) doping cannot improve the sensitivity of the LaFeO3 to the H2CO gas.
Keywords: Density functional theory (DFT); M2+ doping; Binding energy; Charge transfer;
The effect of geometry and post-annealing on surface acoustic wave characteristics of AlN thin films prepared by magnetron sputtering by Duy-Thach Phan; Gwiy-Sang Chung (8696-8701).
► AlN thin films by reactive magnetron sputtering. ► Effects of geometry on SAW resonators. ► Effects of post-annealing on AlN film quality. ► Effects of post-annealing on SAW properties.This paper describes experimental relationship between surface acoustic wave (SAW) properties of two-port SAW resonators based on polycrystalline aluminum nitride (AlN) thin films grown on Si substrates by using a pulsed reactive magnetron sputtering system and their geometry's parameters. Moreover, the influence of post-deposition heat treatment on SAW properties of AlN thin films was investigated at different annealing temperature (600 °C and 900 °C). The measurement results show the number of the inter-digital transducers (IDT) finger pairs (N), the number of reflectors grating pairs (R) and the IDT center-to-center distance (L) related to insertion loss of SAW resonators. The best result of insertion loss was 15.6 dB for SAW resonators with R = 160 pair, N = 5 pair and L = 750 μm. At the same geometry parameters, the SAW velocity and insertion loss were improved slightly after annealing at 600 °C and were worse for the films annealed at 900 °C by changes in the surface morphology and stress on the film.
Keywords: AlN films; SAW resonator; Geometry; Post-annealing;
Facile method of fabricating Sn nanoparticle monolayer using solid-supported liquid–crystalline phospholipid membrane by Hyeun Hwan An; Jung Hoon Kim; Seung Jae Lee; Won Bae Han; Jong Ho Lee; Hee-Soo Kim; Sang Hee Suh; Im Taek Yoon; Yoon Shon; Chong Seung Yoon (8702-8711).
Summary: 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) phospholipid membrane was used to fabricate a tightly packed 2-dimensional array of oxide-covered Sn nanoparticles through direct deposition of Sn on the DOPC membrane. The SnO x oxide shell was developed from the surface oxidation of the nanoparticle surface by the encapsulating DOPC molecules.Display Omitted► Phospholipid membrane was used to fabricate oxide-covered Sn nanoparticle monolayer. ► The oxide shell developed from the surface oxidation by the encapsulating lipids. ► Sn nanoparticle monolayer was formed on top of the lipid membrane. ► Sn nanoparticle monolayer exhibited photoluminescence after plasma etching.1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) phospholipid membrane was used to fabricate a tightly packed 2-dimensional array of Sn nanoparticles through direct deposition of Sn on the DOPC membrane. Major advantage of the proposed method was that the vertical ordering of the nanoparticles extended to a centimeter (2 cm × 2 cm substrate) scale in the as-prepared state. It was also shown that the particle size and morphology were altered depending on processing conditions. Experimental evidences indicated that the Sn nanoparticle surface, which spontaneously oxidized during deposition, was encapsulated by the DOPC molecules. After removing the encapsulating lipid layer, the oxide-covered Sn nanoparticles exhibited strong photoluminescence. It was also demonstrated that the Sn particle morphology and ordering are related to the lipid membrane structure and chemistry. The proposed method can be easily extended to other metals that are susceptible to oxidation to produce various metal oxide nanoparticles.
Keywords: Phospholipid; Liquid–crystalline membrane; Self-assembly; Sn nanoparticle;
Enhanced formation of periodic arrays of low-resistivity NiSi nanocontacts on (0 0 1)Si0.7Ge0.3 by nanosphere lithography with a thin interposing Si layer by S.L. Cheng; C.Y. Zhan; S.W. Lee; H. Chen (8712-8717).
► Enhanced growth of low-resistivity NiSi nanodot arrays on (0 0 1)Si0.7Ge0.3 has been achieved by using a novel Ni/amorphous-Si(a-Si) bilayer nanodot structure. ► The size, interspacing, and shape of the low-resistivity NiSi nanodots remain almost unchanged even after annealing as high as 800 °C. ► The presence of the a-Si interlayer was found to effectively prevent Ge segregation and maintain the interface stability in forming NiSi nanodots on Si0.7Ge0.3 substrate. ► 10–45 nm-diameter amorphous SiO x nanowires were found to grow on the 900 °C annealed nanodots sample.In this study, we demonstrated significant enhancement of the formation of low-resistivity NiSi nanocontacts with controlled size on (0 0 1)Si0.7Ge0.3 substrates by combining the nanosphere lithography with the use of a new Ni/a-Si bilayer nanodot structure. Low-resistivity NiSi with an average size of 78 nm was observed to be the only silicide phase formed in samples annealed at 350–800 °C. The presence of the interposing Si layer with appropriate thickness was found to effectively prevent Ge segregation and maintain the interface stability in forming NiSi nanocontacts on (0 0 1)Si0.7Ge0.3. As the annealing temperature was increased to 900 °C, amorphous SiO x nanowires were observed to grow from silicide nanocontact regions. The NSL technique in conjunction with a sacrificial Si interlayer process promises to be applicable in fabricating periodic arrays of other low-resistivity silicide nanocontacts on Si1−x Ge x substrates without complex lithography.
Keywords: Nanosphere lithography; NiSi; Nanocontacts; Si interlayer; SiGe; SiO x nanowires;
Characteristics of high Al content AlGaN grown by pulsed atomic layer epitaxy by Xu Pan; Xiaoliang Wang; Hongling Xiao; Cuimei Wang; Cuibai Yang; Wei Li; Weiying Wang; Peng Jin; Zhanguo Wang (8718-8721).
► 3.7 μm Al0.91Ga0.09N epilayers was grown on sapphire (0 0 0 1) substrates by PALE. ► The crystalline quality of sample is better. ► The sample's Raman spectrum supports the results that asymmetric photoluminescence peak is caused by the exciton-phonon coupling. ► Deep ultraviolet photoluminescence spectroscopy and Raman scattering spectroscopy analysis show that there possibly exists a high density of deeper localized state (∼90 meV) as the center of radiative recombination.Al0.91Ga0.09N epilayers have been obtained by pulsed atomic layer epitaxy (PALE) technique on sapphire (0 0 0 1) substrates. Deep ultraviolet (DUV) photoluminescence (PL) spectroscopy and Raman scattering spectrum have been employed to study the optical transitions in Al0.91Ga0.09N epilayers. We found the exciton-phonon interaction by fitting the asymmetric PL peak, in which the transverse optical phonon (TO) and the longitudinal optical (LO) phonon are the main contributor. The abnormal S-shaped temperature dependence of the PL band peak is less pronounced or has disappeared. Further analysis shows that there possibly exists a high density of deeper localized state (∼90 meV) in Al0.91Ga0.09N. The formation of these localized states provides a favorable condition for efficient light emission.
Keywords: Photoluminescence; Raman scattering; Pulsed atomic layer epitaxy; AlGaN alloys;
Synthesis and microstructure observation of titanium carbonitride nanostructured coatings using reactive plasma spraying in atmosphere by Lin Zhu; Jining He; Dianran Yan; Lisong Xiao; Yanchun Dong; Jianxin Zhang; Hanlin Liao (8722-8727).
► Nanostructured TiCN coating was deposited by atmospheric reactive plasma spraying. ► The coating was mainly composed of columnar nanograins perpendicular to the substrate surface. ► The nanostructured coating displayed superior hardness and toughness characteristics.In the present study, nanostructured titanium carbonitride (TiCN) coatings were successfully deposited by reactive plasma spraying (RPS) technology using a self-designed gas tunnel mounted on a normal plasma spray torch. The phase composition and microstructure of the TiCN coatings were characterised by XRD, SEM and TEM. The results indicated that the main phase of the coatings was FCC TiC0.2N0.8 with a small amount of Ti3O. The coating that was deposited using 35 kW displayed better microstructure and properties. The coating exhibited a typical nanostructure including 90 nm diamertrical equiaxed grains and 400 nm long columnar grains by TEM images. The SEM observation further revealed that the equiaxed grains in parallel direction to the substrate surface in TEM images were actually the columnar grains perpendicular to the substrate surface. The formation mechanism of the nanostructured coatings was also discussed. The measured microhardness value of the coating was approximately 1659 Hv100 g, and the calculated crack extension force was about 34.9 J/m2.
Keywords: Titanium carbonitride; Reactive plasma spraying; Nanostructured coating; Microhardness; Toughness;
Effect of substrates and anions of zinc salts on the morphology of ZnO nanostructures by Yu Lin; Qifei Jiang (8728-8731).
.Display Omitted► ZnO nanostructures were hydrothermally synthesized on glass and Al substrates. ► Different ZnO nanostructures are obtained, such as nanorods, nanosheets, and so on. ► Substrates and anions of zinc salts have important effects on the morphologies.The ZnO nanostructures were hydrothermally synthesized on glass and Al substrates, respectively, using zinc chloride, zinc nitrate, and zinc acetate as precursor. The as-prepared products were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Different ZnO nanostructures were obtained, such as nanorods, nanosheets, flower-like nanostructures and so on. The effects of the substrates and anions of zinc salts on the morphologies of the resulting products have been investigated.
Keywords: ZnO nanostructures; Hydrothermal process; Substrates; Anions;
Preparation, characterization, and photocatalytic properties of silver carbonate by Chengwei Xu; Yuanyuan Liu; Baibiao Huang; Hui Li; Xiaoyan Qin; Xiaoyang Zhang; Ying Dai (8732-8736).
► Silver carbonate (Ag2CO3) nanorods were prepared using a precipitation method. ► The results of DRS suggested that the optical transition of Ag2CO3 was indirectly allowed, and its band gap was determined to be 2.08 eV. ► The prepared Ag2CO3 displayed a high activity towards degradation of phenol and MB under visible light. ► In addition, Ag2CO3 displayed enhanced photocatalytic activities for the destruction of E. coli due to its photogenerated electron–hole pairs.Silver carbonate (Ag2CO3) short rods were prepared using a precipitation method. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflective spectra (DRS) and photocatalytic degradation of organic pollutants and destruction of E. coli measurements. The results of DRS suggested that the optical transition of Ag2CO3 was indirectly allowed, and its band gap was determined to be 2.08 eV. The prepared Ag2CO3 displayed a high activity towards degradation of phenol and MB under visible light. The total organic carbon (TOC) value decreased during the photocatalytic process, which suggests that phenol was truly photodegraded. The stability of Ag2CO3 was greatly improved when Na2CO3 was added into the photocatalytic system. In addition, Ag2CO3 displayed enhanced photocatalytic activities for the destruction of E. coli due to its photogenerated electron–hole pairs.
Keywords: Silver carbonate; Photocatalysis; Antibacterial activity;
Surface modification of polypropylene with an atmospheric pressure plasma jet sustained in argon and an argon/water vapour mixture by Abdollah Sarani; Anton Yu Nikiforov; Nathalie De Geyter; Rino Morent; Christophe Leys (8737-8741).
► Plasma jet in Ar/water vapor mixture for polypropylene film modification. ► Rotational temperature of OH radicals is around 650 K in active zone of the jet. ► Plasma treatment can add up to 15.1% of oxygen containing groups to the PP surface. ► The adding water vapour to the argon feeding gas results in a more pronounced oxygen incorporation.In this paper, an atmospheric pressure plasma jet sustained in pure argon and an argon/water vapour mixture has been used to modify the surface of polypropylene (PP) films. The gas temperature of the plasma jet was found to be 625 K in an active zone between the electrodes and was found to increase in the afterglow. Based on these results, the PP films are placed as close as possible to the edge of the capillary in order to avoid thermal damage to the polymer. XPS results on the untreated and modified PP samples revealed incorporation of a significant amount of oxygen on the polymer surface, however, this oxygen inclusion is more pronounced for the argon/water vapour jet due to the higher radicals density in the jet afterglow. One can therefore conclude that adding water vapour to an argon plasma jet can be a convenient way to increase the efficiency of plasma surface modification.
Keywords: Atmospheric pressure plasma jet; OH radicals; X-ray photoelectron spectroscopy; Surface modification;
Influence of surface preparation on CdZnTe nuclear radiation detectors by Q. Zheng; F. Dierre; J. Crocco; V. Carcelen; H. Bensalah; J.L. Plaza; E. Dieguez (8742-8746).
Display Omitted► Bromine methanol etching shows the highest crystalline quality. ► Fine mechanical polishing increases infrared transmission. ► Bromine methanol etching decreases the infrared transmission. ► Low concentration of bromine methanol etching provides pitting effect. ► High concentration of bromine methanol etching displays waving effect.High resolution X-ray diffraction (HRXRD), Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM) techniques were used to characterize the surface of CdZnTe (CZT) samples treated by mechanical lapping, polishing and chemical etching processes. The results confirm that the etching process produces the highest intensity diffraction peak, and the best full-width-at-half-maximum (FWHM). Fourier Transform Infrared (FTIR) spectroscopy shows that fine polishing increases the infrared transmission of the CZT sample, while etching with 2% bromine methanol (BM) etching decreases the infrared transmission. Different etchants and concentrations were investigated by comparing the surface morphology and roughness. The bromine methanol etching has shown more flat surface with lower roughness than the other etchants.
Keywords: Crystalline quality; CdZnTe; Infrared transmission; Etching; Surface morphology;
In situ X-ray photoelectron spectroscopy characterization of Al2O3/GaSb interface evolution by S. McDonnell; D.M. Zhernokletov; A.P. Kirk; J. Kim; R.M. Wallace (8747-8751).
► 300°C annealing causes the O and S bonded to Sb to transfer to Ga ► 300°C annealing causes leaves the top 5-6 nm of the substrate Sb rich ► TMA reduces the sulfur detected ► Sb-Sb, Sb-O and Sb-S bonds are not detected after annealing or ALD ► Ga-O and Ga-S remain detectable after annealing and ALDGaSb(0 0 1) was treated with (NH4)2S x and the evolution of the interfacial chemistry was investigated, in situ, with monochromatic X-ray photoelectron spectroscopy (XPS), following heat treatment and exposure to trimethylaluminum (TMA) and deionized water (DIW) in an atomic layer deposition reactor. Elemental Sb (Sb–Sb bonding) as well as Sb3+ and Sb5+ chemical states were initially observed at the native oxide/GaSb interface, yet these diminished below the XPS detection limit after heating to 300 °C. No evidence of Ga–Ga bonding was observed whereas the Ga1+/Ga–S chemical state was robust and persisted after heat treatment and exposure to TMA/DIW at 300 °C.
Keywords: XPS; Atomic layer deposition; Al2O3; GaSb; High mobility substrates;
Comment on “Low temperature synthesis wide optical band gap Al and (Al, Na) co-doped ZnO thin films” by Mingsong Wang (8752-8753).
Response to the comment on “Low temperature synthesis wide optical band gap Al and (Al, Na) co-doped ZnO thin films” by Tao Wang; Yanmei Liu (8754).