Applied Surface Science (v.257, #10)
Study on the binding equilibrium between surfactant FC95 and DNA by resonance light-scattering technique by Ling Li; Quan Pan; Ying Xi Wang; Gong Wu Song; Zu Shun Xu (4547-4551).
▶ FC95 was used to determine DNA. ▶ RLS technique is used in comprehension of the binding of PFOS to DNA. ▶ The mechanisms of the interaction was studied by UV spectra and RLS spectra.The binding equilibrium of potassium perfluorooctanesulfonate (FC95) to DNA was studied by UV spectra and resonance light scattering technique in the present paper. It was found that the interaction resulted in strongly enhanced resonance light scattering signals characterized by the RLS peak at 370 nm. The results indicated that the conformation of the DNA has changed during the interaction because the micro environment of DNA changed. The binding constant K f and the number of binding n were calculated according to the equilibrium equation, which was established based on the data of the resonance light scattering measurements at 370 nm. It was found that the binding K f and the number of binding n were 6.02 × 103 and 2.0, respectively.
Keywords: Fluorinated surfactant; DNA; Resonance light scattering; Conformation;
Initial attachment and spreading of MG63 cells on nanopatterned titanium surfaces via through-mask anodization by Terje Sjöström; Georgi Lalev; Jason Peter Mansell; Bo Su (4552-4558).
▶ Nanotopography is important in modulating the behaviour of cells. ▶ The attachment and spreading of osteoblast-like MG63 cells can be controlled by the dimension of nanodots on Ti substrates. ▶ The results could lead to improved osseointegration of dental and orthopaedic implants.It is well established that nanosized surface topography significantly affects cell response at a biomaterial surface. Here we used a through-mask anodization technique to fabricate well-defined titania nanopillars with tunable feature sizes from 15 to 100 nm on bulk titanium (Ti) substrates and studied their effects on initial attachment and spreading of osteoblast-like cells (MG63). An increase of titania pillar height from 15 to 100 nm resulted in reduced spreading of MG63 osteoblast-like cells and the higher pillar structures also gave rise to heavily elongated cells. By using a FIB/SEM dual beam microscope the interface between MG63 cells and nanopatterned Ti surfaces could be studied in more detail. It was found that the higher pillar structures prevented the cells to conform to the surface topography leaving voids in between the cells and the substrates. The results found in this study agree with previous studies that cells response better to surfaces with smaller (<20 nm) features.
Keywords: Nanotopography; Osteoblast; Cell attachment; Cell spreading; Titania nanopillars; Titanium surfaces; Through-mask anodization;
Two-dimensional self-assembly of esters with different configurations at the liquid–solid interface by Xinrui Miao; Li Xu; Chenyi Liao; Zhuomin Li; Jian Zhou; Wenli Deng (4559-4565).
▶ Ester groups in HP and TADE molecules can be distinguished from the chain skeleton by STM. ▶ HP and TADE with ester group self-assemble on HOPG surface with different configurations. ▶ The perpendicular orientation of HP and the parallel orientation of TADE on HOPG are confirmed by MM simulations.Self-assembled monolayers of hexadecyl palmitate (HP) and 3,3′-thiodipropionic acid di-n-octadecyl ester (TADE) physisorbed on highly oriented pyrolytic graphite (HOPG) are investigated using scanning tunneling microscope (STM) and computer simulation. Both molecules form alkane-like linear shapes to maximize the interactions with substrate when they adsorb on HOPG surface. The HP molecules self-assemble into lamellae with the chain-trough angle of 48°, which is the result of a shifting 3/2 units from the adjacent molecule in a lamella. Based on the simulation insights combined with STM images, we confirm that a perpendicular orientation appears in which the HP molecular backbone is rotated 90° with respect to the substrate such that the carbonyl points away from the HOPG surface. TADE molecules form three kinds of configurations with chain-trough angles of 90°, 72° and 60° by shifting 0, 1/2 and 1 units from their adjacent molecules, respectively. The bright stripes in STM images reveal the electron density distribution of the part between two ester groups. The energy differences of three TADE adsorption configurations by molecular mechanics (MM) simulation are used to explain the structural coexistence phenomenon. It is also shown that lattice match between alkyl chain of molecules and HOPG substrate could change molecular conformation upon self-assembly.
Keywords: Self-assembly; Scanning tunneling microscopy (STM); Ester; Liquid–solid interface; Computer simulation;
Experimental and theoretical study of silicon-doped Sb2Te3 thin films: Structure and phase stability by Xuelai Li; Feng Rao; Zhitang Song; Kun Ren; Weili Liu; Zhimei Sun (4566-4568).
▶ We studied the structure and phase stability of Si doped on Sb2Te3 thin films. ▶ As the Si contents increases, the crystallization temperature increases. ▶ The incorporation of Si atoms into Sb2Te3 lattice is energetically unfavorable. ▶ Si atoms most probably accumulated in the boundaries of Sb2Te3 grains.The influence of Si in Sb2Te3 on structure and phase stability was studied by experiments and ab initio calculations. With the increase of Si content in Sb2Te3 samples, the crystallization temperature increases and the crystalline grain size decreases. The incorporation of Si atoms into Sb2Te3 lattice is energetically unfavorable and hence Si atoms most probably accumulated in the boundaries of Sb2Te3 grains.
Keywords: Sb2Te3; Crystallization temperature; PCRAM; Ab initio calculations;
Film morphology, orientation and performance of dodecyl/carboxyl functional polysiloxane on cotton substrates by Qiufeng An; Kefeng Wang; Yun Jia (4569-4574).
Display Omitted▶ Morphology and characterization of dodecyl/carboxyl functional polysiloxane film. ▶ Performance properties of the treated fabric by dodecyl/carboxyl functional polysiloxane. ▶ An interaction mechanism of the dodecyl/carboxyl polysiloxane with the substrates.A novel polysiloxane (RCAS) bearing dodecyl and carboxyl side groups was synthesized by reaction of a dodecyl/amino functionalized polysiloxane with maleic anhydride. Film morphology, molecular orientation and performance of the synthesized polysiloxane on cotton substrates were investigated by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray photoelectron microscope (XPS) and so on. Affected by the dodecyl and polar carboxyl side groups, RCAS formed a semi hydrophilic, macroscopic smooth but actually uneven siloxane film with many pillar-likes or small humps on the treated substrate surfaces. On the natural cotton surface, RCAS may take such an orientation to form its film that the Si-CH3, Si-C12H25 groups projected outward into air, while the carboxyl groups pointed inward to the substrate, interacting with the hydroxyls of the cotton substrates in ester and hydrogen bonds or twisted away from the negatively charged cotton fiber surface. As a result of such a film-formation, RCAS provided the treated fabric with not only a good wettability of about 22.96 s and a whiteness of 88.44°, but also an improved softness as well as thickening handle.
Keywords: Dodecyl/carboxyl polysiloxane; Film morphology; Cotton fabric; Orientation;
Bioactive coating on titanium implants modified by Nd:YVO4 laser by Edson de Almeida Filho; Alexandre F. Fraga; Rafael A. Bini; Antonio C. Guastaldi (4575-4580).
▶ ( ACP ) _ C a 10 − x H 2 x ( P O 4 ) 6 ( OH ) 2 → ( OCP ) _ C a 8 H 2 ( P O 4 ) 6 • 5 H 2 O → ( HA ) C a 10 ( P O 4 ) 6 ( OH ) 2 ( 1 ) Apatite coating was applied on titanium surfaces modified by Nd:YVO4 laser ablations with different energy densities (fluency) at ambient pressure and atmosphere. The apatites were deposited by biomimetic method using a simulated body fluid solution that simulates the salt concentration of bodily fluids. The titanium surfaces submitted to the fast melting and solidification processes (ablation) were immersed in the simulated body fluid solution for four days. The samples were divided into two groups, one underwent heat treatment at 600 °C and the other dried at 37 °C. For the samples treated thermally the diffractograms showed the formation of a phase mixture, with the presence of the hydroxyapatite, tricalcium phosphate, calcium deficient hydroxyapatite, carbonated hydroxyapatite and octacalcium phosphate phases. For the samples dried only the formation of the octacalcium phosphate and hydroxyapatite phases was verified. The infrared spectra show bands relative to chemical bonds confirmed by the diffraction analyses. The coating of both the samples with and without heat treatment present dense morphology and made up of a clustering of spherical particles ranging from 5 to 20 μm. Based on the results we infer that the modification of implant surfaces employing laser ablations leads to the formation of oxides that help the formation of hydroxyapatite without the need of a heat treatment.
Keywords: Laser ablation; Apatites; Titanium; Biomimetic method;
Instability of nanostructures patterned in polystyrene under high electric field gradients by Sergei F. Lyuksyutov; Mindaugas Rackaitis; Victoria Nedashkivska (4581-4585).
▶ Surface of polystyrene 150-nm films remains stable within 320 h. ▶ Instability of nanostructures patterned with AFM-assisted electrostatic nanolithography in annealed samples may be associated with electric charge dissipation on polystyrene surfaces. ▶ Relaxation of nanostructures in non-annealed films happens within several minutes and is accompanied by non-local surface deformations.A nanolithography technique based on the lateral displacement of electrically biased AFM tip was developed for nanostructures formation of 30–100 nm in width and 1–10 nm in height in the polystyrene (PS) films. It was demonstrated that the nanostructures patterned in annealed PS films (90K Mw) show slow exponential relaxation between 55 and 265 h depending on their size. Relaxation of the nanostructures in non-annealed films usually occurred in minutes. It was observed that in the annealed samples a negative electric charge accumulated in the areas where the nanostructures formed while in the non-annealed samples only the positive charge in exposed areas was detected using the electric force microscopy. After 320 h of monitoring under the humidity maintained between 25 and 27% it was suggested that slow dynamical changes of the nanostructures can be attributed to the negative electric charge dissipation in the annealed samples.
Keywords: Polystyrene; Atomic force microscopy; AFMEN lithography; Glass transition in polymer films;
Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces by Guotuan Gu; Yuping Tian; Zhantie Li; Dongfang Lu (4586-4588).
▶ A simple and effective method of electrostatic spraying method has been developed to create superhydrophobic coatings with very good mechanical properties. ▶ The superhydrophobic surfaces show long-term stability not only for pure water but also for corrosive liquids including acidic, basic and NaCl solutions. ▶ The superhydrophobic coatings with a water contact angle of 165° and low contact angle hysteresis of 6°.Nano-sized Al2O3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al2O3 particles in the coating. As the Al2O3 concentration in the coating was increased from 0% to 8%, WCA increased from 68° to 165°. Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.
Keywords: Nanocomposites; Surfaces; Superhydrophobicity; Electrostatic powder spraying; Polyester powder coatings;
Effect of chemical surface treatments on interfacial and electrical characteristics of atomic-layer-deposited Al2O3 films on Ge substrates by Xuefei Li; Aidong Li; Xiaojie Liu; Youpin Gong; Xiaochun Chen; Hui Li; Di Wu (4589-4592).
▶ It is found that the combination of HBr and (NH4)2S can remove more Ge–O bonds on the Ge surface compared to that of conventional HF and (NH4)2S with excellent stability. ▶ HBr and (NH4)2S-treated Ge sample has a slightly smaller roughness of 0.30 nm than HF and (NH4)2S-treated one of 0.35 nm in root-mean-square (RMS). ▶ The Al2O3 films on HBr and (NH4)2S treated Ge substrates exhibits better electrical properties such as large capacitance, decreased leakage current density by ∼two orders of magnitude, and less C–V hysteresis.The Ge surfaces were cleaned and passivated by two kinds of chemical pretreatments: conventional combination of HF + (NH4)2S, and new one of HBr + (NH4)2S. The chemical states and stability at passivated Ge surfaces were carefully characterized. The influence of chemical surface treatments on the interface and electrical properties of Al2O3 gate dielectric films on Ge grown by atomic layer deposition (ALD) has been investigated deeply. It is found that the combination of HBr and (NH4)2S can remove more Ge–O bonds on the Ge surface compared to that of conventional HF and (NH4)2S with excellent stability. X-ray photoelectron spectroscopy (XPS) reveals that HBr and (NH4)2S treated Ge surface has a mixture states of GeO x (9.25%) and GeS (7.40%) while HF and (NH4)2S treated Ge surface has a mixture states of GeO x (16.45%) and GeS (3.37%). And the Ge–S peak from the surface of Ge substrates decreases a little after the HBr and (NH4)2S treated Ge surface was exposed in the ambient for 300 min, which suggests the Ge surface is stable to oxidants. The Al2O3 films on HBr and (NH4)2S treated Ge substrates exhibits better electrical properties such as large capacitance, decreased leakage current density by ∼two orders of magnitude, and less C–V hysteresis. This indicates that a reduction in charge traps possibly at the interface and more interface traps are terminated by sulfur. The surface treatment of HBr and (NH4)2S seems to be very promising in improving the quality of high-k gate stack on Ge substrates.
Keywords: Ge substrate; Surface passivation; Hydrogen bromide; Sulfur passivation;
Effect of the incident electron fluence on the electron emission yield of polycrystalline Al2O3 by M. Belhaj; Th. Tondu; V. Inguimbert (4593-4596).
▶ Al2O3 is submitted to electron irradiation. ▶ The incident electron fluence affects the electron emission yield of Al2O3 is investigated. ▶ Recombination of the generated secondary electrons with the accumulated holes leads to the decline of the electron emission yield. ▶ Higher the electron emission yield and faster its decrease with the incident charge is.The electron emission yield due to electron impact on polycrystalline Al2O3 is measured with a technique based on the use of a Kelvin probe (KP method) and a pulsed electron beam. The KP method allows the clear discrimination between the external effects of charging and internal ones. The effect of the incident electron fluence on the yield in the region where the yield is higher than one is investigated. An overall drop of the electron emission yield with increasing the electron fluence is observed. This result is clearly associated to the internal effects of positive charging. Indeed, the recombination of the generated secondary electrons with the accumulated holes beneath the irradiated surface leads to the decrease of their mean free path and to the decay of the secondary electron emission yield.
Keywords: Secondary electrons; Electron emission yield; Insulators; Electron impact; Charging; Kelvin probe; Al2O3;
Copper nanoparticles grown under hydrogen: Study of the surface oxide by D.E. Diaz-Droguett; R. Espinoza; V.M. Fuenzalida (4597-4602).
▶ Copper nanoparticles between 10 nm and 50 nm were grown by condensation in hydrogen. ▶ The TEM examination showed single crystal particles with well-faceted shapes. ▶ The stable oxide and the main oxidation state around the nanoparticles was Cu2O.Copper nanoparticles with sizes between 10 nm and 50 nm were grown by condensation in hydrogen at pressures from 10 Pa to 1200 Pa. The crystallite size ranged from 10 nm to 25 nm using the Scherrer method. X-ray diffraction showed the reflections of metallic copper occasionally mixed with an oxidized phase (CuO or Cu2O). As shown by TEM examination, the smaller particles that did not exceed 25 nm exhibited faceted morphologies whereas the bigger ones had ovaled-spherical forms sometimes containing twins. X-ray photoelectron spectroscopy revealed that the nanoparticles consist of a copper core, completely surrounded by a Cu2O shell, which is oxidized to CuO at the surface layer.
Keywords: Copper nanoparticles; Hydrogen; Oxide; Surface; Gas condensation;
Metrological orientation-confirmation of Si(h h k) using scanning tunneling microscopy by Huiting Li; Hidong Kim; Jae M. Seo; D.L. Kendall (4603-4607).
▶ Identification of any surface orientation between (0 0 1) and (1 1 1) using STM. ▶ Orientation determination using the weighted-average method. ▶ Metrological application of STM.For the periodicity-modulation of the Si(h h k) template between (0 0 1) and (1 1 1), it is necessary to prepare the surface with any orientation within this range, most especially for fabricating useful one-dimensional nanostructures. Especially, when there are no strong X-ray signals using the standard Cu K-α source in the vicinity of any arbitrarily chosen (H H K), it turns out that the line-profile analysis on the topographic image of scanning tunneling microscopy can be a unique way for confirming the orientation of the prepared surface. Though there are a number of small-width facets on the reconstructed surface, if any of well-defined facets, such as (1 1 1), (3 3 7), (1 1 2), and (3 3 5), are included in these facets it is possible to determine the orientation using the weighted-average method.
Keywords: Scanning tunneling microscopy; Silicon; High index single;
Improved electron injection of OLEDs with a thin PBD layer at Alq3/Cs2CO3 interface by Jiarong Lian; Yawei Liu; Fangfang Niu; Pengju Zeng (4608-4611).
▶ A PBD thin layer was inserted at Alq3/Cs2CO3 interface to improve electron injection and electroluminescence efficiency of OLEDs. ▶ The mechanism for the enhanced electron injection has been studied. ▶ The profile in UV–vis absorption spectra of PBD was changed when it contacts with Cs2CO3. ▶ The nitrogen and oxygen atoms in oxadiazole moiety are likely to form coordinate bonds with cesium atoms. ▶ PBD/Cs2CO3 EIL has a potential in fabricating efficient OLEDs with low driving voltage.In this study, the effect of one oxadiazole derivative (PBD) using as an electron injection layer (EIL) at Alq3/Cs2CO3 interface has been investigated. The present of PBD EIL was showed an interesting enhanced electron injection for OLEDs although the nominal electron injection barrier for PBD based OLEDs is much larger, because PBD owns an obvious higher intrinsic the Lowest Unoccupied Molecular Orbital level (2.3 eV) than that of Alq3 (3.0 eV). For example, the current density of OLEDs at 8 V was increased from 54 mA/cm2 to 168 mA/cm2 when inserting a thin PBD layer (5 nm) at Alq3/Cs2CO3 interface. Here the increased current is suggested associating with the changed electronic structure of PBD when it contacts with Cs2CO3.
Keywords: Oxadiazole, Cesium carbonate, Electron injection mechanism, Electronic structure;
Compaction of poly(dimethylsiloxane) (PDMS) due to proton beam irradiation by Szabolcs Zoltan Szilasi; Janos Kokavecz; Robert Huszank; Istvan Rajta (4612-4615).
▶ The degree of compaction is determined by: irradiation fluence, structure distances ▶ At low fluences the topography does not follow the irradiation pattern exactly ▶ Chemical composition and/or rigidity change also occur in the irradiated regions ▶ Significant compaction occurs at the regions irradiated with high fluences ▶ Regular curvature surface can be formed for symmetric structures, e.g. microlensesThis work is about the detailed investigation of the changes of the surface topography, the degree of compaction/shrinkage and its relation to the irradiation fluence and the structure spacing in poly(dimethylsiloxane) (PDMS) patterned with 2 MeV proton microbeam. The irradiated periodic structures consisted of parallel lines with different widths and spacing. To achieve different degrees of compaction, each structure was irradiated with more different fluences. At the irradiated areas the surface topography, the adhesion, the wettability and the rigidity of the surface also changes due to the chemical/structural change of the basic poly(dimethylsiloxane) polymer. The surface topography, the phase modification of the surface, and the connection between them was revealed with using an atomic force microscope (AFM).
Keywords: Poly(dimethylsiloxane) (PDMS); Compaction; Topography; Irradiation; Proton Beam Writing (PBW);
Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment by Zhiming Li; Shiqiang Qian; Wei Wang (4616-4620).
▶ Electrophoretic deposition (EPD), a low cost technique, was shown to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. ▶ The microstructure and composition of the NiCoCrAlY coatings were characterized by XRD, SEM and EDAX, then the dispersal behavior of some elements and other characteristics were expounded. ▶ Isothermal-oxidation tests were performed at 1100 °C in static air for 100 h. The isothermal-oxidation kinetics and oxidation products of this coating were investigated.Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ′-Ni3Al phases, also there is an extremely small quantity of Al2O3 in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO2 is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.
Keywords: Oxidation; NiCoCrAlY coating; Nickel based superalloys; Electrophoretic deposition; Vacuum heat treatment;
Photoelectrocatalytic degradation of organic contaminants at Bi2O3/TiO2 nanotube array electrode by Xu Zhao; Huijuan Liu; Jiuhui Qu (4621-4624).
▶ The Bi2O3 nanoparticles were deposited onto self-organized TiO2 nanotube arrays from amorphous complex via dip-coating method. ▶ TiO2 nanotube coated by Bi2O3 nanoparticles provide a composite vertically oriented nanostructure. ▶ TiO2 nanotube coated by Bi2O3 nanoparticles exhibited high photoelectrocatalytic activities towards the degradation of organic contaminants under UV and visible light irradiation.In the current work, TiO2 nanotube array was prepared via electrochemical anode method. Then the Bi2O3 nanoparticles were deposited onto the TiO2 nanotube array via dip-coating method from an amorphous complex precursor. The crystal structures were characterized via X-ray diffraction analysis. Their surface textures were observed via electron-scanning microscope. The prepared composite array electrode exhibited high photoelectrocatalytic activities towards degrading organic contaminants under visible light irradiation. High photoelectrocatalytic activities were also exhibited under UV light irradiation. The catalytic mechanism was discussed based on the analysis of electrochemical and degradation kinetics results. It is suggested a P (Bi2O3)–N (TiO2) junction was formed to increase the catalytic activates. The stability of the electrode materials was confirmed finally.
Keywords: TiO2 nanotube array; Bi2O3; Photoelectrocatalysis; Visible light; Photocatalyst;
Olefin metathesis reaction on GaN (0 0 0 1) surfaces by Matthew S. Makowski; Dmitry Y. Zemlyanov; Albena Ivanisevic (4625-4632).
Proof-of-concept reactions were performed on GaN (0 0 0 1) surfaces to demonstrate surface termination with desired chemical groups using an olefin cross-metathesis reaction. To prepare the GaN surfaces for olefin metathesis, the surfaces were hydrogen terminated with hydrogen plasma, chlorine terminated with phosphorous pentachloride, and then terminated with an alkene group via a Grignard reaction. The olefin metathesis reaction then bound 7-bromo-1-heptene. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and water contact angle measurements following each step in the reaction scheme. The XPS data was used to qualitatively identify surface chemical species and to quantitatively determine molecular surface coverage. The bromine atom in 7-bromo-1-heptene served as a heteroatom for identification with XPS. The reaction scheme resulted in GaN substrates with a surface coverage of 0.10 monolayers and excellent stability towards oxidation when exposed to oxygen plasma.
Keywords: Gallium nitride; X-ray photoelectron spectroscopy; Olefin metathesis;
The effect of etching time on the CdZnTe surface by H. Bensalah; J.L. Plaza; J. Crocco; Q. Zheng; V. Carcelen; A. Bensouici; E. Dieguez (4633-4636).
▶ The surface quality of CdZnTe plays an important role. ▶ Chemical etching is an important step after polishing. ▶ Roughness increases the leakage current.The surface quality of CdZnTe plays an important role in the performance of sensors based on this material. In this paper the effect of chemical etching on Cd0.9Zn0.1Te sensor performance was examined. Sample surfaces were treated with the same concentration 2% Br-MeOH for different etching times (30 s, 2, 4, 6, 8 min). The surfaces were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and I–V Measurement. These results demonstrate that the best surface quality can be obtained by chemical etching for 30 s. Under these experimental conditions, the surface composition Te/Cd + Zn approaches 1, the roughness is lower than 3 nm, and the leakage current shows a value lower than 10 nA.
Keywords: Surface quality; AFM; SEM; Electrical properties; Semiconducting II–VI materials;
EBSD study of crystallographic identification of Fe–Al–Si intermetallic phases in Al–Si coating on Cr–Mo steel by Wei-Jen Cheng; Chaur-Jeng Wang (4637-4642).
▶ EBSD provides crystallographic information regardless of the content of materials. ▶ Mapping and EBSPs functions in EBSD provide a reliable phase identification. ▶ A phase constitution in the aluminide layer has been described in detail. ▶ Cubic τ5(C)-Al7(Fe,Cr)2Si and hexagonal τ5(H)-Al7Fe2Si are identified.5Cr–0.5Mo steel was coated by hot-dipping in a molten Al–10 wt.% Si bath at 700 °C for 10, 60, 120 or 180 s. The identification of the phases in the Fe–Al–Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The EDS results show a τ5(H)-Al7Fe2Si phase, which exhibited 2 distinct morphologies, small particles widely dispersed and a continuous layer. Also revealed by EDS were τ6-Al4FeSi and τ4-Al3FeSi2 phases, which showed plate-shaped morphology, in an Al–Si topcoat. However, the XRD results show the intermetallic phases in the aluminide layer were composed of outer cubic τ5(C)-Al7(Fe,Cr)2Si and inner hexagonal τ5(H)-Al7Fe2Si. EBSPs and mapping functions in EBSD helped to clarify the confused phase identifications yielded by EDS and XRD. In this way, the small intermetallic particles and the continuous intermetallic layer were identified as cubic τ5(C)-Al7(Fe,Cr)2Si and hexagonal τ5(H)-Al7Fe2Si, respectively, and the plate-shaped intermetallic phase was identified as monoclinic τ6-Al4FeSi and tetragonal τ4-Al3FeSi2 with the same metallographic morphology. EBSD proved to be a very effective technique for local phase identification of aluminide layers with complicated multiphase morphologies.
Keywords: 5Cr–0.5Mo steel; Hot-dipping; Aluminide layer; Electron backscatter diffraction; Phase identification;
Electrochemical synthesis of ZnO nanoflowers and nanosheets on porous Si as photoelectric materials by Huanhuan Kou; Xin Zhang; Yongling Du; Weichun Ye; Shaoxiong Lin; Chunming Wang (4643-4649).
▶ ZnO nanostructures, consisting of nanoflowers and nanosheets, have been successfully synthesized on porous Si (PS) by electrodeposition method. ▶ Optical band gap measurements give a band gap of 3.35 eV for the as-prepared ZnO on PS. ▶ Open circuit potential shows that ZnO grown on PS is beneficial to photoelectric applications.Well-aligned ZnO nanoflowers and nanosheets were synthesized on porous Si (PS) at different applied potentials by electrodeposition approach. The deposits were grown using the optimized program and were characterized by means of cyclic voltammetry (CV), amperometry I-t (I-t), open-circuit potentiometry. X-ray diffraction (XRD) analysis proved a strong preferential orientation (1 0 0) on PS. Scanning electronic microscopy (SEM) observation showed the deposits consist of nanoflowers with uniform grain size of about 100 nm in diameter and nanosheets, which may have potential applications in nanodevices and nanotechnologies. Thus, ZnO grown on PS can be used as photoelectric materials due to its larger photoelectric effect compared to Si wafer according to open-circuit potential (OCP) study. Optical band gap measurements were made on samples using UV–visible spectrophotometer thus giving a band gap of 3.35 eV.
Keywords: ZnO; Si; PS; Electrodeposition; OCP; Band gap;
Electrochemical albumin sensing based on silicon nanowires modified by gold nanoparticles by Dae Hoon Kwon; Hyeun Hwan An; Hee-Soo Kim; Jong Ho Lee; Sang Hee Suh; Young Ho Kim; Chong Seung Yoon (4650-4654).
Si nanowire array was modified by Au nanoparticles using a self-assembled monolayer of aminopropyltriethoxysilane (APTES) and used for direct sensing of the bovine serum albumin. It was shown that repeated thermal treatment of the sensor greatly enhanced the reliability by increasing the electrical conductivity largely from carbonization of the APTES molecules and from bringing the Au nanoparticles in intimate contact with the nanowire surface.Display Omitted▶ Si nanowire array was modified by Au nanoparticles using a self-assembled monolayer. ▶ The modified Si nanowire array was used to detect bovine serum albumin. ▶ Repeated thermal annealing improved the reliability of the Si nanowire sensor.Si nanowires (SiNWs) were modified by Au nanoparticles (AuNPs) using a self-assembled monolayer of aminopropyltriethoxysilane (APTES) and used for direct sensing of the bovine serum albumin (BSA). It was shown that repeated thermal treatment of the sensor greatly enhanced the reliability of the SiNW sensor by increasing the electrical conductivity largely from carbonization of the APTES molecules and from bringing the AuNPs in intimate contact with the SiNW surface. The AuNP-modified SiNW array sensor was able to detect 1–7 μM of BSA. The sensor exhibited a good sensitivity over the tested concentration range and linear behavior. It is expected that the proposed label-free biosensor can be further developed to selectively detect and quantify biomolecules other than BSA.
Keywords: Amperometric; Silicon nanowire; Gold nanoparticle; Albumin; APTES;
A novel one-step synthesis of mesostructured silica-pillared clay with highly ordered gallery organic–inorganic hybrid frame by Huihui Mao; Xiaoxin Gao; Jihe Yang; Baoshan Li (4655-4662).
▶ Organic–inorganic hybrid mesostructured silica-pillared clay (HSPC) has been prepared. ▶ The templates were removed by solvent extraction. ▶ The extracted materials have a high surface area and ordered gallery pore size. ▶ HSPCs were hydrophobic and acidic. ▶ The physical chemistry properties activate the HSPCs for application in catalysis, adsorption, separation chemistry and biochemistry.A new class of organic–inorganic hybrid mesostructured silica-pillared clay (HSPC) has been prepared through the surfactant directed assembly of organosilica in the galleries of montmorillonite. The surfactant templates were removed from the pores by solvent-extraction. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), nitrogen adsorption–desorption measurements, solid-state 29Si and 13C NMR, and Fourier-transform infrared (FT-IR) spectra. XRD patterns indicated a regular interstratifications of the clay layers for HSPCs. Depending on loading of phenyl groups, HSPCs had BET surface areas of 395–602 m2 g−1, pore volumes of 0.34–0.79 cm3g−1, and the framework pore sizes in the supermicropore to small mesopore range (1.3–2.6 nm). HSPCs were hydrophobic and acidic. The number of silanol groups on the surface of HSPC materials has been titrated by a surface reaction with hexamethyldisilazane, followed by quantification of the liberated NH3. Based on this method extracted HPCHs have high silanol numbers, a very important feature with respect to the amount of catalytic sites that can eventually be grafted onto the surface.
Keywords: Organic–inorganic hybrid; Silica-pillared clay; Montmorillonite; Solvent-extraction; Surface;
Study of microstructure and phase evolution of hot-dipped aluminide mild steel during high-temperature diffusion using electron backscatter diffraction by Wei-Jen Cheng; Chaur-Jeng Wang (4663-4668).
▶ EBSD provides crystallographic information regardless of the content of materials. ▶ Mapping and EBSPs functions in EBSD provide a reliable phase identification. ▶ The formation mechanism of tongue-like Fe2Al5 layer has been addressed. ▶ Serration-like substrate will be flattened by the growing FeAl2 and FeAl phases.Mild steel was coated by hot-dipping into a molten aluminum bath. The microstructure and phase evolution in the aluminide layer during diffusion at 750 °C in static air were analyzed by electron backscatter diffraction (EBSD). The results showed that the aluminide layer of the as-coated specimen consisted of an outer aluminum topcoat, minor FeAl3 and major Fe2Al5, respectively. Also, Fe2Al5 possessed a tongue-like morphology, which caused corresponding serration-like morphology in the steel substrate. A portion of the peaks of serration-like substrate were isolated, after short exposure at 750 °C, and accompanied by the formation of voids, which continued to appear with further exposure at 750 °C. As the aluminum topcoat was consumed, FeAl3 phase disappeared and left an aluminide layer of Fe2Al5 phase. After 60 min of exposure, FeAl2 and FeAl phases formed at the interface between Fe2Al5 and the steel substrate. With increasing exposure time, the voids condensed and the serration-like morphology disappeared, while FeAl2 and FeAl phases kept growing. After prolonged exposure, the aluminide layer was composed of FeAl2 and FeAl and possessed a flat interface between FeAl and steel substrate.
Keywords: Mild steel; Hot-dipping; EBSD; Aluminide layer; Tongue-like morphology;
XPS depth profiling study on the passive oxide film of carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties by P. Ghods; O.B. Isgor; J.R. Brown; F. Bensebaa; D. Kingston (4669-4677).
▶ Thickness of the oxide films formed in saturated Ca(OH)2 solution was around 4 nm. ▶ Oxide film close to the steel substrate was mainly composed of Fe2+ oxides. ▶ Oxide film near the free surface consisted mostly of Fe3+ oxides. ▶ Longer passivation time resulted in an increase in Fe2+/Fe3+ near the steel surface. ▶ Chloride addition decreased oxide thickness and Fe2+/Fe3+ near the steel surface.X-ray photoelectron spectroscopy (XPS) was used to study the properties of passive oxide film that form on carbon steel in saturated calcium hydroxide solution and the effect of chloride on the film properties. The thickness of the oxide films was determined to be approximately 4 nm and was not affected by the exposure time. Near the film/substrate interface the concentration of the Fe2+ oxides was higher than the concentration of the Fe3+ oxides; the layers near the free surface of the film mostly contained Fe3+ oxides. Chloride exposure decreased the thickness of the oxide films and changed their stoichiometry such that near the film/substrate interface Fe3+/Fe2+ ratio increased.
Keywords: Carbon steel; Passive film; Iron oxide; Concrete pore solution; Chloride; XPS;
TiO2 thick films supported on reticulated macroporous Al2O3 foams and their photoactivity in phenol mineralization by Melinda Vargová; Gustav Plesch; Ulrich F. Vogt; Miroslav Zahoran; Michal Gorbár; Karol Jesenák (4678-4684).
▶ Titania coated reticulated alumina ceramic foams as photocatalysts. ▶ Sulphated precipitated anatase and Aeroxide P25 thick films. ▶ Thick titania coatings on foams are effective photocatalysts in phenol degradation. ▶ Complete mineralization of phenol in aqueous solution under UVA light was observed.TiO2 thick films deposited on macroporous reticulated Al2O3 foams with pore size of 10 ppi and 15 ppi were prepared using dip coating from slurries of Aeroxide® P25 nanopowder and precipitated titania. All prepared films have sufficiently good adhesion to the surface of the substrate also in case of strongly cracked films. No measurable release of deposited TiO2 after repeated photocatalytic cycles was observed. The photocatalytic activity was characterized as the rate of mineralization of aqueous phenol solution under irradiation of UVA light by TOC technique. The best activity was obtained with Aeroxide® P25 coated Al2O3 foam with the pore size of 10 ppi, annealed at 600 °C. The optimal annealing temperature for preparation of films from precipitated titania could be determined at 700 °C. Films prepared by sol–gel deposition technique were considerably thinner compared to coatings made of suspensions and their photocatalytic activity was significantly smaller.
Keywords: Titanium dioxide; Macroporous Al2O3 foam; Thick film; Dip coating; Microstructure; Photocatalytic activity;
Electroluminescence of the p-ZnO:As/n-ZnO LEDs grown on ITO glass coated with GaAs interlayer by Wang Zhao; Long Zhao; Zhifeng Shi; Xiaochuan Xia; Xiangping Li; Xin Dong; Yuchun Chang; Baolin Zhang; Guotong Du (4685-4688).
▶ Prepare n-ZnO/p-ZnO:As homojunction LED by metal organic chemical vapor deposition (MOCVD). ▶ Transparent devices on ITO substrate. ▶ Use GaAs interlayer as p-type doping source.In this paper, we proposed a new p-type ZnO doping method with metal organic chemical vapor deposition (MOCVD) technology by inserting a GaAs interlayer between substrate and ZnO epitaxial layer. The doping concentration of p-type ZnO film is able to be controlled by adjusting the thickness of the GaAs interlayer. With this method, we fabricated n-ZnO/p-ZnO:As homojunction light-emitting diode (LED) on ITO-glass substrate pre-coated with 20 nm GaAs interlayer. The device exhibits a typical rectifying behavior by current–voltage (I–V) measurement. When the device is forward biased, UV–vis electroluminescence (EL) emissions can be observed clearly.
Keywords: ZnO homojunction; Arsenic; Light-emitting diode; Metal organic chemical vapor deposition;
The electrodeposition behaviors and magnetic properties of Ni–Co films by Liangliang Tian; Jincheng Xu; Chengwen Qiang (4689-4694).
▶ The ITO glasses were used as the substrate in the field of Ni–Co film. ▶ Higher Co2+ concentration causes a negative shift of the oxidation peak. ▶ The oxidation currents increase with the increase of Co2+ concentration. ▶ Structures of the heated films were specifically discussed.Ni–Co films with different compositions and microstructures were produced on ITO glasses by electrodeposition from sulphate bath at 25 °C. Cyclic voltammograms give a result that the increase in the Co2+ concentration displaces Ni–Co alloy oxidation peaks to negative potential with high Co current distributions. It is observed that the content of cobalt in the films increases from 22.42% to 56.09% as the molar ratio of CoSO4/NiSO4 varying from 0.015/0.085 to 0.045/0.055 in electrolyte. XRD patterns reveal that the structure of the films strongly depends on the Co content in the deposited films. The saturation magnetization (M s) moves up from 144.84 kA m−1 to 342.35 kA m−1 and coercivity (H c) falls from 15.27 kA m−1 to 7.27 kA m−1 with the heat treatment temperature increasing from 25 °C to 450 °C. The saturation magnetization (M s) and coercivity (H c) move up from 340.97 kA m−1 and 7.98 kA m−1 to 971.58 kA m−1 and 18.62 kA m−1 with the Co content increasing from 22.42% to 56.09% after annealing at 450.
Keywords: Ni–Co film; Electrodeposition; Heat treatment; Magnetic property;
Generation of oxygen vacancies in the surface of ferroelectric Pb(Nb,Zr,Ti)O3 by E. Ramos-Moore; D.E. Diaz-Droguett; P. Spring; J.T. Evans; A.L. Cabrera (4695-4698).
▶ Manipulation of ferroelectric domains motivates the exploration of surface reactivity ▶ Oxygen vacancies affects gas–surface interaction ▶ PNZT surface reduction was monitored by AES and XPS ▶ Temperature was not a key parameter of the process in the range of 200–300 °C ▶ Oxygen vacancies generation rates as slow as 0.21% per minute were achieved.Controlled generation of oxygen vacancies in the surface of ferroelectric thin films is crucial to study how surface reduction affects molecular adsorption and catalysis of gas–surface phenomena. We demonstrate the effective reduction in the surface of 4% niobium doped 20/80 PZT (PNZT) thin films. The sample was characterized by X-ray diffraction (XRD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), and heated at 200, 250 and 300 °C in a high vacuum system at 10−5 T of H2. Auger peak-to-peak intensities was used to study the elemental concentrations during the reduction experiment. High-resolution XPS spectra were acquired before and after reduction process for detecting the changes of the oxygen signal. Vacancies production rates as slow as 0.21% per minute were achieved and the temperature was not a key parameter in the process. Experiments at higher hydrogen pressures and lower temperatures might improve the control of the vacancies production.
Keywords: Ferroelectric thin films; Oxygen vacancies; Auger electron spectroscopy; X-ray photoelectron spectroscopy; Surface reduction;
Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition by Y. Tang; Y.S. Li; Q. Yang; A. Hirose (4699-4705).
▶ We studied α-C thin films deposited by End-Hall (EH) ion beam at 24∼48 eV. ▶ The films are smooth and uniform on a large scale and intrinsically particulate-free. ▶ The films have reasonably high hardness and Young's modulus. ▶ The hardness and Young's modulus increase with the increase of ion energy. ▶ The films may be used as protective coatings in magnetic disk storage technology.Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5–0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp3 bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.
Keywords: Amorphous carbon; End-Hall ion source; Ion beam deposition;
Fabrication of titanium dioxide nanofibers via anodic oxidation by K.P. Beh; F.K. Yam; S.S. Tneh; Z. Hassan (4706-4708).
▶ Temperature used in obtaining rutile phase earlier achived than reported. ▶ Catalytic grown rutile phase may not be stable. ▶ Rutile phase revert to anatase when calcinated at higher temperature.In this work, titanium dioxide (TiO2) nanofibers were obtained from anodic oxidation process. A piece of titanium sheet was anodized in 1.0 M sodium chloride (NaCl) solution, at 30 V. The as-anodized sample was calcinated at 400 °C for one hour. Subsequently the sample was characterized using field-emission scanning electron microscopy (FE-SEM), high resolution X-ray diffraction (HR-XRD), and Raman spectroscopy. Interestingly, results showed rutile phase dominates over anatase phase, which is rarely reported. In addition, the possible chemical reactions that lead to the formation of nanofibers were proposed. It was found that the nanofibers having an average length of 3 μm, also diameter of 83 nm.
Keywords: TiO2; Raman spectrum; Nanofibers; Rutile; Anodization;
FT-IR study of the photocatalytic degradation of gaseous toluene over UV-irradiated TiO2 microballs: enhanced performance by hydrothermal treatment in alkaline solution by Xinyong Li; Zhengru Zhu; Qidong Zhao; Shaomin Liu (4709-4714).
▶ TiO2 microballs were obtained via a hydrothermal treating of commercial P25 in alkaline solution. ▶ A blue-shifted SPV threshold edge was observed for the TiO2 microballs. ▶ The TiO2 microballs were more active than P25 in photocatalytic oxidation of gaseous toluene.In this study, photocatalysts of TiO2 microballls were obtained via a hydrothermal treating of commercial P25 in alkaline solution, and then characterized with SEM, XRD, BET, DRS and surface photovoltage spectroscopy (SPS) techniques. The photovoltage response of the prepared TiO2 microballs on spectrum features a quantum size effect brought about by the reduced grain size with respect to the precursor. The UV-assisted photodegradation of gaseous toluene over P25 and the prepared TiO2 microballs was monitored by an in situ infrared technique. The results demonstrated that the prepared TiO2 microballs in anatase form were more active than commercial P25 in photocatalytic oxidation of gaseous toluene. The promoted activity of the hydrothermal-treated TiO2 is attributed to the increasing specific surface area and larger band gap induced by the reduced crystallite size.
Keywords: TiO2 microballs; Toluene; Photocatalytic oxidation; Surface photovoltage; In-situ FT-IR;
In-situ bridging of SnO2 nanowires between the electrodes and their NO2 gas sensing characteristics by Byeong-Guk Kim; Dong-Gun Lim; Jae-Hwan Park; Young-Jin Choi; Jae-Gwan Park (4715-4718).
▶ A simple and efficient way of making highly sensitive SnO2 nanowire-based gas sensors without an individual lithography process was proposed. ▶ The SnO2 nanowires network was floated upon the substrate by separating the Au catalyst. ▶ As the electric current is transported along the networks of the nanowires, the gas sensitivities could be maximized in this networked and floated structures.A simple and efficient way of making highly sensitive SnO2 nanowire-based gas sensors without an individual lithography process was studied. The SnO2 nanowires network was floated upon the Si substrate by separating the Au catalyst layer from the substrate. As the electric current is transported along the networks of the nanowires, not along the surface layer on the substrate, the gas sensitivities could be maximized in this networked and floated structures. The sensitivity was 5–30 when the NO2 concentration was 1–10 ppm. The response time was ca. 20–60 s.
Keywords: Nanowires; SnO2; Gas sensor; NO2;
Synthesis and characterization of polyurethane/SiO2 nanocomposites by Xiaoyan Gao; Yanchao Zhu; Xu Zhao; Zichen Wang; Dongmin An; Yuejia Ma; Shuang Guan; Yanyan Du; Bing Zhou (4719-4724).
▶ Surface modification of SiO2 nanoparticles with PPG-P. ▶ Good dispersion of SiO2 nanoparticles in PU matrix. ▶ Preparation of PU/SiO2 nanocomposites with higher performance via in situ polymeration.In order to achieve good dispersion of nano-SiO2 and increase the interactions between nano-SiO2 and PU matrix, nano-SiO2 was firstly modified with poly(propylene glycol) phosphate ester (PPG-P) which was a new polymeric surfactant synthesized through the esterification of poly(propylene glycol) (PPG) and polyphosphoric acid (PPA). Then a series of polyurethane (PU)/SiO2 nanocomposites were prepared via in situ polymerization. The surface modification of nano-SiO2, the microstructure and the properties of nanocomposites were investigated by FTIR, SEM, XRD and TGA. It was found that good dispersion of nano-SiO2 achieved in PU/SiO2 nanocomposite after the modification with PPG-P. The segmented structures of PU were not interfered by the presence of nano-SiO2 in these nanocomposites.
Keywords: Nano-SiO2; Phosphate ester; Surface modification; Polyurethane; Nanocomposite; Dispersion;
Aerosol-assisted flow synthesis of W x Ti1−x O2 solid solution spheres with enhanced photocatalytic activity by Zhihui Ai; Xiao Song; Yu Huang; Lizhi Zhang; Shuncheng Lee (4725-4730).
▶ W x Ti1−x O2 solid solutions (x = 0.000, 0.005, 0.010, 0.015, and 0.020) microspheres were synthesized with an aerosol-assisted flow synthesis method. ▶ These solid solutions exhibited higher photocatalytic activities on degradation of RhB than pure TiO2.In this paper, W x Ti1−x O2 solid solutions (x = 0.000, 0.005, 0.010, 0.015, and 0.020) microspheres were synthesized with an aerosol-assisted flow synthesis method. The resulting samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, UV–vis diffuse reflectance spectrum (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the as-prepared catalysts were measured by the degradation of rhodamine B (RhB) under visible light irradiation (λ ≥ 420 nm). All the solid solutions exhibited higher photocatalytic activities than pure TiO2 and the W0.015Ti0.985O2 solid solution possessed the highest photocatalytic activity. The degradation constant of RhB on W0.015Ti0.985O2 solid solution catalyst was about 15 times of that of the pure TiO2 and 25 times of that of Degussa P25, respectively. This study provides an effective method to prepare visible light photocatalysts on a large scale.
Keywords: Photocatalysis; Solid solution; Tungsten; TiO2;
Hybrid surface from self-assembled layer and its effect on protein adsorption by Lalit M. Pandey; Sudip K. Pattanayek (4731-4737).
▶ Silica surfaces is modified with hybrid self assembled monolayer. ▶ The adsorption of BSA on the hybrid and mixed mono-layers follows Langmuir adsorption isotherm. ▶ The adsorbed amount and elasticity of the adsorbed BSA is lesser on the hybrid surface.We synthesized hybrid self-assembled monolayer (SAM) with short chain hydrophobic and hydrophilic groups on the same molecule. The physical characteristics such as surface roughness and surface energy of the synthesized hybrid SAM were compared with mono SAMs of amine, octyl and mixed amine-octyl SAM. We also compared the response of the surfaces towards adsorption of bovine serum albumin (BSA) using quartz crystal microbalance (QCM). We determined adsorbed amount (Γ) of BSA on the various surfaces from its various bulk concentrations. It follows the Langmuir adsorption isotherm in the concentration range of our study. The strength of adsorbed protein was characterized from the dissipation factor (ΔD). The highest ΔD value of adsorbed BSA was observed for the adsorption on hybrid surface. The arrangement of BSA on hybrid surface such that it leaded to soft layer, corresponded to the highest ΔD value. These findings suggest that the hybrid surface is a potential surface modifying agent of biomaterials.
Keywords: SAMs; Contact angle; QCM; Protein adsorption;
Structure and hardness of a-C:H films prepared by middle frequency plasma chemical vapor deposition by Guangwei Guo; Guangze Tang; Yajun Wang; Xinxin Ma; Mingren Sun; Liqin Wang; Ken Yukimura (4738-4742).
▶ The effect of precursors of CH4 and C2H2 + H2 on the structure of a-C:H films is investigated. ▶ The a-C:H films from CH4 precursor is DLCH, while for C2H2 + H2 precursors is PLCH. ▶ These two types a-C:H films show also opposite evolution trends with bias voltage increasing.a-C:H films were prepared by middle frequency plasma chemical vapor deposition (MF-PCVD) on silicon substrates from two hydrocarbon source gases, CH4 and a mixture of C2H2 + H2, at varying bias voltage amplitudes. Raman spectroscopy shows that the structure of the a-C:H films deposited from these two precursors is different. For the films deposited from CH4, the G peak position around 1520 cm−1 and the small intensity ratio of D peak to G peak (I(D)/I(G)) indicate that the C–C sp3 fraction in this film is about 20 at.%. These films are diamond-like a-C:H films. For the films deposited from C2H2 + H2, the Raman results indicate that their structure is close to graphite-like amorphous carbon. The hardness and elastic modulus of the films deposited from CH4 increase with increasing bias voltage, while a decrease of hardness and elastic modulus of the films deposited from a mixture of C2H2 + H2 with increasing bias voltage is observed.
Keywords: a-C:H films; MF-PCVD; Structure; Hardness; Elastic modulus;
Comparison of anti-corrosion properties of polyurethane based composite coatings with low infrared emissivity by Yajun Wang; Guoyue Xu; Huijuan Yu; Chen Hu; Xiaoxing Yan; Tengchao Guo; Jiufen Li (4743-4748).
▶ Influences of different resins on the anti-corrosion properties of low infrared emissivity coatings are proposed and researched which have not been discussed before. ▶ The anti-corrosion mechanisms of the coatings with different resins are analyzed in detail. ▶ The conclusion that the introduction of epoxy group and atomic fluorine can highly improve the corrosion resistant properties of the low infrared emissivity is obtained which establishes a foundation of later researches.Four polyurethane resins, pure polyurethane (PU), epoxy modified polyurethane (EPU), fluorinated polyurethane (FPU) and epoxy modified fluorinated polyurethane (EFPU), with similar polyurethane backbone structure but different grafting group were used as organic adhesive for preparing low infrared emissivity coatings with an extremely low emissivity near 0.10 at 8–14 μm, respectively. By using these four resins, the effect of different resin matrics on the corrosion protection of the low infrared emissivity coatings was investigated in detail by using neutral salt spray test, SEM and FTIR. It was found that the emissivity of the coatings with different resin matrics changes significantly in corrosion media. And the results indicated that the coating using EFPU as organic adhesive exhibited excellent corrosion resistance property which was mainly attributed to the presence of epoxy group and atomic fluorine in binder simultaneously.
Keywords: Corrosion resistance; Polyurethane; Epoxy group; Atomic fluorine; Low infrared emissivity coating;
Role of cleaning methods on bond quality of Ti coated glass/imidex system by Nusrat Lubna; Gregory Auner; Rahul Patwa; Hans Herfurth; Golam Newaz (4749-4753).
▶ Two cleaning methods are used for cleaning glass wafer: (i) regular cleaning and (ii) special cleaning. ▶ We observed significant contamination removal for samples prepared by special cleaning method. ▶ Good bond strengths are also obtained for the samples prepared by special cleaning method compared to regular cleaning method.Thin film materials are widely used in the fabrication of semiconductor microelectronic devices. In thin film deposition, cleanliness of substrate surface have become critically important as over 50% of yield losses in integrated circuit fabrication are caused by microcontamination . There are many wafer cleaning techniques. The most successful approach for silicon wafer cleaning technique is RCA clean . But for glass substrate it is still not known which procedure of cleaning is the best. This paper provides an understanding of the right way of glass wafer cleaning method, with a focus towards identifying good bond strength. Two wafer cleaning techniques have been used for cleaning glass substrates in the context of laser micro-joining of dissimilar substrates. First cleaning procedure involves two steps, first cleaning in acetone solution and then in DI water solution. After each step dried with N2. Second cleaning procedure involves four steps, first cleaning with 1% Alconox solution, second in DI water, third in acetone solution and finally in a methanol solution and dried with N2 after each step. Deposition of Ti thin film on top of these two types of substrate using DC magnetron sputtering method also showed better adhesion of Ti film on glass for the second type of cleaning method. Scanning electron microscopy (SEM) analyses of the lap shear tested failed surfaces for these two kinds of samples revealed strong bond for samples prepared by second cleaning method compared to first cleaning method. Characterization of these two sets of samples using X-ray photoelectron spectroscopy (XPS) has shown excellent contamination removal for the second cleaning method. This modification is believed to be due to reduction of carbon contamination.
Keywords: Thin film deposition; Wafer cleaning; Bond strength; Scanning electron microscopy (SEM); X-ray photoelectron spectroscopy (XPS); Carbon contamination;
Removal and recovery of mercury from aqueous solution using magnetic silica nanocomposites by Bo Yune Song; Yujin Eom; Tai Gyu Lee (4754-4759).
▶ CoFe2O4 nanoparticles were synthesized and grown to 13 nm in size. ▶ Core of the CoFe2O4 nanoparticles was treated with PVA and coated with silica. ▶ For Hg adsorption, pores were created and surfaces were reformed into thiol groups. ▶ Amount of Hg adsorbed by magnetic silica nanocomposite was 19.79 mg Hg/g of adsorbent.Thiol-functionalized magnetic silica nanocomposite was synthesized and tested for its mercury pick-up capability in aqueous solution. Magnetic property was to be utilized upon the collection of the adsorbents and the recovery adsorbed Hg by subsequent separation process. Cobalt ferrite nanoparticle, the core of magnetic silica nanocomposite, was synthesized using a thermal decomposition method and grown to a particle having an average size of 13 nm. The dispersed nanoparticles were then further arranged into spherical groups using a nanoemulsion method to enhance the reactivity toward magnets followed by tetraethyl orthosilicate coating using a modified Stöber method. The pore structure was modified by an additional coating of cetyltrimethylammonium bromide and tetraethyl orthosilicate. Finally, the surface of the magnetic silica nanocomposite was functionalized with thiol group. When tested for mercury adsorption capacity, a sufficiently high Hg adsorption capacity of 19.79 mg per g of adsorbent was obtained at room temperature and a pH of 5.5.
Keywords: Cobalt ferrite; Silica-CoFe2O4; Magnetic silica nanocomposite; Thiol; Mercury;
Ablative property of HfC-based multilayer coating for C/C composites under oxy-acetylene torch by Yong-Jie Wang; He-Jun Li; Qian-Gang Fu; Heng Wu; Dong-Jia Yao; Bing-Bo Wei (4760-4763).
To improve ablation resistance of C/C composites, HfC-based coating and SiC coating were prepared on the surface of C/C composites by chemical vapor deposition. The coating exhibits dense surface and outstanding anti-ablation ability. Compared with uncoated C/C, the linear and mass ablation rates of the coated C/C decreased by 33.3% and 66.7%, respectively, after ablation for 20 s. The residual oxides can prevent oxygen from diffusing inwardly; large amounts of heat can be taken away by the gas generated during ablation, which is also helpful for protection.
Keywords: Ablation; HfC; C/C composites; Chemical vapor deposition;