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Roles of metal nanoparticles (NPs) on graphene-based devices were investigated in terms of gas-sensing characteristics of NO2 and NH3, and flexible gas sensing was also realized for future applications. The synergistic combination of metal NPs and graphene modulates the electronic properties of graphene, leading to enhancement of selectivity and sensitivity in gas-sensing characteristics. Introduction of palladium (Pd) NPs on the graphene accumulates hole carriers of graphene, resulting in the gas sensor being sensitized by NH3 gas molecular adsorption. In contrast, aluminum (Al) NPs deplete hole carriers, which dramatically improves NO2 sensitivity. Furthermore, the sensitivity of flexible graphene-based gas sensors was also enhanced via the same approach, even after 104 bending cycles and was maintained after 3 months. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA)-containing polymers have been proposed for improving the biological properties of bone cements. Poly(methyl methacrylate) (PMMA) has long been used to secure orthopedic implants to skeletal bones. The aim of this study was to determine whether the incorporation of HA nanoparticles into the PMMA nanofibrous scaffolds enhances the biological functions of osteoblasts. The number of os-teoblasts adhered and proliferated on the PMMA/HA nanofibrous scaffolds was significantly larger than that on the PMMA alone. The cytoskeletal organization and alkaline phosphatase (ALP) activity of the osteoblasts on the PMMA/HA nanofibrous scaffolds were clearly higher than that on the PMMA con-trol. The amount of calcium ions released from 20 wt% HA-containing PMMA nanofibrous scaffolds (PMMA/HA20) was much higher than that released from 10 wt% HA-containing PMMA nanofibrous scaffolds (PMMA/HA 10) (HA, 10 wt%). These findings suggested that osteoblast differentiation was ac-celerated by the incorporation of HA into the PMMA nanofibrous scaffolds. Therefore, the incorporation of HA into the PMMA nanofibrous scaffolds could be a useful method. This can be used for providing PMMA scaffolds with enhanced osteogenic properties. [ABSTRACT FROM AUTHOR]

Composite nanofiber mats (HA/TiO2) consisting of hydroxyapatite (HA) and titania (TiO2) were fabricated via an electrospinning technique and then collagen (type I) was immobilized on the surface of the HA/TiO2 composite nanofiber mat to improve tissue compatibility. The structure and morphology of the collagen‐immobilized composite nanofiber mat (HA/TiO2‐col) was investigated using an X‐ray diffractometer, electron spectroscopy for chemical analysis, and scanning electron microscope. The potential of the HA/TiO2‐col composite nanofiber mat for use as a bone scaffold was assessed by an experiment with osteoblastic cells (MC3T3‐E1) in terms of cell adhesion, proliferation, and differentiation. The results showed that the HA/TiO2‐col composite nanofiber mats possess better cell adhesion and significantly higher proliferation and differentiation than untreated HA/TiO2 composite nanofiber mats. This result suggests that the HA/TiO2‐col composite nanofiber mat has a high‐potential for use in the field of bone regeneration and tissue engineering. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. [ABSTRACT FROM AUTHOR]

Background: In oral implantology there has been a general trend away from machine-turned minimally rough and acid-etched and blasted implants toward intermediary roughened surfaces. Mechanical interlocking at micron resolution is claimed to be the dominant reason for the fixation of such implants in bone. However, clinical demands for stronger and faster bone bonding to the implant (eg, in immediately loaded and compromised bone cases) have motivated the development of novel surfaces capable of chemical bonding. Purpose: The purpose of the present study is to investigate bone tissue reactions to a newly developed calcium-incorporated oxidized implant. The specific aim is to assess the effect of calcium surface chemistry on the bone response. Materials and Methods: Calcium (Ca) ion-incorporated implants were prepared by micro arc oxidation methods. Surface oxide properties were characterized by using various surface analytic techniques involving scanning electron microscopy, x-ray diffractometry, x-ray photoelectron spectroscopy, and optical interferometry. Twenty screw-shaped commercially pure (CP) titanium implants (10 turned implants [controls] and 10 Ca-incorporated implants [tests]) were inserted in the femoral condyles of 10 New Zealand White rabbits. Results: After a healing period of 6 weeks, resonance frequency analyses and removal torque measurements of the Ca-incorporated oxidized implants demonstrated statistically significant improvements of implant integration with bone in comparison to machine-turned control implants (p = 0.013 and p = 0.005, respectively). Conclusions: The Ca-reinforced surface chemistry of the oxidized implants significantly improved bone responses in a rabbit model. The present study suggests that biochemical bonding at the bone-implant interface, in combination with mechanical interlocking, may play a dominant role in the fixation of Ca-incorporated oxidized implants in bone. The observed rapid and strong integration of test C... [ABSTRACT FROM AUTHOR]

Aluminum-doped zinc oxide (AZO) films (70 nm thick) with dissimilar surface roughness were created on indium tin oxide coated glass and were used as electrodes for inverted organic solar cells. The photovoltaic performance of the devices depended strongly on the surface roughness of the AZO films. Increases in the surface root-mean-square roughness of AZO films from 2.5 to 10.9 nm enhanced power conversion efficiency from 0.5% to 1.4% due to increased contact area between electrode and active layer. [ABSTRACT FROM AUTHOR]

Anodic aluminum oxide (AAO) templates were fabricated by anodizing Al films. After the Co catalyst had been electrochemically deposited into the bottom of the AAO template, carbon nanotubes (CNTs) were grown by the catalytic pyrolysis of C[sub 2]H[sub 2] at 650 °C. Overgrowth of CNTs on the AAO templates was observed. The diameter of the CNTs strongly depends on the size of the pores in the AAO template. The electron field emission measurements on the samples showed a turn-on field of 1.9-2.1 V/μm and a field enhancement factor of 3360-5200. Our observation concerning the low turn-on field and high field enhancement factors is explained in terms of a low field screening effect. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules. [ABSTRACT FROM AUTHOR]

This work describes the preparation of a doped layer-free hydrogenated amorphous silicon (a-Si:H) thin film solar cell consisting of a vanadium pentoxide (V2O5-x) window layer, an intrinsic a-Si:H absorber layer, and a lithium fluoride (LiF)/aluminum (Al) back electrode. The large difference between the work functions of the V2O5-x layer and the LiF/Al electrode permitted photogenerated carriers in the i-a-Si:H absorber layer to be effectively separated and collected. The effects of the V2O5-x layer thickness and the oxidation states on the photovoltaic performance were investigated in detail. X-ray photoelectron spectroscopy analysis confirmed that the major species of the sputtered V2O5-x thin films were V5+ and V4+. Optimization of the V2O5-x window layer yielded a power conversion efficiency of 7.04%, which was comparable to the power conversion efficiency of a typical a-Si:H solar cell (7.09%). [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) films under in situ hydrogen plasma were deposited via atomic layer deposition (ALD) at an extremely low temperature (100 °C). Diethyl zinc ((C2H5)2Zn) and deionized water were used as the zinc and oxygen source, respectively. The growth rate of the ZnO films decreased to 1.26 and 1.06 Å/cycle due to changes in the hydrogen plasma treatment power and exposure time, respectively. The resistivity of the ZnO films decreased to 7.6 × 10-4 Ω cm, even at 100 °C, with a very high carrier concentration (1.4 × 1021 cm-3) due to the increasing oxygen deficiencies in the ZnO films. The carrier mobility was decreased slightly to 8.6 cm2/Vs via grain boundary scattering due to the enhanced polycrystallization. Based on the x-ray diffraction and x-ray photoelectron spectroscopy, the carrier concentration and mobility were strongly correlated to the oxygen deficiency and crystallinity, respectively. In addition, the in situ hydrogen plasma in the ZnO ALD had an important role in sequentially generating oxygen deficiencies and enhancing polycrystal growth. [ABSTRACT FROM AUTHOR]

The effect of temperature/humidity treatment conditions on the interfacial adhesion energy between an electroless-plated Ni film and a polyimide substrate was evaluated by using a 180° peel test. The measured peel strength values decrease from 506.1 ±18.6 to 231.9 ±33.3 J/m2 due to the temperature/humidity treatment at 85 °C/85% relative humidity for 1000 h. X-ray photoelectron spectroscopy analysis of the peeled surfaces indicates that peeling occurs cohesively inside of the polyimide; this is related to both the decrease in the interfacial adhesion energy and the polyimide degradation when small quantities of the remaining alkali ions react with the polyimide's functional groups during the temperature/humidity treatment. [ABSTRACT FROM AUTHOR]

How KOH and ethylenediamine (EDA) pretreatment conditions on polyimide film surfaces affect the interfacial adhesion energy between electroless-plated Ni and polyimide film was investigated by the 180° peel test. Estimated values of interfacial adhesion energy monotonically increase from 240.3 to 326.0 J/m2 by increasing the KOH treatment time from 1 to 5 min, and they monotonically decrease from 310.2 to 219.0 J/m2 by increasing the EDA treatment time from 1 to 5 min. It was found that chemical pretreatment produces carboxyl bonding, which is closely related to the strong interfacial bonding mechanism and leads to cohesive failure. Finally, it is speculated that the interfacial adhesion energy seems to be controlled by carboxyl bonding on polyimides surface during KOH and EDA treatment. [ABSTRACT FROM AUTHOR]

Abstract: Micro-arc oxidation method is a useful process for mesoporous titanium dioxide films. In order to improve the photocatalytic activity of the TiO2 film, N–Eu co-doped titania catalyst was synthesized by micro-arc oxidation in the H2SO4/Eu(NO3)3 mixture solution. The specific surface area and the roughness of the anodic titania film fabricated in the H2SO4/Eu(NO3)3 electrolyte, were increased compared to that of the anodic TiO2 film prepared in H2SO4 solution. The absorbance response of N–Eu titania film shows a higher adsorption onset toward visible light region, and the incorporated N and Eu ions during anodization as a dopant in the anodic TiO2 film significantly enhanced the photocatalytic activity for dye degradation. After dye decomposition test for 3h, dye removal rates for the anodic TiO2 film were 60.7% and 90.1% for the N–Eu doped titania film. The improvement of the photocatalytic activity was ascribed to the synergistic effects of the surface enlargement and the new electronic state of the TiO2 band gap by N and Eu co-doping. [Copyright &y& Elsevier]

Abstract: We investigated the effects of hydrogen plasma treatment on the physical and electrical properties of fluorine-doped tin oxide (FTO) films used for amorphous silicon (a-Si) thin film solar cells. A slight increase in carrier concentration by the hydrogen doping effect was observed for the FTO film exposed to the hydrogen plasma for 5 min. For further exposure to the plasma, the chemical reduction became prominent and resulted in deterioration of the electrical and optical properties of the film. XPS analysis revealed that the chemical reduction of SnO2 to Sn metallic state occurs on the surface region. It was found that the defects formed by hydrogen plasma act as recombination centers at the interface between FTO electrode and p-layer of a-Si solar cells. This phenomenon resulted in the deterioration of the cell performance. The averaged conversion efficiency (6.82%) of the cells on pristine FTO hydrogen substrate was decreased to 5.81% for the cells on FTO treated for 5 min, which is mainly attributed to the decrease in short-circuit current density. [Copyright &y& Elsevier]

Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens. Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices. Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent. Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties. However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture, and poor adhesion to substrates. These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized. In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix. This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode.