Bimetallic Au@M (M = Ag, Pd, Fe, and Cu) Nanoarchitectures Mediated by 1,4-Phenylene Diisocyanide Functionalization.

Hybridization with gold has attracted a lot of attention in many application areas such as energy, nanomedicine, and catalysts. Here, we demonstrate electrochemical hybridization of two different metals by using bare and 1,4-phenylene diisocyanide (PDI) functionalized gold nanoislands (GNIs) supported on a Si substrate. As pristine GNIs are not tightly locked on the Si surface, bimetallic Au@M (M = Ag, Pd, Fe, and Cu) core-shell type nanostructures are produced by an electric-field-induced clustering of GNIs and metal deposition. On the other hand, upon functionalization of GNIs by PDI, 3D island growth on the functionalized GNI template is observed as PDI acts as a protector against the electric-field-induced clustering. Depth-profiling X-ray photoelectron spectroscopy reveals no discernible difference in the interfacial electronic structures of hybrid metals prepared by using pristine and PDI-functionalized GNI templates. This work demonstrates a new approach to produce a secured template and to manipulate growth of hybrid nanoparticles on this template supported on a Si substrate by using electrodeposition and organic functionalization.

White and Tunable Emission from and Rhodamine B Detection by Modified Zinc Oxide Nanowalls.

To gain better optical and optoelectrical properties, doping trivalent lanthanide cations into host materials is a very attractive approach in nanoscience. Here, we use a transparent conducting oxide, zinc oxide, as the host material to directly embed trivalent terbium cations without the need for any postgrowth treatment, and we investigate the photophysical effect of the dopant. Trivalent Tb cations embedded in ZnO nanowalls produce hypersensitive green emission (at 545 nm, corresponding to the 5D4 → 7F5 transition) and convert the emission color of ZnO from yellow into white. Evidently, the photoluminescence emission intensity of Tb(III) is further increased by close to 10-fold due to the plasmonic effect introduced by noble metal (Ag and Pt) nanoparticles. The characteristic Tb(III) emission is found to be tunable from white to red and is examined for its potential chemosensing application for rhodamine B involving a plausible cascade energy transfer mechanism from ZnO to rhodamine B via Tb(III) cations.

Defect-Rich Dopant-Free ZrO2 Nanoclusters and Their Size-Dependent Ferromagnetism.

As an intermediate form of matter between a single atom or molecule and the bulk, nanoclusters (NCs) provide novel properties because of their high surface area-to-volume ratios and distinct physical and electronic structures. These ultrasmall NCs offer a new approach to advance charge-spin manipulation for novel devices, including spintronics and magnetic tunneling junctions. Here, we deposit monosized ZrO2 NCs over a large area by using gas-phase aggregation followed by in situ size selection by a quadrupole mass filter. These size-specific NCs exhibit sub-oxide photoemission features at binding energies that are dependent on the cluster size (from 3 to 9 nm), which are attributed to different oxygen vacancy defect states. These dopant-free ZrO2 NCs also show strongly size-dependent ferromagnetism, which provides distinct advantages in solubility and homogeneity of magnetism when compared to traditional dilute magnetic semiconductors. A defect-band hybridization-induced magnetic polaron model is proposed to explain the origin of this size-dependent ferromagnetism. This work demonstrates a new protocol of magnetization manipulation by size control and promises potential applications based on these defect-rich size-selected NCs.

Poly(dimethyl siloxane) membrane for high temperature proton exchange membrane fuel cells.

Sulfonic acid-based membrane gives the relatively high conductivity only in the presence of water, but phosphoric acid presents the relatively high proton conductivity without water because of its self dissociation natures to develop high temperature PEMFCs. We synthesized the thermostable material that has phosphorous groups based on poly(dimethyl siloxane) (PDMS). PDMS, which is intrinsically hydrophobic was modified to be amphiphilic by substituting end groups with hydrophilic phosphorous groups. Phase separation resulted in forming the proton conducting channels. The membranes maintained the constant proton conductivity above 130 degrees C under dry conditions. Also they were thermally stable up to 300 degrees C and may be used as high temperature proton conducting membrane at low humid conditions.

Characterization of Nafion/zirconium sulphophenyl phosphate nanocomposite membrane for direct methanol fuel cells.

Layered structure zirconium sulphophenyl phosphate (ZrSPP) was prepared from the precipitation of Zr4+ ion and m-sulphophenyl phosphonic (SPP) acid at a mole ratio of P to Zr = 2.0. The reflective index measurement indicated that the methanol permeability of unmodified Nafion 117 was 2.3 x 10(-6) cm2/s at RT while that of the Nafion/ZrSPP membrane (approximately 50 micro/m thick) decreased to 6.5 x 10(-7) cm2/s. Nafion/ZrSPP (10 wt%) nanocomposite membranes delivered constant power output 104 mW/cm2 at 0.4 V under 1 M MeOH/dry air at 70 degrees C even in the wide range of air stoichiometry from 1.5 to 3.0.

Blue-Light-Emitting Photostable Hybrid Films for High-Efficiency Large-Area Light Converter and Photonic Applications.

A blue fluorophore of Schiff base zinc complex is prepared by a hydrolysis-free solution-based synthetic method. Under ultraviolet (UV) excitation, the complex produces blue emission with a quantum yield ( Q) of 42.6% in methylene chloride and 24.0% in standalone powder form. Quantum mechanical calculations show that the blue emission is generated by the change in the chemical state of the ligand associated with the complexation with Zn cations. Thin films of Zn complexes incorporated in polymethylmethacrylate (PMMA) and cellulose acetate butyrate (CAB) polymers are also prepared by dispersing the complexes into the polymer matrices. These hybrid polymer films exhibit several notable features, particularly enhanced luminescence efficiency (with maximum Q of 85.8% for PMMA and 30.0% for CAB) and scalability for fabrication over a large area while retaining the original properties of the host polymers. Light-emitting diodes are also fabricated using the CAB hybrid thin films, and they show a Q of 43.2% with excellent photostability. The complex and its hybrid films demonstrate their great potential for such applications as UV-to-blue conversion devices in photoelectronics, solar-cell concentrators, solid-state lighting and display, and greenhouse agriculture.

Highly Conducting Hybrid Silver-Nanowire-Embedded Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) for High-Efficiency Planar Silicon/Organic Heterojunction Solar Cells.

Embedding nanowires, such as silver nanowires (AgNWs), in a transparent conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to enhance its conductivity is technologically important for improving the performances of devices comprising transparent conductive layers. Addition of nanowires in the highly conducting form of cosolvent (ethylene glycol) or mixed-cosolvent (ethylene glycol and methanol) modified PEDOT:PSS could change the nanowire structure and significantly alter the conductivity. Here, we report a simple method to embed AgNWs in PEDOT:PSS efficiently to improve its conductivity. By incorporating nanowires in the mixed cosolvent matrix prior to addition into PEDOT:PSS, this method preserves the structure of the nanowires while enabling conductivity enhancement. In contrast, the addition of AgNWs into cosolvent-premodified PEDOT:PSS leads to breaking of nanowires and conductivity impediment. The hybrid films with efficiently embedded AgNWs and mixed-cosolvent-modified PEDOT:PSS show a sheet resistance of 104 Ω/□, which is among the lowest ever reported for the as-deposited films, with conductivity enhancement of 33% relative to that of mixed-cosolvent-modified PEDOT:PSS. The resulting planar heterojunction solar cell (HSC) based on AgNW-embedded PEDOT:PSS exhibits a power conversion efficiency of greater than 15%. This demonstrates the importance of reducing sheet resistance by integrating nanowires into the PEDOT:PSS matrix as effective charge-transfer conduits interconnecting the highly conducting quinoid chains. The present approach to efficiently embed AgNWs in PEDOT:PSS could be readily extended to other nanowires or nanoparticles for improving the performance of PEDOT:PSS for applications in not just HSCs but indeed other electronic devices that require both transparent and highly conductive layers.

IFN-gamma regulates the expression of B7-H1 in dermal fibroblast cells.

BACKGROUND: Programmed cell death ligand 1 (B7-H1) was recently cloned in antigen presenting cells (APCs) and represents a third member of the B7 family. Thus, B7-H1 may be a novel target for clinical intervention in human inflammatory disease. OBJECTIVE: The aim of this study is to investigate the signal transduction mechanism and transcriptional regulation of B7-H1 expression in human dermal fibroblasts. METHODS: We performed reverse transcription PCR (RT-PCR) for the detection of mRNA expression, luciferase reporter assays with B7-H1 promoter constructs, and Western blot analysis. RESULTS: From RT-PCR analysis, IFN-gamma can induce the expression of B7-H1 mRNA in dermal fibroblast. This expression is similar to the results of luciferase reporter assay with B7-H1 promoter. Western blot analysis and EMSA revealed that NF-kappaB transcription factors mediate the induction of B7-H1 expression via the transient phosphorylation of ERK1/2 and PI3K when cells are stimulated by IFN-gamma. Also, Specific destruction of the NF-kappaB binding site abolished the induction of the promoter activity by IFN-gamma. CONCLUSION: Our data not only provides the first evidence to demonstrate that dermal fibroblast express the B7-H1 mRNA in the process of skin inflammation, but also suggests the involvement of NF-kappaB and MAPK and PI3K, that may play some important roles in inflammation process in human skin diseases.

Reversible structural transformation and enhanced performance of PEDOT:PSS-based hybrid solar cells driven by light intensity.

Hybrid solar cells made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT: PSS) and appropriate amounts of a cosolvent and a fluorosurfactant on planar n-type silicon substrates showed a photoconversion efficiency (PCE) of above 13%. These cells also exhibited stable, reproducible, and high external quantum efficiency (EQE) that was not sensitive to light-bias intensity (LBI). In contrast, solar cells made of pristine PEDOT: PSS showed low PCE and high EQE only under certain measurement conditions. The EQE was found to degrade with increasing LBI. Here we report that the LBI-sensitive variation of EQE of the low-PCE cells is related to a reversible structural transformation from a quinoid to a benzoid structure of PEDOT.