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UV Illumination (uv + illumination)
Selected AbstractsElectrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Jong G. Ok Abstract The fabrication and characterization of hybrid architectures of ZnO nanowires (ZNWs) grown on organized carbon nanotubes (CNTs), by a two-step chemical vapor deposition (CVD) process involving CNT growth from a hydrocarbon source followed by ZNW growth using a Zn metal source, is reported. The ZNWs grow uniformly and radially from individual CNTs and CNT bundles, and the aligned morphology of the CNTs is not disturbed by the ZNW growth process. The nucleation and growth of ZnO crystals on CNTs are analyzed in relation to the classical vapor,solid mechanism. Importantly, the CNTs make uniform and distributed electrical contact to the ZNWs, with up to a 1000-fold yield advantage over conventional ZNW growth on a flat substrate. Hybrid ZNW/CNT sheets are fabricated by scalable CVD, rolling, and printing methods; and their electrical properties, which are governed by transport through the anisotropic CNT network, are characterized. Functional interaction between the ZNWs and CNTs is demonstrated by photoconductive behavior and photocurrent generation of the hybrid material under UV illumination. There is significant future opportunity to extend these processing methods to fabricate other functional oxides on CNTs, and to build devices that harness the attractive properties of ZNWs and CNTs with high volumetric efficiency over large areas. [source] Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine RingsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Massimiliano Tomasulo Abstract Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring-opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6,ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4-nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first-order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance. [source] Modifying the Output Characteristics of an Organic Light-Emitting Device by Refractive-Index Modulation,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2006T. Höfler Abstract In order to modify the output characteristics of organic light-emitting devices (OLEDs), the optical properties of an active layer within the device are patterned without introducing any thickness modulation. For this purpose a new conjugated copolymer, which serves as a hole-transporting material and at the same time can be index patterned using UV techniques, is synthesized. Poly(VC- co -VBT) (VC: N -vinylcarbazole; VBT: 4-vinylbenzyl thiocyanate) is prepared by free-radical copolymerization of VC and VBT. The material contains photoreactive thiocyanate groups that enable altering of the material's refractive index under UV illumination. This copolymer is employed as a patternable hole-transporting layer in multilayer OLEDs. Refractive-index gratings in poly(VC- co -VBT) are inscribed using a holographic setup based upon a Lloyd mirror configuration. The fourth harmonic of a Nd:YAG (YAG: yttrium aluminum garnet) laser (266,nm) serves as the UV source. In this way 1D photonic structures are integrated in an OLED containing AlQ3 (tris(8-hydroxyquinoline) aluminum) as the emitting species. It is assured that only a periodical change of the refractive index (,n,=,0.006 at ,,=,540,nm) is generated in the active material but no surface-relief gratings are generated. The patterned devices show more forward-directed out-coupling behavior than unstructured devices (increase in luminosity by a factor of five for a perpendicular viewing direction). This effect is most likely due to Bragg scattering. For these multilayer structures, optimum outcoupling was observed for grating periods ,,,,390,nm. [source] Quantum Dot,Polymer Composites for Displays: Inkjet-Printed Quantum Dot,Polymer Composites for Full-Color AC-Driven Displays (Adv. Mater.ADVANCED MATERIALS, Issue 21 200921/2009) Vladimir Bulovic and co-workers show on p. 2151 that colloidal quantum dot-polymer composites are used for inkjet print-deposition of high resolution, patterned, multicolored thin films in the fabrication of robust, bright, full-color AC-driven displays. The inside cover shows an inkjet nozzle with a quantum dot solution and a completed device on a flexible substrate under UV illumination, with inset examples of the achievable high resolution and patterning. [source] Inkjet-Printed Quantum Dot,Polymer Composites for Full-Color AC-Driven DisplaysADVANCED MATERIALS, Issue 21 2009Vanessa Wood Colloidal quantum dot,polymer composites are used for inkjet-print deposition of high-resolution, patterned, multicolored thin films in the fabrication of robust, bright, full-color AC-driven displays. The left panel shows a photograph of a complete device on a flexible substrate under UV illumination, while the right panel shows photographs of the electroluminescence of red, green, and blue 80 mm2 pixels. [source] Highly Reactive Multilayer-Assembled TiO2 Coating on Electrospun Polymer NanofibersADVANCED MATERIALS, Issue 12 2009Jung Ah Lee Highly efficient photocatalytically active TiO2 -coated polymer fibers are prepared using a facile and universal method involving layer-by-layer assembly of TiO2 nanoparticles and POSS molecules on various electrospun fibers. The TiO2 -coated fibers display excellent photocatalytic properties in degradation of allyl alcohol under UV illumination, without degradation of substrates. [source] A novel CD4-conjugated ultraviolet light-activated photocatalyst inactivates HIV-1 and SIV efficiently,JOURNAL OF MEDICAL VIROLOGY, Issue 8 2008Koushi Yamaguchi Abstract In this study, we found that the electric potential derived from the redox reaction of ultraviolet (UV)-illuminated CD4-conjugated titanium dioxide (TiO2) inactivated a wide range of high-titered primary HIV-1 isolates, regardless of virus co-receptor usage or genetic clade. In vitro incubation of HIV-1 isolates with CD4-conjugated TiO2 (CD4-TiO2) followed by UV illumination led to inhibition of viral infectivity in both H9 cells and peripheral blood mononuclear cells as well as to the complete inactivation of plasma virions from HIV-1-infected individuals. Treatment with a newly established extra-corporeal circulation system with the photocatalyst in rhesus macaques completely inactivated plasma virus in the system and effectively reduced the infectious plasma viral load. Furthermore, plasma viremia and infectious viral loads were controlled following a second therapeutic photocatalyst treatment during primary SIVmac239 infection of macaques. Our findings suggest that this therapeutic immunophysical strategy may help control human immunodeficiency viral infection in vivo. J. Med. Virol. 80:1322,1331, 2008. © 2008 Wiley-Liss, Inc. [source] Cross-Linked Conjugated Polymers for Achieving Patterned Three-Color and Blue Polymer Light-Emitting Diodes with Multi-Layer StructuresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2009Xianyu Deng Abstract Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross-linking of the main polymer chains. The cross-linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three-color polymer light-emitting diodes (PLEDs) with a multi-layer structure can be easily realized by a dry photo-pattern in an active-gas-free environment. Multi-layer blue devices with dramatically enhanced efficiency can also be achieved conveniently. [source] Towards optical-quality nanocrystalline diamond with reduced non-diamond contentPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009Z. Remes Abstract Our nominally undoped nanocrystalline diamond (NCD) films were deposited on fused silica substrates by the microwave plasma enhanced chemical vapor deposition (MW CVD) at a relatively low temperature below 600,°C. They show high dark resistivity and measurable photosensitivity after surface oxidation. We present the "true" optical absorptance spectra calculated from transmittance T and reflectance R measurements corrected on the surface scattering and compare them with the normalized photocurrent spectra. The optical scattering does not allow to evaluate the small optical absorption in visible and near IR range from the T and R spectra. The photocurrent spectra were measured in the ultraviolet, visible, and near infrared optical range using the dual beam photocurrent spectroscopy (DBP) under constant UV illumination. Previously, NCD films often showed non-diamond content with the photo-ionization threshold at 0.8,eV increasing significantly the optical absorption in near IR and visible region. Here, we show that the non-diamond content can be reduced by several orders of magnitude by depositing NCD on the carefully selected UV-grade fused silica substrates under the optimized growth conditions followed by the post-deposition chemical etching and cleaning. Unlike the NCD layers with high non-diamond content, the NCD layers with reduced non-diamond content are stable up to 450,°C. [source] Photo-induced effect in quantum paraelectric materials: Transient birefringence measurementPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009Y. Koyama Abstract The photo-induced effects in quantum paraelectric materials, strontium titanate SrTiO3 and Ca-doped SrTiO3, are investigated. The observed birefringence for Cadoped SrTiO3 shows that an optical anisotropy along the [100] axis is generated by the ultraviolet (UV) illumination. The transient birefringence in a pulsed electric field is studied to probe the dynamical property of the polarization under dark and UV illumination. Under the UV illumination, the change of birefringence is reduced, and the dielectric response of relaxation type was observed both in SrTiO3 and in Ca-doped SrTiO3. It was found that the ferroelectric phase transition temperature is shifted toward the lower temperature side under the UV illumination. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] GaN on Si substrates for LED and LD applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004Suzuka Nishimura Abstract GaN epitaxial layer has been grown on 2 inch diameter Si substrates by using highly conductive BP buffer crystal. It has been found that the 2-inch GaN on BP/Si wafers are remarkably flat after epitaxial process. BP layer has grown flat and continuously on a large size silicon wafer. GaN has been found to grow continuously on such a substrate.?BP crystals have been found to be highly conductive and controllable depending on the gas ratio. In addition, UV illumination enables us to study the chamber conditions such as contamination by impurity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Long-term stability of dye-sensitised solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2001A. Hinsch Accelerated ageing tests on large numbers of nanocrystalline dye-sensitised solar cells (nc-DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye-sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd. [source] Studies of Photokilling of Bacteria Using Titanium Dioxide NanoparticlesARTIFICIAL ORGANS, Issue 2 2008Yang-Hwei Tsuang Abstract:, Metal pins used to apply skeletal traction or external fixation devices protruding through skin are susceptible to the increased incidence of pin site infection. In this work, we tried to establish the photokilling effects of titanium dioxide (TiO2) nanoparticles on an orthopedic implant with an in vitro study. In these photocatalytic experiments, aqueous TiO2 was added to the tested microorganism. The time effect of TiO2 photoactivation was evaluated, and the loss of viability of five different bacteria suspensions (Escherichia coli, Pseudomonas aeruginosa, Staphylococus aureus, Enterococcus hirae, and Bacteroides fragilis) was examined by the viable count procedure. The bactericidal effect of TiO2 nanoparticle-coated metal plates was also tested. The ultraviolet (UV) dosage used in this experiment did not affect the viability of bacteria, and all bacteria survived well in the absence of TiO2 nanoparticles. The survival curve of microorganisms in the presence of TiO2 nanoparticles showed that nearly complete killing was achieved after 50 min of UV illumination. The formation of bacterial colonies above the TiO2 nanoparticle-coated metal plates also decreased significantly. In this study, we clearly demonstrated the bactericidal effects of titanium dioxide nanoparticles. In the presence of UV light, the titanium dioxide nanoparticles can be applicable to medical facilities where the potential for infection should be controlled. [source] Preparation and Characterization of Bi3+ -TiO2 and its Photocatalytic ActivityCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007H. Zuo Abstract Bi3+ -TiO2 photocatalysts were prepared by doping bismuth ion into the TiO2 structure in a sol-gel process. The catalyst samples were then characterized by UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Rodamine-B (RhB) was used in this study as a model chemical with the aim of organic pollutants control. The photocatalytic degradation of RhB demonstrated that an optimal loading of bismuth 0.7,at.,% achieved the highest photodegradation rate, with the rate constant increasing by a factor of 3.89 over neat TiO2 (P25) under UV illumination (, , 320,nm). The degradation of p -nitrobenzonic acid (pNBA) was also examined to prevent/preclude/exclude/ the photosensitization pathway. GC-MS results show that pNBA can be effectively degraded and minerized to small molecules, such as quinone, acetic acid and formic acid. [source] | |||||||||||||