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Longer Lifetime (longer + lifetime)
Selected AbstractsStability Enhancement of All-Solid-State H+ ISEs with Cross-Linked Silicon-Urethane MatricesELECTROANALYSIS, Issue 8 2005Nak-Hyun Kwon Abstract An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KTpClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and CO in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH,2,11.5) with the slope of 60±2,mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0×10,6,M up to 0.1,M). The ASHISE showed a result comparable to a commercial clinical blood analyzer. [source] Synthesis, Structures, and Electronic Spectroscopy of Luminescent Acetylene- and (Buta-1,3-diyne)platinum ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2007Ke Zhang Abstract The electronic absorption and emission spectroscopy of a series of diphenylaceylene- and (buta-1,3-diyne)-Pt0 complexes (L)Pt[(1,2-,2)-R,(C,C)n,R] and [(dppp)Pt]2[,-(1,2-,2):(3,4-,2)-R,(C,C)2,R] {R = Ph or CH3, L = dppp or(PPh3)2, n = 1 or 2} was investigated. The structures of(dppp)Pt[(1,2-,2)-Ph,C,C,Ph], (dppp)Pt[(1,2-,2)-PhC4Ph] and [(dppp)Pt]2[,-(1,2-,2):(3,4-,2)-Ph,(C,C)2,Ph] were characterized by X-ray diffraction. The complexes all display intense absorptions that were attributed to Pt,P(d,*) and Pt,acetylene(,x*) transitions. Except for the CH3C4CH3 complexes, the complexes all exhibit two emissions at 380,550 nm and 500,800 nm. The higher energy emission could arise from the 3[P(d,*),Pt] transition, and the lower energy emission, which has a longer lifetime than the higher energy one, was attributed to the 3[acetylene(,x*),Pt] transition. The energy of the MLCT absorption and emission was affected by the electronic properties of the acetylenes and the ancillary phosphanes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Highly Efficient Hole Injection Using Polymeric Anode Materials for Small-Molecule Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Kaushik Roy Choudhury Abstract A novel, highly efficient hole injection material based on a conducting polymer polythienothiophene (PTT) doped with poly(perfluoroethylene-perfluoroethersulfonic acid) (PFFSA) in organic light-emitting diodes (OLEDs) is demonstrated. Both current,voltage and dark-injection-current transient data of hole-only devices demonstrate high hole-injection efficiency employing PTT:PFFSA polymers with different organic charge-transporting materials used in fluorescent and phosphorescent organic light-emitting diodes. It is further demonstrated that PTT:PFFSA polymer formulations applied as the hole injection layer (HIL) in OLEDs reduce operating voltages and increase brightness significantly. Hole injection from PTT:PFFSA is found to be much more efficient than from typical small molecule HILs such as copper phthalocyanine (CuPc) or polymer HILs such as polyethylene dioxythiophene: polystyrene sulfonate (PEDOT-PSS). OLED devices employing PTT:PFFSA polymer also demonstrate significantly longer lifetime and more stable operating voltages compared to devices using CuPc. [source] Development of a benzaldehyde sensor utilizing chemiluminescence on nanosized Y2O3LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2008Yayan Wu Abstract A chemiluminescence sensor has been proposed for sensitive determination of benzaldehyde, with nanosized Y2O3 as the sensing material. Under optimized conditions, the linear range of the CL intensity vs. the concentration of benzaldehyde vapour is 1.8 ng/mL,10.8 µg/mL (r2 = 0.9996), with a detection limit of 0.90 ng/mL (signal:noise ratio = 3:1). The sensor also exhibits high selectivity to benzaldehyde because no or weak CL signals have been detected when foreign substances are introduced into the sensor. In addition, the sensor also shows good stability and longer lifetime within 100 h. The results indicate that the proposed sensor, which has high sensitivity and selectivity, shows great potential for the detection of benzaldehyde. Copyright © 2008 John Wiley & Sons, Ltd. [source] Primary Photoprocesses in a Fluoroquinolone Antibiotic Sarafloxacin,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Fernando Lorenzo The photophysical properties of the fluoroquinolone antibiotic sarafloxacin (SFX) were investigated in aqueous media. SFX in water, at pH 7.4, shows intense absorption with peaks at 272, 322 and 335 nm, (, = 36800 and 17000 dm3 mol,1 cm,1, respectively). Both the absorption and emission properties of SFX are pH-dependent; pKa values for the protonation equilibria of both the ground (5.8 and 9.1) and excited singlet states (5.7 and 9.0) of SFX were determined spectroscopically. SFX fluoresces weakly, the quantum yield for fluorescence emission being maximum (0.07) at pH 8. Laser flash photolysis and pulse radiolysis studies have been carried out in order to characterize the transient species of SFX in aqueous solution. Triplet,triplet absorption has a maximum at 610 nm with a molar absorption coefficient of 17,000 ± 1000 dm3 mol,1 cm,1. The quantum yield of triplet formation has been determined to be 0.35 ± 0.05. In the presence of oxygen, the triplet reacts to form excited singlet oxygen with quantum yield of 0.10. The initial triplet (3A*) was found to react with phosphate buffer to form triplet 3B* with lower energy and longer lifetime and having an absorption band centered at 700 nm. SFX triplet was also found to oxidize tryptophan to its radical with concomitant formation of the anion radical of SFX. Hence the photosensitivity of SFX could be initiated by the oxygen radicals and/or by SFX radicals acting as haptens. [source] Ratiometric Singlet Oxygen Nano-optodes and Their Use for Monitoring Photodynamic Therapy NanoplatformsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2005Youfu Cao ABSTRACT Ratiometric photonic explorers for bioanalysis with biologically localized embedding (PEBBLE) nanoprobes have been developed for singlet oxygen, using organically modified silicate (ORMOSIL) nanoparticles as the matrix. A crucial aspect of these ratiometric singlet-oxygen fluorescent probes is their minute size. The ORMOSIL nanoparticles are prepared via a sol-gel,based process and the average diameter of the resultant particles is about 160 nm. These sensors incorporate the singlet-oxygen,sensitive 9,10-dimethyl anthracene as an indicator dye and a singlet-oxygen,insensitive dye, octaethylporphine, as a reference dye for ratiometric fluorescence-based analysis. We have found experimentally that these nanoprobes have much better sensitivity than does the conventional singlet-oxygen,free dye probe, anthracene-9, 10-dipropionic acid disodium salt. The much longer lifetime of singlet oxygen in the ORMOSIL matrix, compared to aqueous solutions, in addition to the relatively high singlet oxygen solubility because of the highly permeable structure and the hydrophobic nature of the outer shell of the ORMOSIL nanoparticles, results in an excellent overall response to singlet oxygen. These nanoprobes have been used to monitor the singlet oxygen produced by "dynamic nanoplatforms" that were developed for photodynamic therapy. The singlet oxygen nanoprobes could potentially be used to quantify the singlet oxygen produced by macrophages. [source] The Lifetimes of Pharaonis Phoborhodopsin Signaling States Depend on the Rates of Proton Transfers,Effects of Hydrostatic Pressure and Stopped Flow Experiments,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Takashi Kikukawa Pharaonis phoborhodopsin (ppR), a negative phototaxis receptor of Natronomonas pharaonis, undergoes photocycle similar to the light-driven proton pump bacteriorhodopsin (BR), but the turnover rate is much slower due to much longer lifetimes of the M and O intermediates. The M decay was shown to become as fast as it is in BR in the L40T/F86D mutant. We examined the effects of hydrostatic pressure on the decay of these intermediates. For BR, pressure decelerated M decay but slightly affected O decay. In contrast, with ppR and with its L40T/F86D mutant, pressure slightly affected M decay but accelerated O decay. Clearly, the pressure-dependent factors for M and O decay are different in BR and ppR. In order to examine the deprotonation of Asp75 in unphotolyzed ppR we performed stopped flow experiments. The pH jump-induced deprotonation of Asp75 occurred with 60 ms, which is at least 20 times slower than deprotonation of the equivalent Asp85 in BR and about 10-fold faster than the O decay of ppR. These data suggest that proton transfer is slowed not only in the cytoplasmic channel but also in the extracellular channel of ppR and that the light-induced structural changes in the O intermediate of ppR additionally decrease this rate. [source] Infrared detector based on modulation-doped quantum-dot structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006V. Mitin Abstract We investigate a detector model, where quantum dots are surrounded by potential barriers created by modulation doping. Strong separation of the localized ground states and continuum conducting states drastically increases the photoelectron capture time. At room temperatures the photoelectron capture is conditioned by electron diffusion in the potential relief. Monte-Carlo modeling with diffusion-limited capture in the modulation-doped quantum-dot structures is used to calculate carrier lifetime and photoconductive gain as functions of the electric field. We evaluate the photodetector characteristics and show that photoconductive gain is substantially improved due to longer lifetimes of photoelectrons. Optimized quantum-dot structures have a strong potential for development IR room-temperature detectors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tryptophanyl fluorescence lifetime distribution of hyperthermophilic ,-glycosidase from molecular dynamics simulation: A comparison with the experimental dataPROTEIN SCIENCE, Issue 9 2000Ettore Bismuto Abstract A molecular dynamics simulation approach has been utilized to understand the unusual fluorescence emission decay observed for ,-glycosidase from the hyperthermophilic bacterium Solfolobus sulfataricus (S,gly), a tetrameric enzyme containing 17 tryptophanyl residues for each subunit. The tryptophanyl emission decay of (S,gly) results from a bimodal distribution of fluorescence lifetimes with a short-lived component centered at 2.5 ns and a long-lived one at 7.4 ns Bismuto E, Nucci R, Rossi M, Irace G, 1999, Proteins 27:71,79). From the examination of the trajectories of the side chains capable of causing intramolecular quenching for each tryptophan microenvironment and using a modified Stern,Volmer model for the emission quenching processes, we calculated the fluorescence lifetime for each tryptophanyl residue of S,gly at two different temperatures, i.e., 300 and 365 K. The highest temperature was chosen because in this condition S,lgy evidences a maximum in its catalytic activity and is stable for a very long time. The calculated lifetime distributions overlap those experimentally determined. Moreover, the majority of trytptophanyl residues having longer lifetimes correspond to those originally identified by inspection of the crystallographic structure. The tryptophanyl lifetimes appear to be a complex function of several variables, such as microenvironment viscosity, solvent accessibility, the chemical structure of quencher side chains, and side-chain dynamics. The lifetime calculation by MD simulation can be used to validate a predicted structure by comparing the theoretical data with the experimental fluorescence decay results. [source] Lanthanide (Eu3+, Tb3+) Centered Mesoporous Hybrids with 1,3-Diphenyl-1,3-Propanepione Covalently Linking SBA-15 (SBA-16) and Poly(methylacrylic acid)CHEMISTRY - AN ASIAN JOURNAL, Issue 7 2010Ya-Juan Li Dr. Abstract 1,3-Diphenyl-1,3-propanepione (DBM)-functionalized SBA-15 and SBA-16 mesoporous hybrid materials (DBM-SBA-15 and DBM-SBA-16) are synthesized by co-condensation of modified 1,3-diphenyl-1,3-propanepione (DBM-Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 and Pluronic F127 as a template, respectively. The as-synthesized mesoporous hybrid material DBM-SBA-15 and DBM-SBA-16 are used as the first precursor, and the second precursor poly(methylacrylic acid) (PMAA) is synthesized through the addition polymerization reaction of the monomer methacrylic acid. These precursors then coordinate to lanthanide ions simultaneously, and the final mesoporous polymeric hybrid materials Ln(DBM-SBA-15)3PMAA and Ln(DBM-SBA-16)3PMAA (Ln=Eu, Tb) are obtained by a sol-gel process. For comparison, binary lanthanide SBA-15 and SBA-16 mesoporous hybrid materials (denoted as Ln(DBM-SBA-15)3 and Ln(DBM-SBA-16)3) are also synthesized. The luminescence properties of these resulting materials are characterized in detail, and the results reveal that ternary lanthanide mesoporous polymeric hybrid materials present stronger luminescence intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary lanthanide mesoporous hybrid materials. This indicates that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system. In addition, the SBA-15 mesoporous hybrids show an overall increase in luminescence lifetime and quantum efficiency compared with SBA-16 mesoporous hybrids, indicating that SBA-15 is a better host material for the lanthanide complex than mesoporous silica SBA-16. [source] | ||||||||||