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Visible Region (visible + region)
Kinds of Visible Region Selected AbstractsOptical properties of 2-aminopyridinium nitrato silverCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2010K. P. Bhuvana Abstract Crystals of 2-aminopyridinium nitrato silver have been synthesized by slow evaporation method. Grown crystals have been subjected to FTIR, Single crystal X-Ray diffraction and UV-Visible studies in order to investigate the structural and optical properties of the crystal. The FTIR spectrum reveals the presence of the functional group that corresponds to both 2-aminopyridine and silver nitrate, suggesting the formation of the compound, 2-aminopyridinium nitrato silver. From XRD it is observed that the crystal crystallizes in the structure of monoclinic with the space group of P21/c. The optical transmittance spectrum shows the maximum transparency of about 95% in the visible region is in consistent with the wide band gap, estimated as 4.738 eV. The optical constants n and k has also been determined from the transmittance data. The static dielectric constant is found to be 0.851. The wide band gap and the less dielectric constant suggest the suitability of this compound material for photoconductive applications. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Investigation of optical band gap in potassium acid phthalate single crystalCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2008S. Krishnan Abstract Optical absorption in photonic crystals of potassium acid phthalate has been measured at room temperature, from which the band gap has been determined and the optical band gap was calculated by using absorption spectrum. The analysis of absorption coefficient in the absorption region reveals a direct band gap of 3.70 eV. Further this study includes the theoretical calculations to determine the optical constant of the material and a technique for photonic band gap tuning which is minimally required to develop the optoelectronic device. It was confirmed that potassium acid phthalate crystal has maximum transparency in the entire visible region and hence it exhibits industrial application oriented properties. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, growth and characterization of single crystals of pure and thiourea doped L-glutamic acid hydrochlorideCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2007R. Sathyalakshmi Abstract L(+)Glutamic acid hydrochloride [HOOC (CH2)2CH(NH2) COOH·HCl], a monoamino dicarboxylic acid salt of L-Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L-Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV-Vis-NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L-Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X-ray diffraction analysis and it crystallizes in orthorhombic space group P212121. UV-Vis-NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L-Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L-Glutamic acid hydrochloride crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Highly Efficient Visible-Light-Induced Photocleavage of DNA by a Ruthenium-Substituted Fluorinated PorphyrinEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2009Michelle Cunningham Abstract A new porphyrin, meso -5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2,-bipyridine) to the pyridyl nitrogen atoms in the 10,15-positions gives the target complex. Electronic transitions associated with the ruthenium,porphyrin include an intense Soret band and four less intense Q-bands in the visible region of the spectrum. An intense ,,,* transition in the UV region associated with the bipyridyl groups and a metal-to-ligand charge-transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = ,0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double-strand breaks of the DNA.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Uncommon Solvent Effect in Oxidative Addition of MeI to a New Dinuclear Platinum Complex Containing a Platina(II)cyclopentane MoietyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2008S. Jafar Hoseini Abstract The reaction of the known complex cis,cis -[Me2Pta(,-dppm)(,-SMe2)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] [dppm = bis(diphenylphosphanyl)methane] with phthalazine (NN) proceeded by replacement of the labile bridging SMe2 ligand with the bidentate N-donor ligand NN to give cis,cis -[Me2Pta(,-dppm)(,-NN)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] (1) as a pale red solid in good yield. The complex was fully characterized by multinuclear (1H, 31P, 195Pt) NMR spectroscopy. The subsequent reaction of complex 1 with excess MeI gave the colorless diplatinum(IV) complex [Me3Pta(,-dppm)(,-I)2Ptb{CH2(CH2)2CcH2(Ptb,Cc)}Me], in which the bridging NN ligand is replaced by bridging iodido ligands. The reddish color of complex 1, which is due to a metal-to-ligand charge transfer (MLCT) band in the visible region, was used to monitor its reaction with MeI in the solvents acetone, CH2Cl2, and benzene. The kinetic data revealed that the reactions in nonpolar benzene or slightly polar CH2Cl2 proceeded in two steps, each following a common SN2 mechanism. In the first step, MeI attacked the platina(II)cyclopentane center rather than the dimethylplatinum(II) center, because the first center is more electron-rich than the second center. In the more polar acetone, the reaction proceeded similarly, with the exception that each step was accompanied by a solvolytic reaction, which was suggested to be responsible for the unusually slower reaction rate in acetone than in benzene or CH2Cl2. Consistently, the reaction rate in the highly polar solvent CH3CN was too slow for any meaningful measurement.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Reactivity of Cationic Lanthanide(III) Monoporphyrinates towards Anionic Cyanometallates , Preparation, Crystal Structure, and Luminescence Properties of Cyanido-Bridged Di- and Trinuclear d,f ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2008Xunjin Zhu Abstract The metathesis reaction between two equivalents of [Ln(tpp)(H2O)3]Cl (Ln = Yb, Er; tpp2, = tetraphenylporphyrinate dianion) and one equivalent of cyanometallate in dmf at room temperature under nitrogen for 24 hours gave the cyanido-bridged d,f trinuclear complexes [{Ln(tpp)(dmf)n}2{(,-NC)2M(CN)2}] (Ln = Yb, n = 2, M = Ni, 1; Ln = Er, n = 3, M = Ni, 2; Ln = Yb, n = 2, M = Pt, 3; Ln = Er, n = 3, M = Pt, 4), a trinuclear complex [{Er(tpp)(dmf)2}{(,-NC)2Fe(CN)4}{Er(Htpp)(dmf)2}] (5), and a dinuclear complex [{Er(tpp)(dmf)(H2O)}(,-NC)Ag(CN)] (6) when the cyanometallate used was the dianion [M(CN)4]2, (M = Ni, Pt), the trianion [Fe(CN)6]3,, and monoanion [Ag(CN)2],, respectively. The solid-state structures of these complexes were ascertained by X-ray crystallography. Photoluminescence studies of complexes 1,4 showed that these complexes displayed photophysical properties characteristic of normal metal,porphyrinato complexes. Their absorption bands and emission peaks in the visible region are typical of the intraligand ,,,* transitions of the porphyrinato ligand. Furthermore, these complexes also exhibited emission characteristic of the lanthanide(III) ion in the near-infrared (NIR) region, which was quenched by the cyanometallates. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] N -(Aryl)picolinamide Complexes of Ruthenium: Usual Coordination and Strategic CyclometalationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2007Sumon Nag Abstract Reaction of five N -(4- R -phenyl)picolinamides (R = OCH3, CH3, H, Cl, and NO2) with [Ru(PPh3)2(CO)2Cl2] in refluxing 2-methoxyethanol in the presence of a base (NEt3) affords two geometrical isomers of a group of complexes (1-R and 2-R), each of which contains an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphanes, a carbonyl, and a hydride. Similar reaction of N -(naphthyl)picolinamide with [Ru(PPh3)2(CO)2Cl2] affords an organometallic complex, 3, in which the amide ligand is coordinated to the metal center, by C,H activation of the naphthyl ring at the 8-position, as a dianionic tridentate N,N,C donor along with two triphenylphosphanes and one carbonyl. Structures of the 1-OCH3, 2-CH3, and 3 complexes have been determined by X-ray crystallography. In all the complexes the two triphenylphosphanes are trans. In the 1-R complexes the hydride is trans to the pyridine nitrogen and in the 2-R complexes it is trans to the amide-nitrogen. All the complexes are diamagnetic, and show characteristic 1H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a RuII,RuIII oxidation within 0.71,0.93 V versus SCE. An oxidation and a reduction of the coordinated amide ligand are also observed within 1.29,1.69 V versus SCE and ,1.02 to ,1.21 V versus SCE respectively.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] High-Yield Synthesis and Electrochemical and Photovoltaic Properties of Indene-C70 BisadductADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Youjun He Abstract [6, 6]-Phenyl-C61 -butyric acid methyl ester (PC60BM) is the widely used acceptor material in polymer solar cells (PSCs). Nevertheless, the low LUMO energy level and weak absorption in visible region are its two weak points. For enhancing the solar light harvest, the soluble C70 derivative PC70BM has been used as acceptor instead of PC60BM in high efficiency PSCs in recent years. But, the LUMO level of PC70BM is the same as that of PC60BM, which is too low for the PSCs based on the polymer donors with higher HOMO level, such as poly (3-hexylthiophene) (P3HT). Here, a new soluble C70 derivative, indene-C70 bisadduct (IC70BA), is synthesized with high yield of 58% by a one-pot reaction of indene and C70 at 180 °C for 72 h. The electrochemical properties and electronic energy levels of the fullerene derivatives are measured by cyclic voltammetry. The LUMO energy level of IC70BA is 0.19 eV higher than that of PC70BM. The PSC based on P3HT with IC70BA as acceptor shows a higher Voc of 0.84 V and higher power conversion efficiency (PCE) of 5.64%, while the PSC based on P3HT/PC60BM and P3HT/PC70BM displays Voc of 0.59 V and 0.58 V, and PCE of 3.55% and 3.96%, respectively, under the illumination of AM1.5G, 100 mW cm,2. The results indicate that IC70BA is an excellent acceptor for the P3HT-based PSCs and could be a promising new acceptor instead of PC70BM for the high performance PSCs based on narrow bandgap conjugated polymer donor. [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] Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support ArchitecturesADVANCED FUNCTIONAL MATERIALS, Issue 5 2009David R. Baker Abstract TiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons. [source] Color- and Reflectance-Tunable Multiple Reflectors Assembled from Three Polymer FilmsADVANCED MATERIALS, Issue 14 2010Na Young Ha Tunings of reflectance and colors of multiple photonic bandgaps are demonstrated in the whole visible region by changing the polarization state of incident light. Two tunable systems are assembled from the same three materials of an anisotropic polymeric nematic liquid crystal film and two kinds of isotropic polymer film. The only difference between the two systems is the stacking sequence. [source] Metal-Containing Carbon Nitride Compounds: A New Functional Organic,Metal Hybrid MaterialADVANCED MATERIALS, Issue 16 2009Xinchen Wang The electronic and optical functions of polymeric C3N4 can be easily modified by the inclusion of metal species such as Fe in its structure. The metal species lowers the bandgap and expands the light absorption of the material further into the visible region of the electromagnetic spectrum, while keeping a sufficient overpotential for carrying out oxidation reactions. [source] An Electro- and Thermochromic Hydrogel as a Full-Color Indicator,ADVANCED MATERIALS, Issue 19 2007K. Ueno Electric-field-triggered "two-state switching" between two arbitrary structural colors (see figure) in the entire visible region at certain temperatures is shown by a stimuli-responsive chromic hydrogel. The external rapid tuning in the structural color of this hydrogel is successfully achieved by introducing a periodically ordered interconnecting porous structure. [source] Application of Surface Photo Charge Effect for Milk Quality ControlJOURNAL OF FOOD SCIENCE, Issue 7 2009O. Ivanov ABSTRACT:, The potential difference induced by the interaction of samples with electromagnetic radiation in the visible region is used for food characterization. In this article we show that the above effect can be applied for the understanding of specific reactions and processes taking place in milk such as change of the acidity and changes caused by an added reagent. We also propose a technique for instantaneous detection of inhibitors of starter bacteria in milk. We suggest possible methods for quality control of milk and other foods. Instantaneous results, practically no expenses for consumables, and possibilities for field measurements will be some of the advantages of this approach. [source] Synthesis and characterization of cyclopentadithiophene-based low bandgap copolymers containing electron-deficient benzoselenadiazole derivatives for photovoltaic devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010In Hwan Jung Abstract We have synthesized two cyclopentadithiophene (CDT)-based low bandgap copolymers, poly[(4,4-bis(2-ethyl-hexyl)-4H -cyclopenta[2,1- b:3,4- b,]dithiophene-2,6-diyl)- alt -(benzo[c][1,2,5]selenadiazole-4,7-diyl)] (PCBSe) and poly[(4,4-bis(2-ethyl-hexyl)-4H -cyclopenta[2,1- b:3,4- b,]dithiophene-2,6-diyl)- alt -(4,7-dithiophen-2-yl-benzo[c][1,2,5]selenadiazole-5,5,-diyl)] (PCT2BSe), for use in photovoltaic applications. Through the internal charge transfer interaction between the electron-donating CDT unit and the electron-accepting benzoselenadiazole, we realized exceedingly low bandgap polymers with bandgaps of 1.37,1.46 eV. The UV,vis absorption maxima of PCT2BSe were subjected to larger hypsochromic shifts than those of PCBSe, because of the distorted electron donor,acceptor (D,A) structures of the PCT2BSe backbone. These results were supported by the calculations of the D,A complex using the ab initio Hartree-Fock method with a split-valence 6-31G* basis set. However, PCT2BSe exhibited a better molar absorption coefficient in the visible region, which can lead to more efficient absorption of sunlight. As a result, PCT2BSe blended with [6,6]-phenyl-C61 -butyric acid methyl ester (PC61BM) exhibited a better photovoltaic performance than PCBSe because of the larger spectral overlap integral with respect to the solar spectrum. Furthermore, when the polymers were blended with PC71BM, PCT2BSe showed the best performance, with an open circuit voltage of 0.55 V, a short-circuit current of 6.63 mA/cm2, and a power conversion efficiency of 1.34% under air mass 1.5 global illumination conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1423,1432, 2010 [source] Synthesis and white electroluminescent properties of multicomponent copolymers containing polyfluorene, oligo(phenylenevinylene), and porphyrin derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Hui Li Abstract Two novel multicomponent copolymers (P1 and P2) containing polyfluorene (PF), oligo(phenylenevinylene) (OPV), and porphyrin (Por) derivatives were synthesized according to the Suzuki polymerization method. The structures, optical, and electrochemical properties of the two model compounds (OPV and Por) and multicomponent copolymers were characterized by 1H NMR, FTIR, elemental analysis, UV,vis spectroscopy, photoluminescence, and cyclic voltammetry, respectively. Both of the copolymers exhibit thermotropic liquid crystalline properties and represent the characteristic Schlieren textures in a wide temperature range. Electroluminescence spectra of these copolymers exhibit broadband emissions covering the entire visible region from 400 to 700 nm. The single layer polymer light emitting diodes device based on P2 with a configuration of indium tin oxide/poly(ethylenedioxythiophene):poly(styrenesulfonic acid)/polymers/Ca/Al emits white light with the Commission Internationale de l,Eclairage chromaticity coordinates of (0.29, 0.30), maximum brightness of 443 cd/m2. The white-light-emitting devices based on the novel multicomponent copolymers exhibit low turn-on voltage, and good color stability at different driving voltages as well. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5291,5303, 2009 [source] Highly stable electrochromic polyamides based on N,N -bis(4-aminophenyl)- N,,N,-bis(4- tert -butylphenyl)-1,4-phenylenediamineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2009Sheng-Huei Hsiao Abstract A new triphenylamine-containing aromatic diamine monomer, N,N -bis(4-aminophenyl)- N,,N,-bis(4- tert -butylphenyl)-1,4-phenylenediamine, was synthesized by an established synthetic procedure from readily available reagents. A novel family of electroactive polyamides with di- tert -butyl-substituted N,N,N,,N,-tetraphenyl-1,4-phenylenediamine units were prepared via the phosphorylation polyamidation reactions of the newly synthesized diamine monomer with various aromatic or aliphatic dicarboxylic acids. All the polymers were amorphous with good solubility in many organic solvents, such as N -methyl-2-pyrrolidinone (NMP) and N,N -dimethylacetamide, and could be solution-cast into tough and flexible polymer films. The polyamides derived from aromatic dicarboxylic acids had useful levels of thermal stability, with glass-transition temperatures of 269,296 °C, 10% weight-loss temperatures in excess of 544 °C, and char yields at 800 °C in nitrogen higher than 62%. The dilute solutions of these polyamides in NMP exhibited strong absorption bands centered at 316,342 nm and photoluminescence maxima around 362,465 nm in the violet-blue region. The polyamides derived from aliphatic dicarboxylic acids were optically transparent in the visible region and fluoresced with a higher quantum yield compared with those derived from aromatic dicarboxylic acids. The hole-transporting and electrochromic properties were examined by electrochemical and spectro-electrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium-tin oxide-coated glass substrate exhibited two reversible oxidation redox couples at 0.57,0.60 V and 0.95,0.98 V versus Ag/AgCl in acetonitrile solution. The polyamide films revealed excellent elcterochemical and electrochromic stability, with a color change from a colorless or pale yellowish neutral form to green and blue oxidized forms at applied potentials ranging from 0.0 to 1.2 V. These anodically coloring polymeric materials showed interesting electrochromic properties, such as high coloration efficiency (CE = 216 cm2/C for the green coloring) and high contrast ratio of optical transmittance change (,T%) up to 64% at 424 nm and 59% at 983 nm for the green coloration, and 90% at 778 nm for the blue coloration. The electroactivity of the polymer remains intact even after cycling 500 times between its neutral and fully oxidized states. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2330,2343, 2009 [source] Novel two-dimensional donor,acceptor conjugated polymers containing quinoxaline units: Synthesis, characterization, and photovoltaic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Lijun Huo Abstract Novel two-dimensional donor,acceptor (D,A) structured conjugated polymers, P1,P4, were designed and synthesized by introducing electron-deficient quinoxaline as core and electron-rich alkoxyl-phenylenevinylene in side chains and p -phenylenevinylene, triphenylamine, or thiophene in main chain. Benefited from the D,A structures, the polymers possess low bandgaps of 1.75 eV, 1.86 eV, 1.59 eV, and 1.58 eV for P1, P2, P3, and P4, respectively, and show broad absorption band in the visible region: the shorter wavelength absorption peak at ,400 nm ascribed to the conjugated side chains and the longer wavelength absorption peak between 500 nm and 750 nm belonging to the absorption of the conjugated main chains. Especially, the absorption band of P4 film covers the whole visible range from 300 nm to 784 nm. The power conversion efficiencies of the polymer solar cells based on P1,P4 as donor and PCBM as acceptor are 0.029%, 0.14%, 0.46%, and 0.57%, respectively, under the illumination of AM 1.5, 100 mW/cm2. The polymers with the low bandgap and broad absorption band are promising photovoltaic materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4038,4049, 2008 [source] Translucent ,-Sialon Ceramics by Hot PressingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2004Xinlu Su The single-phase ,-sialon ceramics with high optical transmittance have been prepared by hot pressing. The maximum transmittance reached 65.2% and 52.2% in the infrared wavelength region, 58.5% and 40% in the visible region for the samples 1.0 and 1.5 mm thickness, respectively. The material also exhibited good mechanical properties of high hardness (20 GPa) and better fracture toughness (5.1 MPa·m1/2). Both high optical transmittance and improved toughness of ,-sialon ceramics were attributed to the less-grain-boundary glassy phase and the homogeneous microstructure, which was obtained by a proper process and confirmed by SEM and TEM observation, compared to that prepared by ordinary sintering. It is, therefore, expected that the translucent ,-sialon ceramics could be a promising optical window material. [source] Combustion synthesis of Na2Sr(PO4)F:Dy3+ white light emitting phosphorLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2010I. M. Nagpure Abstract The synthesis, X-ray diffraction, photoluminescence, TGA/DTA and FTIR techniques in Dy3+ activated Na2Sr(PO4)F phosphor are reported in this paper. The prepared phosphor gave blue, yellow and red emission in the visible region of the spectrum at 348 nm excitation. CIE color co-ordinates of Na2Sr(PO4)F:Dy3+ are suitable as white light-emitting phosphors. Copyright © 2009 John Wiley & Sons, Ltd. [source] Investigation of a CuII,Poly(, -Glutamic Acid) Complex in Aqueous Solution and its Insulin-Mimetic ActivityMACROMOLECULAR BIOSCIENCE, Issue 4 2007Subarna Karmaker Abstract The complexation between cupric ions (CuII) and poly(, -glutamic acid) (, -PGA) in aqueous solutions (pH 3,11) has been studied by UV-visible absorption and electron spin resonance (ESR) techniques. Formation of the CuII - , -PGA complex is confirmed by the observation of the blue shift of the absorption band in the visible region, anisotropic line shapes in the ESR spectrum at room temperature, and a computer simulation of the visible absorption spectrum of the complex. The structure of the CuII - , -PGA complex, depending on the pH, has been determined. The in vitro insulin-mimetic activity of the CuII - , -PGA complex is examined by determining both inhibition of free fatty acid release and glucose uptake in isolated rat adipocytes treated with epinephrine, in which the concentration of the CuII - , -PGA complex for 50% inhibition of free fatty acid release is very similar to that of CuSO4. However, it is significantly lower than that of a previously reported insulin-mimetic bis(3-hydroxypicolinato)copper(II), [Cu(3hpic)2], complex. [source] Tuning the Photoluminescence of Silsesquioxanes with Short Substituted Urea BridgesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2008María L. Gómez Abstract The polycondensation of a precursor synthesized by the reaction of 3-(anilinepropyl)trimethoxysilane with 3-(isocyanatopropyl)triethoxysilane led to a silsesquioxane bearing a substituted urea group in the short organic bridge. The self-assembly of organic bridges, analyzed by SAXS and FTIR spectra, could be controlled by varying the conditions of the synthesis. Depending on the size of organic clusters, the silsesquioxane exhibited photoluminescence either in the green or red regions of the spectra, or an emission that could be tuned in the whole visible region by the excitation wavelength. [source] Novel Cobalt (II) Phthalocyanine-Containing Polyimides: Synthesis, Characterization, Thermal and Optical PropertiesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2006Eva M. Maya Abstract Summary: A novel class of polymer has been prepared by reaction of a copolyimide containing carboxylic acid groups, and a cobalt phthalocyanine peripherally substituted with a reactive hydroxyl group. The incorporation of the phthalocyanine ring was achieved by esterification of the carboxylic acid groups of the polyimide with the free hydroxyl group of the phthalocyanine. In this work, a limited number of phthalocyanine rings have been introduced in order to avoid extensive modification of the copolyimide properties. The extent of modification (percentage of esterified carboxylic groups) was estimated to be about 18%. The resulting material showed good thermal stability and a high glass transition temperature (above 300,°C). The incorporation of the bulky phthalocyanine ring brought about a light decrease of thermal properties, relative to those of the initial polyimide. The presence of phthalocyanine was confirmed by the absorption band at 670 nm showing in the visible region for the modified polyimide. The novel copolyimide also exhibited a remarkable emission peak at 430 nm, when excited at 350 nm, corresponding to the emission of the cobalt phthalocyanine moiety. Schematic representation of the PI-CoPc molecule and the chemical structure of the repeat unit. [source] Structure and Photoreaction of Photoactive Yellow Protein, a Structural Prototype of the PAS Domain Superfamily,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2007Yasushi Imamoto Photoactive yellow protein (PYP) is a water-soluble photosensor protein found in purple photosynthetic bacteria. Unlike bacterial rhodopsins, photosensor proteins composed of seven transmembrane helices and a retinal chromophore in halophilic archaebacteria, PYP is a highly soluble globular protein. The ,/, fold structure of PYP is a structural prototype of the PAS domain superfamily, many members of which function as sensors for various kinds of stimuli. To absorb a photon in the visible region, PYP has a p -coumaric acid chromophore binding to the cysteine residue via a thioester bond. It exists in a deprotonated trans form in the dark. The primary photochemical event is photo-isomerization of the chromophore from trans to cis form. The twisted cis chromophore in early intermediates is relaxed and finally protonated. Consequently, the chromophore becomes electrostatically neutral and rearrangement of the hydrogen-bonding network triggers overall structural change of the protein moiety, in which local conformational change around the chromophore is propagated to the N-terminal region. Thus, it is an ideal model for protein conformational changes that result in functional change, responding to stimuli and expressing physiological activity. In this paper, recent progress in investigation of the photoresponse of PYP is reviewed. [source] Circular Dichroism of the Photoreceptor Pigment OxyblepharisminPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2005Osvaldo Pieroni ABSTRACT Circular dichroism (CD) was used to study the structure of oxyblepharismin (OxyBP), the photoreceptor chromophore for the photophobic response of the blue form of Blepharisma japonicum. Both the chromophore associated to its native protein and the free chromophore in ethanol solution were investigated. CD spectra in the far-UV range indicate that OxyBP induces a slight increase in the ,-helix content of the protein matrix. CD spectra in the near-UV and visible region of the spectrum show that OxyBP adopts a chiral conformation with a preferential geometry not only when associated to its protein matrix, but also when isolated and dissolved in ethanol. This experimental result is related to the existence of a high-energy interconversion barrier between two enantiomeric structures of the molecule and discussed on the basis of an asymmetric biosynthesis of its precursor, blepharismin. [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] Spectroscopic ellipsometry studies of Mg-doped ZnO thin films prepared by the sol,gel methodPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009Shenghong Yang Abstract Zn1,xMgx O (ZMO) thin films with x = 0, 0.1, 0.2, and 0.3 were prepared on Si(100) substrates by the sol,gel method. The influence of Mg content on the structural and the optical properties was studied by X-ray diffraction and spectroscopic ellipsometry (SE) in the UV,visible region. The measured SE spectra were analyzed with an appropriate procedure to accurately determine the thickness and the optical constants of the thin films. It was found that the optical constants of the ZMO films are functions of the film composition. The refractive indices of the ZMO films decrease with increasing Mg content, and the optical bandgap energy exhibits nonlinear behavior or a bowing effect with the change of Mg mole fraction. A maximum band gap of ,3.91 eV was achieved at x = 0.3. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Patterned transparent zinc oxide films produced by sol,gel embossingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008J. Rao Abstract A low cost zinc oxide embossing technique is reported as a method of fabricating structures relevant to a variety of applications. A zinc based sol,gel material was prepared from zinc acetate [Zn(C2H3O2)2], monoethanolamine [H2NC2H4OH] and isopropanol. The sol,gel was cast into a polydimethylsiloxane (PDMS) mould a track design, placed in contact with the substrate and dried under vacuum at 70 °C for 3 hours. The formed track pattern was further densified to provide a stable conductor film that retained the embossed shape. An optimum Zn sol,gel content of 0.6 M was identified. The embossed films had a transparency of greater than 83% in the visible region. The optical bandgap energy was evaluated to be 3.306 eV. The influence of ZnO sol,gel film synthesis and embossing parameters on the microstructure, morphology and optical transparency of fabricated structures is described. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low temperature growth of transparent conducting ZnO films by plasma assisted depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006A. Nishii Abstract Transparent conducting ZnO films are deposited by plasma assisted deposition technique on glass and plastic substrates at temperatures 60 , 300 °C using metallic Zn, metallic Ga and plasma-excited oxygen as source materials. Deposited films were characterized by X-ray diffraction (XRD), optical transmittance in the visible and infrared region, Raman scattering, and Hall measurements. Film properties are controlled by substrate temperature, oxygen source/zinc source supply ratio, and Ga doping. 350 nm-thick Ga-doped ZnO films deposited at 290 °C showed low resistivity (,2 × 10,4 , cm) and high transmittance in the visible region (,85%). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nitridation and reoxidation of high- k metal oxide thin films using argon excimer sourcesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006J. J. Yu Abstract We report for the first time the nitridation and reoxidation of metal oxide films with the active nitrogen and oxygen species produced by argon excimer sources. Preliminary results on 9 nm Ta2O5 films using this method exhibited excellent electrical properties with the leakage current density being up to 3 orders of magnitude lower than the as-deposited films. Breakdown fields were found to be greater than 13 MV/cm. Accumulation capacitance with the nitrided film increased by 25% compared with the as-deposited film. Optical transmittance was as high as 99% in the visible region and more than 74% in the UV region. The refractive index at 632.8 nm was high up to 2.2. The Ar excimer source emitted energetic VUV photons which could break nitrogen triple bonds to produce active nitrogen species and photodissociate O2 to form strong oxidant O3 and highly reactive O (1S) atoms, leading to the nitridation and reoxidation of Ta2O5 without the need for the use of H2O, NH3 and high temperature substrate heating. The nitridation process for a specific film thickness can be optimised by adjusting the VUV irradiation time to achieve increased accumulation capacitance and improved leakage property simultaneously. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||