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Visible Absorption Spectra (visible + absorption_spectrum)
Selected AbstractsPreparation of Nearly Monodisperse Nanoscale Inorganic PigmentsCHEMISTRY - AN ASIAN JOURNAL, Issue 1-2 2006Dingsheng Wang Abstract Many different important commercial pigments have been synthesized based on the liquid,solid,solution (LSS) phase-transfer and separation process. Transmission electron microscopy (TEM) measurement results show that they are very small in size and have a narrow size distribution. Visible absorption spectra were taken to examine the very pure and brilliant colors of the pigments. They can be well-dispersed in cyclohexane and remain non-agglomerated, even over several months. These nearly monodisperse nanoscale inorganic pigments may have wide applications in many important fields and could bring about new developments in the pigment industry. [source] Temperature effects on the UV,Vis electronic spectrum of trans-stilbeneINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2001S. P. Kwasniewski Abstract The ultraviolet (UV),Visible absorption spectrum of trans-stilbene (tS) is computed at different temperatures by coupling molecular dynamics (MD) simulations with the classical MM3 force field to ZINDO/S-CIS calculations of vertical excitation energies and transition dipole moments. The selection of a large number of structures along the MD trajectories enables a consistent treatment of temperature effects in the vacuum, whereas the ZINDO/S-CIS calculations permit a reliable treatment of electron correlation and relaxation, taking account of multistate interactions in the final state. Thermal motions are found to alter very differently the width and shape of bands. Structural alterations such as the stretching and the torsion of the vinyl single and double bonds very strongly influence the appearance of the first valence state, pertaining to the highest occupied and lowest unoccupied molecular orbital (HOMO,LUMO) transition. At temperatures less than 400 K, these are found to yield a merely Gaussian and very pronounced thermal broadening of the related band (A), up to nearly 30 nm, together with a minor blue shift of its maximum ,max. In contrast, a red shift by several nanometers occurs due to thermal motions for the remaining three valence bands. As can be expected, the broadening intensifies at higher temperatures, and for the A-band, becomes markedly asymmetric when T exceeds 400 K. The combination of MD(MM3) and ZINDO/S-CIS computations enables also consistent calculations of hot bands, which are forbidden by symmetry at 0 K. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 [source] Synthesis of some novel bis(hetaryl)azo disperse dyes and investigation of their absorption spectraHETEROATOM CHEMISTRY, Issue 6 2007Zeynel Sefero 3-Amino-2-cyano-4,6-disubstituted-thieno{2,3-b}pyridines and 3-aminopyridine were diazotized and coupled with 2-phenylindole, 2-methylindole, and 1-methyl-2-phenylindole, respectively. These dyes were characterized by UV-Visible, FT-IR, 1H NMR, and mass spectroscopic techniques. Solvent effects on the visible absorption spectra of the dyes were evaluated. The color of the dyes is discussed with respect to the nature of the heterocyclic ring and substituent present therein. In addition, effects of temperature, concentration, as well as acid and base on the visible absorption maxima of the dyes are reported. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:622,630, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20361 [source] A Thermally Stable Semiconducting PolymerADVANCED MATERIALS, Issue 11 2010Shinuk Cho The thermal stability of the poly(2,7-carbazole) derivative (PCDTBT) is investigated. UV,visible absorption spectra and X-ray photoelectron spectroscopy data demonstrate that the electronic structure of PCDTBT is stable in air at annealing temperatures up to 150,°C and in N2 even after exposure to temperatures up to 350,°C. Field-effect transistors fabricated with PCDTBT show stable characteristics and hole mobility up to 150,°C (air) and 350,°C (N2). [source] Synthesis and properties of phenothiazylene vinylene-based polymers: New organic semiconductors for field-effect transistors and solar cellsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Seon-Kyoung Son Abstract A series of new phenothiazylene vinylene-based semiconducting polymers, poly[3,7-(4,-dodecyloxyphenyl)phenothiazylene vinylene] (P1), poly[3,7-(4,-dodecyloxyphenyl)phenothiazylene vinylene- alt -1,4-phenylene vinylene] (P2), and poly[3,7-(4,-dodecyloxyphenyl)phenothiazylene vinylene- alt -2,5-thienylene vinylene] (P3), have been synthesized via a Horner-Emmons reaction. FTIR and 1H NMR spectroscopies confirmed that the configurations of the vinylene groups in the polymers were all - trans (E). The weight-averaged molecular weights (Mw) of P1, P2, and P3 were found to be 27,000, 22,000, and 29,000, with polydispersity indices of 1.91, 2.05, and 2.25, respectively. The thermograms for P1, P2, and P3 each contained only a broad glass transition, at 129, 167, and 155 °C, respectively, without the observation of melting features. UV,visible absorption spectra of the polymers showed two strong absorption bands in the ranges 315,370 nm and 450,500 nm, which arose from absorptions of the phenothiazine segments and the conjugated main chains. Solution-processed field-effect transistors fabricated from these polymers showed p -type organic thin-film transistor characteristics. The field-effect mobilities of P1, P2, and P3 were measured to be 1.0 × 10,4, 3.6 × 10,5, and 1.0 × 10,3 cm2 V,1 s,1, respectively, and the on/off ratios were in the order of 102 for P1 and P2, and 103 for P3. Atomic force microscopy and X-ray diffraction analysis of thin films of the polymers show that they have amorphous structures. A photovoltaic device in which a P3/PC71BM (1/5) blend film was used as the active layer exhibited an open-circuit voltage (VOC) of 0.42 V, a short circuit current (JSC) of 5.17 mA cm,2, a fill factor of 0.35, and a power conversion efficiency of 0.76% under AM 1.5 G (100 mW cm,2) illumination. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 635,646, 2010 [source] Dendrimer complexes: Fine control of metal assembly in macromoleculesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005Kimihisa Yamamoto Abstract New phenylazomethine dendrimers have been developed, with each dendrimer having a unique single structure. From ultraviolet,visible absorption spectra, we determined that stannous chloride added to dendritic polyphenylaz omethine (DPA) was assembled in a stepwise manner from the core shell to the periphery. The selective binding was achieved by the electron density gradient formed in the dendrimer, and it was confirmed by shell-selective imine reduction, transmission electron microscopy, and NMR measurements. The complex formation constants of the respective shells were estimated to be considerably different by a simulation analysis of ultraviolet,visible absorption spectra. The reversible assembly and release of iron into and out of the dendrimer were possible by electrochemical oxidation and reduction, respectively. DPA with a porphyrin at the core was found to function as an effective reduction catalyst of carbon dioxide. DPA with aryl amine at the core was demonstrated to function as a hole-transporting material in electroluminescent devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3719,3727, 2005 [source] Synthesis, absorption characteristics and solvatochromism of some novel heterocyclic cyanine dyesCOLORATION TECHNOLOGY, Issue 5 2007H A Shindy Novel heterocyclic monomethine, bis monomethine, trimethine and bis trimethine cyanine dyes incorporating benzo [2,3-b; , - ] bis furo [3,2-d] pyrazole nuclei were synthesised. The absorption characteristics of the prepared cyanines were studied and determined through measuring their electronic visible absorption spectra in 95% ethanol. The solvatochromism of some of the synthesised dyes was investigated. [source] Synthesis and fluorescence properties of a porphyrin,fullerene molecular wire,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2004Sean A. Vail Abstract The synthesis and photophysical studies of a butadiyne-linked porphyrin,C60 dyad (ZnP,C60) 6 are described. This is the first porphyrin,[60]fullerene dyad in which the two chromophores are conjugatively linked through a ,molecular wire'. The UV,visible absorption spectrum for dyad 6 is slightly red shifted relative to the porphyrin precursor 5 whose fluorescence is all but quenched by the attached C60. Copyright © 2004 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] Atomic resolution structure of pseudoazurin from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans: structural insights into its spectroscopic propertiesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009Daisuke Hira The crystal structure of native pseudoazurin (HdPAz) from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans has been determined at a resolution of 1.18,Å. After refinement with SHELX employing anisotropic displacement parameters and riding H atoms, Rwork and Rfree were 0.135 and 0.169, respectively. Visualization of the anisotropic displacement parameters as thermal ellipsoids provided insight into the atomic motion within the perturbed type 1 Cu site. The asymmetric unit includes three HdPAz molecules which are tightly packed by head-to-head cupredoxin dimer formation. The shape of the Cu-atom ellipsoid implies significant vibrational motion diagonal to the equatorial xy plane defined by the three ligands (two His and one Cys). The geometric parameters of the type 1 Cu site in the HdPAz structure differ unambiguously from those of other pseudoazurins. It is demonstrated that their structural aspects are consistent with the unique visible absorption spectrum. [source] | |||||||||||||