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Infrared Absorption (infrared + absorption)

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Chemistry53%

Terms modified by Infrared Absorption

  • infrared absorption spectrum
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    Selected Abstracts

    Enhanced Infrared Absorption of C60 on Thin Evaporated Pd Island Films

    ISRAEL JOURNAL OF CHEMISTRY, Issue 3 2006
    Toshimasa Wadayama
    Infrared transmission spectra of C60 multilayers on thin Pd films deposited onto surface-oxidized Si(100) and hydrogen-terminated Si(111) substrates are reported. In both cases, the spectra in the 1500,1100 cm,1 region exhibited bands at 1444, 1429, and 1182 cm,1 due, respectively, to the Ag (2), T1u (4), and T1u (3) modes. The appearance of the Ag (2) mode, which is originally infrared inactive (Raman active), reveals electron transfer from the metal to chemisorbed C60. Indeed, increasing the thickness of C60, the Ag (2) mode intensity saturated more rapidly than the T1u (4) and T1u (3) modes. The originally infrared active T1u (4) and T1u (3) modes were enhanced in intensity depending upon the Pd thickness. Actually, while both substrates gave nearly the same magnitude of enhancement, the optimum Pd thickness was smaller on the hydrogen-terminated surface than on the surface-oxidized surface. On the other hand, the Ag (2) mode was less intense on the hydrogen-terminated surface than on the oxidized surface, suggestive of a shortage of chemisorbed C60 and thus pointing out the importance of the metal film morphology. Indeed, Pd films deposited on the two substrates gave rise to quite different AFM images. We also show that, regardless of the substrate, the Ag (2) mode is an order of magnitude smaller than for Ag deposition, though no remarkable intensity differences were observed with respect to the T1u (4) and T1u (3) modes. [source]

    Cover Picture: Spectroscopic and Photophysical Properties of a Highly Derivatized C60 Fullerol (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 1 2006
    Mater.
    Abstract The photo-oxidative stress in aqueous milieus can readily be generated in the presence of newly synthesized highly derivatized fullerenes (fullerols) reported in the Full Paper by Vileno and co-workers on p.,120. Their basic structural and photophysical properties were characterized using a range of methods, including X-ray photoelectron and IR spectroscopies, and electron spin resonance. Moreover, a significant drop of the local stiffness of a living cell was monitored using atomic force microscopy. This cell softening was attributed to the early effects of the photo-oxidative stress. Hydroxylated C60 molecules, also called fullerols, are a class of water-soluble fullerenes. Here we report the synthesis in acidic conditions of a highly derivatized fullerol (up to 36 carbons per C60 are oxidized). Spectroscopic investigations (X-ray photoelectron spectroscopy and infrared absorption) highlight the coexistence of both acidic and basic forms for the hydroxyl addends of derivatized C60. pH titrimetry reveals that, at millimolar concentrations, only ten protons per fullerol molecule are labile. Such a low value, as compared to 36 hydroxyl groups, is explained by the formation of clusters. A UV-vis absorption study performed over a large range of concentrations also points to the aggregation phenomenon. Moreover, this study shows that the clusters of fullerols appear at relatively low (micromolar) concentrations. An electron spin resonance (ESR) study, based on the attack of singlet oxygen (1,g) on 2,2,6,6-tetramethyl-4-piperidinol (TMP-OH), has proved the potential of hydroxylated C60 for performing efficient generation of singlet oxygen in aqueous solution. ESR measurements, which allow detection and quantification of 1,g, have also revealed the generation of reactive oxygen species (ROS). The yield of generation of 1,g and ROS is strongly correlated to the concentration of fullerol, thus also pointing to the aggregation of fullerol molecules. Exposing glioblastoma cells to oxidative stress in the presence of hydroxylated C60 and visible light has also been performed. Atomic force microscopy is used to monitor the relevant diminishment of the Young's modulus values for cells exposed to the oxidative stress. These results point to a possible application field of fullerols for performing bio-oxidations. [source]

    Vibrational spectra of barium formate crystal

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2001
    Jianjun Liu
    The Raman spectra of barium formate were investigated at room temperature and liquid nitrogen temperature and the infrared absorption and reflection spectra at room temperature. The presence of two crystallographically non-equivalent sets of formate ions in the lattice results in the doubling of the internal modes in the vibrational spectra. The observed high-wavenumber vibrational bands are assigned to the internal vibrations of formate ions. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    SERS-active sites on various copper substrates

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2001
    C. Siemes
    The wavenumbers of the Raman bands of ethylene adsorbed on Cu in ultra-high vacuum depend on the surface structure of the copper substrate. Thus it is possible to differentiate between ethylene adsorbed at Cu(110) sites, Cu(111) sites and surface defect sites of unknown configuration. These latter are the ,SERS-active sites.' Only when these sites are annealed does the distance dependence of SERS follow the expectations from the electromagnetic model of SERS. In the presence of the SERS-active sites, also the signal of ethylene at (111) sites shows a ,first layer effect.' Ethylene adsorbed on cold-deposited copper films shows strong infrared absorption at the same wavenumber as the ethylene at SERS-active sites in Raman scattering, irrespective of the Raman,infrared exclusion rule for the free centrosymmetric ethylene molecule. This raises the possibility that SERS-active sites are also infrared-active sites. The SERS-active sites at stepped Cu surfaces decorated by 3 nm of cold-deposited copper anneal below 200 K, whereas they prevail beyond 400 K on Cu island films. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Chemical bonding of nitrogen in dilute InAsN and high In-content GaInAsN

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007
    D. N. Talwar
    Abstract To assess the preferential chemical bonding of N in dilute InAsN and high In content GaInNAs alloys we have analyzed the recent infrared absorption and Raman scattering data by using a comprehensive Green's function theory within an 11 parameter rigid-ion-model. Our theoretical results provided firm corroboration to some of the observed N- related modes to specific bonding (micro clusters) configurations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Defect-impurity interactions in irradiated tin-doped Cz-Si crystals

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2003
    L. I. Khirunenko
    Abstract Results of a combined infrared absorption (IR) and deep-level transient spectroscopy (DLTS) study of defects induced by irradiation with fast electrons in Sn-doped Czochralski-grown Si crystals are reported. Tin atoms were found to interact effectively with vacancy as well as with interstitial-type radiation-induced defects. Manifestations of stable tin-vacancy and tin-interstitial carbon atom complexes were observed in DLTS and IR absorption spectra. Defect transformations upon heat-treatments of the irradiated samples were studied. Tin atoms were found to be effective traps for mobile vacancy,oxygen (V,O) complexes. A local vibrational mode of a Sn,V,O complex has been identified. [source]

    Radiation-induced defects and their transformations in oxygen-rich germanium crystals

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2003
    V. P. Markevich
    Abstract Defects induced by irradiation with fast electrons and 60Co gamma-rays in oxygen-rich Ge crystals have been studied by means of infrared absorption, deep level transient spectroscopy (DLTS) and Hall effect measurements. It is found that the vacancy,oxygen (V,O) complex in Ge has three charge states (doubly negative, singly negative and neutral ones) and two corresponding energy levels in the gap at about Ec,,,0.21 eV and Ev + 0.27 eV. Three absorption bands at 621.4, 669.1 and 716.2 cm,1 are identified as oxygen-related asymmetrical stretching vibrations for the neutral, singly negatively charged and doubly negatively charged states of the V,O complex, respectively. [source]

    Thin film solar cells incorporating microcrystalline Si1,xGex as efficient infrared absorber: an application to double junction tandem solar cells

    PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2010
    Takuya Matsui
    Abstract We have fabricated efficient (,7,8%) hydrogenated microcrystalline Si1,xGex (µc-Si1,xGex:H, x,,,0.1,0.17) single junction p-i-n solar cells with markedly higher short-circuit current densities than for µc-Si:H (x,=,0) solar cells due to enhanced infrared absorption. By replacing the conventional µc-Si:H with the µc-Si1,xGex:H as infrared absorber in double junction tandem solar cells, the bottom cell thickness can be reduced by more than half while preserving the current matching with hydrogenated amorphous silicon (a-Si:H) top cell. An initial efficiency of 11.2% is obtained for a-Si:H/µc-Si0.9Ge0.1:H solar cell with bottom cell thickness less than 1,µm. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Geochemistry, Petrography and Spectroscopy of Organic Matter of Clay-Associated Kerogen of Ypresian Series: Gafsa-Metlaoui Phosphatic Basin, Tunisia

    RESOURCE GEOLOGY, Issue 4 2008
    Mongi Felhi
    Abstract This work presents geochemical characterization of isolated kerogen out of clay fraction using petrography studies, infrared absorption and solid state 13C nuclear magnetic resonance (NMR) spectroscopy, with N -alkane distributions of saturated hydrocarbon. Mineralogical study of clay mineral associations was carried out using X-ray diffraction (XRD), on Ypresian phosphatic series from Gafsa-Metlaoui basin, Tunisia. The XRD data indicate that smectite, palygorskite and sepiolite are the prevalent clay minerals in the selected samples. In this clay mineral association, the N -alkane (m/z = 57) distribution indicates that the marine organic matter is plankton and bacterial in origin. The kerogens observed on transmitted light microscopy, however, appear to be totally amorphous organic matter, without any appearance of biological form. The orange gel-like amorphous organic matter with distinct edges and homogenous texture is consistent with a high degree of aliphaticity. This material has relatively intense CH2 and CH3 infrared bands in 13C NMR peaks. This aliphatic character is related to bacterial origin. Brown amorphous organic matter with diffuse edges has a lower aliphatic character than the previous kerogen, deduced from relatively low CH2 and CH3 infrared and 13C NMR band intensities. [source]

    The complete chirospectroscopic signature of the peptide 310 -helix in aqueous solution

    BIOPOLYMERS, Issue 1 2004
    Claudio Toniolo
    Abstract We synthesized by solution methods a water-soluble, terminally blocked heptapeptide based on five markedly helicogenic, C, -tetrasubstituted ,-amino acids C, -methyl- L -norvalines and two strongly hydrophilic 2-amino-3-[1-(1,4,7-triazacyclononane)]- L -propanoic acid residues at positions 2 and 5. A Fourier transform infrared absorption and NMR analysis in deuterated chloroform and aqueous solutions of the heptapeptide and two side-chain protected synthetic precursors confirmed our working hypothesis that all oligomers are folded in the 310 -helical conformation. Based on these findings, we exploited this heptapeptide as a chiral reference compound for detailed electronic CD, vibrational CD, and Raman optical activity characterizations of the 310 -helix in aqueous solution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source]

    Spectroscopic rationalization of the separation abilities of decaproline chiral selector in dichloromethane,isopropanol solvent mixture

    CHIRALITY, Issue 2 2007
    Peng Zhang
    Abstract A chiral column, with decaproline as the chiral selector, has broad chiral selectivity. To understand the separation mechanism of this chiral column, multiple spectroscopic techniques, including optical rotation, electronic circular dichroism, infrared absorption and vibrational circular dichroism, have been used here to study the conformation of the decaproline oligomer in isopropanol(IPA)/dichloromethane(DCM) mixtures. These studies indicate that decaproline oligomer adopts polyproline II conformation in IPA/DCM solvent system (0% IPA , 100% IPA). Hydrogen bonding interactions between CO groups of decaproline and IPA molecules increase as the content of IPA in the solvent mixture increases up to 60% and become less significant from then onwards. These spectroscopic observations are found to have a good correlation with the enantiomeric separation of racemic 2,2,2-trifluoro-1-[10-(2,2,2-trifluoro-1-hydroxy-ethyl-anthracen-9-yl]-ethanol by the decaproline column. Chirality 2006. © 2006 Wiley-Liss, Inc. [source]

    Infrared Spectra of U.S. Automobile Original Finishes.

    JOURNAL OF FORENSIC SCIENCES, Issue 3 2006

    ABSTRACT: The identification, analysis, and occurrence in U.S. automobile original finishes (1974,1989) of Nickel Titanate (yellow) and Chrome Titanate (yellow,orange) are described in this report. The titanate pigments are based on the rutile (titanium dioxide) structure and there are only minor differences between the infrared absorptions of rutile and the titanates. Titanate pigment absorptions in paint spectra can thus be easily mistaken for those of rutile. Each of the titanates, however, contains two elements in addition to titanium that can serve to distinguish them using elemental analyses. Fourier transform infrared (4000,220 cm,1) and X-ray fluorescence instruments were used in combination for the in situ analysis of the titanates. In addition to titanium, nickel, and antimony, the three main detectable elements comprising Nickel Titanate, all of the commercial products of this pigment that were examined also contained impurities of zirconium, niobium, and usually lead. These elements were also detected in most of the monocoats in which Nickel Titanate was identified, as well as in the Chrome Titanate pigments, and the zirconium to niobium ratio was found to exhibit a wide variation. Nickel Titanate is a relatively common pigment that was identified in nearly three dozen U.S. automobile yellow nonmetallic monocoats (1974,1989), while Chrome Titanate appears to have been used in only a few yellow and orange nonmetallic monocoats. The use of the titanate pigments likely increased after this time period as they were replacements for lead chromate pigments (last used in a U.S. automobile original finish in the early 1990s), and are more amenable for use in basecoat/clearcoat finishes than in monocoats. Minor distortions of the infrared absorptions of rutile, anatase, and the titanates obtained using accessories with diamond windows were noted, and their origins are discussed. [source]

    Structural Identification of Spectroscopic Substates in Neuroglobin

    CHEMPHYSCHEM, Issue 1 2010
    Karin Nienhaus Dr.
    Abstract The structural origins of infrared absorptions of photodissociated CO in murine neuroglobin (Ngb) are determined by combining Fourier transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulations. Such an approach allows to identify and characterize both the different conformations of the Ngb active site and the transient ligand docking sites. To capture the influence of the protein environment on the spectroscopy and dynamics, experiments and simulations are carried out for the wild type protein and its F28L and F28W mutants. It is found that a voluminous side chain at position 28 divides site B into two subsites, B' and B". At low temperatures, CO in wt Ngb only migrates to site B' from where it can rebind, and B" is not populated. The spectra of CO in site B' for wt Ngb from simulations and experiments are very similar in spectral shift and shape. They both show doublets, red-shifted with respect to gas-phase CO and split by,8 cm,1. The FTIR spectra of the F28L mutant show additional bands which are also found in the simulations and can be attributed to CO located in substate B". The different bands are mainly related to different orientations of the His64 side chain with respect to the CO ligand. Large red-shifts arise from strong interactions between the HistidineNH and the CO oxygen. After dissociation from the heme iron, the CO ligand visits multiple docking sites. The locations of the primary docking site B and a secondary site C, which corresponds to the Mb Xe4 cavity, could be identified unambiguously. Finally, by comparing experiment and simulations it is also possible to identify protonation of its , position (His,64 NgbCO) as the preferred heme-bound conformation in the wild type protein with a signal at 1935 cm,1. [source]