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Transform IR Spectroscopy (transform + ir_spectroscopy)

Distribution by Scientific Domains
Chemistry66%

Kinds of Transform IR Spectroscopy

  • fourier transform ir spectroscopy
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    Selected Abstracts

    Spectroscopy of single-walled carbon nanotubes in aqueous surfactant dispersion

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009
    Dania Movia
    Abstract Optical studies of single-walled carbon nanotubes (SWNTs) dispersed in aqueous surfactant suspensions have made significant progress since the discovery of their bright band-gap fluorescence in the near-infrared region [M. J. O'Connell et al., Science 297, 593,596 (2002)]. In this article we report the systematic investigation of the effect of chemical purification and oxidation on the spectroscopic properties of SWNTs. The SWNTs samples we prepared differ for the percentage of impurities present, the amount of defects introduced in their graphitic structure and/or the functional groups expressed on their surface. The generation of carboxylic groups on the nanotubes surface by oxidative treatment was validated by means of thermal gravimetric analysis and ATR/Fourier transform IR spectroscopies, as well as Raman spectroscopy. We have solubilized pristine, purified SWNTs (p-SWNTs) and oxidized SWNTs (o-SWNTS) in Milli-Q water using sodium dodecylbenzene sulphonate (SDBS). While our Vis-NIR Absorption spectra of p-SWNTs and o-SWNTS dispersions in aqueous SDBS solution show the loss of the resolution of the characteristic van Hove singularities, NIR Photoluminescence spectra are characterized by structured emission peaks. [source]

    Replication and Coating of Silica Templates by Hydrothermal Carbonization,

    ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007
    M.-M. Titirici
    Abstract Hierarchical carbon materials with functional groups residing at the surface are prepared for the first time by using nanostructured silica materials as templates in combination with hydrothermal carbonization at mild temperatures (180,°C). Different carbon morphologies (e.g., macroporous casts, hollow spheres, carbon nanoparticles, and mesoporous microspheres) can be obtained by simply altering the polarity of the silica surface. The surface functionality and hydrophilicity of the resulting materials are assessed by Fourier transform IR spectroscopy, X-ray photoelectron analysis, and water porosimetry. Raman spectroscopy and X-ray diffraction measurements show that the materials are of the carbon-black type, similar to charcoal. [source]

    Characteristics of hydrogen bond formation between sugar and polymer in freeze-dried mixtures under different rehumidification conditions and its impact on the glass transition temperature

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008
    Koreyoshi Imamura
    Abstract The characteristics of hydrogen bond formation between trehalose and polyvinylpyrrolidone (PVP) in amorphous mixtures at different hydration states were quantitatively investigated. Amorphous trehalose,PVP mixtures were prepared by freeze-drying and equilibrated at different relative humidities (RH). Infrared (IR) spectra of the trehalose,PVP mixtures were obtained by Fourier transform IR spectroscopy,(FTIR) and the IR band corresponding to CO groups of PVP was deconvolved into the component bands responsible for CO groups that were free and restricted by hydrogen bonds, to estimate the degree of the trehalose,PVP interactions. The FTIR analysis indicated that approximately 80% of the CO groups of PVP formed hydrogen bonds with trehalose in the presence of more than 3 g of trehalose per gramme of PVP, independent of the RH. IR analysis of the OH stretching vibration of the sugar demonstrated that the presence of PVP lead to an increase in the free hydroxyl groups of trehalose that did not form hydrogen bonds at RH 0%. On the other hand, the water sorption behavior of the trehalose,PVP mixtures suggested that rehumidification diminished the effect of PVP on increasing the free OH groups. Thus a peculiar relationship may exist between Tg, RH and the composition of the mixture: The presence of PVP increased Tg at RHs 0 and above 23% but decreased Tg at 11%. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1301,1312, 2008 [source]

    Structure and mechanical properties of nanocrystalline boron nitride thin films ,

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2001
    Paolo M. Ossi
    Abstract Boron nitride thin films have been deposited on (100) Si wafers, kept at low temperature, by radio frequency (r.f.) magnetron sputtering. The r.f. target power was fixed at 150,W and the substrate bias voltage ranged between ,50 and ,130,V. Film composition was checked by Auger electron spectroscopy; the structure was investigated by Fourier transform IR spectroscopy, glancing-angle X-ray diffraction and micro-Raman spectroscopy. Film hardness and Young's modulus were measured by nanoindentation. Film composition is nearly equiatomic, with a low degree of gaseous contamination. All samples are very fine grained, and nanocrystalline. Film coordination is mixed sp2,sp3, and the fraction of tetrahedral coordination depends critically on the bias voltage value. In hexagonal sp2 -bonded films the hardnesses and Young's moduli are low and increase considerably with the content of sp3 -coordinated cubic phase. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Conformation of , zeins in solid state by Fourier transform IR

    BIOPOLYMERS, Issue 6 2003
    Lucimara A. Forato
    Abstract The major maize storage proteins (, zeins) are deposited as an insoluble mass in the protein bodies of the endosperm. Because they are insoluble in water, most structural studies are performed in alcohol solutions. To solve the question raised by several authors about denaturation of the , zein structure by alcohol, we analyze the secondary structure of , zeins prepared with and without solubilization in alcohol (corn gluten meal and protein bodies with high concentrations of , zeins and traces of , zeins). The secondary structures of , zeins are analyzed in the solid state by Fourier transform IR spectroscopy (FTIR) in KBr pellets and solid-state 13C-NMR spectroscopy. The proportion of secondary structures obtained by FTIR of , zeins prepared with and without solubilization in alcohol yield almost identical proportions of , helices and , sheets. The proportion of , helices (43%) agrees with that measured by circular dichroism in an alcohol solution. However, the proportion of , sheets (28%) is higher than the one measured by the same technique. Gluten and protein body samples with high , zein content showed higher , sheet and lower , helix proportions than that obtained for , zein preparations. The solid-state 13C-NMR spectra show the carbonyl peak for the , zeins at , 176 and for the sample rich in , zeins at , 172, which demonstrates the presence of a high content of , helices and , sheets, respectively. These results indicate that alcohol solubilization does not affect the conformation of , zeins, validating the secondary structure measurements in solution. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy), 2003 [source]

    Changes in protein conformation and dynamics upon complex formation of brain-derived neurotrophic factor and its receptor: Investigation by isotope-edited Fourier transform IR spectroscopy

    BIOPOLYMERS, Issue 1 2002
    Tiansheng Li
    Abstract The interactions of brain-derived neurotrophic factor (BDNF) with the extracellular domain of its receptor (trkB) are investigated by employing isotope-edited Fourier transform IR (FTIR) spectroscopy. The protein secondary structures of individual BDNF and trkB in solutions are compared with those in their complex. The temperature dependence of the secondary structures of BDNF, trkB, and their complex is also investigated. Consistent with the crystal structure, we observe by FTIR spectroscopy that BDNF in solution contains predominantly , strands (,53%) and relatively low contents of other secondary structures including , turns (,16%), disordered structures (,12%), and loops (,18%) and is deficient in , helix. We also observe that trkB in solution contains mostly , strands (52%) and little , helix. Conformational changes in both BDNF and trkB are observed upon complex formation. Specifically, upon binding of BDNF, the conformational changes in trkB appear to involve mostly , turns and disordered structures while the majority of the ,-strand conformation remains unchanged. The IR data indicate that some of the disordered structures in the loop regions are likely converted to , strands upon complex formation. The FTIR spectral data of BDNF, trkB, and their complex indicate that more amide NH groups of trkB undergo H,D exchange within the complex than those of the ligand-free receptor and that the thermal stability of trkB is decreased slightly upon binding of BDNF. The FT-Raman spectra of BDNF, trkB, and their complex show that the six intramolecular disulfide bonds of trkB undergo significant conformational changes upon binding of BDNF as a result of changes in the tertiary structure of trkB. Taken together, the FTIR and Raman data are consistent with the loosening of the tertiary structure of trkB upon binding of BDNF, which leads to more solvent exposure of the amide NH group and decreased thermal stability of trkB. This finding reveals an intriguing structural property of the neurotrophin ligand,receptor complex that is in contrast to other ligand,receptor complexes such as a cytokine,receptor complex that usually shows protection of the amide NH group and increased thermal stability upon complex formation. © 2002 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 67: 10,19, 2002; DOI 10.1002/bip.10038 [source]