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Fourier Transform IR (fourier + transform_ir)
Terms modified by Fourier Transform IR Selected AbstractsSynthesis and Lithium Storage Properties of Co3O4 Nanosheet-Assembled Multishelled Hollow SpheresADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Xi Wang Abstract Single-, double-, and triple-shelled hollow spheres assembled by Co3O4 nanosheets are successfully synthesized through a novel method. The possible formation mechanism of these novel structures was investigated using powder X-ray diffraction, scanning and transmission electron microscopies, Fourier transform IR, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Both poly(vinylpyrrolidone) (PVP) soft templates and the formation of cobalt glycolate play key roles in the formation of these novel multishelled hollow structures. When tested as the anode material in lithium-ion batteries (LIBs), these multishelled microspheres exhibit excellent cycling performance, good rate capacity, and enhanced lithium storage capacity. This superior cyclic stability and capacity result from the synergetic effect of small diffusion lengths in the nanosheet building blocks and sufficient void space to buffer the volume expansion. This facile strategy may be extended to synthesize other transition metal oxide materials with hollow multishelled micro-/nanostrucutures, which may find application in sensors and catalysts due to their unique structural features. [source] Ultralow Dielectric Constant Tetravinyltetramethylcyclotetrasiloxane Films Deposited by Initiated Chemical Vapor Deposition (iCVD)ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Nathan J. Trujillo Abstract Simultaneous improvement of mechanical properties and lowering of the dielectric constant occur when films grown from the cyclic monomer tetravinyltetramethylcyclotetrasiloxane (V4D4) via initiated chemical vapor deposition (iCVD) are thermally cured in air. Clear signatures from silsesquioxane cage structures in the annealed films appear in the Fourier transform IR (1140,cm,1) and Raman (1117,cm,1) spectra. The iCVD method consumes an order of magnitude lower power density than the traditional plasma-enhanced CVD, thus preserving the precursor's delicate ring structure and organic substituents in the as-deposited films. The high degree of structural retention in the as-deposited film allows for the beneficial formation of intrinsically porous silsesquioxane cages upon annealing in air. Complete oxidation of the silicon creates ,Q' groups, which impart greater hardness and modulus to the films by increasing the average connectivity number of the film matrix beyond the percolation of rigidity. The removal of labile hydrocarbon moieties allows for the oxidation of the as-deposited film while simultaneously inducing porosity. This combination of events avoids the typical trade-off between improved mechanical properties and higher dielectric constants. Films annealed at 410,°C have a dielectric constant of 2.15, and a hardness and modulus of 0.78 and 5.4,GPa, respectively. The solvent-less and low-energy nature of iCVD make it attractive from an environmental safety and health perspective. [source] Specific Functionalization of Carbon Nanotubes for Advanced Polymer NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Nanda Gopal Sahoo Abstract A novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making advanced polymeric nanocomposites with liquid crystalline polymers (LCPs) is presented. In this approach, two types of chemical moieties (i.e., carboxylic and hydroxyl benzoic acid groups) are selectively introduced onto the sidewalls of the MWCNTs. Fourier transform IR and Raman spectroscopy are used to examine the interaction between the functionalized MWCNTs and the LCP. The strong interaction between the functionalized MWCNTs and the LCP greatly improved the dispersion of MWCNTs in the polymer matrix as well as the interfacial adhesion. The dispersion of the MWCNTs in the LCP matrix is observed by optical microscopy and field-emission scanning electron microscopy. As a result, the addition of 1,wt% MWCNTs in the LCP resulted in the significant improvement (41 and 55%) in the tensile strength and modulus of the LCP. [source] Synthesis, Mechanism, and Gas-Sensing Application of Surfactant Tailored Tungsten Oxide NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Suman Pokhrel Abstract Widely applicable nonaqueous solution routes have been employed for the syntheses of crystalline nanostructured tungsten oxide particles from a tungsten hexachloride precursor. Here, a systematic study on the crystallization and assembly behavior of tungsten oxide products made by using the bioligand deferoxamine mesylate (DFOM) (product I), the two chelating ligands hexadecyltrimethylammoniumbromide (CTAB) (II) and poly(alkylene oxide) block copolymer (Pluronic P123) (III) is presented. The mechanistic pathways for the material synthesis are also discussed in detail. The tungsten oxide nanomaterials and reaction solutions are characterized by Fourier transform IR, 1H, and 13C NMR spectroscopies, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. The indexing of the line pattern suggests WO3 is in its monoclinic structure with a,=,0.7297,nm, b,=,0.7539,nm, c,=,0.7688,nm, and ,-i;,=,90.91,°. The nanoparticles formed have various architectures, such as chromosomal shapes (product I) and slates (II), which are quite different from the mesoporous one (III) that has internal pores or mesopores ranging from 5 to 15,nm. The nanoparticles obtained from all the synthetic procedures are in the range of 40,60,nm. The investigation of the gas-sensing properties of these materials indicate that all the sensors have good baseline stability and the sensors fabricated from material III present very different response kinetics and different CO detection properties. The possibility of adjusting the morphology and by that tuning the gas-sensing properties makes the preparation strategies used interesting candidates for fabricating gas-sensing materials. [source] High Molar Extinction Coefficient Ion-Coordinating Ruthenium Sensitizer for Efficient and Stable Mesoscopic Dye-Sensitized Solar Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007D. Kuang Abstract Ru(4,4-dicarboxylic acid-2,2,-bipyridine) (4,4,-bis(2-(4-(1,4,7,10-tetraoxyundecyl)phenyl)ethenyl)-2,2,-bipyridine) (NCS)2, a new high molar extinction coefficient ion-coordinating ruthenium sensitizer was synthesized and characterized using 1H,NMR, Fourier transform IR (FTIR), and UV/vis spectroscopies and cyclic voltammetry. Using this sensitizer in combination with a nonvolatile organic-solvent-based electrolyte, we obtain a photovoltaic efficiency of 8.4,% under standard global AM,1.5 sunlight. These devices exhibit excellent stability when subjected to continuous thermal stress at 80,°C or light soaking at 60,°C for 1000,h. An electrochemical impedance spectroscopy study revealed that device stability is maintained by stabilizing the TiO2/dye/electrolyte and Pt/electrolyte interface during the aging process. The influence of Li+ present in the electrolyte on the device photovoltaic parameters was studied, and the FTIR spectral and photovoltage transient study showed that Li+ coordinates to the triethyleneoxide methylether side chains on the K60 sensitizer molecules. [source] Synthesis and characterization of polyaniline doped with organic acidsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2004Milind V. Kulkarni Abstract Spectroscopic [UV,visible and Fourier transform IR (FTIR)] and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media (acetic, citric, oxalic, and tartaric acid). The optical spectra show the presence of a greater fraction of fully oxidized insulating pernigraniline phase in polyaniline doped with acetic acid. In contrast, the selectivity in the formation of the conducting phase is higher in oxalic acid as a protonic acid media. The FTIR spectra of these polymers reveal a higher ratio of the relative intensities of the quinoid to benzenoid ring modes in acetic acid doped polyaniline. Scanning electron micrographs revealed a sponge-like structure derived from the aggregation of the small granules in acetic acid and oxalic acid doped polyaniline. A three-step decomposition pattern is observed in all the polymers, regardless of the protonic acid used for the doping. The second step loss related to the loss of dopant is found to be higher in the oxalic acid doped polymer. In accordance with these results the conductivity is also found to be higher in oxalic acid doped material. The temperature dependent conductivity measurements show the thermal activated behavior in all the polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2043,2049, 2004 [source] Density functional and vibrational spectroscopic analysis of ,-caroteneJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2003S. Schlücker Abstract We report a computational study on the structural, energetic and vibrational spectroscopic characteristics of ,-carotene employing density functional theory (DFT). The optimized geometry and the complete vibrational spectrum calculated at the BPW91/6,31G* level, including infrared (IR) intensities and Raman activities, are presented. The centrosymmetric structure of ,-carotene is verified both theoretically and experimentally, by identifying a stable calculated structure with Ci symmetry and the mutually exclusive occurrence of bands in the experimental Fourier transform IR and Raman spectrum, respectively. The calculated vibrational spectra reflect the major characteristic features observed experimentally. Differences in the calculated IR intensities and Raman activities for a few dominant modes of two ,-carotene configuration isomers, the all- trans and the natural abundant (C6,C7) s- cis form, are explained qualitatively by the corresponding eigenvectors. At the level of theory employed, s- cis -,-carotene was found to be 8.8 kJ mol,1 more stable than the all- trans form. Calculations on ,-carotene model systems were performed to separate electronic from steric contributions. The higher stability of s- cis -,-carotene is explained by an energetically favored ,-ionone ring conformation, compensating for its shorter conjugation length in comparison with the all- trans form. Copyright © 2003 John Wiley & Sons, Ltd. [source] Conformation of , zeins in solid state by Fourier transform IRBIOPOLYMERS, Issue 6 2003Lucimara 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 spectroscopyBIOPOLYMERS, Issue 1 2002Tiansheng 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] | |||||||||||||