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Stretching Vibrations (stretching + vibration)
Kinds of Stretching Vibrations Selected AbstractsSymmetric Stretching Vibration of CH4 in Clathrate Hydrate StructuresCHEMPHYSCHEM, Issue 14 2010Dr. Hiroshi Ohno Movers and shakers: Vibrational states of CH4 molecules encaged in three clathrate hydrate structures are studied (see picture). Guest methane distribution in the structure-H 512 and 435663 host cavities is revealed for the first time. Raman profiles of the CH4 vibration are dependent not only on types of water cages, but also on clathrate structures (guest compositions), suggesting distinctive differences in molecular interactions between the three hydrate systems. [source] Resonance Raman study of multihemic c -type cytochromes from Desulfuromonas acetoxidansFEBS JOURNAL, Issue 4 2000Geneviève Chottard Two multihemic cytochromes c from the sulfur reducing bacteria Desulfuromonas acetoxidans have been studied by optical and resonance Raman spectroscopy: cytochrome c551.5, a trihemic cytochrome and cytochrome c Mr 50 000, a recently isolated high molecular mass cytochrome. The redox and Raman characteristics of cytochrome c551.5 are compared to those of the tetrahemic cytochromes c3 from Desulfovibrio. While the redox behavior, followed by spectroelectrochemistry, is similar to that of cytochrome c3, showing the same conformational change after reduction of the highest potential heme, the Raman data show a contribution from a His, form of the axial ligands and lead to the assignment of a band at 218 cm,1 to the Fe(III),(His)2 stretching vibration. The Raman data on cytochrome c Mr 50 000 are in favor of an entirely low spin species with two different sets of axial ligands. A partially reduced state is easily accessible by ascorbate addition. [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 temperatureJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008Koreyoshi 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] Solvent dependent study of carbonyl vibrations of 3-phenoxybenzaldehyde and 4-ethoxybenzaldehyde by Raman spectroscopy and ab initio calculationsJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Veerabahu Ramakrishnan Abstract A Raman spectroscopy investigation of the carbonyl stretching vibrations of 3-phenoxybenzaldehye (3Phbz) and 4-ethoxybenzaldeheyde (4Etob) was carried out in binary mixtures with different polar and nonpolar solvents. The purpose of this study was twofold: firstly, to describe the interaction of the carbonyl groups of two solute molecules in terms of a splitting in the isotropic and anisotropic components and secondly, to analyze their spectroscopic signatures in a binary mixture. Changes in wavenumber position, variation in the anisotropic shift and full width half maximum were investigated for binary mixtures with different mole fractions of the reference systems. In binary mixtures, the observed increase in wavenumber with solvent concentration does not show linearity, indicating the significant role of molecular interactions on the occurrence of breaking of the self-association of the solute. In all the solvents, a gradual decrease in the anisotropic shift reflects the progressive separation of the coupled oscillators with dilution. ,i(,c), 3Phbz,solvent mixtures, exhibit a gradual decrease with decrease in the concentration of the solute which is an evidence on the influence of micro viscosity on linewidth. For 4Etob, the carbonyl stretching vibration shows two well-resolved components in the Raman spectra, attributed to the presence of two distinct carbonyl groups: hydrogen-bonded and free carbonyl groups. The intensity ratio of the carbonyl stretching vibration of these two types of carbonyl groups is studied to understand the dynamics of solute/solvent molecules owing to hydrogen bond interactions. Ab initio calculations were employed for predicting relevant molecular structures in the binary mixtures arising from intermolecular interactions, and are related to the experimental results. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]·8H2OJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2008Ray L. Frost Abstract The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm,1 were assigned to the symmetric stretching modes of the (UO2)2+ and (SeO3)2, units, respectively. These values gave the calculated UO bond lengths in uranyl of 1.799 and/or 1.814 Å. Average UO bond length in uranyl is 1.795 Å, inferred from the X-ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm,1 was assigned to the ,3 antisymmetric stretching mode of the (UO2)2+ (calculated UO bond length 1.808 Å). The band at 739 cm,1 was attributed to the ,3 antisymmetric stretching vibration of the (SeO3)2, units. The ,4 and the ,2 vibrational modes of the (SeO3)2, units were observed at 424 and 473 cm,1. Bands observed at 257, and 199 and 139 cm,1 were assigned to OUO bending vibrations and lattice vibrations, respectively. OH···O hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermo-Raman spectroscopy of synthetic nesquehonite , implication for the geosequestration of greenhouse gasesJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2008Matthew C. Hales Abstract Pure nesquehonite (MgCO3·3H2O)/Mg(HCO3)(OH)·2H2O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm,1, which shifts to 1105 cm,1 at 450 °C, assigned to the ,1CO32, symmetric stretching mode. Two bands at 1419 and 1509 cm,1 assigned to the ,3 antisymmetric stretching mode shift to 1434 and 1504 cm,1 at 175 °C. Two new peaks at 1385 and 1405 cm,1 observed at temperatures higher than 175 °C are assigned to the antisymmetric stretching modes of the (HCO3), units. Throughout all the thermo-Raman spectra, a band at 3550 cm,1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm,1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175 °C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO3)·2H2O. Copyright © 2008 John Wiley & Sons, Ltd. [source] Concentration dependent Raman and IR study on salicylaldehyde in binary mixturesJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2007A. Anis Fathima Abstract A vibrational spectroscopic study of binary mixtures of salicylaldehyde (SA) in three different solvents (polar and nonpolar) is presented. The vibrational modes ,(CO), hydroxyl stretching mode (COH) and aldehydic (CH) stretching vibration were analyzed. Changes in wavenumber position and full width half maximum have been explained for neat as well as binary mixtures with different volume fractions of the reference system, SA, in terms of inter- and intramolecular hydrogen bonding. The IR spectra of these mixtures have also been taken and compared with the Raman data. The spectral changes have been well explained using the concentration fluctuation model and solute,solvent interaction. Copyright © 2007 John Wiley & Sons, Ltd. [source] A Raman spectroscopic study of the uranyl selenite mineral haynesiteJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2006Ray L. Frost Abstract The mineral haynesite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 and 77 K. Two bands at 811.5 and 800.2 cm,1 are assigned to the symmetric stretching modes of the (UO2)2+ and (SeO3)2, units respectively. These values give calculated UO bond lengths of 1.799 and/or 1.801 Å. The broad band at 861.8 cm,1 is assigned to the ,3 antisymmetric stretching mode of the (UO2)2+ (calculated UO bond length 1.813 Å). Additional bands are observed in the 77 K spectrum. In the spectroscopy of selenite compounds, the position of the antisymmetric stretching vibration occurs at lower wavenumbers than the symmetric stretching mode and thus the band at 740.5 cm,1 is attributed to the ,3 antisymmetric stretching vibration of the (SeO3)2, units. The ,4 and the ,2 vibrational modes of the (SeO3)2, units are observed at 418.5 and 472.1 cm,1. Bands observed at 278.3, 257.3 and 218.8 cm,1 are assigned to OUO bending vibrations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Single-crystal Raman study of erythrite, Co3(AsO4)2·8H2OJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2004Wayde N. Martens Abstract Single-crystal Raman and infrared spectra of natural and synthetic erythrite, Co3(AsO4)2·8H2O, are reported and compared with the spectra polycrystalline, synthetic annabergite, Ni3(AsO4)2·8H2O, and hörnesite, Mg3(AsO4)2·8H2O. Factor group analysis and single-crystal considerations were used to interpret the experimental data. The Raman spectra of erythrite reveal the ,1 arsenate stretching vibration at 850 cm,1 (Ag) with the corresponding infrared band at 821 cm,1 (Bu). The ,3 antisymmetric vibration is split into three components, observed at 796 (Ag), 788 (Ag) and 803 (Bg) cm,1. The ,2 symmetric bending modes are observed at 375 (Ag) and 385 (Bg) cm,1. The ,4 bending modes are predicted to split into three bands which are observed at 441 (Ag), 446 (Bg) and 457 (Ag) cm,1. Lattice vibrations are found at 112 (Ag), 124 (Bg), 145 (Ag), 157 (Bg), 165 (Ag), 179 (Ag), 189 (Ag), 191 (Bg), 201 (Bg), 210 (Ag), 227 (Ag), 250 (Ag), 264 (Ag), 264 (Ag), 280 (Bg), 302 (Bg), 321 (Bg) and 338 cm,1(Ag). Hydroxyl stretching modes are observed at 3050, 3218, 3333, 3449 and 3479 cm,1 in the infrared spectrum. Raman-active hydroxyl bands are detected at 3009 (Bg), 3052 (Ag), 3190 (Bg) 3203 (Bg), 3281 (Ag) and 3310 (Bg), 3436 (Bg) and 3443 (Ag) cm,1. Infrared hydroxyl bands at 3050 and 3218 cm,1 are from water type II, short hydrogen bonding distances, and the bands at 3449 and 3479 cm,1 are due to water I, long hydrogen bonding distances. Water bending modes are detected in the infrared spectrum at 1571, 1621, 1641 and 1682 cm,1, but owing to the inherent weak Raman scattering cross-section of water these could not be detected in the Raman spectra. Copyright © 2004 John Wiley & Sons, Ltd. [source] Detection of single lipid bilayers with coherent anti-Stokes Raman scattering (CARS) microscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2003Eric O. Potma Abstract We investigated vibrational imaging of phospholipid bilayers with CARS microscopy. Single lipid membranes of supported bilayers, giant unilamellar vesicles and intact erythrocyte membrane are detected with the strong resonant signal of the C,H stretching vibration. In addition, it is shown that the CARS signal field of the lipids near the glass/water interface is amplified through mixing with the back-reflected non-resonant CARS field of the glass coverslip. Furthermore, interference effects between two separate bilayers are observed, allowing intermembrane distances to be determined beyond the diffraction-limited resolution of the microscope. Copyright © 2003 John Wiley & Sons, Ltd. [source] Research on alkali-catalyzed gasification of coal black liquor slurry cokes made up by five different coals,ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007Kuang Jian-ping Abstract The black liquor from paper mills contains large quantities of sodium compounds and other organic matter, such as lignin and cellulose. The sodium compounds will provide the catalytic action in coal black liquor slurry (CBLS) gasification, while lignin and cellulose can enhance the heat value in the process of gasification. Five black liquor slurries were made from coals from different regions: Xin Wen, Huang Ling, Zao Zhuang, Shen Mu and Shen Hua. Alkali-catalyzed gasification experiments on the different samples of CBLS and coal water slurry (CWS) were made on a thermobalance and a fixed-bed reactor. The residues of gasification were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results reveal that many mesopores and micropores exist on the surface of the CBLS coke, which play a key role in the catalytic gasification process, and sodium as a catalyst can quicken the gasification reaction rate. XRD shows that NaCl and sodium silicate are the main crystal components in dry samples of CBLS and CWS. The C-O stretching vibration peak shifting to a lower wavenumber means that the energy for the C-O stretching vibration in the CBLS carbon matrix decreases after partial gasification. Not only the coal rank but also the oxygen-containing groups and minerals influence coal coke's gasification activity. Of the five different CBLS, the gasification reactivity of CBLS made by the Huang Ling coal was found to be higher than that of the others. The higher the degree of coalification, the lower the activity of the coke. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source] FTIR-spectroscopic characterization of humic acids and humin fractions obtained by advanced NaOH, Na4P2O7, and Na2CO3 extraction proceduresJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2007Michael Tatzber Abstract Aim of our study was the development of the methodological basis for the characterization of humic fractions of a long-term field experiment. Humic acids (HAs) were extracted from three layers of a nontilled soil using three different extractants (1 M NaOH, 0.1 M Na4P2O7, 1 M Na2CO3), and the humin fraction was enriched. NaOH as extractant for FTIR analysis of humic substances yields higher resolved IR spectra, especially in the important regions of stretching vibrations including aromatic and aliphatic groups and in the fingerprint area including amides, aliphats, and aromats than the other extractants. The NaOH extraction has lower extraction yields as compared to Na4P2O7 and Na2CO3 and represents a different part of the soil organic matter (SOM). This is reflected by lower C : N ratios and higher E4 : E6 and fulvic acid,to,humic acid ratios as compared to the other extractants. The FTIR band areas of HA fraction obtained by NaOH showed an increase of the aromatic and carbonyl groups and a decrease of amide groups with increasing soil depth. Aliphatic groups showed contradicting results: The bands of the stretching vibrations increased, and the band of the bending vibrations decreased. We assume that band interactions in the bending vibrations were responsible for that phenomenon under the assumption of an increase of aliphatic groups with increasing soil depth. The IR bands of the enriched humin fraction showed a decreasing trend in case of both aliphatic bands deriving from stretching vibrations and an increase of aromatic characteristics with depth. Our study led to the conclusion that HA fractions obtained by 1 M NaOH represent a small and dynamic fraction indicated by the measured yields in combination with values of Nt, C : N, E4 : E6 ratios, and ratios of fulvic acids (FA) to HA. The humin fraction has a high contribution to the total organic C and represents a more stabilized fraction of SOM which still shows changes in its aromatic and aliphatic characteristics with soil depth. [source] Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2OJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Ray L. Frost Abstract Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (SO4)2, units and of water molecules. The published formula of pseudojohannite is Cu6.5(UO2)8[O8](OH)5[(SO4)4]·25H2O. Raman bands at 805 and 810 cm,1 are assigned to (UO2)2+ stretching modes. The Raman bands at 1017 and 1100 cm,1 are assigned to the (SO4)2, symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm,1 are assigned to the (SO4)2,,2 bending modes. The bands at 210 and 279 cm,1 are assigned to the doubly degenerate ,2 bending vibration of the (UO2)2+ units. UO bond lengths in uranyl and OH···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] The analysis of pH-dependent protonated conformers of 1-hydroxyethylidene-1,1-diphosphonic acid by means of FT-Raman spectroscopy, multivariate curve resolution and DFT modellingJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Werner Barnard Abstract 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) solutions in the pH range 0.98,13.00 were analysed using FT-Raman spectroscopy and 31P and 23Na NMR spectroscopy. Vibrational bands for different protonated species were observed in the Raman spectra, whereas only a single NMR signal that shifted with pH was observed for all samples over the entire pH range. No significant shift in the 23Na NMR signal was observed, confirming that formation of Na+(aq) complexes did not take place; hence, no interference with the different protonated forms of HEDP occurred. Vibrational bands were assigned using density functional theory(DFT)-calculated spectra of the most likely conformers in solution. Multivariate curve resolution was performed on the Raman spectra in the region containing the PO stretching vibrations to determine the number of protonated species formed over the entire pH range. Chemometric analysis compares very favourably with the experimental species distribution diagram which was generated using the reported log KH values. Copyright © 2009 John Wiley & Sons, Ltd. [source] Flexibility of paramagnetic (d1) organometallic dithiolene complex [Cp2Mo(dmit)]+, studied by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Roman, wietlik Abstract We report on the experimental and theoretical studies of the flexible organometallic complex Cp2Mo(dmit) which often exhibits a folding in the solid state. Raman spectra of charge-transfer salts formed by Cp2Mo(dmit) with various anions (Br,, BF4,, PF6,, SbF6,, ReO(dmit)2,, TCNQF4,) were measured at room temperature using red (632.8 nm) and near-infrared (780 nm) excitations. The influence of the folding of the MoS2C2 metallacycle in [Cp2Mo(dmit)]+, cation on the Raman spectra was investigated. Due to folding of [Cp2Mo(dmit)]+,, the bands related to the CC and some CS stretching vibrations shift toward lower wavenumbers by about 0.5,0.6 cm,1deg,1. The bond lengths, charge distribution on atoms, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, and dipole moments for neutral and ionized complex with various folding angles were calculated by density functional theory (DFT) methods. Additionally, the normal vibrational modes and theoretical Raman spectra were calculated and compared with experimental data. Our results indicate that vibrational spectroscopy can be applied for investigation of complex deformations in the solid state. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the magnesium-carbonate minerals,artinite and dypingiteJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Ray L. Frost Abstract Magnesium minerals are important in the understanding of the concept of geosequestration. The two hydrated hydroxy magnesium-carbonate minerals artinite and dypingite were studied by Raman spectroscopy. Intense bands are observed at 1092 cm,1 for artinite and at 1120 cm,1 for dypingite, attributed ,1 symmetric stretching mode of CO32,. The ,3 antisymmetric stretching vibrations of CO32, are extremely weak and are observed at 1412 and 1465 cm,1 for artinite and at 1366, 1447 and 1524 cm,1 for dypingite. Very weak Raman bands at 790 cm,1 for artinite and 800 cm,1 for dypingite are assigned to the CO32,,2 out-of-plane bend. The Raman band at 700 cm,1 of artinite and at 725 and 760 cm,1 of dypingite are ascribed to CO32,,2 in-plane bending mode. The Raman spectrum of artinite in the OH stretching region is characterised by two sets of bands: (1) an intense band at 3593 cm,1 assigned to the MgOH stretching vibrations and (2) the broad profile of overlapping bands at 3030 and 3229 cm,1 attributed to water stretching vibrations. X-ray diffraction studies show that the minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality, and explains why the Raman spectra of these minerals have not been previously or sufficiently described. Copyright © 2008 John Wiley & Sons, Ltd. [source] Solvent dependent study of carbonyl vibrations of 3-phenoxybenzaldehyde and 4-ethoxybenzaldehyde by Raman spectroscopy and ab initio calculationsJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Veerabahu Ramakrishnan Abstract A Raman spectroscopy investigation of the carbonyl stretching vibrations of 3-phenoxybenzaldehye (3Phbz) and 4-ethoxybenzaldeheyde (4Etob) was carried out in binary mixtures with different polar and nonpolar solvents. The purpose of this study was twofold: firstly, to describe the interaction of the carbonyl groups of two solute molecules in terms of a splitting in the isotropic and anisotropic components and secondly, to analyze their spectroscopic signatures in a binary mixture. Changes in wavenumber position, variation in the anisotropic shift and full width half maximum were investigated for binary mixtures with different mole fractions of the reference systems. In binary mixtures, the observed increase in wavenumber with solvent concentration does not show linearity, indicating the significant role of molecular interactions on the occurrence of breaking of the self-association of the solute. In all the solvents, a gradual decrease in the anisotropic shift reflects the progressive separation of the coupled oscillators with dilution. ,i(,c), 3Phbz,solvent mixtures, exhibit a gradual decrease with decrease in the concentration of the solute which is an evidence on the influence of micro viscosity on linewidth. For 4Etob, the carbonyl stretching vibration shows two well-resolved components in the Raman spectra, attributed to the presence of two distinct carbonyl groups: hydrogen-bonded and free carbonyl groups. The intensity ratio of the carbonyl stretching vibration of these two types of carbonyl groups is studied to understand the dynamics of solute/solvent molecules owing to hydrogen bond interactions. Ab initio calculations were employed for predicting relevant molecular structures in the binary mixtures arising from intermolecular interactions, and are related to the experimental results. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the uranyl phosphate mineral dumontite Pb2 [(UO2)3O2(PO4)2]·5H2 OJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2009Ray L. Frost Abstract Raman spectra of dumontite were measured at 298 and 77 K. Observed bands were attributed to the stretching and bending vibrations of uranyl and phosphate units and OH stretching vibrations of water molecules. U,O bond lengths in uranyls and approximate O,H···O bond lengths were calculated. The values of the U,O bond lengths are in agreement with the data from the single crystal structure analysis of dumontite. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermo-Raman spectroscopy of synthetic nesquehonite , implication for the geosequestration of greenhouse gasesJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2008Matthew C. Hales Abstract Pure nesquehonite (MgCO3·3H2O)/Mg(HCO3)(OH)·2H2O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm,1, which shifts to 1105 cm,1 at 450 °C, assigned to the ,1CO32, symmetric stretching mode. Two bands at 1419 and 1509 cm,1 assigned to the ,3 antisymmetric stretching mode shift to 1434 and 1504 cm,1 at 175 °C. Two new peaks at 1385 and 1405 cm,1 observed at temperatures higher than 175 °C are assigned to the antisymmetric stretching modes of the (HCO3), units. Throughout all the thermo-Raman spectra, a band at 3550 cm,1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm,1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175 °C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO3)·2H2O. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis and Raman spectroscopic characterisation of hydrotalcite with CO32, and (MoO4)2, anions in the interlayerJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2008Sara J. Palmer Abstract Raman spectroscopy has been used to characterise synthetic mixed carbonate and molybdate hydrotalcites of formula Mg6Al2(OH)16((CO3)2,,(MoO4)2,)·4H2O. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features on the basis of the carbonate anion, the molybdate anion, the hydroxyl units and water units. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions are identified: (1) carbonate hydrogen-bonded to water in the interlayer, (2) carbonate hydrogen-bonded to the hydrotalcite hydroxyl surface, (3) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite, as it is hydrogen bonded to both the carbonate and the hydroxyl surface. The spectra have been used to assess the contamination of carbonate in an open reaction vessel in the synthesis of a molybdate hydrotalcite of formula Mg6Al2(OH)16((CO3)2,, (MoO4)2,)·4H2O. Bands are assigned to carbonate and molybdate anions in the Raman spectra. Importantly, the synthesis of hydrotalcites from solutions containing molybdate provides a mechanism for the removal of this oxy-anion. Copyright © 2007 John Wiley & Sons, Ltd. [source] Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr3JOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2008Liubov V. Stepakova Abstract Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching CuIIX modes in the equatorial plane, were found in the ranges 247,288 cm,1 for X = Cl, and 173,189 cm,1 for X = Br, while the low-wavenumber stretching modes for the weaker axial CuX interactions varied considerably. The tetrahedral coordination for Cs2CuCl4 and Cs2CuBr4 leads to somewhat lower CuX symmetric stretching wavenumbers, 295 and 173 cm,1, respectively. The assignments of the copper,ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged CuX stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn,Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal,halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M2X6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr3 (K2Cu2Br6), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu2Br6]2, complexes held together by weak axial CuBr interactions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Pressure effects on inter- and intramolecular vibrations in hydrogen-bonded L -ascorbic acid crystalJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2008Hiroko Shimada Abstract Pressure effects on the Raman spectra due to the inter- and intramolecular vibrations of the L -ascorbic acid crystal were studied. The intensity of the Raman bands due to the intermolecular vibrations varies in three different ways by application of pressure. The bands of the first group become stronger, those of the second one become weaker and the third group shows no prominent change in their intensity with increasing pressure. The bands due to the intermolecular vibrations show a blue shift, while the bands due to the intramolecular vibrations shift to the blue or red depending on the vibrational modes by application of pressure. The bands assigned to the OH stretching vibrations shift to the red, the bands assigned to the CO and CC stretching vibrations shift a little to the red and the bands assigned to the other vibrations shift to the blue under high pressure. The following conclusions were derived. (1) The hydrogen bonds forming helixes become stronger and the isolated hydrogen bond becomes weaker with increasing pressure. (2) The bands of the first group owing to the intermolecular vibrations are ascribed to the vibrations related to the helix hydrogen bonds and the second group bands to the isolated hydrogen bond. (3) The CO stretching vibration couples with the CC stretching vibration. (4) The phase transitions take place at 1.8 and 4 GPa in the crystal. Copyright © 2007 John Wiley & Sons, Ltd. [source] Raman spectroscopy of the borosilicate mineral ferroaxiniteJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2007Ray L. Frost Abstract Raman spectroscopy, complemented by infrared spectroscopy, has been used to characterise the ferroaxinite minerals of the theoretical formula Ca2Fe2+Al2BSi4O15(OH), a ferrous aluminium borosilicate. The Raman spectra are complex but are subdivided into sections on the basis of the vibrating units. The Raman spectra are interpreted in terms of the addition of borate and silicate spectra. Three characteristic bands of ferroaxinite are observed at 1082, 1056 and 1025 cm,1 and are attributed to BO4 stretching vibrations. Bands at 1003, 991, 980 and 963 cm,1 are assigned to SiO4 stretching vibrations. Bands are found in these positions for each of the ferroaxinites studied. No Raman bands were found above 1100 cm,1 showing that ferroaxinites contain only tetrahedral boron. The hydroxyl stretching region of ferroaxinites is characterised by a single Raman band between 3368 and 3376 cm,1, the position of which is sample-dependent. Bands for ferroaxinite at 678, 643, 618, 609, 588, 572, 546 cm,1 may be attributed to the ,4 bending modes and the three bands at 484, 444 and 428 cm,1 may be attributed to the ,2 bending modes of the (SiO4)2,. Copyright © 2006 John Wiley & Sons, Ltd. [source] Raman spectra of apatites: La10,x Si6,y (Al,Fe)y O26±,JOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2007G. Lucazeau Abstract Raman spectra of eight polycrystalline apatites of the general formula La10,xSi6,yM,yO26 ± , with M, = Al or Fe were obtained at 300 K. Raman spectra of La10Si4Fe2O26 and La9.83Si4.5Al1.5O26 were investigated in the range 80,1000 K and 80,623 K, respectively. Tentative assignments of bands to stretching and bending modes of SiO4 tetrahedra and to M'O vibrations are proposed. Except for the two new bands, which appear around 700 cm,1 when Al is replaced by Fe, only some band broadenings and relative intensity changes are observed as a function of the rate of O5 or La vacancies. Most of the bands soften and broaden continuously when raising the temperature. This is an indication that the Al- and Fe-substituted apatites do not undergo any structural change up to 1000 K. Above 1000 K, the broad and weak shoulder observed at 850 cm,1 for La10Si4Fe2O26 is replaced by a strong band at 868 cm,1, suggesting that SiO4 tetrahedra undergo a structural modification. All compounds show the same residual band broadening at 80 K. This suggests that there is a small rate of static disorder preferentially related to the solubility of Al and Fe in the Si sublattice rather than to other defects. Moreover, the observation of FeO modes indicates that the dynamics of the solid solution obeys the so-called two-mode behavior. The occurrence of FeO stretching vibrations 150 cm,1 lower than for those of SiO suggests that the coordination number of iron could be larger than 4, particularly for the Fe4+ species. Copyright © 2006 John Wiley & Sons, Ltd. [source] Raman spectroscopy of three polymorphs of BiVO4: clinobisvanite, dreyerite and pucherite, with comparisons to (VO4)3 -bearing minerals: namibite, pottsite and schumacheriteJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2006Ray L. Frost Abstract Both Raman and infrared spectroscopy have been used to characterise the three phase-related minerals,dreyerite (tetragonal BiVO4), pucherite (orthorhombic BiVO4) and clinobisvanite (monoclinic BiVO4),and a comparison of the spectra is made with that of the minerals namibite (Cu(BiO2)VO4(OH)), schumacherite (Bi3O(OH)(VO4)2) and pottsite (PbBiH(VO4)2·2H2O). Pucherite, clinobisvanite and namibite are characterised by VO4 stretching vibrations at 872, 824 and 846 cm,1. The Raman spectrum of dreyerite shows complexity in the 750 to 950 cm,1 region with two intense bands at 836 and 790 cm,1 assigned to the symmetric and antisymmetric VO4 modes. The minerals schumacherite and pottsite are characterised by bands at 846 and 874 cm,1. In both the infrared and Raman, spectra bands are observed in the 1000,1100 cm,1 region which are attributed to the antisymmetric stretching modes. The Raman spectra of the low wavenumber region are complex. Bands are identified in the 328 to 370 cm,1 region and in the 404 to 498 cm,1 region and are assigned to the ,2 and ,4 bending modes. The minerals namibite and schumacherite are characterised by intense bands at 3514 and 3589 cm,1 assigned to the symmetric stretching vibrations of the OH units. Importantly, Raman spectroscopy enables new insights into the chemistry of these bismuth vanadate minerals. Raman spectroscopy enables the identification of the bismuth vanadate minerals in mineral matrices where paragenetic relationships exist between the minerals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Raman spectroscopy of walpurgiteJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2006Ray L. Frost Abstract Raman spectra of walpurgite, (UO2)Bi4O4 (AsO4)2·2H2O, recorded at 298 K and 77 K are presented and compared with infrared spectra of walpurgite and phosphowalpurgite. Bands connected with (UO2)2+, (AsO4)3,, and H2O stretch and bend, and BiO stretch are tentatively assigned. Hydrogen bond lengths are calculated from the wavenumbers of the H2O stretching vibrations and compared with those from the crystal structure analysis of walpurgite. Copyright © 2005 John Wiley & Sons, Ltd. [source] Raman spectroscopic study of the vivianite arsenate mineralsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2003Ray L. Frost Abstract The molecular structures of the vivianite-type arsenate minerals were studied using a combination of Raman and infrared spectroscopy. The Raman spectra of the hydroxyl-stretching regions are complex with overlapping bands at 3419, 3209, 3185 and 3010 cm,1. This complexity is reflected in the water HOH bending modes with strong infrared bands in the 1660,1685 cm,1 region indicating strong hydrogen bonding to arsenate anions in adjacent layers. The Raman arsenate AsO stretching region shows strong similarity between the vivianite arsenate minerals. In the infrared spectra complexity exists with multiple antisymmetric stretching vibrations observed, indicating a reduction of symmetry. Strong infrared bands around 700 and 560 cm,1 are attributed to librational modes of water. Vibrational spectra enable the structure of the minerals to be determined and, whilst similarities exist in the spectral patterns, sufficient differences exist to determine the identification of the minerals. In particular, Raman spectroscopy assists in the identification of the complex isomorphous substitution in these vivianite arsenate minerals. Copyright © 2003 John Wiley & Sons, Ltd. [source] Molecular structure of the adelite group of minerals,a Raman spectroscopic studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2003Wayde Martens Abstract The application of Raman microscopy to the study of closely related mineral phases of the adelite group has allowed their molecular characterization. The adelite group of minerals are orthorhombic arsenates and vanadates of general formula AB2+ (XO4)(OH), where X may be As5+ or V5+, cation A may be Ca or Pb and cation B may be Co or Cu and others. Raman spectroscopy has proven most powerful for the identification of these minerals. In particular, the position of the hydroxyl stretching vibrations and most of the arsenate bands have been identified. The two minerals tangeite and calciovolborthite have previously been identified as the same mineral. Raman spectroscopy has proven that the minerals are not identical and have different structures. The application of Raman spectroscopy to the study of these minerals shows that increased distortion of the arsenate anion occurs as the cationic substitution from conichalcite to austinite to duftite occurs. Copyright © 2003 John Wiley & Sons, Ltd. [source] Raman and Fourier transform infrared study of phytol effects on saturated and unsaturated lipid multibilayersJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2003M. Picquart Abstract The effects of phytol on DPPC and OPPC multilayers were investigated using FT-IR and Raman spectroscopy. The results were compared with those obtained with ,-tocopherol (,-T) and ,-tocopherol acetate (,-TA). The chain packing was analyzed using Raman intensity ratios measured in the CH2 stretching region, whereas the number of gauche bonds introduced by phytol was estimated by the measure of the FT-IR absorbance of the CH2 wagging progression modes. It is shown that the chain packing is reduced and that gauche rotamer formation is promoted by phytol in the gel phase. Phytol has a very similar effect on the acyl chains of DPPC to ,-T but does not have the same impact on the CO stretching vibrations of this lipid. The results indicate that phytol perturbs the interfacial region of DPPC causing dehydration or a conformational modification of the ester groups. Furthermore, the modification of the OPPC chain order induced by phytol is slightly different with respect to ,-T. It is concluded that (1) a hydrogen bond between the hydroxyl group of ,-T and the phospholipid carbonyl groups may not necessarily be associated with the stabilization of the membrane, (2) the studied phytyl compounds may be located more or less close to the membrane interface, (3) the presence of the chromanol ring may strongly influence the location of vitamin E within the membrane and, consequently, its capacity to catch free radicals and (4) the hydroxyl group, chroman moiety and phytyl chain all play a crucial role that determines the effects of ,-T on lipid acyl chains and its location within membranes, which in turn can affect its biological function. Copyright © 2002 John Wiley & Sons, Ltd. [source] Structured water in hydrotalcites of formula MgxZn6,xAl2(OH)16(CO3)·4H2O: a Raman microscopic studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2002Therese E. Johnson Raman microscopy was used to characterize synthesized hydrotalcites of formula MgxZn6,xAl2(OH)16 (CO3)·4H2O. The Raman spectra are conveniently subdivided into spectral features based on (a) the carbonate anion, (b) the hydroxyl units and (c) metal,oxygen units. A model is proposed based on a tripod of M3OH units in the hydrotalcite structure. In a simplified model, Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the Mg3OH, Zn3OH and Al3OH units. Bands are also assigned to the hydroxyl stretching vibrations of water. Three types of water are identified: (a) water hydrogen bonded to the interlayer carbonate ion, (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. A model of water in the hydrotalcite structure is proposed in which water is in a highly ordered structure as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface and also forms bridges between the MOH surface and the carbonate anion. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||