bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibrational spectra, conformational stability, structural parameters and ab initio calculations of 2,2,5,5‐tetramethyl‐2,5‐disila‐1‐oxacyclopentane
Authors: Zheng Chao , Yazdi Mehdi R. , Kalasinsky Victor F. , Durig James R. 
Published: January 2006

AbstractThe Raman spectrum (4000–200 cm−1) of liquid and infrared spectra (4000–400 cm−1) of gaseous and liquid 2,2,5,5‐tetramethyl‐2,5‐disila‐1‐oxacyclopentane, c‐OSi(CH3)2CH2CH2Si(CH3)2, have been recorded. Ab initio and density functional theory (DFT) calculations with several different basis sets including diffuse functions have been carried out to predict the conformational stabilities with comparisons to disiloxane (H3SiOSiH3)and 2,5‐disila‐1‐oxacyclopentane (c‐OSiH2CH2CH2SiH2). These calculations predict the twisted C2 conformer as the most stable form of the ring compounds, with the planar C2v conformer a transition state and the envelope Cs conformer not a stable form. These predicted stabilities are supported by the vibrational data. Additionally, force constants, infrared intensities, Raman activities, depolarization ratios and scaled vibrational wavenumbers have been determined from MP2(full)/6–31G(d) calculations for all three molecules and compared with experimental values when available. Predicted r0 structural parameters have been obtained for dimethyl ether, methyl silyl ether and disiloxane, which are compared with the experimentally determined values. On the basis of these data, estimated r0 parameters are provided for both five‐membered rings with the expectation that these values are as accurate as could be measured experimentally in the gas phase. The results are discussed and compared with corresponding quantities for some similar molecules. Copyright © 2006 John Wiley & Sons, Ltd.
Micro‐Raman spectroscopic investigations of graphite in the carbonaceous meteorites Allende, Axtell and Murchison
Authors: Larsen K. L. , Nielsen O. F. 
Published: January 2006

AbstractThe graphite content of the carbonaceous meteorites Allende, Axtell and Murchison was investigated by Raman microscopy. Laser excitation wavelengths at 514.5 (2.43 eV), 785 (1.59 eV) and 1064 nm (1.17 eV) were used for Allende and Axtell. Owing to severe background problems, Raman spectra of Murchison were only recorded at 785 nm. The wavenumber of the order G‐band was independent of the excitation laser wavelength. A linear dependence on the laser excitation energy of the wavenumber for the disorder D‐band was found with an increasing wavenumber for increasing laser energy. The intensity ratios of the D‐band and G‐band for Allende at 514.5 nm were used to find the graphite order diameter (La) for the graphite sheets. This value was used to find correlation factors between the D/G intensity ratios and La in the NIR region at 785 and 1064 nm. La values for Axtell and Murchison were calculated from D/G‐band intensity ratios. The C3‐type meteorites Allende and Axtell show very similar La values around 45 Å, whereas the C2 meteorite Murchison has La around 70 Å. This difference is consistent with different environments during the formation process of the graphite. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐enhanced resonance Raman and hyper‐Raman spectroscopy of water‐soluble substituted stilbene and distyrylbenzene chromophores
Authors: Leng Weinan , Woo Han Young , Vak Doojin , Bazan Guillermo C. , Myers Kelley Anne 
Published: January 2006

AbstractSurface‐enhanced Raman spectra (SERS) are presented for two water‐soluble, donor–donor‐ or donor–acceptor‐substituted phenylene vinylene derivatives adsorbed on the surfaces of colloidal silver nanoparticles. The normally water‐insoluble, substituted stilbene and distyrylbenzene chromophores have been modified by attaching trimethylammoniumalkyl chains to the amino donor group, creating both aqueous solubility and a net positive charge that facilitates binding to citrate‐ or borohydride‐reduced silver colloids. A symmetrically donor‐substituted distyrylbenzene exhibits strong electronically pre‐resonant SERS spectra that are not highly dependent on excitation wavelength and are qualitatively similar to the solution‐phase resonance Raman (RR) spectra. A donor–acceptor‐substituted stilbene exhibits weaker SERS enhancement despite being fully electronically resonant. The spectra vary considerably with excitation wavelength and show new lines not present in the solution‐phase spectra, which are attributed to a photoproduct formed on the surface. Two‐photon resonant hyper‐Raman spectra are also presented for the donor–acceptor stilbene, both with and without surface enhancement. Copyright © 2006 John Wiley & Sons, Ltd.
Molecular interactions between the penetration enhancer 1,8‐cineole and human skin
Authors: Williams A. C. , Edwards H. G. M. , Lawson E. E. , Barry B. W. 
Published: January 2006

AbstractPenetration enhancers are chemicals that temporarily and reversibly diminish the barrier function of the outermost layer of skin, the stratum corneum, to facilitate drug delivery to and through the tissue. In the current study, the complex mechanisms by which 1,8‐cineole, a potent terpene penetration enhancer, disrupts the stratum corneum barrier is investigated using post‐mortem skin samples. In order to validate the use of excised tissue for these and related studies, a fibre optical probe coupled to an FT‐Raman spectrometer compared spectroscopic information for human skin recorded from in vivo and in vitro sampling arrangements. Spectra from full‐thickness (epidermis and dermis) post‐mortem skin samples presented to the spectrometer with minimal sample preparation (cold acetone rinse) were compared with the in vivo system (the forearms of human volunteers). No significant differences in the Raman spectra between the in vivo and in vitro samples were observed, endorsing the use of post‐mortem or surgical samples for this investigational work. Treating post‐mortem samples with the penetration enhancer revealed some unexpected findings: while evidence for enhancer‐induced disruption of the barrier lipid packing in the stratum corneum was detected in some samples, spectra from other samples revealed an increase in lipid order on treatment with the permeation promoter. These findings are consistent with phase‐separation of the enhancer within the barrier lipid domains as opposed to homogeneous disruption of the lipid lamellae. Copyright © 2006 John Wiley & Sons, Ltd.
Study by Raman microscopy of nine variants of the green–blue pigment verdigris
Authors: Chaplin Tracey D. , Clark Robin J. H. , Scott David A. 
Published: January 2006

AbstractThe Raman spectra of nine variants of ‘verdigris’ (organo‐copper complexes) synthesized recently by different methods have been measured at room temperature and at 150 K. The spectra are all characterized by a strong band atca2935 cm−1and weaker bands at 3010, 2985, 2935, 1550, 1445, 1415, 1350 and 940 cm−1at both temperatures; the majority of spectra also feature bands at 220 and 140 cm−1. The features in the 3000–4000 cm−1and 900–50 cm−1regions of the spectra show the greatest differences from sample to sample: those in the high wavenumber region relate directly to the nature of the hydrogen bonding in each sample, while those in the lower region reflect the variations in the Cu–O bonding and crystal structures of each sample. The characteristic bands present in the 900–3000 cm−1region are sufficient for the identification of a sample as a particular form of verdigris. Copyright © 2006 John Wiley & Sons, Ltd.
Introduction of a high‐pressure cell for use with Raman microscopy
Authors: Uhlemann Ute , Schmitt Michael , Oehme Karl‐Ludwig , Notni Johannes , Anders Ernst , Popp Jürgen 
Published: January 2006

AbstractA high‐pressure cell for Raman spectroscopical applications has been developed. By using this cell, it is possible to investigate reactions between solids and gases, applying pressures up to 3000 bar. The cell has been successfully tested on the reaction between ferrocene and carbon monoxide. The results point towards a multi‐step reaction mechanism. Furthermore, first results are presented for the investigation of the reaction path of CO2 with a zinc thiolate complex. Copyright © 2006 John Wiley & Sons, Ltd.
FT‐Raman and NIR‐SERS characterization of the antimalarial drugs chloroquine and mefloquine and their interaction with hematin
Authors: Cîntǎ‐Pînzaru S. , Peica N. , Küstner B. , Schlücker S. , Schmitt M. , Frosch T. , Faber J. H. , Bringmann G. , Popp J. 
Published: January 2006

AbstractRaman and surface‐enhanced Raman scattering (SERS) spectroscopies were employed to probe the interaction of the antimalarial drugs chloroquine (CQ) and mefloquine (MQ) with hematin. NIR‐SERS spectra of both quinoline derivatives were obtained from a colloidal gold surface. Strong chemical interactions of each drug with the Au particles are observed and the similarities of the two NIR‐SERS spectra allowed to predict a similar orientation geometry for both of the drugs on the colloidal surface, namely through the quinoline skeletal part of each molecular structure.Separately, the adsorption behavior of hematin on the Au colloid was studied under nonresonant conditions. In addition, both hematin–antimalarial drug systems (CQ and MQ) were prepared and investigated by NIR‐SERS. Copyright © 2006 John Wiley & Sons, Ltd.
Time‐resolved resonance Raman, time‐resolved UV–visible absorption and DFT calculation study on photo‐oxidation of the reduced form of nicotinamide adenine dinucleotide
Authors: Takahashi Noriko , Shinno Takaaki , Tachikawa Masanori , Yuzawa Tetsuro , Takahashi Hiroaki 
Published: January 2006

AbstractPhotochemical reaction of the reduced form of nicotinamide adenine dinucleotide (NADH) was studied in aqueous solutions using nanosecond time‐resolved resonance Raman and UV–visible absorption spectroscopies combined with DFT/B3LYP calculations. Four transients were detected. A transient exhibiting absorption bands at 370 and 560 nm was assigned to the cation radical NADH+•. A transient having an absorption band at 394 nm was assigned to the deprotonated neutral radical NAD•. A transient exhibiting an absorption band at 493 nm was considered to be attributable to the anion radical NADH−•. The broad and strong band at about 700 nm was assigned to hydrated electrons. It was concluded that the photo‐oxidation of NADH to NAD+ proceeded stepwise via NADH+• and NAD•. The Raman band at 1627 cm−1 of NADH+• was assigned to the CC symmetric stretch of the protonated pyridyl ring of the dihydronicotinamide moiety. It was shown that the CC symmetric stretch of the protonated pyridyl ring exhibited a low‐wavenumber shift from 1688 cm−1 to 1627 cm−1 on going from the ground state to NADH+•. This implies that the protonated pyridyl ring is weakened considerably on ionization in good accord with the DFT calculations. Copyright © 2006 John Wiley & Sons, Ltd.
Identification of the pigments on a sixteenth century Persian book of poetry by Raman microscopy
Authors: Clark Robin J. H. , Mirabaud Sigrid 
Published: January 2006

AbstractA Persian book of poetry—a poetic history of Shah Isma'il—by Mirza Kasim, dating to A.D. 1541, has been studied by Raman microscopy in order to explore the palette used at this time in Persia. The palette was found to include lazurite, indigo, red lead, vermilion, haematite, carbon black, orpiment, lead white and gold. The palette thus differs from that of another contemporary book of Persian poetry, most notably by the inclusion of indigo, and from that of a 1537–1538 Persian codex by the use of an intimate orpiment/indigo mixture for green rather than the copper‐based mineral malachite. The palette also differs in a few respects from that of a Persian Herati manuscript of A.D. 1530 in that the latter uses an intimate mixture of orpiment and lazurite for green and does not include either haematite or indigo. Copyright © 2006 John Wiley & Sons, Ltd.
Study of vibrational dephasing of CCl stretching mode of 2Cl‐pyridine and 3Cl‐pyridine in methanol environment by polarized Raman study and DFT calculations
Authors: Singh Ranjan K. , Srivastava Sunil K. , Ojha Animesh K. , Arvind U. , Asthana B. P. 
Published: January 2006

AbstractRaman spectra of [2Cl‐pyridine (2Cl‐p) + methanol] and [3Cl‐pyridine (3Cl‐p) + methanol] mixtures were recorded in the region 360–480 cm−1 and the concentration dependence of linewidths and peak positions of the isotropic part of the Raman scattered radiation for the CCl stretching mode were studied in the light of the existing models. The analysis of the results revealed that concentration fluctuation and diffusion simultaneously play a role in the dephasing of the CCl stretching mode. The optimized structures of the reference systems, 2Cl‐p and 3‐Cl‐p, and their various complexes with methanol were calculated by density functional theory (DFT) geometry optimization technique using B3LYP functional and 6–31 + G(d,p) basis set. On the basis of the results of geometry optimization and energy minimization calculation, we propose that the complex formed as a result of hydrogen bonding of one 3Cl‐p molecule with three methanol molecules is more stable than the one formed by one 3Cl‐p molecule and two methanol molecules. This study presents an explanation of changes in spectral features of ortho/meta Cl‐substituted pyridines supported by DFT derived optimized geometries. Equilibrium constants have been obtained from the spectral data for one of the systems (2Cl‐pyridine + methanol). Copyright © 2006 John Wiley & Sons, Ltd.
Estimating the influence of experimental parameters on the prediction error of PLS calibration models based on Raman spectra
Authors: Wolthuis Rolf , Tjiang Gilbert C. H. , Puppels Gerwin J. , Bakker Schut Tom C. 
Published: January 2006

AbstractPartial least squares (PLS) calibration is often the method of choice for making multivariate calibration models to predict analyte concentrations from Raman spectral measurements. In the development of such models, it is often difficult to assess beforehand what the prediction error will be, and whether instrumental or model factors limit the lower limit of the prediction error. Here, we present a method to assess the influence of experimental errors such as power fluctuations and spectral shifts, on the PLS prediction errors using simulated datasets. Assumptions that are implicit to PLS calibration and their implications with respect to the choice of experimental parameters for collecting a proper set of Raman spectra are discussed. The influence of various experimental parameters and signal pre‐processing steps on PLS prediction error is demonstrated by means of simulations. The results of simulations are compared with the outcome of PLS calibrations of an experimental dataset. Copyright © 2006 John Wiley & Sons, Ltd.
The electrosorption of 1,2,3‐triazole on gold as studied with surface‐enhanced Raman spectroscopy
Authors: Jbarah Abdel Aziz , Ihle Andreas , Banert Klaus , Holze Rudolf 
Published: January 2006

AbstractThe electrosorption of 1,2,3‐triazole on a polycrystalline gold electrode has been studied with surface‐enhanced Raman spectroscopy (SERS) and cyclic voltammetry. Vibrational wavenumbers were calculated for the 1H‐ and 2H‐1,2,3‐triazole at the B3LYP and MP2 levels using 6–31G* basis set. The data obtained from vibrational wavenumber calculations are used to analyze the SERS spectra. Results imply a tilted orientation of the triazole molecule both from acidic and neutral perchlorate solution with a nitrogen atom interacting directly with the gold surface. Strong adsorption in both cases is also evident from cyclic voltammograms of polycrystalline gold electrodes, indicating strong inhibition of gold hydroxide formation. Copyright © 2006 John Wiley & Sons, Ltd.
4‐Aminobenzonitrile: ab initio calculations, FTIR and Raman spectra
Authors: Palafox M. Alcolea , Rastogi V. K. , Vats J. K. 
Published: January 2006

AbstractThe experimental IR (in different matrices) and Raman spectra of 4‐aminobenzonitrile molecule were recorded. The results were compared with theoretical values. Geometry, vibrational wavenumbers and thermodynamic parameters were calculated using DFT quantum chemical methods. With the help of specific scaling procedures, the experimentally observed FTIR and Raman vibrational wavenumbers were analyzed and assigned to different normal modes of the molecule. The error obtained was, in general, very low. The contributions of the different modes to each wavenumber were determined using potential energy distributions (PEDs). Other general conclusions were also deduced. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐enhanced Raman spectroscopy of imidazole adsorbed on electrode and colloidal surfaces of Cu, Ag, and Au
Authors: Loo B. H. , Tse Y. , Parsons K. , Adelman C. , El‐Hage A. , Lee Y. G. 
Published: January 2006

AbstractSurface‐enhanced Raman spectra have been obtained from imidazole adsorbed on Cu and Ag electrodes, and on Cu, Ag, and Au colloids at pH ranging from 5.6 to 11.0. For these pHs, the imidazole molecule is coordinated through its unshared electron pair on its ‘pyridine’ nitrogen to the metal surfaces. On the Cu and Au colloidal systems, the imidazole molecule adsorbs with the ring perpendicular to the metal surface since only in‐plane vibrations are observed. On the other hand, both the in‐plane and out‐of‐plane vibrations are observed on the Cu and Ag electrodes, and on the Ag colloid, therefore the adsorbed imidazole is tilted at an angle with respect to the surface normal. Copyright © 2006 John Wiley & Sons, Ltd.
Construction of picosecond time‐resolved Raman spectrometers with near‐infrared excitation
Authors: Sakamoto A. , Matsuno S. , Tasumi M. 
Published: January 2006

AbstractWe have constructed two types of picosecond time‐resolved Raman spectrometers with near‐infrared excitation. One system is based on a step‐scan Fourier transform (FT) interferometer equipped with a Ge detector, and the other system is based on a dispersive spectrometer equipped with an InGaAs array detector. For the former system with pulsed Raman excitation, we have developed a new method of signal processing. This method does not require synchronization among laser pulses for Raman excitation, the stepping of the step‐scan interferometer, and the sampling of the analog‐to‐digital converter. In spite of large fluctuation in the probe‐pulse energy, the ordinary FT‐Raman spectra of samples in the ground electronic state can be obtained with satisfactory signal‐to‐noise ratios by the former system. By the latter system, picosecond transient Raman spectra have been obtained from the first excited singlet (S1) state of 9‐phenylanthracene and the second excited singlet (S2) state of all‐trans‐β‐carotene by using 388‐nm light for photoexcitation and 1064‐nm light for Raman excitation. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐ and tip‐enhanced Raman scattering of DNA components
Authors: Rasmussen A. , Deckert V. 
Published: January 2006

AbstractWhile surface‐enhanced Raman scattering (SERS) is an established technique to significantly enhance the Raman signal from samples bound to metal surfaces, a quantitative interpretation is very difficult because of the rough and arbitrary nature of the substrate. A distinction between concentration and enhancement effects is virtually impossible. Tip‐enhanced Raman scattering (TERS), a scattering type of near‐field optical microscopy technique, circumvents the problem of random enhancement by concentrating the roughness to only a small region directly at the apex of a scanning probe tip. In this paper, TERS spectra of DNA pyrimidine bases have been collected and compared with standard SERS and Raman measurements of the nucleotides and the pure bases. The results are discussed in terms of electromagnetic and chemical effects of the SERS enhancement of the TERS probes. Copyright © 2006 John Wiley & Sons, Ltd.
Nondegenerate hard‐mode Raman studies of phase transition in antiferroelectric lead ytterbium niobate‐based perovskite compound
Authors: Ahn Sang‐Jin , Kim Jong‐Jean , Kim Jai‐Hyun , Choo Woong‐Kil 
Published: January 2006

AbstractBy using Slater's phenomenological theory of atomic lattice dynamics, general results for the nondegenerate hard mode of phase transition are rederived in a simpler form. The change in inverse dielectric susceptibility (χ−1) associated with the phase transition is related to the hard‐mode frequency shift (ωQ) as ${\Delta}(\chi^{-1}) = R\omega_{\rm Q}^{2}$, where the proportionality constant R can be determined from the experimental data. This relation ${\Delta}(\chi^{-1}) = R\omega_{\rm Q}^{2}$ between the changes in χ−1 and $\omega_{\rm Q}^{2}$ was verified for the antiferroelectric phase transition observed in 0.94PYN [Pb(Yb1/2Nb1/2)O3]–0.06PT[PbTiO3], with the proportionality constant R as −1.6 × 10−7 cm2 in the antiferroelectric phase. Copyright © 2006 John Wiley & Sons, Ltd.
Femtosecond CARS of methanol–water mixtures
Authors: Pestov Dmitry , Zhi Miaochan , Sariyanni Zoe‐Elizabeth , Kalugin Nikolai G. , Kolomenskii Alexander , Murawski Robert , Rostovtsev Yuri V. , Sautenkov Vladimir A. , Sokolov Alexei V. , Scully Marlan O. 
Published: January 2006

AbstractWe utilize femtosecond time‐resolved coherent anti‐Stokes Raman spectroscopy (CARS) to study the vibrational dynamics of methanol–water solutions. We measure the beat wavenumbers between Raman modes and coherence decay rates of CH stretch modes (at 2835 cm−1 and 2943 cm−1) in methanol. We observe a qualitative dependence of the coherence relaxation rate on the concentration of methanol in its water solution. This may be linked to the formation of the recently observed supramolecular structures in methanol–water mixtures. Copyright © 2006 John Wiley & Sons, Ltd.
Raman spectroscopy at the beginning of the twenty‐first century
Authors: Schmitt M. , Popp J. 
Published: January 2006

AbstractThis paper gives a summary of the Wolfgang Kiefer Honorary Issue of the Journal of Raman Spectroscopy. The contributions in this special issue convincingly demonstrate the great applicability of Raman spectroscopy for almost all natural sciences, making this technique one of the most essential laser spectroscopic methods. Copyright © 2006 John Wiley & Sons, Ltd.
Sensitive capillary GC‐MS‐SIM determination of selective serotonin reuptake inhibitors: Reliability evaluation by validation and robustness study
Authors: Berzas Nevado Juan José , Villaseñor Llerena María Jesús , Guiberteau Cabanillas Carmen , Rodríguez Robledo Virginia , Buitrago Sierra 
Published: January 2006

AbstractA simple, fast, selective and very sensitive capillary GC‐MS method for the simultaneous determination of five antidepressant drugs is described. Fluoxetine, fluvoxamine, citalopram, sertraline and paroxetine belong to the newest and most important drug group termed selective serotonin reuptake inhibitors. Imipramine was used in this method as an internal standard for quantification. Optimum parameters for GC separation were investigated, i. e., flow rate, column head pressure, injector temperature, injection splitless conditions and oven temperature program. MS detection was performed in SIM mode to increase the sensitivity. Stability of the solutions, linear concentration range, accuracy, precision, LOD, LOQ (3.6–41.5 mg/L) and specificity were examined in the presence of excipients for checking the reliability of this method. The robustness was evaluated with a matrix of 15 experiments (seven factors and three levels) using Plackett‐Burman fractional factorial experimental design, and Youden and Steiner statistical treatment. The method was applied to the analysis of these antidepressants in nearly all their pharmaceutical formulations, obtaining recoveries between 98.1% and 102.7% with regard to the claimed values.