bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface enhanced Raman scattering (SERS)—a quantitative analytical tool?
Authors: Sackmann M. , Materny A. 
Published: January 2006

AbstractRaman spectroscopy is a widely used analytical tool capable of providing valuable information about the chemical structure and composition of molecules. In order to detect substances also at a very low concentration levels, Surface Enhanced Raman Scattering (SERS) was introduced. The different amplification mechanisms result in extreme sensitivity, however, a quantitative use of SERS appears to be problematic. Especially, when deploying silver sols as SERS substrates, the reproducibility of the signal intensities for a given substance concentration is questionable. Experimental results of an investigation of this problem for low concentrations of adenine are presented. Comparison with results obtained for different SERS substrates by other authors reveals clearly different dependencies. Only in a very limited concentration range reproducible and therefore quantitatively utilizable data could be obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Vibrational spectra of synthetic crandallite‐type minerals—optical and inelastic neutron scattering spectra
Authors: Breitinger D. K. , Brehm G. , Mohr J. , Colognesi D. , Parker S. F. , Stolle A. , Pimpl Th. H. , Schwab R. G. 
Published: January 2006

AbstractThe vibrational spectra of the synthetic minerals crandallite and goyazite MAl3(OH)6(HPO4)(PO4) (M = Ca and Sr) were studied by means of vibrational (IR and Raman) and inelastic neutron scattering (INS) spectrometries at room and low temperatures. The results were discussed taking into consideration the effects of different types of disorder (random distribution of PO4 and HPO4, orientational distribution with HPO4 and displacement of Ca in crandallite). The consequences of the resulting perturbed symmetry and of the non‐equivalence of the bridging µ‐OH groups in the Al2OH fragments were pointed out (complexity of the ν(Al2OH), δ(Al2OH) and γ(Al2OH) bands). The vibrations of the PO4 and HPO4 groups could be separated. Some aspects of the vibrational behaviour of the AlO2(OH)4 units and of the layers composed therewith were addressed. The translational modes of the interlayer cations Ca2+ and Sr2+ could be observed; the findings support the suggested displacement of Ca in crandallite. Copyright © 2006 John Wiley & Sons, Ltd.
Raman scattering of acoustical modes of silicon nanoparticles embedded in silica matrix
Authors: Ivanda M. , Hohl A. , Montagna M. , Mariotto G. , Ferrari M. , Crnjak Orel Z. , Turković A. , Furić K. 
Published: January 2006

AbstractThe Raman scattering from acoustical phonons of silicon quantum dots in glass matrix was investigated. Two peaks that correspond to symmetric and quadrupolar spheroidal vibrations were found. A model calculation for in‐ and off‐resonance scattering conditions was used, which considered the homogeneous broadening due to interaction with matrix and the inhomogeneous broadening due to particle size distribution. A strong dependence of the light‐to‐vibration coupling coefficient on the particles size was needed for fitting the Raman data. This result suggests that resonance with electronic transitions of the silicon nanoparticles is important for excitation at 514.5 nm. The size distribution obtained from the Raman data is in agreement with the results of high‐resolution transmission electron microscopy. Copyright © 2006 John Wiley & Sons, Ltd.
Continuous‐wave solid‐state Raman laser for spectroscopic applications
Authors: Lisinetskii V. A. , Grabtchikov A. S. , Apanasevich P. A. , Schmitt M. , Kuschner B. , Schlücker S. , Orlovich V. A. 
Published: January 2006

AbstractThe experimental and theoretical investigations of a solid‐state Raman laser operating in the continuous‐wave regime are described. The Raman laser represents the single resonant cavity with a Raman crystal. The theoretically predicted operation threshold is in agreement with that observed experimentally. The Raman conversion efficiency of the Stokes radiation is close to 5%. The analysis of temporal fluctuations of the output Stokes signal shows its super‐Gaussian statistics near the threshold. The output Stokes radiation was used for the measurement of the spontaneous Raman spectrum of CCl4. Copyright © 2006 John Wiley & Sons, Ltd.
Resonance Raman spectra of hydroxyphenyl squaraines: acid–base versus aggregation equilibria
Authors: Lopes José Guilherme S. , Farani Régis A. , de Oliveira Luiz Fernando C. , Santos Paulo S. 
Published: January 2006

AbstractThe optical and resonance Raman spectra (RR) of bis(phloroglucinol)squaraine (I) and bis(resorcinol)squaraine (II) were investigated, revealing that the equilibria between the neutral and anionic species present in solution explain the experimental observations much better than the previously proposed aggregation equilibria. In particular, the RR spectra were invaluable to assign characteristic modes of (I) and its monoanion, since the tuning of the excitation line to the electronic transition band of the neutral or monoanionic specie leads to the enhancement of the respective modes that are exclusive of each species. In addition, small angle X‐ray scattering (SAXS) experiments with (I) did not show any evidence of aggregation. Copyright © 2006 John Wiley & Sons, Ltd.
The excited‐state geometry of 1‐hydroxy‐2‐ acetonaphthone: a resonance Raman and quantum chemical study
Authors: Szeghalmi A. V. , Engel V. , Zgierski M. Z. , Popp J. , Schmitt M. 
Published: January 2006

Abstract1‐Hydroxy‐2‐acetonaphthone (HAN), an intramolecular proton transfer system, was investigated in the present study by means of quantum chemical calculations and resonance Raman spectroscopy. To determine the Franck–Condon parameters, a time‐dependent approach for the analysis of the resonance Raman spectra was applied. About 18 vibrational modes were found to be involved in the initial dynamics of HAN upon photo excitation. Moreover, the excited‐state geometry of HAN was optimized at the CASSCF level of theory and the displacement parameters were determined. A very good agreement between the theoretical and experimentally derived parameters was obtained. The vibrations with the highest displacements correspond to stretching and in‐plane deformation modes of the naphthalene ring and the conjugated carbonyl group, while the OH stretching mode exhibits no observable enhancement. Hence, a general molecular rearrangement takes place upon photo excitation, where the intramolecular oxygen–oxygen distance reduces corresponding to a redistribution of the electron density. Copyright © 2006 John Wiley & Sons, Ltd.
Raman and infrared spectroscopic mapping of human primary intracranial tumors: a comparative study
Authors: Krafft Christoph , Sobottka Stephan B. , Schackert Gabriele , Salzer Reiner 
Published: January 2006

AbstractIntracranial tumors are neoplasias of brain tissue or other tissue inside the skull. Cryosections of the three most frequent primary intracranial tumors—gliomas, meningeomas and schwannomas—were prepared on calcium fluoride windows and studied by both Raman spectroscopy and infrared (IR) spectroscopy. Spectroscopic maps were recorded by sequential acquisition of spectra in a raster pattern. Cluster analyses on selected wavenumber regions were applied for evaluation of these data sets. Raman spectroscopic contributions of proteins including collagen and hemoglobin were identified in cluster centroids, as were nucleic acids and lipids including cholesterol, cholesterol ester (CE) and phosphatidylcholine (PC). Moreover, hydroxyapatite and tricalciumphosphate could be identified as markers for calcification. The spatial distributions of these spectral properties were visualized in pseudocolor Raman and IR maps representing the cluster memberships. The prospects of both methods are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Probing self‐associated structures of the solute molecule, acrylonitrile, the solvent molecule 2Cl‐phenol and their binary complexes via concentration‐dependent Raman study and DFT calculation
Authors: Srivastava S. K. , Ojha Animesh K. , Sinha P. K. , Asthana B. P. , Singh Ranjan K. 
Published: January 2006

AbstractRaman study of CN‐stretching mode of acrylonitrile and ring‐breathing mode of 2Cl‐phenol was made in the binary mixture of (acrylonitrile + 2Cl‐phenol) at different molar ratios of the two components. Raman spectra were recorded in the different spectral regions, 990–1070 cm−1 and 2170–2300 cm−1. Ring‐breathing mode of 2Cl‐phenol exhibited two components, which were attributed to the neat and self‐associated dimer of 2Cl‐phenol molecules. The self‐associated structure of the dimer was obtained by geometry optimization. Other structures, which were calculated, include self‐associated structure of acrylonitrile and the hydrogen‐bonded complex of (acrylonitrile + 2Cl‐phenol). All the geometry optimizations were made using density functional theory (DFT) and B3LYP functional employing the 6–31 + G(d,p) basis set. The variations of the linewidth and the peak position with concentration are explained on the basis of a model, which includes both the effect of concentration fluctuation in a microscopic volume and the influence of concentration‐dependent microviscosity based on a model proposed recently by our group. Copyright © 2006 John Wiley & Sons, Ltd.
Determination of the amide I Raman tensor for the antiparallel β‐sheet: application to silkworm and spider silks
Authors: Tsuboi Masamichi , Kubo Yoshiko , Akahane Kiso , Benevides James M. , Thomas George J. 
Published: January 2006

AbstractThe amide I Raman tensor corresponding to the antiparallel β‐sheet structure in proteins has been determined by polarized Raman microspectroscopy of fowl feather rachis using polarized Raman spectra excited in the near‐infrared (785 nm). For a Raman tensor principal axis system (XYZ), in which X is perpendicular to the plane of the pleated β‐sheet, Y is in the plane of the sheet and perpendicular to the direction of the polypeptide chain, and Z is parallel to the direction of the polypeptide chain, the principal tensor components (αXX, αYY, αZZ) are found to satisfy the following relationships: R1 ≡ αXX/αZZ = 0.32 and R2 ≡ αYY/αZZ = 3.48. With this Raman tensor determination, we show that semiquantitative estimates of the total antiparallel β‐sheet content in β‐rich proteins can be extracted from polarized Raman intensity measurements on the amide I marker of the β‐sheet occurring near 1664 cm−1. We demonstrate this approach for the β‐rich silk proteins of the silkworm and spider. Copyright © 2006 John Wiley & Sons, Ltd.
Spectroscopy of Raman‐shifted solitons in photonic‐crystal fibers
Authors: Serebryannikov E. E. , Hu Ming‐Lie , Wang Ching‐Yue , Li Yan‐Feng , Wang Zhuan , Chai Lu , Ren Xiaomin , Dukel'skii K. V. , Khokhlov A. V. , Shevandin V. S. , Kondrat'ev Yu. N. , Zheltikov A. M. 
Published: January 2006

AbstractWhile femtosecond nonlinear Raman techniques typically deal with packets of vibrational quantum states in molecular systems, the technique proposed and implemented in this work uses the results of spectroscopic measurements to reconstruct the temporal structure of short‐pulse wavepackets undergoing continuous frequency downshifting owing to the Raman effect in special optical fibers. Our numerical simulations and experimental results demonstrate that the temporal structure and time dynamics of solitons in photonic‐crystal fibers can be conveniently reconstructed from spectral measurements performed at the output of the fiber. Copyright © 2006 John Wiley & Sons, Ltd.
The conformations adopted by the octamer peptide (AAKA)2 in aqueous solution probed by FTIR and polarized Raman spectroscopy
Authors: Measey Thomas , Schweitzer‐Stenner Reinhard 
Published: January 2006

AbstractIn an effort to further elucidate the chain length dependence of the poly‐L‐proline 31 helical structure (PPII) in short alanine‐based polypeptides, we utilize FTIR, isotropic and anisotropic Raman, and electronic circular dichroism (ECD) spectroscopies to probe the amide I′ band of the unblocked octamer H‐Ala‐Ala‐Lys‐Ala‐Ala‐Ala‐Lys‐Ala‐OD in D2O. Our results are in disagreement with recent notions suggesting that the 31 helical structure increases with an increase in the number of alanine residues.1, 2 Simulations of the spectra were carried out and found to best reproduce experimental spectra using parameters that suggest a 40/60% PPII/β‐strand (ßs) mixture. The amount of PPII in the octamer is found to be significantly lower than what was determined for unblocked alanine‐based peptides of comparable or even larger size. This is confirmed by the relatively weak ECD minimum and maximum at ∼195 and ∼220 nm, respectively, for the octamer relative to tri‐ and tetraalanine.3 In this paper we also address a recent issue concerning the validity of the delocalized character of the amide I mode in unfolded polypeptides containing a significant amount of PPII structure. We conclude that experimental evidence strongly supports the vibrational coupling model used to interpret the amide I mode in unfolded polypeptides. Copyright © 2006 John Wiley & Sons, Ltd.
Polarized Raman spectra of Gd2(MoO4)3 in its orthorhombic structure
Authors: Guy Lucazeau , Denis Machon 
Published: January 2006

AbstractPolarized Raman spectra of a single crystal of gadolinium molybdate, Gd2(MoO4)3 were obtained between 400 and 80 K. Tentative assignments of high‐wavenumber bands of symmetric and antisymmetric MoO4 stretching modes to the three types of tetrahedra present in the ferroelectric phase described by the C2v8 space group are made on the oriented gas model. A careful analysis of the low‐wavenumber spectra allowed identification of new bands compared to those in the literature. The evolution of wavenumbers in the investigated temperature range indicates that a small structural change takes place at about 200 K. Some modes soften when approaching the ferroelectric–paraelectric transition at 159 °C. Copyright © 2006 John Wiley & Sons, Ltd.
Single‐beam CARS spectroscopy applied to low‐wavenumber vibrational modes
Authors: von Vacano Bernhard , Wohlleben Wendel , Motzkus Marcus 
Published: January 2006

AbstractIn single‐beam coherent anti‐Stokes Raman scattering (CARS) spectroscopy, a complete CARS scheme is accomplished with tailored pulses from a fs‐oscillator by coherent control of the nonlinear signal generation. Here, the application of single‐beam CARS to low‐wavenumber vibrational modes in the range of 50–400 cm−1 is demonstrated by investigating pure liquid‐phase samples and molecules in solution. The spectral resolution (17 cm−1) achieved by coherent control of the CARS process is an order of magnitude better than the spectral width of the excitation pulses (150 cm−1 FWHM). At the same time, nonresonant background is suppressed by more than 1 order of magnitude. It is shown that spectral shaping of the excitation spectrum can drastically extend the accessible range of vibrational modes in single‐beam CARS. The implemented scheme is very well suited for CARS microscopy because of its conceptual simplicity and flexibility, and presents the opportunity for spatially resolved studies of conformational modes in biological samples. Copyright © 2006 John Wiley & Sons, Ltd.
Evaluation of Raman spectroscopy and application of chemometric methods for the differentiation of contemporary ivory specimens I: elephant and mammalian species
Authors: Edwards H. G. M. , Hassan N. F. Nik , Arya N. 
Published: January 2006

AbstractSpecimens of mammoth, African and Asian ivory dentine, and other mammalian species were examined using Fourier–Transform (FT), conventional dispersive (confocal) and remote‐sensing portable Raman spectroscopy, all with near‐infrared laser excitation (1064 and 785 nm). FT‐Raman spectroscopy produced the best quality spectra for differentiation purposes and the application of a fibre probe coupled to a portable Raman spectrometer has also been demonstrated and proposed for the in situ characterization of suspected contraband ivories at airports. In addition to the visual comparison of spectral features, chemometric methods are used to discriminate between African and Asian elephant dentine by analyzing normalized integrated band areas in ten selected wavenumber regions. Principal component analysis separates the spectra of both species into two well‐defined groups based upon their organic and inorganic composition. By means of stepwise discriminant analysis almost 98% of the spectra are correctly classified to their species group memberships. Copyright © 2006 John Wiley & Sons, Ltd.
Time‐resolved resonance Raman spectroscopy of sensory rhodopsin II in the micro‐ and millisecond time range using gated cw excitation
Authors: Naumann Hendrik , Murgida Daniel H. , Engelhard Martin , Klare Johann P. , Hildebrandt Peter 
Published: January 2006

AbstractA time‐resolved resonance Raman (RR) spectroscopic approach is presented that allows probing the dynamics of photoconvertible systems in a wide dynamics range covering more than six decades. It is based on an external opto‐electronic gating of continuous wave (cw) pump and probe lasers. Pump and probe events, the delay time as well as the repetition of this sequence can be varied from the nanosecond to the second time scale and thus adjusted to the desired time‐resolution and the recovery of the photoreversible system. Upon combination with the rotating cell technique, the approach offers several additional advantages, particularly for studying biological photoreceptors. Unlike in capillary flow systems, only small amounts of sample (ca 10 nmol) are required and no harmful mechanical stress is exerted on the proteins. External gating of cw lasers does not only provide freely adjustable pump and probe times but also avoids high pulse energies with pulsed laser excitation, thereby reducing the risk of unwanted photoinduced processes. The high potential of this approach is demonstrated by studying the formation and decay of a long‐lived intermediate (M400) of the sensory photoreceptor NpSRII from Natronobacterium pharaonis. The results are in very good agreement with the kinetic data derived from transient UV–vis absorption spectroscopy and demonstrate that this technique represents a powerful tool for studying the cofactor dynamics of biological photoreceptors in general. Copyright © 2006 John Wiley & Sons, Ltd.
Raman investigation of pigmentary molecules in the molluscan biogenic matrix
Authors: Barnard W. , de Waal D. 
Published: January 2006

AbstractRaman spectra of the pigments of several marine mollusc shells have been obtained using the 514.5 nm laser line of an Ar+laser. Shell species were chosen to obtain a variety of colour. The spectra obtained for the molluscan pigments indicated that they are polyacetylenic in nature, and, from the spectral features, it was deduced that the pigments were carotenoids, with unmethylated polyacetylenic backbones of various conjugation lengths. A logarithmic relationship was established between the number of conjugated double bonds (N) and the CC vibration (ν1) of previous reported data for finite polyacetylenic systems, and this relationship was used to evaluate the data obtained in this study. The aragonite and calcite phases of CaCO3were also identified to be present in different species of molluscs. Copyright © 2006 John Wiley & Sons, Ltd.
Quantitative diagnostics of a methane/air mini‐flame by Raman spectroscopy
Authors: Fernández J. M. , Punge A. , Tejeda G. , Montero S. 
Published: January 2006

AbstractWe present a quantitative investigation by linear Raman spectroscopy of a methane/air premixed flame from a commercial burner. Rotational temperatures and absolute densities of the major species, N2, O2, CH4, CO2, and H2O have been measured in a grid of points across the flame section. Axial and radial profiles of temperature and densities are reported, and mass balances along the flame axis are discussed. We show the capabilities of this technique for combustion studies by using currently available standard detectors and spectrometers. Copyright © 2006 John Wiley & Sons, Ltd.
Indole ring orientations of Trp189 in the ground and M intermediate states of bacteriorhodopsin as studied by polarized UV resonance Raman spectroscopy
Authors: Asakawa Kazuhiro , Masuda Satoshi , Takeuchi Hideo 
Published: January 2006

AbstractPolarized resonance Raman spectroscopy provides a means for orientation analysis of proteins in aligned samples. Previously, we developed a Raman linear intensity difference (RLID) method to determine the orientations of aromatic amino acid side chains in flow‐oriented or membrane‐bound proteins. In this study, we have applied the RLID method to Trp189 in bacteriorhodopsin (BR), a transmembrane protein that acts as a light‐driven proton pump. Among the eight Trp residues in BR, the Raman spectrum of Trp189 has been extracted by subtracting the spectrum of the Trp189 → Phe mutant from that of wild‐type BR. By examining the 251.3‐nm‐exited polarized resonance Raman intensities of two indole ring vibrations of Trp189, the directions of the La and Bb transition moments have been determined with respect the membrane normal in the light‐adapted ground state (BR568) and a photo‐excited intermediate (M). Comparison of the orientations of the Trp189 indole ring derived from the La and Bb inclination angles has shown that the indole ring slightly but significantly reorients toward the ionone ring of the retinal chromophore in the M intermediate. The reorientation of Trp189 is consistent with the previous observation that helix F, on which Trp189 is located, undergoes an outward tilt and the hydrophobic interaction of Trp189 increases in the M intermediate. The RLID method combined with 251.3 nm excitation and point mutation is useful for detecting even a small reorientation of a targeted Trp residue. Copyright © 2006 John Wiley & Sons, Ltd.
Raman and SERS investigations of potassium benzylpenicillin
Authors: Iliescu T. , Baia M. , Pavel I. 
Published: January 2006

AbstractRaman spectroscopic investigations in combination with density‐functional theory (DFT) calculations were performed on the potassium benzylpenicillin (KBP) molecule. The theoretical values of the geometrical parameters and the vibrational wavenumbers were compared with the experimental X‐ray diffraction and Raman data and a fairly good agreement was obtained. The SER spectrum of the KBP molecule on silver colloid at pH value of 6 was recorded and analyzed. The adsorbed molecule is bonded to the silver surface through the carboxylate group. The comparison between KBP aqueous solution Raman spectrum and SERS data demonstrates that benzene, beta‐lactam, and thiazolidine rings are situated at a relatively large distance to the silver surface and for these rings the electromagnetic mechanism of enhancement can be implied. Copyright © 2006 John Wiley & Sons, Ltd.