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Scattering Spectroscopy (scattering + spectroscopy)
Selected AbstractsPhotodiagnostic techniques for the endoscopic detection of premalignant gastrointestinal lesionsDIGESTIVE ENDOSCOPY, Issue 3 2003Ralph S. DaCosta Considerable attention is given to the clinical diagnosis of gastrointestinal (GI) malignancies as they remain the second leading cause of cancer-associated deaths in developed countries. Detection and intervention at an early stage of preneoplastic development significantly improve patient survival. High-risk assessment of asymptomatic patients is currently performed by strict endoscopic surveillance biopsy protocols aimed at early detection of dysplasia and malignancy. However, poor sensitivity associated with frequent surveillance programs incorporating conventional screening tools, such as white light endoscopy and multiple random biopsy, is a significant limitation. Recent advances in biomedical optics are illuminating new ways to detect premalignant lesions of the GI tract with endoscopy. The present review presents a summary report on the newest developments in modern GI endoscopy, which are based on novel optical endoscopic techniques: fluorescence endoscopic imaging and spectroscopy, Raman spectroscopy, light scattering spectroscopy, optical coherence tomography, chromoendoscopy, confocal fluorescence endoscopy and immunofluorescence endoscopy. Relying on the interaction of light with tissue, these ,state-of-the-art' techniques potentially offer an improved strategy for diagnosis of early mucosal lesions by facilitating targeted excisional biopsies. Furthermore, the prospects of real-time ,optical biopsy' and improved staging of lesions may significantly enhance the endoscopist's ability to detect subtle preneoplastic mucosal changes and lead to curative endoscopic ablation of these lesions. Such advancements within this specialty will be rewarded in the long term with improved patient survival and quality of life. [source] Multiscale Approach of Photochromism: Synthesis and Photochromic Properties of a Diarylethene in Solution, in Nanoparticles, and in Bulk Crystals,ADVANCED MATERIALS, Issue 3 2009Arnaud Spangenberg A new photochromic diarylethene, 1,2-bis(5,-ethoxy-2,-(2,-pyridyl) thiazolyl) perfluorocyclopentene (1), is synthesized. Nanoparticles are obtained by laser ablation at both 355 and 532 nm, corresponding to the absorption wavelengths of the open and the closed forms. 1 can be reversibly photoswitched in various states: organic solution, bulk crystal, nanoparticle colloidal solution, and single nanoparticle, as demonstrated by dark-field scattering spectroscopy. [source] Synthesis and characterization of a poly(GMA)-graft-poly(Z- L -lysine) graft copolymer with a rod-like structureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009You-Liang Tu Abstract This study applied the macromonomers and glycidyl methacrylate (GMA) to synthesize a series of the graft copolymers, poly(GMA)-graft-poly(Z- L -lysine), and investigated the conformation of the graft copolymer. The graft copolymers were synthesized with different GMA monomer ratios (28 to 89%) and different degrees of polymerization (DP) (8 to 15) of the poly(Z- L -lysine) side chain to analyze secondary structure relationships. Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and both wide angle and small angle X-ray scattering spectroscopy (WAXS, SAXS) were used to investigate the relationship between the microstructure and conformation of the graft copolymers and the different monomer ratios and side chain DP. In AFM images, n8-G89 (the graft copolymer containing 89% GMA units and the macromonomer DP is 8) showed tiny and uniform rod-like structures, and n14-G43 (the graft copolymer containing 43% GMA units and the macromonomer DP is 14) showed uniform rod-like structures. FTIR spectra of the graft copolymers showed that the variations of ,-helix and ,-sheet secondary structures in the graft copolymers relate to the monomer ratios of the graft copolymers. However, the X-ray scattering patterns indicated that the graft copolymer conformations were mainly dependent on the poly(Z- L -lysine) side chain length, and these results were completely in accordance with the AFM images. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4655,4669, 2009 [source] FT-Raman, FTIR and density functional theory studies of a hydrogen-bonded formamide:pyridine complexJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2009Filipe S. F. Jacinto Abstract Raman and IR experiments have been carried out on formamide (FA) and pyridine (Py) mixtures at different compositions. The appearance of a new Raman band at 996 cm,1 (,1 region of Py), whose intensity depends on the FA concentration, is assigned to an FA:Py adduct and this result is in excellent agreement with those of other authors who employed noisy light-based coherent Raman scattering spectroscopy (I(2) CARS). Another band at 1587 cm,1 (,8 region of Py) has been observed for the first time by using Raman and IR spectroscopies. Its intensity shows the same dependence on the FA concentration and this fact allows us to also attribute it to an FA:Py adduct. The good relationship between the Raman and IR data demonstrates the potential of the vibrational spectroscopy for this kind of study. Owing to higher absolute Raman scattering cross section, the ,1 region of Py has been chosen for the quantitative analysis and a stoichiometry of 1:1 FA:Py is reported. The experimental data are very well supported by the density functional theory (DFT) calculation, which was employed for the first time to the present system. Furthermore, the actual investigation shows an excellent agreement with those reported from computational calculations for similar systems. A comparison with our previous studies confirms that the solvent dielectric constant determines the stoichiometry of a given Lewis acid,base adduct in the infinite dilution limit. Copyright © 2009 John Wiley & Sons, Ltd. [source] A study of collective motions in liquid tert -butanol from low-wavenumber Raman scatteringJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009P. Sassi Abstract The collective properties of liquid tert -butyl alcohol (TBA) were analysed by low-wavenumber Raman (LWR) scattering spectroscopy. Vibrational and relaxation phenomena of this H-bonding system were assessed in pure liquid phase at different temperatures in the 15,70 °C range, and in solution with 2,2,-dimethyl butane (2,2,-DMB) and water as a function of composition in the 0.7,xTBA,0.9 range at constant temperature (T = 25 °C). The LWR spectrum of pure TBA (below 150 cm,1) was expressed by the dynamical (or Raman) susceptibility ???? and reproduced by curve fitting using three functional forms. The high-wavenumber band, whose intensity is poorly dependent on the temperature, was assigned to the ultrafast librational mode; the remaining components with an intensity that increased with temperature were attributed to relaxation dynamics in the range of picosecond (,slow' 3 ps) and sub-picosecond (,fast', 0.4 ps) timescales. Adding 2,2,-DMB to TBA had no significant effect on the intermolecular interactions in alcohol-rich solutions, with almost unchanged LWR scattering features. On the other hand, water added to TBA determined an increase in interactions, similar to the effect of a temperature decrease in pure liquid alcohol; this was clearly depicted by the LWR profiles. Moreover, through the analysis of the OH stretching bands of water in solution, the confinement of aqueous pools in the hydrophilic spaces of alcohol-rich solutions was confirmed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Coadsorption of trimethyl phosphine and thiocyanate on colloidal silver: a SERS study combined with theoretical calculationsJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2009Gengshen Hu Abstract The adsorption of trimethyl phosphine (TMP) on colloidal silver has been investigated by means of surface-enhanced Raman scattering spectroscopy (SERS). On the basis of surface selection rules, it is deduced from the SERS results that TMP adsorbs on silver surface via its P atom. The electron donor effect of TMP can be sensitively probed by the coadsorbed SCN,. The Raman wavenumber of ,CN of the adsorbed SCN, shifts to lower wavenumbers when TMP is coadsorbed with SCN, and the red shift of C,N stretching wavenumber is found to increase with increasing surface coverage of TMP. This could be explained in terms of the electron donor effect of TMP. Density functional theory (DFT) calculations further confirm the experimental results that the charge transfer is from TMP to silver surface rather than reversely. Natural bond orbital (NBO) analysis indicates that the red shift of C,N stretching mode is due the increase of electronic populations of ,* orbital of C,N bond induced by coadsorbed TMP, consequently the C,N bond is weakened, and the ,CN shifts to lower wavenumbers. An NBO analysis also indicates that the conjugated effect between S atom and C,N bond could easily make the charge transfer from silver surface to C,N bond. Copyright © 2008 John Wiley & Sons, Ltd. [source] Surface-enhanced Raman scattering spectroscopy via gold nanostarsJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2009E. Nalbant Esenturk Abstract Anisotropic metallic nanoparticles (NPs) have unique optical properties, which lend them to applications such as surface-enhanced Raman scattering (SERS) spectroscopy. Star-shaped gold (Au) NPs were prepared in aqueous solutions by the seed-mediated growth method and tested for Raman enhancement using 2-mercaptopyridine (2-MPy) and crystal violet (CV) probing molecules. For both molecules, the SERS activity of the nanostars was notably stronger than that of the spherical Au NPs of similar size. The Raman enhancement factors (EFs) for 2-MPy on Au nanostars and nanorods are comparable and estimated as greater than 5 orders of magnitude. However, the enhancement for CV on nanostars was significantly higher than for nanorods, in particular at CV concentrations of 100 nM or lower. This article is a US Government work and is in the public domain in the USA. Published in 2008 by John Wiley & Sons, Ltd. [source] Adsorption of pyridine, ,-picoline and isonicotinonitrile on Ag colloidal particles studied by surface-enhanced Raman scattering spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2005Tomoe Osaki Abstract The surface-enhanced Raman scattering (SERS) spectra of pyridine and related compounds, ,-picoline and isonicotinonitrile, in Ag colloids were studied. Electron diffraction measurement indicated that the Ag colloidal particles are composed of Ag crystals. Models for the molecules adsorbed on Ag particles were proposed and the optimized geometries of the models were determined through calculations of the stabilization energies due to adsorption made for the models with Gaussian 98 using the Hartree,Fock theory with the 3,21G basis set. The normal vibrations of the molecules adsorbed on Ag particles were calculated using the optimized models and assignments of the vibrational bands of the SERS spectra were made. On the basis of the results obtained, it was concluded that (1) pyridine and related compounds are adsorbed on Ag particles through NAg bonds and (2) the N atoms of the molecules are bound to the pointed ends of the surface of Ag particles on adsorption. Copyright © 2004 John Wiley & Sons, Ltd. [source] Study of structural defects in ,-MnO2 by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2002C. Julien The structural arrangement of ,-MnO2 is currently explained by a random intergrowth of pyrolusite layers in a ramsdellite matrix. The structures of a large variety of ,-MnO2 samples with various structural parameters Pr were studied by x-ray powder diffraction and Raman scattering spectroscopy. We show that elucidation of the quantitative determination of the structural disorder present in ,-MnO2 is accurate by Raman scattering spectroscopy. The Raman data for manganese dioxides with the ,-type structure are treated by a local environment model, which allows one to consider the relationship between the band wavenumber and the pyrolusite intergrowth that corresponds to the structural De Wolff defects. Copyright © 2002 John Wiley & Sons, Ltd. [source] Low-wavenumber Raman scattering spectroscopy in studies of new gallium-doped silica glass-based transparent vitroceramic mediumJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2001R. Ceccato Optically transparent, silica glass-based vitroceramic material doped with gallium oxide was obtained by standard glass fusion and appropriate thermal treatments. Low-wavenumber Raman scattering spectroscopy allowed the determination of the microstructure and in particular the size distribution of nanoparticles embedded in the amorphous matrix. The nanocrystal growth was accurately controlled by heat treatment conditions. Transmission electron microscopy and X-ray diffraction measurements revealed the presence of a single crystalline phase, spherical-shaped nanoaggregates, homogeneously distributed in the transparent composite medium. Copyright © 2001 John Wiley & Sons, Ltd. [source] ALD growth of Al2O3 on GaAs: Oxide reduction, interface structure and CV performancePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010H. D. Lee Abstract We have studied the effect of the trimethylaluminum (TMA) precursor on the reduction of surface "native" oxides from GaAs substrates using medium energy ion scattering spectroscopy (MEIS), X-ray photoelectron spectroscopy (XPS) and electrical measurements. Our data show that after one single TMA pulse a substantial part of the native oxide is reduced and an oxygen-rich aluminum oxide layer is formed. Al2O3 films grown with the normal atomic layer deposition cycles of TMA and water show that the growth rate of the Al oxide during this initial reduction of the native oxides is faster than the rate once this reduction is completed. Furthermore, the results of C-V measurements of Al2O3/GaAs grown under the same conditions along with post deposition annealing indicate a good quality interface. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhanced luminescence and two-photon absorption of silver nano-clustersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009A. V. Aiboushev Abstract Luminescence of silver nanoparticles photo-deposited on titan dioxide nanoparticles of mesoporous film is studied. Luminescence was registered under the two-photon excitation by femto-second laser pulses of Ti:sapphire laser. It was observed that Ag/ TiO2 mesoporous films have high concentration of bright luminescence spots which reveal stability to degradation under long illumination. Various configurations of silver nanoparticles are analyzed to explain the physics of bright luminescence spots ("hot spots"). Luminescence intensity reveals "hot spots" dependence on the polarization of excitation laser pulse. Properties of Ag/TiO2 system can be useful for single molecule spectroscopy and visualization of biological objects. Aapplication of Ag/ TiO2 mesoporous films for Raman scattering spectroscopy de-menstruated for the case of Rhodamine B. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectroscopic detection and evaluation of morphologic and biochemical changes in early human oral carcinoma,CANCER, Issue 7 2003Markus G. Müller Ph.D. Abstract BACKGROUND Understanding the development and progression of head and neck squamous cell carcinoma is key in the quest for the early diagnosis and prevention of this type of malignancy. The current study correlated early biochemical and histologic changes in oral tissue with spectral features in fluorescence, reflectance, and light scattering spectra acquired in vivo to diagnose early stages of oral malignancies. METHODS A total of 91 tissue sites from 15 patients with varying degrees of malignancy (normal, dysplastic, and cancerous sites) and 8 healthy volunteers were analyzed with 3 spectroscopic techniques. Direct biochemical information regarding oral tissue native fluorophores was obtained with intrinsic fluorescence spectroscopy by fitting a linear combination of collagen and the reduced form of nicotinamide adenine dinucleotide (NADH) fluorescence spectra to the intrinsic tissue fluorescence spectra excited with 337 nanometer (nm) and 358-nm laser light. Diffuse reflectance spectroscopy was used to provide information regarding tissue absorption and structure, such as hemoglobin concentration and stroma density, by measuring the wavelength-dependent absorption and scattering coefficients. By subtracting the diffusely reflected component from the measured reflectance, light scattering spectroscopy (LSS) information resulting from single backscattering from epithelial cell nuclei was obtained. LSS provides information concerning the size distribution of cell nuclei. RESULTS These optically extracted tissue parameters provide biochemical or structural information in vivo without the need for tissue excision, and can be used to diagnose tissue abnormalities. By combining the information provided by the three techniques, a method known as trimodal spectroscopy, a sensitivity and specificity of 96% and 96%, respectively, in distinguishing cancerous/dysplastic (mild, moderate, and severe) from normal tissue was achieved. In addition, the authors were able to distinguish dysplastic from cancerous tissue with a sensitivity of 64% and a specificity of 90%. CONCLUSIONS The results of the current study demonstrated that Trimodal spectroscopy is a highly sensitive and specific technique with which to diagnose tissue abnormalities. Cancer 2003;97:1681,92. © 2003 American Cancer Society. DOI 10.1002/cncr.11255 [source] Geminal Ionic Liquids: A Combined Approach to Investigate Their Three-Dimensional OrganisationCHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009Francesca D'Anna Dr. Abstract Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3,-di- n -butyl-1,1,-(1,3-phenylenedimethylene)diimidazolium and 3,3,-di- n -butyl-1,1,-(1,4-phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co-solvent such as methanol. [source] | ||||||||||||||||