Search

Raman spectroscopy study of hexagonal InN thin films grown by metal-organic vapor-phase epitaxy is reported with the emphasis on frequencies and linewidths of E(sub 2)(high) and A(sub 1)(LO) modes in the temperature range from 93 to 443 K. Micro-Raman mapping results also demonstrate the high uniformity of the studied InN.

A Raman-scattering study of the phonon behavior of the In(sub x)Ga(sub 1-x)N alloy over the entire composition range is reported. The frequencies of the A(sub 1)[longitudinal-optical (LO)] and E(sub 2) modes are described and show a good agreement with the one-mode behavior dispersion predicted by the modified random-element isodisplacement model.

Three kinds of silver colloids, self-assembled nanowires, triangular nanoplates and quasispherical nanoparticles are synthesized by solution-based method. TEM studies revealed that they exposed different crystal planes such as {111} crystal planes to triangular nanoparticles, mainly {100} and {111} planes to self-assembly nanowires.

The interface processes of 1,10-phenanthroline (phen) at a roughened Au electrode by surface-enhanced Raman scattering (SERS) is reported. The results prove the formation of surface complexes 1,10-phenAu2X6 or [1,10-phenAuX2]AuX4 during the electro-oxidation process of Au while phen and X coadsorbed on the surface.

The halide anion effect on the adsorption of 1,2,3-triazole on Ag and Au colloidal nanoparticles is investigated by means of surface enhanced Raman scattering (SERS), UV- visible absorption spectroscopy and scanning electron microscopy. Analogous behavior is observed in the case of basified Au collids, whereas at the usual pH of the hydrosols the adsorption of 1,2,3- triazole is the same of that observed in halide-free colloids.

Two groups exploit the Raman effect in silicon to shift the wavelength of incident light and amplify the scattered light in an optical cavity. Silicon's band structure accounts for its reluctance to emit light.

The postgrowth micro-Raman stress imaging of cracks in (111) homoepitaxial diamond films are reported. Possible origins of the high tensile stress observed in the (111) homoepitaxial diamond films are discussed.

A combined ultrafast time-resolved study on photophysical process of two -hydroxyphenacyl (pHP) caged compound pHP diethyl phosphate (HPDP) and pHP acetate (HPA) in neat acetonitrile (MeCN) and H(sub 2)O/MeCN mixed solvent is reported. The strong dependence of the deprotection on the leaving group ability suggests a heterolysis cleavage mechanism may be involved in the deprotection mechanism.

The assignments and conformational dependencies of the UV resonance Raman bands of the amide peptide and its isotopically substituted derivatives in both their alpha-helical and PPII states is examined. The analysis confirms the complex nature of the amide III region, which contains many vibrational modes.

A protein sensor based on nanostructural adaptive silver films (ASFs) is developed for soft protein adsorption and detection using surface-enhanced Raman scattering (SERS). The sensor is used to examine differences in Raman spectra of two insulin isomers, human insulin and its analogue insulin lispro. Studies indicate that SERS detection using ASF's could lead to efficient proteomic sensing technology.

Surface-enhanced Raman scattering (SERS) of 4-nitrothioanisole (4-NTA) is investigated in Ag sol. The molecule is found to adsorb on Ag as 4-NTA via the sulfur atom.

The vibrational structure of the chromophore in the primary photoproduct of vision, bathorhodopsin, is investigated to determine the cause of the anomalously decoupled and intense C(sub 11)=C(sub 12) hydrogen-out-of-plane (HOOP) wagging modes and their relation to energy storage in the primary photoproduct. The results suggest that the distortions are caused by three constraints consisting of an electrostatic anchor between the protonated Schiff base and the Glu113 counterion, as well as steric interactions of the 9- and 13-methyl groups with surrounding residues.

Oriented arrays of silver nanowires are fabricated and then used to illustrate the special and strongly polarization-dependent enhancement possible in interwire region.

The isotropic Raman line shape of room-temperature nitrogen over a wide range of densities, from the dilute gas to the dense fluid is calculated. The goal of this calculation is to assess the robustness of the model developed by Everitt and Skinner.

Resonance Raman studies indicates that mutations result in hydrogen-bonding interactions as well as significant perturbations to the structure of the bacteriochlorophyll macrocycles. Effects of hydrogen bonding and structure of the accessory bacteriochlorophylls on charge separation in Rb. capsulatus reaction centers are studied.

A model developed for the more general situation in which each monomer has multiple vibrational modes coupled to the electronic transition is discussed. Resonance Raman excitation profiles and depolarization ratios as well as hyper-Rayleigh scattering intensities for this model is examined.

Surface-enhanced Raman scattering spectra (SERS) of BPS were obtained in si lver sol to examine the excitation-wavelength dependence of their surface-induces photoreaction on silver. The C-S bond cleavage of BPS on Ag to produce benzenethiolate was confirmed to be very effective under green light at 514.5nm.

A detailed resonance Raman and electronic absorption investigation is carried out on a series of novel distal and proximal variants of recombinant catalase-peroxidase from the cyanobacterium. It is found that the distal Asp-IIe hydrogen bond is important bond is important for the stability of the heme architecture and its alteration changes markedly the proximal Hos-Asp hydrogen-bond interaction.

A study was conducted, by means of surface enhanced Raman scattering (SERS), to examine the adsorption of 1,2,3-triazole on silver and gold colloidal nanoparticles. The result shows that the molecular interaction of 1,2,3-triazole on silver takes place via the lone pairs of N1 and N3 atoms.

A simple technique for fabricating electrically controllable Raman-Nath phase defraction gratings is described. Dynamic response and the relaxation dynamics of the first-order peak are measured by applying a dc electric field on and off respectively, and are found to be very fast.

The lattice vibration characteristics of ZnS(sub 1-x)Te(sub x) alloys are studied by Raman scattering measurements. Broadening and asymmetry in the Raman line shape was found to be dependent on theTe composition x and could be explained by the 'Spatial Correlation' model.

The thermal and photochemical characteristics of silver 4-nitrobenzoate (Ag-4NBA) was investigated using various analytical tools, such as X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform electron spectroscopy, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Because the organic moieties anchored on the Ag nanoparticles can be completely removed by heating to 750 K or higher, optically tunable, surface-enhanced Raman scattering (SERS)-active Ag films can be reproducibly fabricated on glass microscope slides.

The silicon substrates machined by single-point diamond turning at machining scales ranging from 10 to 100 nm under plane strain conditions was examined by using laser micro-Raman spectroscopy. The results showed that the subsurface layer was partially transformed to amorphous, the extent of amorphization depending strongly on the undeformed chip thickness.

The actuation mechanism of an electrochemical actuator was understood and associated parameters were determined by investigating the charge transfer dynamics on the surface of single-wall carbon nanotube sheets using in situ Raman spectroscopy. The impact of these findings on the suitability of such material for use in electrochemical devices such as actuators is emphasized.

Raman scattering measurements were made on polycrystalline Mn(sub 0.62)Zn(sub 0.30)Fe(sub 2.08)O(sub 4) ferrites in the temperature range from 175 to 603 K with various degrees of stress generated during the polishing process. It was thus found that the Raman intensity associated closely with the magnetic ordering is highly sensitive to the residual stress in crystal.

Measurements of stress in GaN epitaxial layers grown on 6H-SiC and &-Al(sub 2)O(sub 3) substrates are reported and the Raman-stress factor is obtained. A phenomenological model is developed, which describes the thermal stress of the epitaxial GaN as a superposition of that for ideal GaN and the free volume existing in the layers due to the threading dislocations.

The crystal and solution structures of Arthromyces ramosus peroxidase complexed with salicylhydroxamic and bezohydroxamic acids show only small differences by Raman spectal analysis. However, results reveal the existence of multiple species and two binding sites in the protein, a high- and a low affinity sites for salicylhydroxamic acid.

Silver-containing structures are fabricated reproducibly for Surface-Enhanced Raman Scattering (SERS) spectroscopy use in analytical chemistry. The conclusion arrived is that in tdhe system studied the effective area of the SERS 'site'' must be large compared to the area occupied by the adsorbed pyridine, so that the SERS signal is proportional to the surface coverage, averaged over the adsorbent.

The Raman spectroscopy is used to study the effect of Mg, Si, O, and N ion implantation , in epitaxially grown GaN samples. A marginal increase of the build-in hydrostatic stress, is caused by the ion implantation.

Raman scattering photoluminescence (PL) emission of Cu(sub x)Ga(sub y)Se(sub 2) thin films, are studied at room or low temperatures as a function of composition. An increase in defect concentration and an intensity enhancement of defect related PL emission, coincides with the increase in intensity of the modes.

A detailed study of the Raman scattering of single-crystal PbTiO3 made by Burns and Scott is described. The origins of the anomalous behavior of the E (1 TO) phonon in its subpeak structure in Ba-doped single crystals of PbTiO3 are discussed.

The variation of strain, sp(sup 2) hybridized carbon combination and defect density through the thickness by micro-Raman scattering and microphotoluninescence spectroscopy is evaluated. The results are correlated with curvature observations on detached films, which reflect through thickness strain gradients in the films.

Results show that cytochrome c molecules in mitochondria are membrane-bound and their structure alters upon binding. The changes in the resonance Raman spectral property at 675 centimeter exhibited by intact, swollen, and fractionated mitochondria suggest that structural alterations may occur in b-type cytochromes also in intact and calcium-exposed mitochondria.

A model having a completely aligned fraction, x-ray fiber diagrams and polarized Raman scattering was used to study maagnetically aligned single wall carbon nanotubes (SWNT), in order to characterize the field-induced alignment. Results suggest that in the SWNTs, the anisotropic electrical and thermal transport properties were caused due to the anisotropic morphology of magnetic field-aligned SWNTs.

The changes of spectroscopic features of the forward SRS while varying the bulk liquid temperature was analyzed for utilizing the enhancement phenomena for spectroscopic analysis of the local hydrogen bonding network environment in liquid water. The temperature dependence of the SRS indicated that it sensitively reflected the local change of hydrogen binding network environments under ambient conditions.

A theoretical model, which is formulated to describe the stress distribution in AIN/6H-SiC heterostructures, is presented. The stress introduced during the growth is negligible compared to the stress created by the thermal expansion mismatch during cooling down.

The Raman-scattering investigations, and polarized absorption and luminescence properties of Nd:GdCOB crystals, are presented. The characteristic spectra of Nd:GdCOB are mainly associated with BO3 triangles and partly with Ca(1)O6 octahedra.

The concentration dependence of the Raman noncoincidence effect (NCE) of the C-O and O-H stretching bands of methanol is investigated in methanol/CCl4 mixtures. One of the main conclusions obtained shows that the magnitude of the negative NCE observed for the v(C-O) band increases upon dilution f methanol in CCl4 down to xm ~ 0.2, while the positive NCE of the v(O-H) band remains almost the same upon dilution.

The coherent anti-Stokes Raman scattering correlation spectroscopy (CARS-CS) is described. Its probing of dynamical processes with chemical selectivity is examined, which indicates that the properties of CARS-CS are characterized with measurements of diffusion dynamics of small polystyrene spheres.

The features of the broad radiation in the visible emitted by the cerium dioxide particles excited with sub-band-gap are presented. The concomitant with this emission is the near disappearance of the Stokes and anti-Stokes Raman scattering peaks.

The Raman-scattering measurements were used to study the microstructural changes of amorphous V2O5 films with lithium intercalation. The result shows two broad peaks around at 520 and 650 cm(super -1), due to the stretching modes of the V3-O and V2-O bonds respectively.

The intensity of the radial mode of single-wall carbon nanotubes (SWNT) is shown, which varies markedly in a nonmonotonic manner as a function of negative bias. This arises from the reduction of the energy gaps E(sub ii) between the one-dimensional van Hove singularities through a decrease of the overlap integral between the nearest-neighbor carbon atoms.

The adsorption of L-cysteine (L-Cys) onto a polycrystalline silver electrode surface was investigated by in situ spectroelectrochemical methods. Surface-enhanced Raman spectroscopy (SERS) and surface-enhanced second-harmonic generation (SESHG) measurements are performed in a 0.2 M KCl solution in the presence and absence of L-Cys. The experimental results indicated that L-Cys strongly adsorbs onto silver and remains on the surface at potentials as negative as -900 mV (vs Ag/AgCl).

The Raman scattering in cubic GaN doped with Si and in intrinsically doped cubic Al(sub x)Ga(sub 1-x)N alloys were used to study the plasmon-longitudinal optical (LO) phonon collective excitations. The specific asymmetry of the corresponding Raman lines, associated with the dispersion of the coupled excitations was clearly detected in GaN.

A consistent material description for unreacted ammonium perchlorate (AP) single crystals, describing both the mechanical and thermodynamic properties of the shocked material, is developed. The measurements from the Raman scattering experiments provide a stringent test of the material description.

The sensitivity of the amide III vibration which takes place due to the ultraviolet resonance Raman studies of peptide and protein secondary structure is explained. This sensitivity takes place because of the Ramachandran dihedral psi angle dependent coupling of the amide nitrogen-hydrogen motion.

Wavelet decompositions of Raman spectra were investigated with respect to their usability for spike removal and denoising of the raw data. It could be shown that those operations should be performed sequentially. Suppression of spikes is not straightforwardly possible by wavelet transformation; however, the wavelet transform may be used to recognize the spikes by their first level detail coefficients. Spike locations could be projected from the details to the approximations and, further, to appropriate locations of the original spectrum. After spike recognition, those regions will be replaced by interpolated values. To complete processing, denoising is performed with the despiked spectrum by repeated application of wavelet transform methods.

The Langmuir-Blodgett (LB) technique has been used to obtain spatially resolved surface-enhanced resonance Raman scattering (SERRS) spectra of single dye molecules dispersed in the matrix of a fatty acid. The experimental results presented here mimic the original electrochemical surface-enhanced Raman scattering (SERS) work where the background bulk water did not interfere with the detection of the SERS signal of molecules adsorbed onto the rough silver electrode. LB monolayers of the dye in fatty acid have been fabricated on silver island films with a concentration, in average, of one probe molecule per micrometer square. The properties of single-molecule spectroscopy were investigated using micro-Raman including mapping and global images. Blinking of the SERRS signal was also observed.

Resonance Raman spectral intensities per average bacterial cell have been measured quantitatively for Gram-negative Escherichia coli, Citrobacter freundii, and Enterobacter aerogenes, as well as Gram-positive Bacillus subtilis and Staphylococcus epidermidis. Spectra have been obtained from cultures in the lag, log, and stationary growth phases excited in turn by 228.9, 244.0, and 248.2 nm light. Although Raman spectral peak positions ([cm.sup.-1]) excited by a given wavelength are very similar for all five bacterial species, the organisms are characterized by significantly different spectral intensity values. Intensity changes are associated with growth phase changes in all of the species as well. A comparison of measured with estimated average intensities has been made for spectra of log-phase E. coli. It is possible to compare measured intensities with intensities estimated for log-phase E. coli on the basis of the knowledge of its known average cellular molecular composition. A significant degree of hypochromism is observed in E. coli nucleic acid spectra. In contrast, strong average hyperchromism characterizes all aromatic amino acid peaks belonging to the same E. coli cells. Results suggest that knowledge of spectral intensity values will enhance significantly the capability to identify bacteria by means of their UV resonance Raman spectra.

The benefits of retrieving ozone concentration profiles by a use of a single Raman signal rather than the Raman differential absorption lidar (DIAL) technique are investigated by numerical simulations applied either to KrF- (248 nm) or to quadrupled Nd:YAG- (266 nm) based Raman lidars, which are used for both daytime and nighttime monitoring of the tropospheric water-vapor mixing ratio. It is demonstrated that ozone concentration profiles of adequate accuracy and spatial and temporal resolution can be retrieved under low aerosol loading by a single Raman lidar because of the large value of the ozone absorption cross section both at 248 nm and at 266 nm. Then experimental measurements of Raman signals provided by the KrF-based lidar operating at the University of Lecce (40 [degrees] 20'N, 18 [degrees] 6'E) are used to retrieve ozone concentration profiles by use of the Raman DIAL technique and the nitrogen Raman signal.[C] 2001 Optical Society of America OCIS codes: 010.3640, 010.4950.