Search results for "raman scattering"
showing 10 items of 284 documents
Effects of isotopic substitution on the conformational properties of polymeric aqueous solutions
2000
Abstract This work deals with a side-by-side comparison between the PEO conformational properties in H 2 O and D 2 O. The gyration radius, evaluated by SANS, the hydrodynamic radius, evaluated by PCS, and the Raman D-LAM band analysis furnish valuable information on the structural arrangement of the molecules. The findings clearly show different behavioural properties of the polymer in H 2 O and D 2 O.
Anomalous intensity of the 335 cm−1 phonon in YBa2Cu3O7−δ
1991
Abstract We report results on Raman scattering for the intensity of the 335 cm −1 phonon of A g (pseudo B 1g ) symmetry in thin YBa 2 Cu 3 O 7−δ films on MgO and LaAlO 3 substrates. The intensity of this phonon shows a pronounced increase below 100 K and saturates at low temperatures. We also observe an additional intensity peaking at temperatures close to the superconducting transition T C . This may indicate a structural phase transition in the vicinity of T C .
Growth, characterization, and high-pressure optical studies of CuWO4
2008
Copper tungstate (CuWO4) crystals grown by the top-seeded solution growth method were characterized by X-ray diffraction, Raman scattering, and optical measurements. CuWO4 has a triclinic structure (P 1¯) with a = 4.709 A, b = 5.845 A, c = 4.884 A, α = 88.3°, β = 92.5°, and γ = 97.2°. It consists of corner-linked CuO6 and WO6 octahedra, the former having a pseudo-tetragonally elongated geometry caused by the Cu2+ Jahn–Teller effect. Fifteen out of the eighteen Raman modes of CuWO4 are reported, discussed, and compared with those of other tungstates. We also determined the indirect band-gap energy of CuWO4 (2.3 eV) and its negative pressure coefficient up to 25 GPa. The pressure evolution of…
Orientation-Dependent Handedness of Chiral Plasmons on Nanosphere Dimers: How to Turn a Right Hand into a Left Hand
2016
Optical activity, which is used as a discriminator of chiral enantiomers, is demonstrated to be orientation dependent on individual, and nominally achiral, plasmonic nanosphere dimers. Through measurements of their giant Raman optical activity, we demonstrate that L/R-handed enantiomers can be continuously turned into their R/L-handed mirror images without passing through an achiral state. The primitive uniaxial multipolar response, with demonstrable broken parity and time reversal symmetry, reproduces the observations as resonant Raman scattering on plasmons that carry angular momentum. The analysis underscores that chirality does not have a quantitative continuous measure and recognizes t…
Spectral dynamics of incoherent waves with a noninstantaneous nonlinear response
2013
We study the influence of a constant background noise on the dynamics of spectral incoherent solitons, which are incoherent structures sustained by a noninstantaneous (Raman-like) nonlinearity. As the level of the noise background increases, the incoherent wave enters a novel nonlinear regime characterized by oscillatory dynamics of the incoherent spectrum, which develop within a spectral cone during the propagation. In contrast to the conventional Raman-like spectral red shift, such incoherent spectral dynamics can be characterized by a significant spectral blue shift. On the basis of the kinetic wave theory, we derive explicit analytical expressions of these incoherent oscillatory spectra…
Monitoring Chemical Reactions with SERS-Active Ag-Loaded Mesoporous TiO2 Films
2020
Monitoring chemical reactions that occur in small spaces or confined environments is challenging. Surface-enhanced Raman scattering (SERS) spectroscopy offers the unique possibility to monitor spectral changes with high sensitivity and time resolution. Herein, we report the application of composite mesoporous TiO2 films loaded with Ag nanoparticles (NPs) to track in situ chemical processes in real time. In particular, the AgNPs@TiO2 system was employed to monitor two chemical reactions: one occurring on the Ag NPs surface and another taking place in the surrounding solution. In the first case, we monitored the decarboxylation reaction of 4-mercaptobenzoic acid on Ag NPs, which allowed us to…
Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles in metal–dielectric nanocomposites
2008
We report the preparation of a new type of nanocomposite containing cobalt and silver nanoparticles organized in parallel layers with a well controlled separation. This arrangement allows the observation of an enhanced low-frequency Raman signal at the vibration frequency of cobalt nanoparticles excited through the surface plasmons of silver nanoparticles. Numerical simulations of the electric field confirm the emergence of hot spots when the separation between silver and cobalt nanoparticles is small enough. © IOP Publishing Ltd.
Dependence of the emission properties of the germanium lone pair center on Ge doping of silica
2011
We present an experimental investigation regarding the changes induced by the Ge doping level on the emission profile of the germanium lone pair center (GLPC) in Ge doped silica. The investigated samples have been produced by the sol-gel method and by plasma-activated chemical vapor deposition and have doping levels up to 20% by weight. The recorded photoluminescence spectra show that the GLPC emission profile is the same when the Ge content is lower than ∼ 1% by weight, whereas it changes for higher doping levels. We have also performed Raman scattering measurements that show the decrease of the D1 Raman band at 490 cm( - 1) when the Ge content is higher than 1% by weight. The data suggest…
<title>Micro-Raman scattering and infrared spectra of hemoglobin</title>
2008
Confocal micro-Raman and FT-IR spectroscopies have been used for detection of radiation influence of hemoglobin of patients examined by radio-isotopes diagnosis (Tc99m). After irradiation we observed some little changes of the Raman scattering bands which connected with out of plane porphyrine bending vibrations, also we observed additional band due to methemoglobin. Radiation of blood lead to the transition from hemoglobin (Fe2+) to methemoglobin (Fe3+) with a delocalization of iron from porphyrine plane. It was shown that FT-IR spectra indicate the radiation effects on hemoglobin.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is per…
Spatial localization of hotspots in Fano-resonant plasmonic oligomers for surface-enhanced coherent anti-Stokes Raman scattering
2020
AbstractRealization of Fano resonance in plasmonic oligomers is often exploited to design efficient plasmonic substrates for surface-enhanced coherent anti-Stokes Raman scattering. Disk-type Fano-resonant plasmonic oligomers are widely used to enhance the Raman signal of the probe material. Generally, hot spots are generated in those oligomers at different spatial locations at different wavelengths and only a few spatially overlapping hot spots at multiple wavelengths can be achieved with oblique incidence of excitation light. In this work, we proposed hexagonal gold nanoparticle based Fano-resonant plasmonic oligomers that can yield higher number of spatially overlapped hot spots compared …