Topic
Raman spectroscopy
About: Raman spectroscopy is a research topic. Over the lifetime, 122605 publications have been published within this topic receiving 2891083 citations. The topic is also known as: Raman Spectrum Analysis & spectrum Analysis, Raman.
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TL;DR: In this paper, the optical constants n and k of liquid H 2 O and D 2 O were calculated by iteration using the Kramers-Kronig transformation which has been adapted to the problem of fringe correction for a flat absorbing sample in contact with highly refractive silicon substrates.
337 citations
TL;DR: In this paper, a review of the results on the Raman spectroscopic investigations of optical phonon confinement in nanocrystalline semiconductor and ceramic/dielectric materials, including those in selenium, cadmium sulphide, zinc oxide, thorium oxide, and nano-diamond, is presented.
Abstract: If the medium surrounding a nano-grain does not support the vibrational wavenumbers of a material, the optical and acoustic phonons get confined within the grain of the nanostructured material. This leads to interesting changes in the vibrational spectrum of the nanostructured material as compared to that of the bulk. Absence of periodicity beyond the particle dimension relaxes the zone-centre optical phonon selection rule, causing the Raman spectrum to have contributions also from phonons away from the Brillouin-zone centre. Theoretical models and calculations suggest that the confinement results in asymmetric broadening and shift of the optical phonon Raman line, the magnitude of which depends on the widths of the corresponding phonon dispersion curves. This has been confirmed for zinc oxide nanoparticles. Microscopic lattice dynamical calculations of the phonon amplitude and Raman spectra using the bond-polarizability model suggest a power-law dependence of the peak-shift on the particle size. This article reviews recent results on the Raman spectroscopic investigations of optical phonon confinement in several nanocrystalline semiconductor and ceramic/dielectric materials, including those in selenium, cadmium sulphide, zinc oxide, thorium oxide, and nano-diamond. Resonance Raman scattering from confined optical phonons is also discussed. Copyright © 2007 John Wiley & Sons, Ltd.
337 citations
TL;DR: The SOCl2-induced conductivity increase by p-type doping of the pristine material is interpreted as a Fermi level shift into the valence band, and is consistent with the temperature dependence of the thermopower.
Abstract: Chemical modification by SOCl2 of an entangled network of purified single-wall carbon nanotubes, also known as 'bucky paper', is reported to profoundly change the electrical and mechanical properties of this system. Four-probe measurements indicate a conductivity increase by up to a factor of 5 at room temperature and an even more pronounced increase at lower temperatures. This chemical modification also improves the mechanical properties of SWNT networks. Whereas the pristine sample shows an overall semiconducting character, the modified material behaves as a metal. The effect of SOCl2 is studied in terms of chemical doping of the nanotube network. We identified the microscopic origin of these changes using SEM, XPS, NEXAFS, EDX, and Raman spectroscopy measurements and ab initio calculations. We interpret the SOCl2-induced conductivity increase by p-type doping of the pristine material. This conclusion is reached by electronic structure calculations, which indicate a Fermi level shift into the valence band, and is consistent with the temperature dependence of the thermopower.
337 citations
TL;DR: The diamond was characterized by Raman spectroscopy and scanning electron microscopy as discussed by the authors, showing that approximately 50% of the initial diamond nuclei appear to be aligned with the C(001) planes parallel to the SiC(001), and C[110] directions parallel to SiC within 3°.
Abstract: Textured diamond films have been deposited on β‐SiC via microwave plasma chemical vapor deposition preceded by an in situ bias pretreatment that enhances nucleation. Approximately 50% of the initial diamond nuclei appear to be aligned with the C(001) planes parallel to the SiC(001), and C[110] directions parallel to the SiC[110] within 3°. The diamond was characterized by Raman spectroscopy and scanning electron microscopy.
336 citations
TL;DR: The photoactivities of the as-prepared samples for the rhodamine-B photodegradation were investigated systematically in this paper, where the photoactivity of the catalyst in relationship with the hydrothermal temperature, the crystal and band structure were also discussed in detail.
Abstract: Nanosized Bi 2 WO 6 was synthesized by a hydrothermal crystallization process. The as-prepared samples were characterized by X-ray diffraction, Brunauer–Emmet–Teller surface area and porosity measurements, transmission electron microscopy, Raman spectra, and diffuse reflectance spectroscopy. The photoactivities of the as-prepared samples for the rhodamine-B photodegradation were investigated systematically. As a result, the sample prepared at 180 °C exhibited the highest photochemical activity under visible-light irradiation. The further experiments revealed that the catalyst was active in a wide spectral range. Density functional theory calculations suggested that the visible-light response was due to the transition from the valence band formed by the hybrid orbitals of Bi 6s and O 2p to the conduction band of W 5d. The photoactivity of the catalyst in relationship with the hydrothermal temperature, the crystal and band structure were also discussed in detail.
336 citations