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: A simple biogenic approach for the promotion of oxygen vacancies in pure zinc oxide (p-ZnO) nanostructures using an electrochemically active biofilm (EAB), which is different from traditional techniques for narrowing the band gap of nanomaterials, resulted in band gap narrowing of the ZnO nanostructure.
Abstract: Band gap narrowing is important and advantageous for potential visible light photocatalytic applications involving metal oxide nanostructures. This paper reports a simple biogenic approach for the promotion of oxygen vacancies in pure zinc oxide (p-ZnO) nanostructures using an electrochemically active biofilm (EAB), which is different from traditional techniques for narrowing the band gap of nanomaterials. The novel protocol improved the visible photocatalytic activity of modified ZnO (m-ZnO) nanostructures through the promotion of oxygen vacancies, which resulted in band gap narrowing of the ZnO nanostructure (Eg = 3.05 eV) without dopants. X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and high resolution transmission electron microscopy confirmed the oxygen vacancy and band gap narrowing of m-ZnO. m-ZnO enhanced the visible light catalytic activity for the degradation of different classes of dyes and 4-nitrophenol compared to p-ZnO, which confirmed the band gap narrowing because of oxygen defects. This study shed light on the modification of metal oxide nanostructures by EAB with a controlled band structure.
504 citations
TL;DR: The excited electronic states of noble metal Au and Ag nanocrystals are very different than those of molecules as discussed by the authors, which makes them ideal nanoantennas, in that they focus incident light into the local neighborhood of subwavelength size.
Abstract: The excited electronic states of noble metal Au and Ag nanocrystals are very different than those of molecules. Ag and Au nanocrystal optical transitions (plasmons) in the visible can be so intense that they significantly modify the local electromagnetic field. Also, coherent elastic Rayleigh light scattering is stronger than normal electronic absorption of photons for larger nanocrystals. These two facts make Au and Ag nanocrystals ideal nanoantennas, in that they focus incident light into the local neighborhood of subwavelength size. Surface-enhanced Raman scattering (SERS), in which the Raman scattering rate of nearby molecules increases by many orders of magnitude, is a consequence of this nanoantenna effect. Metallic nanocrystals also have no band gap; this makes them extraordinarily polarizable. Their electronic transitions sense the local environment. An extreme case is the interaction of two 30 nm Ag nanocrystals separated by a 1 nm gap. Their mutual polarization completely transforms the nature o...
504 citations
TL;DR: The lattice structure and constant of the nanowires as determined from x-ray diffraction (XRD) are nearly identical to those of bulk Si, although the relative XRD peak intensities are different from those of randomly oriented Si crystallites.
Abstract: Silicon nanowires have been synthesized in high yield and high purity by using a high-temperature laser-ablation method with growth rates ranging from 10 to 80 μm/h. Transmission electron microscopic investigation shows that the nanowires are crystalline Si, and have diameters ranging from 3 to 43 nm and length up to a few hundreds microns. Twins and stacking faults have been observed in the Si core of the nanowires. The lattice structure and constant of the nanowires as determined from x-ray diffraction (XRD) are nearly identical to those of bulk Si, although the relative XRD peak intensities are different from those of randomly oriented Si crystallites. Raman scattering from the nanowires shows an asymmetric peak at the same position as that of bulk crystalline silicon.
503 citations
Journal Article•
502 citations
TL;DR: In this article, the Raman scattering intensity of the 1100 cm−1 polarized band reached a maximum at the disilicate composition and increased sharply as the Na2O concentration increases above 30 moles.
Abstract: The Raman scattering intensity of the 1100 cm−1 polarized band, which appears on the addition of Na2O to SiO2 glass, reaches a maximum at the disilicate composition. The intensity of the polarized band at 950 cm−1 increases sharply as the Na2O concentration increases above 30 mole %. These data were interpreted by normal mode calculations and by IR and Raman intensity calculations for the silicate anion structural units: SiO4 isolated tetrahedra, Si2O7 dimers, Si2O6 chain links, Si2O5 sheet units, and Si2O4 framework units. According to these simplified models, the polarized high frequency band is due to symmetric stretching of Si–O− nonbridging bonds and the frequency increases with degree of polymerization of the tetrahedra. The previous assignments of the 1100 cm−1 band to the symmetric stretch of tetrahedra containing one nonbridging oxygen and of the 950 cm−1 band to the symmetric stretch of tetrahedra containing two nonbridging oxygens were confirmed. The other main feature of the alkali silicate gl...
501 citations