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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: Fang et al. as mentioned in this paper showed that if the methyl C-H peak is split by the methylene group, then the splitting is too small to detect in this experiment, thus weakening the trans bond.
Abstract: trans to the lone pair, thus weakening the trans bond. Similar effects have been seen previously in m e t h ~ l a m i n e ~ ~ and trimethylamine?’a If the methyl C-H peak is split by the methylene group, then the splitting is too small to detect in this experiment. Thus, in terms of overtone spectroscopy, the nitrogen lone pair significantly influences the methylene hydrogens but not the methyl hydrogens. In addition, the anisotropic environment that the methylene group provides for the methyl group apparently does not affect the methyl group absorption. The two-point harmonic frequencies and anharmonicities calculated for these absorptions compare well among analogous bonds in these molecules and with similar modes in other molecules. There are two N-H stretching peaks in the overtone spectrum, one a t higher frequency corresponding to the N-H trans to a methylene hydrogen and one at lower frequency corresponding to the N-H trans to the N-C bond. This agrees with earlier results on diethylamine and di~nethylamine.~~ The large number of C-H bonds in triethylamine makes detailed analysis of its spectra difficult, especially without accompanying data on deuterated analogues. There are a t least two C-H peaks in the overtone spectra, the one at higher frequency being a methyl absorption, while the one a t lower frequency is a methylene absorption. Data for both of these absorptions were fit to a BirgeSponer plot and the resulting parameters compare well to the data of Fang et al. for dieth~lamine.’~

485 citations

Journal ArticleDOI
TL;DR: In this paper, G-band resonance Raman spectra of single-wall carbon nanotubes (SWNTs) at the singlenanotube level have been reported and conclusively determined the dependence of the two most intense features on the nanotube structure.
Abstract: We report G-band resonance Raman spectra of single-wall carbon nanotubes ~SWNTs! at the singlenanotube level. By measuring 62 different isolated SWNTs resonant with the incident laser, and having diameters dt ranging between 0.95 nm and 2.62 nm, we have conclusively determined the dependence of the two most intense G-band features on the nanotube structure. The higher-frequency peak is not diameter dependent (v G 51591 cm 21 ), while the lower-frequency peak is given by v G 5v G 2C/dt , with C being different for metallic and semiconducting SWNTs (CM.CS). The peak frequencies do not depend on nanotube chiral angle. The intensity ratio between the two most intense features is in the range 0.1 ,I v G /I v G,0.3 for most of the isolated SWNTs (;90%). Unusually high or low Iv G /I v G ratios are observed for a few spectra coming from SWNTs under special resonance conditions, i.e., SWNTs for which the incident photons are in resonance with the E44 interband transition and scattered photons are in resonance with E33 . Since the Eii values depend sensitively on both nanotube diameter and chirality, the ( n,m) SWNTs that should exhibit such a special G-band spectra can be predicted by resonance Raman theory. The agreement between theoretical predictions and experimental observations about these special G-band phenomena gives additional support for the (n,m) assignment from resonance Raman spectroscopy.

485 citations

Journal ArticleDOI
TL;DR: In this paper, quantum-confined InP nanocrystals from 20 to 50 A in diameter have been synthesized via the reaction of InCl3 and P(Si(CH3)3 )3 in trioctylphosphine oxide (TOPO) at elevated temperatures.
Abstract: Quantum-confined InP nanocrystals from 20 to 50 A in diameter have been synthesized via the reaction of InCl3 and P(Si(CH3)3)3 in trioctylphosphine oxide (TOPO) at elevated temperatures. The nanocrystals are highly crystalline, monodisperse, and soluble in various organic solvents. Improved size distributions have been obtained by size-selectively reprecipitating the nanocrystals. The UV/vis absorption spectra of the particles show the characteristic blue shift of the band gap of up to 1 eV due to quantum confinement, a moderately well-resolved first excitonic excited state, and, in some cases, the resolution of a higher excited state. Structurally, the nanocrystals are characterized with powder X-ray diffraction and transmission electron microscopy. Raman spectroscopy reveals TO and LO modes near the characteristic bulk InP positions as well a surface mode resulting from finite size. The Raman line widths, line positions, and relative intensities are all size-dependent . X-ray photoelectron spectroscopy ...

485 citations

Journal ArticleDOI
TL;DR: The heterostructure SnO(2)-ZnO photocatalyst showed much higher photocatalytic activities for the degradation of methylene blue than those of individual Sno(2) and ZnO nanomaterials and could be easily recycled several times opening new avenues for potential industrial applications.
Abstract: Nanoporous SnO2–ZnO heterojunction nanocatalyst was prepared by a straightforward two-step procedure involving, first, the synthesis of nanosized SnO2 particles by homogeneous precipitation combined with a hydrothermal treatment and, second, the reaction of the as-prepared SnO2 particles with zinc acetate followed by calcination at 500 °C. The resulting nanocatalysts were characterized by X-ray diffraction (XRD), FTIR, Raman, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption analyses, transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectroscopy. The SnO2–ZnO photocatalyst was made of a mesoporous network of aggregated wurtzite ZnO and cassiterite SnO2 nanocrystallites, the size of which was estimated to be 27 and 4.5 nm, respectively, after calcination. According to UV–visible diffuse reflectance spectroscopy, the evident energy band gap value of the SnO2–ZnO photocatalyst was estimated to be 3.23 eV to be compared with those of pure SnO2, that is, 3.7 eV, and Z...

483 citations

Journal ArticleDOI
TL;DR: The surface enhanced Raman scattering (SERS) of a number of species and strains of bacteria obtained on novel gold nanoparticle covered SiO(2) substrates excited at 785 nm is reported, showing the potential of SERS for detection and identification of bacterial pathogens with species and strain specificity on these gold particle covered glassy substrates.
Abstract: The surface enhanced Raman scattering (SERS) of a number of species and strains of bacteria obtained on novel gold nanoparticle (∼80 nm) covered SiO2 substrates excited at 785 nm is reported. Raman cross-section enhancements of >104 per bacterium are found for both Gram-positive and Gram-negative bacteria on these SERS active substrates. The SERS spectra of bacteria are spectrally less congested and exhibit greater species differentiation than their corresponding non-SERS (bulk) Raman spectra at this excitation wavelength. Fluorescence observed in the bulk Raman emission of Bacillus species is not apparent in the corresponding SERS spectra. Despite the field enhancement effects arising from the nanostructured metal surface, this fluorescence component appears “quenched” due to an energy transfer process which does not diminish the Raman emission. The surface enhancement effect allows the observation of Raman spectra of single bacterial cells excited at low incident powers and short data acquisition times....

483 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20235,220
202210,775
20214,240
20204,764
20194,957
20184,893