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.

Analysis and experimental assessment of the sensitivity of stimulated Raman scattering microscopy

Abstract: We theoretically show that the shot-noise-limited sensitivity of stimulated Raman scattering (SRS) microscopy, which enables high-contrast vibrational imaging, is similar to that of coherent anti-Stokes Raman scattering microscopy. We experimentally confirm that the sensitivity of our SRS microscope is lower than the shot-noise limit only by <15 dB, which indicates that the high-sensitivity of SRS microscopy is readily available.

In Situ Spectroscopic Investigation of the Molecular and Electronic Structures of SiO2 Supported Surface Metal Oxides

Abstract: Groups 5−7 transition metal oxides (V2O5, Nb2O5, Ta2O5, CrO3, MoO3, WO3, Re2O7) were anchored on a SiO2 support via incipient wetness impregnation and calcination. The molecular and electronic structures of the dehydrated supported metal oxides and the SiO2 support were determined by combined in situ Raman, IR, and UV−vis spectroscopy under dehydrated conditions. In situ Raman characterization reveals that the supported metal oxides are only present as surface species below the maximum dispersion limit (where crystalline metal oxide nanoparticles are absent). In situ IR analysis shows that the surface metal oxides anchor to the SiO2 support at Si−OH and adjacent Si−O−Si sites. The corresponding in situ UV−vis diffuse reflectance spectroscopy indicates that the dehydrated surface metal oxide species are present as isolated structures. Isotopic D2O−H2O exchange demonstrates that the dehydrated surface MOx species possess the MO oxo functionality but no MOH bonds. The number of MO oxo bonds was found to be r...

Boron carbide structure by Raman spectroscopy

Abstract: We have obtained and analyzed Raman spectra of single-crystal, hot-pressed, and chemical-vapor-deposited boron carbide materials over their single-phase region (from {similar to}9 to {similar to}20 at. % carbon). These spectra provide insight into the substitutional disorder that characterizes these structurally ordered solids. In particular, although icosahedra and chain structures occupy regular lattice positions, there is local substitutional disorder resulting from the occupancy of certain sites within the icosahedra and chains by either boron or carbon atoms. Comparison of boron carbide Raman spectra with the Raman spectra of {alpha}-rhombohedral boron, boron phosphide, and boron arsenide has confirmed the following structural model derived from theoretical considerations and electrical and thermal transport data. The boron carbide composition with nearly 20 at. % carbon is composed of B{sub 11}C icosahedra linked by carbon-boron-carbon chains. As the carbon content is reduced toward approximately 13 at. %, carbon-boron-carbon chains are progressively replaced by carbon-boron-boron chains. Further reduction in the carbon content results in the replacement of B{sub 11}C icosahedra with B{sub 12} icosahedra.

Direct growth of bilayer graphene on SiO₂ substrates by carbon diffusion through nickel.

Abstract: Here we report a transfer-free method of synthesizing bilayer graphene directly on SiO2 substrates by carbon diffusion through a layer of nickel. The 400 nm nickel layer was deposited on the top of SiO2 substrates and used as the catalyst. Spin-coated polymer films such as poly(methyl methacrylate), high-impact polystyrene or acrylonitrile–butadiene–styrene, or gas-phase methane were used as carbon sources. During the annealing process at 1000 °C, the carbon sources on the top of the nickel decomposed and diffused into the nickel layer. When cooled to room temperature, bilayer graphene was formed between the nickel layer and the SiO2 substrates. The nickel films were removed by etchants, and bilayer graphene was then directly obtained on SiO2, eliminating any transfer process. The bilayer nature of the obtained graphene films on SiO2 substrates was verified by Raman spectroscopy and transmission electron microscopy. The Raman spectroscopy mapping over a 100 × 100 μm2 area indicated that the obtained graph...

Consistent porphyrin force field. 2. Nickel octaethylporphyrin skeletal and substituent mode assignments from nitrogen-15, meso-d4, and methylene-d16 Raman and infrared isotope shifts

Abstract: Resonance Raman spectra with variable-wavelength excitation are reported for nickel octaethylporphyrin and its isotopomers containing {sup 15}N, and {sup 2}H at the methine (meso-d{sub 4}) and methylene (methylene-d{sub 16}) carbon atoms. The {sup 15}N, meso-d{sub 4} double isotopomer is also examined. The infrared spectrum of the methylene-d{sub 16} isotopomer is reported, and the frequencies are combined with recently published infrared results for the other isotopomers. Essentially all of the porphyrin skeletal modes have been assigned and have been allocated to local coordinates which recognize the pyrrole rings as cooperative vibrational units. The assignments are supported by a normal-coordinate analysis with a valence force field involving standard ethyl force constants and porphyrin in-plane force constants which are transferred nearly intact from Ni porphine and Ni tetraphenylporphine. Many vibrational modes of the NiOEP ethyl substituents have also been located in the spectra and assigned. Bands assignable to ethyl C-C stretching and C-H bending modes are surprisingly strong in the resonance Raman spectra and suggest appreciable involvement of the ethyl groups in the porphyrin {pi}-{pi}{sup *} excited states. The conformations of the ethyl substituents have a marked influence on the low-frequency vibrational spectra.