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.

Hydrogen bonding and Raman, IR, and 2D-IR spectroscopy of dilute HOD in liquid D2O

Abstract: We present improvements on our previous approaches for calculating vibrational spectroscopy observables for the OH stretch region of dilute HOD in liquid D2O. These revised approaches are implemented to calculate IR and isotropic Raman spectra, using the SPC/E simulation model, and the results are in good agreement with experiment. We also calculate observables associated with three-pulse IR echoes: the peak shift and 2D-IR spectrum. The agreement with experiment for the former is improved over our previous calculations, but discrepancies between theory and experiment still exist. Using our proposed definition for hydrogen bonding in liquid water, we decompose the distribution of frequencies in the OH stretch region in terms of subensembles of HOD molecules with different local hydrogen-bonding environments. Such a decomposition allows us to make the connection with experiments and calculations on water clusters and more generally to understand the extent of the relationship between transition frequency and local structure in the liquid.

Raman Analysis of Mode Softening in Nanoparticle CeO2−δ and Au-CeO2−δ during CO Oxidation

Abstract: Oxygen vacancy levels are monitored during the oxidation of CO by CeO2−δ nanorods and Au-CeO2−δ nanorods, nanocubes, and nanopolyhedra by using Raman scattering. The first-order CeO2 F2g peak near 460 cm–1 decreases when this reaction is fast (fast reduction and relatively slow reoxidation of the surface), because of the lattice expansion that occurs when Ce3+ replaces Ce4+ during oxygen vacancy creation. This shift correlates with reactivity for CO oxidation. Increases in the oxygen deficit δ as large as ∼0.04 are measured relative to conditions when the ceria is not reduced.

Layer-Controlled, Wafer-Scale, and Conformal Synthesis of Tungsten Disulfide Nanosheets Using Atomic Layer Deposition

Abstract: The synthesis of atomically thin transition-metal disulfides (MS2) with layer controllability and large-area uniformity is an essential requirement for their application in electronic and optical devices. In this work, we describe a process for the synthesis of WS2 nanosheets through the sulfurization of an atomic layer deposition (ALD) WO3 film with systematic layer controllability and wafer-level uniformity. The X-ray photoemission spectroscopy, Raman, and photoluminescence measurements exhibit that the ALD-based WS2 nanosheets have good stoichiometry, clear Raman shift, and bandgap dependence as a function of the number of layers. The electron mobility of the monolayer WS2 measured using a field-effect transistor (FET) with a high-k dielectric gate insulator is shown to be better than that of CVD-grown WS2, and the subthreshold swing is comparable to that of an exfoliated MoS2 FET device. Moreover, by utilizing the high conformality of the ALD process, we have developed a process for the fabrication of...

Alkyne-Tag Raman Imaging for Visualization of Mobile Small Molecules in Live Cells

Abstract: Alkyne has a unique Raman band that does not overlap with Raman scattering from any endogenous molecule in live cells. Here, we show that alkyne-tag Raman imaging (ATRI) is a promising approach for visualizing nonimmobilized small molecules in live cells. An examination of structure–Raman shift/intensity relationships revealed that alkynes conjugated to an aromatic ring and/or to a second alkyne (conjugated diynes) have strong Raman signals in the cellular silent region and can be excellent tags. Using these design guidelines, we synthesized and imaged a series of alkyne-tagged coenzyme Q (CoQ) analogues in live cells. Cellular concentrations of diyne-tagged CoQ analogues could be semiquantitatively estimated. Finally, simultaneous imaging of two small molecules, 5-ethynyl-2′-deoxyuridine (EdU) and a CoQ analogue, with distinct Raman tags was demonstrated.

Raman investigation of ring configurations in vitreous silica

Abstract: Random network models of glass structures1 provide satisfactory qualitative descriptions of many properties of glasses (see reviews in refs 2–4). However, to obtain good quantitative agreement between theoretical analyses and experimental observations5–11 it is often necessary to assume that specific ring structures in the random networks have special importance. In the case of vitreous silica (v-SiO2), distributions of loops of SiO4 tetrahedra in the random network have been invoked5–9 to match calculated and experimental X-ray radial distribution functions (RDF). High resolution X-ray photoelectron spectra12 of v-SiO2 and quartz also provide evidence for the occurrence of four-, six- and higher-membered rings of SiO4 tetrahedra in v-SiO2. Raman spectra are also sensitive to local microstructures in vitreous solids. We have therefore examined the question of rings in the structure of v-SiO2 by comparing its Raman spectrum with spectra of crystalline silica polymorphs whose shortest loops contain four (coesite) and six (for example, α-quartz) tetrahedra. This comparison indicates that the sharp shoulder at 490 cm−1 in the spectrum of v-SiO2, previously attributed to a defect structure3 or a longitudinal optic mode14, can be assigned to four-membered ring structure. We discuss here possible basis for the stability of four-membered rings of SiO4 tetrahedra in v-SiO2 at ambient pressure. Possible reasons for the absence of the 490 cm−1 band in the vibrational density-of-states derived for a random network model by Bell and co-workers12,15 are discussed.