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.

High-Capacitance Mechanism for Ti3C2Tx MXene by in Situ Electrochemical Raman Spectroscopy Investigation

Abstract: MXenes represent an emerging family of conductive two-dimensional materials. Their representative, Ti3C2Tx, has been recognized as an outstanding member in the field of electrochemical energy storage. However, an in-depth understanding of fundamental processes responsible for the superior capacitance of Ti3C2Tx MXene in acidic electrolytes is lacking. Here, to understand the mechanism of capacitance in Ti3C2Tx MXene, we studied electrochemically the charge/discharge processes of Ti3C2Tx electrodes in sulfate ion-containing aqueous electrolytes with three different cations, coupled with in situ Raman spectroscopy. It is demonstrated that hydronium in the H2SO4 electrolyte bonds with the terminal O in the negative electrode upon discharging while debonding occurs upon charging. Correspondingly, the reversible bonding/debonding changes the valence state of Ti element in the MXene, giving rise to the pseudocapacitance in the acidic electrolyte. In stark contrast, only electric double layer capacitance is reco...

In-Plane Anisotropy in Mono- and Few-Layer ReS2 Probed by Raman Spectroscopy and Scanning Transmission Electron Microscopy

Abstract: Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1T phase. The reduced symmetry of this system leads to in-plane anisotropy in various material properties. Here, we demonstrate the strong anisotropy in the Raman scattering response for linearly polarized excitation. Polarized Raman scattering is shown to permit a determination of the crystallographic orientation of ReS2 through comparison with direct structural analysis by scanning transmission electron microscopy (STEM). Analysis of the frequency difference of appropriate Raman modes is also shown to provide a means of precisely determining layer thickness up to four layers.

Longitudinal Optical Vibrations in Glasses: Ge O 2 and Si O 2

Abstract: We show that longitudinal optical (LO) vibrational modes account for several previously unexplained peaks in the Raman spectra of vitreous Ge${\mathrm{O}}_{2}$ and Si${\mathrm{O}}_{2}$. Identification of LO modes in these and other glasses reduces the complexity of the spectra that must be explained by simple structural models. It also follows that long-range (Coulomb) forces should be included in complete theories of the vibrational properties of many glasses.

Two-dimensional arrays of colloidal gold particles : A flexible approach to macroscopic metal surfaces

Abstract: Covalent attachment of nanometer-scale colloidal Au particles to organosilane-coated substrates is a flexible and general approach to formation of macroscopic Au surfaces that have well-defined nanostructure. Variations in substrate (glass, metal, Al2O3), geometry (planar, cylindrical), functional group (−SH, −P(C6H5)2, −NH2, −CN), and particle diameter (2.5−120 nm) demonstrate that each component of these assemblies can be changed without adverse consequences. Information about particle coverage and interparticle spacing has been obtained using atomic force microscopy, field emission scanning electron microscopy, and quartz crystal microgravimetry. Bulk surface properties have been probed with UV−vis spectroscopy, cyclic voltammetry, and surface enhanced Raman scattering. Successful application of the latter two techniques indicates that these substrates may have value for Raman and electrochemical measurements. The assembly method described herein is compared with previous methods for controlling the na...

Raman Spectroscopy of Few-Quintuple Layer Topological Insulator Bi2Se3 Nanoplatelets

Abstract: We report on Raman spectroscopy of few quintuple layer topological insulator bismuth selenide (Bi2Se3) nanoplatelets (NPs), synthesized by a polyol method. The as-grown NPs exhibit excellent crystalline quality, hexagonal or truncated trigonal morphology, and uniformly flat surfaces down to a few quintuple layers. Both Stokes and anti-Stokes Raman spectroscopy for the first time resolve all four optical phonon modes from individual NPs down to 4 nm, where the out-of-plane vibrational A(1g)(1) mode shows a few wavenumbers red shift as the thickness decreases below ~15 nm. This thickness-dependent red shift is tentatively explained by a phonon softening due to the decreasing of the effective restoring force arising from a decrease of the van der Waals forces between adjacent layers. Quantitatively, we found that the 2D phonon confinement model proposed by Faucet and Campbell cannot explain the red shift values and the line shape of the A(1g)(1) mode, which can be described better by a Breit–Wigner–Fano resonance line shape. Considerable broadening (~17 cm(–1) for six quintuple layers) especially for the in-plane vibrational mode E(g)(2) is identified, suggesting that the layer-to-layer stacking affects the intralayer bonding. Therefore, a significant reduction in the phonon lifetime of the in-plane vibrational modes is probably due to an enhanced electron–phonon coupling in the few quintuple layer regime.