Journal of Raman Spectroscopy

The triple-resonant second-order Raman scattering mechanism in graphene is re-examined. It is shown that the magnitude of the triple-resonant contribution to the photon-G′ mode coupling function in graphene is one order of magnitude larger than the widely accepted two-resonant coupling. Enhancement of the order of 100 in the Raman intensity, with respect to the usual double-resonant model, is found for the G′ band in graphene.

Dental adhesive systems are used by dentists in restoration of teeth for bonding dental resins to enamel and dentin. The bonding systems used in this study were of the etch-and-rinse type. The purpose of this study was to compare the molecular structure of the adhesive–dentin and adhesive–enamel interface using Raman microspectroscopy. Raman images were obtained from univariate and multivariate methods. The dentin–resin interface was also studied using scanning electron microscopy and small-angle X-ray scattering.

Stability curve of the protein in the presence of 4 M urea was determined from the analysis of amide I band in the 260–360 K temperature range. Low wavenumber analyses have shown the important influence of solvent dynamics on cold and heat protein denaturations.

Using Raman spectroscopic mapping, the biochemical modifications associated with murine oocyte and early embryo development have been investigated, revealing a distinct asymmetrical organisation of macromolecules in the mature oocyte.

A combined Raman and AFM investigation was used to study in situ early Silurian enigmatic organic-walled microfossils classified traditionally to an informal taxonomic group named acritarcha. Based on the detection of internal spore-like bodies, acritarchs have been recently re-interpreted as vegetative cells of unicellular green algae (chlorococcales). To prove the identity of the internal bodies as spores, confocal Raman microscopy was applied to examine their chemical and mineral content.

The peak intensity from 55 nm Au@1.2 nm MnO₂ NPs is about 10 times of that from 55 nm Au@4 nm SiO₂ NPs. In SHINERS, the distance of the SERS-active core and the substrate is controlled by the thickness of the shell. Considering a much thinner shell thickness of MnO₂ than that of SiO₂, higher signal intensity obtained in the former system is reasonable. The improved signal intensity of Au@MnO₂ SHINERS NPs has a strong advantage in increasing the sensitivity and decreasing the detection limit.

Benzotriazole film formation was investigated on single-crystal and polycrystalline Cu surfaces with SHINERS. Potential-dependent spectra display reversible BTA film formation on polycrystalline Cu and irreversible film formation on single-crystal Cu.

FT-Raman and IR spectra acquired for four arginine vasopressin (AVP) analogs containing L-diphenylalanine (Dpa): [Dpa²]AVP, [Cpa¹,Dpa²]AVP, [Dpa³]AVP, and [Cpa¹,Dpa³]AVP were compared and analyzed. In addition, the FT-Raman spectra were compared to the corresponding SERS spectra recorded in an aqueous silver colloidal dispersion. The geometry of these molecules etched on the silver surface was deduced from observed changes in the intensity enhancement, broadness, and shift in wavenumber of the Raman bands in the spectra of the bound versus free species.

Significant enhancements in SERS signals were observed when the probing molecules of 4-mercaptobenzoic acid were adsorbed on the surface of Co-doped ZnO nanoparticles. The crystalline defects of the CoZnO nanoparticles caused by Co doping play an important role in the SERS activity.

Mixed populations of the bound substrate are identified in the active site of the Arthrobacter enzyme where the 4-hydroxy groups are present as 4-O⁻ and 4-OH.

Raman spectroscopic studies of the zone-centre E₂^high optical phonon of a bent ZnO nanowire show a systematic red shift as the junction of the two arms of the nanowire is approached. The analysis of the Raman spectrum indicates the presence of tensile strain on the nanowire. Strain in the bent nanowire is also investigated using photoluminescence (PL) spectroscopy. Results of both Raman and PL study confirm that the bend nanowire is under tensile strain.

Oxygen-induced microstructural changes in annealed nanocrystalline CeO_2−x were investigated by X-ray diffraction and Raman spectroscopy. Analysis of structural and vibrational properties of annealed ceria demonstrated that microstrain changes, because of variable defect content, dominate over the crystallite size effect in annealed samples. A new Raman mode (S), ascribed to surface mode, originates from the defective and disordered structure.

Translational relaxations of alcohol molecules in pure and water solution have been studied with polarized Raman spectroscopy. Temperature-dependent measurements show that the hydrogen-bonding (HB) and hydrophobic interactions control the translational motion. The hydrophobic interaction reduces the relaxation time more apparently for CH₃ group than the skeleton motion. By adding water in alcohol liquids, translational motions generally slow down but show different concentration-dependent behaviors. Different mechanisms have been proposed to interpret these interesting observations, which are related to the HB networks in aqueous alcohols.

A design extension of the only commercial Raman optical activity (ROA) spectrometer, the ChiralRAMAN which provides only scattered circular polarization ROA, is implemented for the simultaneous acquisition of all four forms of CP ROA.

Vibrational spectroscopy is used to evaluate molecular geometry in cyclic tetraynes via analysis of C≡C stretching bands that are activated when the center of symmetry in a polyyne structure is lost through bending of the ring.

This article presents the application of Raman and FT-IR spectroscopy for complex investigation of morphine, its metabolite and salts as well as a pharmaceutical product. Experimental analysis is supported by quantum-chemical calculations performed at the B3LYP/6–311++G(d,p) level.

There are only a few small inorganic molecules of fundamental importance for which thecrystal structures are unknown. Carbonic acid (H₂CO₃) is one of them. Raman and IR spectra of the two known polymorphs of carbonic acid are reported here. Based on the data, local structural hydrogen-bonding motifs are presentedand suggested as building blocks of the crystal structures of α-H₂CO₃ and β-H₂CO₃.

Two of the five possible conformers have been identified in the vibrational spectra of 2,2,3,3,3-pentafluoropropylamine. The enthalpy difference between these two conformers has been determined using variable temperature spectra of the sample dissolved in liquid xenon.

First-order and multiphonon Raman active excitations are studied in YbVO₃ as a function of temperature. Below T ≃ 170 K, new excitations are activated, following the G-orbital ordering and the concomitant orthorhombic to monoclinic phase transition. The observed phonon combinations around 1400 cm⁻¹ with a dominant Jahn-Teller vibration ∼690 cm⁻¹ are related to a possible orbiton-phonon coupling.

Raman spectra obtained at points along line scans of multilayer white paints show the change in composition between each layer and thus provide a method of discriminating optically identical paint samples.

We report the first in situ high-pressure Raman investigations of fully deuterated α-glycine up to ∼20 GPa. The spectral changes in the ND₃⁺ and COO⁻ modes indicate subtle structural rearrangements across 3 GPa. The decrease in the intensity of ND₃⁺ torsional mode is found to be similar to that of undeuterated α-glycine. The pressure-induced stiffening of ND and CD₂ stretching modes is discussed in the context of changes in the hydrogen-bonding interactions.

In this article, we report a high-pressure Raman spectroscopy study of the palmitic acid (PA, C form) from ambient pressure up to 21 GPa. The effects of hydrostatic pressure on the vibrational spectrum of PA are reported, and the data show that PA experiences a rich sequence of phase transformations. These changes in the crystal structure occur gradually as the pressure increases and they are related with the highly flexible crystalline structure.

A detailed description of phase transitions occurring in the Li_xV₂O₅ active material in a composite electrode (0≤x < 2) is provided here for the first time using Raman spectroscopy. The successive emergence of the various phases governing the electrochemical properties of this cathode material is spectroscopically observed. This work demontrates that Raman spectroscopy constitutes a powerful tool to explore the structural changes induced by electrochemical Li insertion-extraction reactions in electrode materials for lithium batteries.

Differentiation of healthy and diseased tissues from the Brazilian octocoral Phyllogorgia dilatata was performed by in situ Raman Spectroscopy analysis. Spectral data of the healthy portion showed major vibrational bands at ca. 1520, 1160, and 1000 cm⁻¹ due to ν(CC), ν(CC), and ρ(CCH₃) respectively, corresponding to carotenoids. However, the diseased tissue, which has a purple pigmentation, showed bands at ca. 1500 and 1120 cm⁻¹ attributed to polyenals belonging to psittacofulvin class.

Point-by-point standoff Raman measurements are made of distant samples using a precise pan-tilt system and then combined into a molecular species image of the distant target area.

The Raman spectra of a number of MAX phases (Ti₂AlN, Ti₂AlC_0.5N_0.5, [Ti_0.5,V_0.5]₂AlC, Ti₂AlC, V₂AlC, Ti₃AlC₂ and Ti₃GeC₂), mostly not spectroscopically investigated before, are measured and compared to the calculated mode wavenumbers via density functional theory. The 211 phases only show modes associated to atomic displacements of the ‘M’ and ‘A’ atomic planes, while the Ti₃AlC₂ and Ti₃GeC₂ also show modes that correspond with vibrations of the ‘X’ sublattice relative to itself.