Journal of Raman Spectroscopy

A review is presented on important developments published within the Journal of Raman Spectroscopy (JRS) during 2010. This third overview again highlights advances in the field of research, provides readers of JRS with introductions to developments within the various subfields of Raman spectroscopy and reflects the trends of research of the Raman community.

Furan, furan derivatives, and levulinic acid were characterized via Raman spectroscopy and their vibrational wavenumbers were compared with the calculated results using the B3LYP/6-31 + G(2df,p). After using the solvent effects and scaling factor, the discrepancies in wavenumbers reduced to ∼25 cm⁻¹ (2%). An empirical method based on the chemical structure similarities is able to predict the HMF Raman spectrum from the combined furfural and FA spectra.

This pilot study aims to develop a model that allows close identification of the redox conditions in a variety of smelting processes by analysing the free iron oxides. Characterisation by RM and EBA of archaeological iron smelting slag from Northern Zimbabwe reveals free iron oxides, as haematite and magnetite, oxidised forms of magnetite and wüstite, Al³⁺-substituted magnetite and a solid solution between magnetite and hercynite.

Poly(vinylpyrrolidone)-stabilized silver nanoparticles (NPs) were investigated for strained-silicon SERS using a 488 nm Ar⁺ micro-Raman excitation source. Strained silicon of thickness 9, 17.5, and 42 nm grown on Si_0.8−0.7Ge_0.2−0.3 virtual substrates were analyzed. Optimum SERS enhancements were shown for NPs of diameter 80 ± 18 nm.

The pressure dependences of the low wavenumber mode widths reveal a rigid structure without any structural modification in the case of pure SrZrO₃ and the sequence of pressure-induced structural modifications for both Yb-modified non-protonated and protonated SrZrO₃. Perturbations of the host perovskite structure due to the Yb substitution and insertion of protonic species are discussed.

Time-resolved CARS impulsively excited by supercontinuum is investigated. We show that it is critical to optimize the temporal overlapping of the constituent solitons of a supercontinuum in order to impulsively excite vibrational modes over a broader frequency range. The cross-correlation frequency resolved optical gating technique is utilized to retrieve the optical response function of molecules under supercontinuum impulsive excitation, and background-free CARS with spectral resolution significantly better than the bandwidth of the probe pulses is achieved.

UV resonance Raman spectroscopy was used to determine the position of the amide II′ proline band, which is sensitive to content of the cis peptide bond, for a series of short proline-rich antioxidant peptides isolated from human milk. Both antioxidant activity and contents of proline cis bond depend on the relative position of proline and tyrosine residues in the peptide.

In order to resolve the dispute on the origin of the b₂-type bands in the surface-enhanced Raman scattering (SERS) of 4-aminobenzenethiol (4-ABT), we have measured its SERS spectra under a variety of conditions. We conclude that the b₂-type bands are intrinsic to 4-ABT, appearing in conjunction with the chemical enhancement mechanism in SERS.

The single-crystal Raman spectra of natural mineral finnemanite Pb₅(AsO₃)₃Cl^• are presented. Band assignments were made on the basis of band symmetry, experimental band positions from literature, DFT-calculated Raman spectrum and spectral comparison with other ortho-arsenite minerals reinerite, cafarsite and nealite as well as with synthetic lead arsenite compounds Pb₂(AsO₂)₃Cl, Pb₂As₂O₅ and PbAs₂O₄.

Multiphonon resonant Raman scattering in Zn_1−xMn_xO thin films is investigated to determine the states responsible for the emission of higher order LO lines, under the condition, where the incident photon energy does not differ from the bandgap or exciton energy by more than a few multiples of the LO energy (ħω_LO). A modification to the cascade model is suggested to include the trap states as intermediaries for the emission of higher order RRS lines.

Raman scattering results on single-crystal silicon monoarsenide (SiAs) are presented. Based on a comparison between Raman measurements and first-principles density functional theory calculations, evidence is found that SiAs will occur in a monoclinic crystal structure. A detailed discussion of the vibrational properties of the monoclinic structure is provided.

This work seeks to identify the slight changes in the characteristic CH stretching region (3100–2800 cm⁻¹ region) of a protein-based binder and fatty acid esters from egg yolk, which may occur in complex paint samples due to the presence of particular pigments. All samples were analyzed in this region by Raman microscopy coupled with principal component analysis for three color groups (red, white and blue) separately. The effectiveness of applying this methodology for identifying the interaction processes between binders and pigments is demonstrated.

The most relevant chromophores along with additional components coming from chemical deterioration processes of the wall painting Historia de Concepción were analyzed and identified by means of micro-Raman spectroscopy. Spectral information concerning mainly pigments and composition on the surface clearly corresponds to the fresco technique. The pollutants identified suggest that the strong pulverization observed may be due to the successive transformation of calcite into gypsum. Pulverization continues because of the high humidity in Concepción, Chile.

Stray light appearing in the low wavenumber region of Raman spectra was studied. The origin of the stray light is found and verified as the second maxima of the diffraction grating both by theory and experiment.

With large Raman cross-sections, versatile synthetic chemistry and complete lack of fluorescence, free dipyrrins and their complexes are ideal candidates for Raman spectroscopy but the Raman and Surface Enhanced (Resonance) Raman Spectroscopy (SERRS) of dipyrrins is largely unknown. We have obtained non-resonant, resonant and surface-enhanced Raman spectra of dipyrrins and their complexes and also the corresponding absolute differential Raman cross-sections. The magnitudes of the resonantly enhanced cross-sections are similar to strong SERRS dyes such as Rhodamine 6G and Crystal Violet.

Raman spectroscopy was used for the first time to probe the paramagnetic interactions occurring between the unpaired electronic spins of carbon materials and the nuclear spins of hydrogen molecules by monitoring the relative population of the H₂ rotational states.

Laser Raman technique has been used to study the complexation of polymer PEO with the cations of salt LiClO₄/ionic liquid BMIMPF₆. The formation of contact ion pairs (Li⁺· ClO and BMIM⁺· PF) and cross-contact ion pairs(Li⁺· PF and BMIM⁺· ClO) in this polymer electrolyte system is also reported.

The early careers of Ernest Rutherford and Chandrasekhara Raman are remarkable; each emerged from improbable backgrounds to win a Nobel Prize and become their country's most famous scientist. Young scientists currently having great difficulty in establishing their careers in science should seek inspiration from careers such as these.

Effects of metal nanoparticles coating on the resonant Raman scattering of ZnO thin films with various crystallinity are studied. The LO phonon scatterings as well as their high-order overtones are enhanced by Ag nanoparticles coating while weakened by Ti nanoparticles coating. The origins are investigated and associated with the presence and modification of surface electric-field of ZnO.