Resonance Raman study of solvent effects on a series of triarylmethane dyes

Abstract

Resonance Raman spectroscopy was used to address questions concerning the influence of the solvent on the structure and aggregation state of a series of triarylmethane dye, These molecules are of interest owing to the dramatic solvent effects exhibited in their optical absorption spectra, which have recently been interpreted in terms of intermolecular interactions which perturb the D, symmetry of the cationic dyes. Raman spectra of parafuchsin, malachite green, crystal violet and ethyl violet were compared in various solvents, in order to explore changes in the vibrational modes brought about by aggregation (in water), ion-pair formation (in non-polar solvents) and iondipole interactions (in polar solution). In triply amino-substituted dyes, the data point to the possibility that a resonance structure exists having a positive charge on one of the three nitrogens. It is discussed how the resulting reduction in the expected D, symmetry of the cation affects the resonance Raman spectrum.

Tip-Enhanced Raman Imaging and Nanospectroscopy: Sensitivity, Symmetry, and Selection Rules

“…Although a faint Raman signature of the molecules is observed with the tip at d > 100 nm, a clear molecular fingerprint is obtained only when the tip is within ∼20 nm from the sample. The prominent bands around 1,615 and 1,365 cm −1 are assigned to combinations of the C=C stretching vibrations of the phenyl ring and the mode at 1,170 cm −1 is due to a methyl group rocking mode or an in-plane C-H bending mode of the phenyl ring [156].…”

Engineering DNA Binding Sites to Assemble and Tune Plasmonic Nanostructures

“…Figure 4 compares SERS spectra from the 300 nm period arrays, with and without the nanoparticle integrated within the bowtie. Taking the strong Raman peak associated with MGÕs C-C stretch mode for comparison, [50] which appears in our measurements at 1605 cm -1 , the isolated nanoparticles show an average intensity of >100 counts for a 5 second acquisition time, whereas the completed bowties, with the same periodicity, show an average of >23300 counts, a SERS signal which is >210x larger than the signal seen from the isolated nanoparticles.…”

Fabrication of stable network-like gold nanostructures in solution and their assessment as efficient NIR-SERS platforms for organic pollutants detection

“…5C parts a and c we acquired the NIR-SERS spectra of basic fuchsin molecules in solution at the final concentrations of 2 Â 10 À6 and 2 Â 10 À7 M. The spectra exhibit the characteristic vibrational bands of basic fuchsin. Therefore, the vibrational bands at 415, 1171, 1380 and 1584 cm À1 are assigned to the out-of-plane benzene ring deformation, C-H bending, N-phenyl stretching and in-plane ring stretching and bending according to the literature [32]. To further demonstrate the superiority of our SERS platform over randomly aggregated spherical gold nanoparticles a comparative experiment was conducted.…”