NIR-FT Raman, FT-IR and surface-enhanced Raman scattering and DFT based theoretical studies on the adsorption behaviour of (S)-phenylsuccinic acid on silver nanoparticles

Abstract

Single crystals of (S)-phenylsuccinic acid (SPSA) were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. The density functional theoretical (DFT) computations were also performed at the B3LYP/6-311G(d, p) level to derive the equilibrium geometry, vibrational wavenumbers and intensities. Vibrational spectral investigation confirmed the formation of cyclic dimers in the crystal, with the carboxyl groups of each acid molecule being hydrogen bonded to those of the adjacent molecules. The Raman vibrational wavenumbers of the adsorption geometry of (S)-phenylsuccinic acid (SPSA) on a silver surface have been simulated using DFT-B3PW91 with lanl2dz basis set and it compared with the experimental spectrum. The large enhancement of in-plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in an 'at least vertical' or slightly tilted orientation, with the ring perpendicular to the silver surface. The calculated vibrational spectra are in agreement with experimental values confirming the validity of the proposed adsorption configurations.

Structural and spectroscopic study of adsorption of anthracene on silver

“…Irrespective of the initial geometry orientations of anthracene and silver, the adsorption geometry was identified to be the one with anthracene at a tilted orientation with respect to the silver cluster and the most stable geometry is reported. Convergence of all the calculations together with the absence of imaginary vibrational frequencies confirms the attainment of a local minimum on the potential energy surface [33][34][35][36]. Theoretical calculations overestimate fundamental vibrational frequencies.…”

“…Theoretically simulated UV spectrum has the corresponding peak at 390 nm. This optical absorption band is caused by the interactions of free electrons of Ag NPs with the electromagnetic radiation incident on the surface as their electronic modes are particularly sensitive to their shape and size, resulting in pronounced effects in the visible part of the spectrum [18,[34][35][36]. The strong narrow absorption peak observed experimentally confirms the spherical shape of synthesised A-Ag NPs as indicated in XRD results.…”

“…The strong narrow absorption peak observed experimentally confirms the spherical shape of synthesised A-Ag NPs as indicated in XRD results. Smaller differences identified in intensities and the absorption wavelengths of the theoretical absorption spectrum and the experimental one are mainly because the calculated spectrum is based on a single isolated A-Ag 'nanoparticle' consisting of a single anthracene and a single Ag 3 cluster which is not spherical in shape, while the measured spectrum is obtained from many A-Ag nanoparticles of approximately the same average diameter which are in each other's electrostatic environments in the solid state [36].…”

Interactions between silver nanoparticles and polyvinyl alcohol nanofibers

“…OC bonds, formed by the adsorption of PVA on silver, that the surface O-H bonds have a tilted geometry. 61,62 The contour maps of Figs. 7(b) and 7(d), correspond to slide models of PVA, silver chain and PVA/Ag systems, respectively.…”

SERS investigations on orientation of 2-bromo-3-methyl-1,4-dimethoxy-9,10-anthraquinone on silver nanoparticles

“…It is stated that if the C-C stretching of benzene is strong, the interaction between benzene rings of the molecule and the surfaces of silver nanoparticles is strong [32]. If C@C stretching vibrational mode strong in SERS, largely redshifted and undergoes band broadening, it is an indication of the compound to be adsorbed perpendicular to the Ag surface [33].…”