Surface-Enhanced Raman Scattering and Density Functional Theoretical Study of Anthranil Adsorbed on Colloidal Silver Particles

Abstract

Surface-enhanced Raman spectrum of anthranil (2,1-benzisoxazole) in activated silver colloid was recorded and compared with the conventional Raman spectrum. The experimentally observed Raman bands along with their corresponding infrared bands were assigned based on the results of density functional theory (DFT) calculations. The significant changes evidenced between the SER and normal Raman spectra combined with the theoretical data obtained for Ag−anthranil model systems demonstrated that this molecule is adsorbed on the colloidal silver particles through the lone pair electrons of the nitrogen atom. The contribution of the chemical mechanism to the SERS enhancement was proved by the behavior of the electronic absorption spectrum of the mixture of activated silver colloid and anthranil solution. The orientation of the adsorbed species with respect to the metal surface was also predicted.

Raman spectroelectrochemical study of Meldola blue, adsorbed and electropolymerized at a gold electrode

“…8a). Enhancement of out-of-plane vibrational modes of aromatic molecules adsorbed in ''flat'' or ''tilted'' orientation with respect to metal surface is well documented in SERS literature [44,45]. According to the surface selection rules [46,47] a band in the SERS spectrum corresponding to vibration with its normal mode component perpendicular to the surface will be more enhanced compared with the one with parallel component.…”

On the importance of optical forces in surface-enhanced Raman scattering (SERS)

“…For example, some single molecule SERS experiments have been conducted under conditions similar to ours, but evaluated under the assumption that the nanoparticles diffuse freely in solution. [40][41][42] …”

SERS and DFT study of 4,4′-biphenyl dicarboxylic acid on silver surfaces: The orientation and vibrational assignment

“…In addition, it is well known that the geometry thus changed may result in the change for the intensity and frequency of the related vibrational modes in the SERS spectrum. [27] As have been expected in the conjugated system, however, the only difference in the spectrum is somewhat shifted C-H in-plane bands according to a degree of the p-p interaction between the two phenyl rings of biphenyl.…”