Formation of p, p′‐azodibenzoate from p‐aminobenzoic acid on silver island films during surface‐enhanced Raman scattering

Abstract

Surface-enhanced Raman scattering (SERS) from p-aminobenzoic acid (PABA) adsorbed on silver island films was investigated. PABA reacted very quickly to form p,p'-azodibenzoate when exposed to atmospheric moisture and laser light. This was evidenced by the appearance of a strong band near 1460 cm-' and a strong doublet near 1150 cm-' that were characteristic of the azodibenzoate. Exposure to a drier environment such as in a desiccator or a vacuum inhibited the reaction. It was concluded that the reaction of PABA to form the azodibenzoate involved two steps, the first being the hydrolysis of the amine and the second dimerization during exposure to laser light.

A comparative study on the adsorption behaviors of PABA in the silver nano-particles

“…The calculations based on DFT have been used in many areas [14][15][16][17]; the results are also in good agreement with the experimental results in calculating vibrational frequencies. In fact, the authors Venkatachalam et al [18] presented an interpretation for the SERS of PABA adsorbed on silvers in 1988. In the paper, a comparative study on the adsorption behaviors of PABA in the silver nano-particles is made.…”

Adsorption and Chemical Modification of Phenols on a Silver Surface

“…The chemical changes induced by the reactive metal surface on the adsorbate have to be considered as a possible reason for the spectral profile changes that sometimes are observed in SERS spectra and that cannot be simply attributed to the effect derived from the particular orientation adopted by the adsorbate on the surface. The chemical modifications that have been reported so far on metal surfaces used in SERS spectroscopy may involve the oxidation (8,9) and the oxidative polymerization of the adsorbates linked to the surface (10)(11)(12). Since the metal interface is more sensitive to the species that are in the vicinity of the metal surface, eliminating the influence of the bulk molecules, it is a powerful method for analyzing small amounts of products formed on the surface.…”

Fourier-transform surface enhanced Raman scattering studies of molecular self-assembly of disulfides on metals and the application in adhesion promotion

“…Second, there is little laser-induced surface reaction in the FT-SERS spectrum. The appearance of new lines at 1435, 1390, and 1145 cm-1 clearly indicates that some of the adsorbed 4-aminophenyl disulfide molecules changed to azo or azoxy compounds under the laser radiation in the visible region [24]. By comparing Figs lA and 1B, one can conclude that FT-SERS excited in the near infrared region appears to have larger enhancement factor and much less photochemistry problem than that excited in the visible spectral region.…”