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⁻¹ and a strong doublet near 1150 cm⁻¹ 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.