SERS-measured and DIFT-calculated vibrational spectra of p-aminoazobenzene

P-Aminoazobenzene (PAAB) is one of the 24 kinds of carcinogenic azo dyes that the European Union forbids but it does not yet have an official method to detect PAAB. This paper experimentally observes the Normal Raman Spectrum (NRS) and infrared absorption spectrum of PAAB and presents theoretical vibrational spectra calculated from a density functional theory (DFT) method on the basis of B3LYP with 6-31 basis set. The calculated results show very good agreement with the experimentally observed IR and Raman frequencies. We also report the SERS spectra of PAAB adsorbed on silver and copper layers, which offer a sensitive but simple method to detect PAAB. Finally, the possible adsorbed states of PAAB on the silver and copper layers are discussed.