Strong b2 peaks (1142, 1391, 1438, and 1583 cm(-1)) in the SERS spectra of 4-aminobenzenethiol (ABT) have been regarded by many as a textbook example of chemically enhanced SERS signals. However, this interpretation is in serious doubt after the recent claim that they arise from 4,4'-dimercaptoazobenzenes (DMAB) photogenerated during the acquisition of SERS, not the genuine chemically enhanced signals of ABT. Subsequent attempts to prove or disprove this claim have failed to provide any decisive verdict. Here we present spectroscopic and mass spectrometric evidence that further support the photogeneration of DMABs from ABTs on an Ag surface. Furthermore, we show that the amount of the DMAB is sufficient to explain the b2 intensities of ABT.
Keywords: SERS; mass spectrometry; photochemistry; plasmonics; vibrational spectroscopy.