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Surface‐enhanced Raman scattering of 4‐aminobenzenethiol on silver: confirmation of the origin of b 2 ‐type bands
Author(s) -
Kim Kwan,
Lee Hyang Bong,
Shin Dongha,
Ryoo Hyunwoo,
Lee Ji Won,
Shin Kuan Soo
Publication year - 2011
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2972
Subject(s) - raman scattering , raman spectroscopy , borohydride , chemistry , methyl orange , electrochemistry , spectral line , analytical chemistry (journal) , photochemistry , electrode , photocatalysis , optics , organic chemistry , physics , astronomy , catalysis
In order to resolve the dispute on the origin of the b 2 ‐type bands in the surface‐enhanced Raman scattering (SERS) of 4‐aminobenzenethiol (4‐ABT), we have measured its SERS spectra under a variety of conditions, including variable temperature and rotation, electrochemistry, and pH, as well as in the presence of a reducing agent. For comparison, the SERS spectra of 4‐nitrobenzenethiol (4‐NBT) and methyl orange (MO), a prototype azo compound, were also measured. First, we found that 4‐ABT on Ag is not subjected to photoreaction, although 4‐NBT is highly photoreactive on a silver surface. In the electrochemical environment, b 2 ‐type bands of 4‐ABT lost their intensity at very negative potentials, but the intensity recovered immediately upon raising the potential. In addition, b 2 ‐type bands were observed under rotation even after lowering the potential. The disappearance and reappearance of the b 2 ‐type bands could also be observed by bringing the sample of 4‐ABT on Ag into contact consecutively with a borohydride solution and water. This is because the surface potential of Ag is lowered by contact with a borohydride solution. Besides, we found that not only the normal Raman but also the SERS spectral features of 4‐ABT are hardly affected by pH variation, while the spectral features of MO are greatly affected, especially in the region of the NN stretching vibration, suggesting that the possibility of a photoconversion of 4‐ABT to an azo compound is low. Altogether, the b 2 ‐type bands were attributed to 4‐ABT, appearing in conjunction with the chemical enhancement mechanism in SERS. Copyright © 2011 John Wiley & Sons, Ltd.