Elimination of oxidation and decomposition by SnCl2 in the SERS study of pyridoxine on a roughened Au electrode

Severe interference from the oxidation and laser carbonization was encountered in the measurements of surface-enhanced Raman scattering (SERS) spectra of pyridoxine (PN) on the roughened gold electrode. However, we found that high-quality SERS spectra of PN could be obtained by the introduction of SnCl2, which only has few Raman peaks at low wavenumbers. SnCl2, as a good reductive, is capable of removing the oxidative species on the gold substrate and the dissolved oxygen in solution, and as a result lowering the open circuit potential (OCP). Sn(II) can also strongly chemically adsorb on the gold surface and interact with PN through coordination/chelation, such that not only to prevent PN from damage by the giant electromagnetic field for the 'first-layer' effect, but also to give rise to very strong Raman scattering signals of PN where chemical enhancement plays an important role. Those are the main reasons for the elimination of the oxidation and decomposition of PN and for the high-quality SERS spectra of PN. The way the SnCl2 confines PN within the enhanced electromagnetic field by its ability of adsorption and coordination/chelation can be utilized to improve the routine SERS analysis of analogous type of reactive organic/biomolecules. In addition, this method has been successfully extended to the SERS measurements of PN on the substrates of roughened silver and copper. Copyright (C) 2008 John Wiley & Sons, Ltd.