Selective detection of aqueous nitrite ions by surface-enhanced Raman scattering of 4-aminobenzenethiol on Au

In this work, we have devised a selective nitrite-ion detection method based on the surface-enhanced Raman scattering (SERS) of 4-aminobenzenethiol (4-ABT) on Au. This is possible because, firstly, SERS is a very surface-sensitive technique with monolayer detection capability, and secondly, the amine group of 4-ABT reacts readily with nitrites in acidic media, forming a diazonium group, which can subsequently form an azo bond by reacting with a variety of benzene derivatives. From the peak intensity of the diazonium group, the presence of nitrite ions above 20 μM can be identified readily. From the peak intensity of the azo moiety alone, it is even possible to detect nitrite ions at concentrations as low as 5 μM, without interference from other anions. This work clearly illustrates the usefulness of SERS in environmental science research.