Binding of p-mercaptobenzoic acid and adenine to gold-coated electroless etched silicon nanowires studied by surface-enhanced Raman scattering

Modern diagnostic tools ever aim to reduce the amount of analyte and the time needed for obtaining the result. Surface-enhanced Raman spectroscopy is a method that could satisfy both of these requirements, provided that for each analyte an adequate substrate is found. Here we demonstrate the ability of gold-sputtered silicon nano-wires (SiNW) to bind p-mercaptobenzoic acid in 10−3,10−4and 10−5n M and adenine in 30 and 100 μM concentrations. Based on the normal mode analysis, presented here for the first time, the binding of p-mercaptobenzoic acid is deduced. The intensity enhancement of the 1106 cm−1 band is explained by involvement of the C—S stretching deformation, and the appearance of the broad 300 cm−1 band attributed to S—Au stretching mode. Adenine SERS spectra demonstr ate the ex istence of the 7H tautomer since the strongest band ob served is at 736 cm−1. The adenine binding is likely to occur in several ways, because the number of observed bands in the1200–1600 cm−1 interval exceeds the number of observed bands in the normal Raman spectrum of the free molecule.