Real-time preparation of surface enhanced Raman scattering substrate for on-line analysis of aromatic molecules in capillary

A new way of real-time preparation of surface enhanced Raman scattering (SERS) substrate was developed by laser photoreduction of AgNO3 mixed with probe molecules (aromatic amine, aromatic mercaptan or phenolic compound) in capillary. The preparation of Ag nanoparticle cluster and acquisition of SERS signal could be performed synchronously and finished within several seconds. Probe molecules were analyzed on line in capillary. It was proposed that the rapid photoreduction process was initiated by photoinduced electron transfer from electron donors aromatic molecule to Ag+ under laser illumination. The p electrons from N (S or O) and π electrons from aromatic ring could form p-π conjugated structure. These delocalized electrons assisted the rapid reduction of Ag+ in such a short time. Additionally, Raman maps with 8 μm increment in X-Y directions (35 spectral spots) demonstrated good point-to-point repeatability of the substrate with the relative standard deviation less than 9%. Under optimal condition, several probe molecules, including benzidine, bisphenol A and so on were determined on line in capillary by this new method.