A simple strategy to improve the sensitivity of probe molecules on SERS substrates

In this work, we report a simple strategy to improve the detection sensitivity as well as the spectral quality of probe molecules on surface-enhanced Raman scattering (SERS) substrates. On normal SERS substrates, due to the decreased absorption capacity and changes in the molecule orientations, SERS signals disappear when the analyte molecule concentrations reach a limit value. To solve this problem, the molecular template reagent (MTR) technique, a simple strategy based on SERS surface selection rules, is considered. By choosing the best MTR according to different samples, the effect of adjusting the molecular orientations of samples can be studied. In this process, 1-butanethiol, 1-hexanethiol, 1-octanethiol, 1-decanethiol, and 1-dodecanethiol, which are MTRs, are used to adjust the orientations of probe molecules under optimized conditions. The use of the MTR technique indicated that the limit of detection (LOD) of the probe molecules of p-aminobenzenethiol and 4-mercaptobenzoic acid on noble metal substrates showed an increase of one order of magnitude over the LOD of the pure probing molecule systems. Hence, the proposed method introduces a way to detect the molecules with an improved sensitivity at extremely low concentrations. The study corresponds to a proof-of-concept study of MTR-assisted SERS for SERS-based applications in ultrasensitive analyses.