New sample preparation procedure for effective improvement on surface-enhanced Raman scattering effects

As shown in the literature, molecules located between two metallic nanoparticles (NPs) can display the greatest surface-enhanced Raman scattering (SERS) enhancement. Thus many methods have been developed to increase these hot spots on SERS-active substrates. Generally, SERS-active substrates were first prepared. Then probe molecules were adsorbed on the prepared substrates to examine the corresponding SERS effects. In this work, we employ a newly developed pathway to prepare SERS-active substrates with Au NPs by sonoelectrochemical deposition-dissolution cycles (SEDDCs). In preparation probe molecules were added in electrolytes to produce SERS-active substrates with analytes-adsorbed Au NPs by one-step. Encouragingly, based on this strategy, the SERS intensity of cation-type dye of model probe molecules of Rhodamine 6G (R6G) with 2 × 10^-6 M in preparation can be increased by more than 20-fold of magnitude, as compared with that of R6G adsorbed on the already-prepared SERS-active substrates by using a general procedure for preparation of SERS samples. This strategy for improved SERS effect is also effective for probe molecules of 4-mercaptopyridine (4-MPy) with 1 × 10^-4 M. Moreover, the improved SERS effect is successfully explained from the viewpoint of electromagnetic (EM) enhancement.