Title : Surface enhanced Raman scattering active substrates prepared using plasmon activated water
Nanoparticles (NPs) of silver (Ag) and gold (Au) with well-defined localized surface plasmon resonance (LSPR) bands in the UV and near-IR regions are popularly employed in surface-science studies of surface-enhanced Raman scattering (SERS) and catalytic chemical reactions based on hot electron transfer (HET). In electrochemical preparations of SERS-active substrates, reactions are generally performed in aqueous solutions using deionized water (DIW) with 0.1 N electrolytes. The prepared SERS- active substrates are then thoroughly rinsed with DIW and dried for subsequent SERS measurements. In this work, we present comprehensive advantages of utilizing innovative plasmon-activated water (PAW) with reduced hydrogen bonds, compared to conventional DIW, on the subsequent signal intensities and reproducibility of SERS performances. Electrochemically roughened gold (Au) and silver (Ag) substrates were additionally immersed in PAW for 15 min to remove impurities, and the relative standard deviations (RSDs) of the SERS signals of model probe molecules of rhodamine 6G (R6G) were lower compared to those of substrates soaked in DIW. Moreover, for the SERS-active substrates prepared with Au/Ag nanocomposites using galvanic replacement reactions (GRRs), the RSD of the SERS signal of R6G was lower for the roughened Ag substrate immersed in the PAW solution containing positively charged Au ions, compared to that which was immersed in a DIW solution. Also, the corresponding SERS signals were higher for Au/Ag nanocomposites based on PAW systems. Similarly, SERS-active filter paper with Au/Ag nanocomposites prepared in a PAW solution, compared to a DIW solution, also demonstrated a better SERS effect. This strategy based on optimally prepared SERS-active Au substrates is also practically applicable for sensing imidacloprid and acetamiprid, commonly used pesticide that are generally detected in farm crops. These interesting findings indicate that SERS-active substrates prepared using PAW are sufficiently sensitive and reliable to develop SERS sensors.