One-step fabrication of SERS-active substrates based on plasmon-induced activated water, with improved activity and excellent reproducibility

Generally, aggregation of Ag or Au nanoparticles (NPs) has emerged as a promising strategy to produce large enhancement of surface-enhanced Raman scattering (SERS). However, reproducibility of the SERS signal may be poor due to the unavoidable random field distribution. Maintaining both a high SERS effect and satisfactory reproducibility in the fabrication of ordered arrays of SERS-active substrates is most commonly adopted, but the corresponding procedures are quite complicated. In this work, we report on an innovative and facile one-step fabrication of SERS-active Au and Ag substrates with improved SERS activity and excellent signal reproducibility using simple oxidation-reduction cycles (ORCs) in 0.1 N KCl. With this new strategy, hot electron transfer-induced activated (HETIA) water is utilized instead of conventional deionized (DI) water. Experimental results indicated that the corresponding SERS effect of the Au or Ag substrate prepared in HETIA-based solutions was higher than that prepared in DI water-based solutions. The SERS-active Au and Ag substrates prepared in AuNT water-based solutions demonstrated large respective enhancement factors (EFs) of 8.5 × 10⁷ and 6.2 × 10⁸. More importantly, the excellent reproducibility of the signal intensity of rhodamine 6G (R6G) was observed on both SERS-active Au and Ag substrates prepared in HETIA water-based solutions. When measuring solid samples, the corresponding relative standard deviations (RSDs) were 6% and 17% for the Au and Ag substrates, respectively. When measuring liquid samples, the corresponding RSDs were significantly reduced to ca. 1.6% and 8.1% for the two batches of experiments. These low RSDs, which are comparable to and even better than those shown in the literature, reported for this simple but innovative strategy ensure its reliable application in SERS-related studies.