In the electrochemical oxidation–reduction cycles (ORC) treatment for preparing surface-enhanced Raman scattering (SERS)-active substrates, chloride electrolyte was generally selected because this facilitates the metal dissolution-deposition process that is known to produce SERS-active roughened surfaces. In this work, SERS-active Ag substrates were electrochemically prepared in HCl solutions containing supplemental electrolytes of HNO3. Encouragingly, the SERS of Rhodamine 6G (R6G) adsorbed on this developed Ag substrate exhibits a higher intensity by 15-fold of magnitude, as compared with that of R6G adsorbed on a roughened Ag substrate prepared in HCl solution. Moreover, limit of detection for probe molecules of R6G can be significantly reduced to 2 × 10−15 M. Also, the significant improvements in thermal stability and anti-aging of SERS-active Ag substrates proposed in this work are observed.
