Preparation of SERS substrates with self-confined nanogaps and their application in pH-sensing

As a molecular-specific and highly sensitive technology, surface-enhanced Raman spectroscopy (SERS) is well-suited to meet the analytical demands of a multidisciplinary range of fields. Nevertheless, the fabrication of SERS substrates that are inexpensive, reproducible, and controllable represents a significant challenge. In this study, a straightforward, reproducible, and controllable strategy was proposed for the fabrication of high-sensitivity SERS substrates based on self-limiting surface reactions. The preparation of the self-confined nanogaps (sCN-Ag) substrate was achieved through the dealloying process of Cu-Ag alloy wires. In this process, the interior nanogaps were self-confined by AgCl produced in situ, thus facilitating the control of "hot spots" on a nanoscale. The sCN-Ag substrate, which can be readily activated by the removal of AgCl with NH₃·H₂O, exhibited high sensitivity, spatial uniformity, and good thermal stability in pH sensing. This self-limiting strategy, which integrates the advantages of controllability, reproducibility, and mass production, is expected to further promote the development and application of SERS.