Etching-dependent SERS activity of Ag triangular nanoplates: From decrease to increase

Bimetallic silver/gold nanostructures with high chemical stability and numerous “hot spots” have received much attention in surface-enhanced Raman scattering (SERS) application. In this work, silver/gold nanoplates were synthesized using a facile etching method based on silver triangular nanoplates (Ag TNPs) template. In the synthetic process, the morphology changes of the Ag/Au nanoplates clearly demonstrate the etching evolves with the increased dosage of HAuCl₄ solution. At the etching continued, the in-plane dipole resonance peak of the etched Ag TNPs exhibited a non-monotonic response: first red-shift and then blue-shift. What's more interesting is that the SERS activity of the etched Ag TNPs was sharply reduced at first, then gradually increased to a certain intensity, and maintained stability subsequently. The observed etching-dependent SERS activity was different with previous reports and the possible reason was discussed. The increased SERS activity of etched Ag TNPs was even higher than that of pure Ag TNPs when using the big Ag TNPs as the template. It is expected that the etching formed Ag/Au nanoplates are ideal candidates in applications related to SERS sensing.