Phenolic-Mediated Synthesis of Plasmonic Au–AgCl Janus Nanostructures for Single-Particle SERS

An Au–AgCl Janus Nanoparticle (JNP) is an emerging plasmonic nanostructure that has attracted attention in the field of surface-enhanced Raman scattering (SERS). However, because of the large lattice mismatch between Au nanoparticles (NPs) and AgCl NPs, the instability of the AgCl NPs leads to very complex nucleation and growth kinetics, and the synthesis of Au–AgCl JNPs has challenges. In this work, we report a method for the synthesis of Au–AgCl JNPs by using Phenolic compounds and photochemical reduction. Phenolic compounds can reduce the adsorption energy between AgCl NPs and Au NPs during the growth process, resulting in the asymmetric deposition of Au atoms on the AgCl NPs surface. By utilizing blue-light irradiation to modulate the Ag atom sites on the AgCl NPs surface, the number of Au domains within the Au–AgCl JNPs can controllably change. The SERS detection limit for single Au–AgCl JNPs is determined to be as low as 10–10 M for Rhodamine 6G (R6G) molecules, outperforming pure Au NPs by 2–3 orders of magnitude. The enhancement is attributed to a synergistic mechanism involving interparticle gap effects that generate intense electromagnetic “hot spots” and efficient electron transfer between Au NPs and AgCl NPs. This work not only demonstrates a scalable strategy for fabricating lattice-mismatched Janus systems but also offers a framework for the rational design of heteronanostructures for SERS.