Facile Preparation of a SERS Substrate for Monitoring Photocatalytic Coupling Reactions

ABSTRACT Gold nanoparticles (AuNPs) are widely recognized as ideal substrate materials for surface‐enhanced Raman spectroscopy (SERS) due to their outstanding plasmonic properties and excellent chemical stability. However, conventional synthesis methods often involve multistep procedures, substantial energy input, and poor control over nanoparticle aggregation. In this work, we report a facile and energy‐efficient synthesis of SERS‐active AuNPs via a microdroplet‐based reaction platform. By tuning the reactant ratio of NaBH 4 to HAuCl 4 , well‐dispersed AuNPs with strong SERS activity were obtained, as confirmed by transmission electron microscopy. These substrates enabled in situ, real‐time monitoring of the photocatalytic coupling reaction of 4‐nitrothiophenol, revealing the critical influence of laser power on the reaction kinetics. This work highlights a green and scalable strategy for fabricating high‐performance SERS substrates, offering new opportunities for studying on‐surface catalytic reactions under ambient conditions.