Controlling and monitoring laser-mediated localized synthesis of silver nanoparticles within gold nanoapertures

Photoreduction of metallic nanoparticles can be used for localized and deterministic synthesis of nanostructures required for various applications. Specifically, in-situ photoreduction of silver nanoparticles (AgNPs) is a facile fabrication route that enables the fabrication of nanoplasmonic substrates. In the present work, we demonstrate an approach to fabricate hybrid plasmonic substrates using in-situ photoreduction of AgNPs within gold nanoapertures (NAs). The approach involves the top-down approach to fabricate NAs followed by a site-specific synthesis of AgNPs within the NAs. Furthermore, we use dark-field imaging to monitor and understand the photoreduction within the gold NAs in real time. We demonstrate that a careful selection of experiment parameters aid to synthesize the AgNPs within NAs and the scattered light intensity can be used to map the characteristics of the formed AgNPs. The illumination time, laser power and AgNO3 concentration can be used to tune the AgNPs characteristics. The demonstrated strategy for realizing hybrid plasmonic substrates can be used for the fabrication of substrates for SERS based sensors, enhancing fluorescence of molecules, and photocatalytic applications.