One-Pot Synthesisof Core–Shell Au@<i>m</i>SiO₂ Nanoparticlesfor Photothermal Applications

Gold-mesoporous silica (Au@<i>m</i>SiO₂) core–shell nanoparticles (NPs) hold great promise for application in nanomedicine as they enable the photostimulated release of guest molecules located within their pores. In this study, we investigated the mechanism of a productive one-pot protocol for the preparation of core–shell Au@<i>m</i>SiO₂ NPs. The formation of gold NPs quickly followed by the formation of a silica shell eliminates the need to isolate and strongly protect the gold cores. A thorough mechanistic analysis provides insights into the relative kinetics of gold and silica formation, which can be fine-tuned to obtain Au@<i>m</i>SiO₂ smaller than 100 nm. The photothermal properties of such Au@<i>m</i>SiO₂ were characterized and modeled. Under the experimental conditions typically used for cargo release experiments, the model predicts a temperature increase for a single particle of less than 1 × 10^–4 °C, demonstrating that the release is due to the collective heating of the medium by a myriad of NPs, rather than by the temperature elevation of individual NPs under irradiation. Overall, the studies developed here will enable better design and preparation of Au@<i>m</i>SiO₂ particles for diverse photothermal applications.