One-Pot Synthesis of Core-Shell Au@mSiO2 Nanoparticles for Photothermal Applications

Gold-mesoporous silica (Au@mSiO2) 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, prioritizing the achievement of atom economy, we used a one-pot synthesis protocol, to produce core-shell Au@mSiO2 NPs from a properly defined precursor state. Upon sodium hydroxide addition, the formation of gold NPs occurs quickly, followed by the formation of a silica shell, eliminating the need to isolate the gold cores. We conducted a comprehensive mechanistic analysis that elucidates the relative kinetics of gold and silica formation, identifying key factors for fine-tuning NPs within the size range of 50 to 100 nm, ideal for biological applications. The photothermal properties of such Au@mSiO2 were characterized and modelled. Under the experimental conditions typically used for cargo release experiments, the model predicts a temperature increase for a single particle of less than 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 more effective design and preparation of Au@mSiO₂ particles, optimizing them for a broad range of photothermal applications.