Photothermal conversion of SiO₂@Au nanoparticles mediated by surface morphology of gold cluster layer

Photothermal effects in SiO₂@Au core-shell nanoparticles have demonstrated great potential in various applications for drug delivery, thermo-photovoltaics and photothermal cancer therapy, etc. However, the photothermal conversion of SiO₂@Au nanoparticles partially covered by disconnected gold clusters has rarely been investigated systematically. Here, we control the surface morphology of gold clusters on the photothermal conversion performance of SiO₂@Au core-shell nanoparticles by means of chemically adjusting the synthesis parameters, including amounts of gold salts, pH value and reducing agent. The macroscopic variations of the photothermal heating of different nanoparticle dispersions are significantly influenced by the nanoscale differences of gold cluster morphologies on the silica core. The temperature rise can be enhanced by the strong near-field coupling and collective heating among gold clusters with a relatively uniform distribution on the silica core. A numerical model of the simplified photothermal system is formulated to interpret the physical mechanism of the experimental observation, and shows a similar trend of temperature rise implying a reasonably good agreement with experimental data. Our work opens new possibilities for manipulating the light-to-heat conversion performance of SiO₂@Au core-shell nanoparticles and potential applications of heat delivery with spatial resolution on the nanoscale.