Photothermal Properties of Plasmonic Nanofluids Containing Ag Nanoparticles Under Off-Resonant Excitation: The Influence of Capping Agents

Plasmonic nanoparticles exhibit remarkable photothermal properties, making them valuable in various fields such as renewable energy and medicine. These photothermal properties depend on several factors, including the type of noble metal, particle size, and the stabilizing layer. This study investigates the photothermal properties of colloidal silver nanoparticles synthesized photochemically using UV LEDs. Silver nanoparticles capped with citrate and a combination of citrate and polyvinylpyrrolidone (PVP) were prepared. While the nanoparticle size remained unaffected by the amount of citrate, the nonlinear refractive index did show dependence. As the citrate concentration increased, the nonlinear refractive index decreased. Additionally, increasing the amount of PVP not only reduces the nanoparticle size—suggesting a reverse Ostwald ripening process induced by UV light—but also leads to a diminished photothermal response.