Plasmon-modified dielectric Mie resonances in laser-synthesized Si@Au nanoparticles for photothermal therapy applications

Dielectric Mie resonances have recently garnered significant research interest due to their wide range of potential applications. Here, we report a laser-assisted synthesis of core-satellite Si@Au nanoparticles (NPs), consisting of large silicon cores decorated with gold nanosatellites. These composite structures exhibit plasmon-modified Mie resonances compared to pure Si NPs, resulting in enhanced absorption in the near-infrared region. Nearly spherical Si NPs were prepared <i>via</i> femtosecond laser ablation of crystalline silicon targets in water, followed by centrifugation and redispersion in aqueous solutions. Two distinct populations with mean diameters of 120 nm and 160 nm were selected, displaying Mie resonances with maxima at approximately 510 nm and 600 nm, respectively. In the subsequent step, the Si NPs were coated with small (5-10 nm) gold (Au) NPs using wet chemical synthesis. This coating led to a pronounced increase in extinction within the red region of the spectrum, attributed to the coupling between plasmonic and dielectric resonances in the composite Si@Au NPs. <i>In vitro</i> experiments with <i>Paramecium caudatum</i> cells demonstrated both low toxicity and high efficiency of the Si@Au NPs as photohyperthermia sensitizers. The observed effect of plasmon-modified Mie resonances indicates strong promise for advancing photothermal therapy as a treatment modality.