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

Abstract

Dielectric Mie resonances are now in the focus of research attention due to a variety of potential applications. Here, we report a laser-assisted synthesis of core-satellite Si@Au nanoparticles (NPs), composed of a large silicon core decorated with gold nanosatellites, which are capable of generating plasmon-modified Mie resonances compared to pure Si NPs, leading to an enhanced absorption in the near-infrared. Nearly spherical Si NPs were prepared by femtosecond laser ablation of crystalline Si targets in water, followed by their centrifugation and redispersion in aqueous solutions. Two populations with mean sizes of 120 nm and 160 nm were selected, which exhibited Mie resonances with maxima around 510 nm and 600 nm, respectively. During the second step, Si NPs were coated with small (5-10 nm) gold (Au) NPs using methods of wet chemical synthesis. Such a coating led to a remarkable increase of extinction in the red part of the spectral slope, which was explained by the coupling of plasmon and dielectric resonances in composite Si@Au NPs. In vitro experiments using Paramecium caudatum cells evidenced low toxicity and high efficiency of Si@Au NPs as sensitizers of photohyperthermia. The observed effect of plasmonic-modified Mie resonances promises a major advancement of photothermal therapy modality.