Au–Si Nanocomposites with High Near-IR Light-to-Heat Conversion Efficiency via Single-Step Reactive Laser Ablation of Porous Silicon for Theranostic Applications

Abstract

Hybrid nanoparticles (NPs) with complex morphology, structure, and chemical composition are considered key building blocks of next-generation optoelectronic devices, catalysts, and sensitizers/agents for diverse biomedical applications. Laser ablation in liquid (LAL) has emerged as a promising route to design and produce unique nanocomposite NPs, yet control over the product's size and structure is limited by tuning laser parameters or the content of the surrounding liquid. In this paper, based on the example of porous Si prepared by electrochemical etching, we demonstrate an alternative route to control the size of the resulting NPs through the modification of the target material's porosity. In particular, we showed a 3-fold size reduction of the LAL-synthesized Si NPs as compared to the product obtained by the ablation of the common monocrystalline Si wafer. The produced nanocrystalline Si NPs demonstrate a narrow monomodal size distribution with an average diameter of around 200 nm, which cover a practically relevant size range, allowing the excitation of Mie resonances at visible and near-IR wavelengths. Moreover, by adding a certain controlled amount of acid metal precursor HAuCl 4 , we fabricated core−satellites and nanocomposite Au−Si NPs via similar facile single-pot reactive laser synthesis. The incorporation of Au into the Si NPs was found to enhance the near-IR light-to-heat conversion performance of the nanohybrids, as confirmed by numerical modeling and single-particle micro-Raman thermometry at 785 nm wavelength matching the NIR-I biological transparency window. The obtained results pave the way toward the milligram-scale production of pure and hybrid Si-based Mie-resonant NPs for photonic, optoelectronic, sensing, and biomedical applications, while highlighting additional degree of freedom for control over the obtained product characteristics.