Laser-Fabricated Fluorescent, Ligand-Free Silicon Nanoparticles: Scale-up, Biosafety, and 3D Live Imaging of Zebrafish under Development

This work rationalizes the scalable synthesis of ultrasmall, ligand-free silicon nanomaterials via liquid-phase pulsed laser ablation process using picosecond pulses at ultraviolet wavelengths. Results showed that the irradiation time drives hydrodynamic NP size. Isolated, monodisperse Si-NPs are obtained at high yield (72%) using post-treatment process. The obtained Si-NPs have an average size of 10 nm (not aggregated) and display photoemission in the green spectral range. We directly characterized the ligand-free Si-NPs in a vertebrate animal (zebrafish) and assessed their toxicity during the development. In vivo assay revealed that Si-NPs are found inside in all the early life stages of embryos and larvae growth, showing that the biosafety of Si-NPs and malformation types are independent of the Si-NP dose. Si-NPs were directly imaged inside developing embryos by spinning disk-imaging technique with optical sectioning capability. We showed that Si-NPs can passively enter inside embryos by the pore canals of chorion, can diffuse in the circulatory system, i.e., blood vessel, and accumulate inside larvae midgut and yolk sac, and in the eye lens, indicating the crossing of the blood barrier.