ИСТИНА

Pulsed laser ablation of silicon in different liquids is a powerful modern tool to produce a variety of nanoparticles with desirable size, physical and chemical properties. Silicon nanoparticles (Si-NPs) fabricated by this technique have potential in different biomedical applications due to high biocompatibility and biodegradability of nanostructured silicon. Note that high-yield production of Si-NPs is quite time-consuming and requires employment of a powerful laser with high pulse repetition rate. To enhance the efficiency of Si-NPs fabrication, we suggest using preliminary nano- or microstructured silicon instead of traditionally used monocrystalline silicon (c-Si) targets. In our work we use silicon nanowire (Si-NW) arrays and mechanically grinded microparticles as targets for picosecond (1064 nm, 34 ps, 10 Hz) laser ablation in water and ethanol. Measurement of the ablation thresholds for Si-NWs targets in liquids revealed that these values are several times less in comparison to the corresponding ones for c-Si. Thus, this approach allowed to increase the ablation product yield. Similar tendency is observed for laser fragmentation of the silicon microparticles. According to scanning electron microscopy and atomic force microscopy studies, Si-NP sizes are in the range of 5 – 170 nm depending on the used target and buffer liquid. Raman spectroscopy analysis revealed almost perfect crystallinity of the formed Si-NPs. The Si-NPs ablated in ethanol exhibit fluorescence emission in the range of 600 – 900 nm. We assume that the observed fluorescence caused by defects in the studied nanocrystalline structures. Spectrophotometry measurements of the ablated Si-NPs suspensions revealed that scattering coefficient reaches value of ~ 1 mm-1 in the spectral range of 400 – 1000 nm indicating their potential as contrast agents in biomedical imaging. Thus, pulsed laser ablation of Si-NW arrays and silicon microparticles provide high-yield fabrication of Si-NPs with relatively small size and high level of crystallinity, that are promising as fluorescence markers and scattering contrast agents in bioimaging.