ИСТИНА

In our work, to fabricate silicon nanoparticles (SiNPs) we propose to employ the technique of laser fragmentation of silicon microparticles (1–6 μm) in water or ethanol exposed to laser pulses (1064 nm, 34 ps). The initial concentrations of the silicon micropowder and irradiation time were varied to optimize the SiNPs outcome. This relatively simple technology allows producing stable crystalline SiNPs in amounts large enough for further use in biomedical applications. The analysis of scanning electron microscopy images revealed that the formed Si-NPs have a relatively smooth surface and a close to spherical shape. Scanning electron microscopy of the fabricated SiNPs and dynamic light scattering in their suspensions revealed dependences of the nanoparticles size (the mean size varied from 110 to 340 nm) on the buffer liquid used, initial concentration of silicon micropowder in suspension, and the laser pulses exposure time. The fabricated SiNPs demonstrates low agglomeration, while Raman spectra of the SiNPs evidence their high crystallinity. Spectrophotometry measurements of the SiNPs suspensions revealed that the scattering coefficient exceeds 2 mm-1 in the spectral range of 400 – 1000 nm and is an order of magnitude higher than the absorption coefficient in this region. The scattering spectra demonstrate nonmonotonic behavior with a typical maximum in the red region, which is explained by presence of a Mie resonance. The obtained results demonstrate that SiNPs fabricated by laser fragmentation of silicon micropowder in liquids are promising for contrasting biological tissues and their phantoms in optical imaging techniques, for example, optical coherence tomography.