0000000001035146
AUTHOR
Victor Yu. Timoshenko
Ultrapure laser-synthesized Si nanoparticles with variable oxidation states for biomedical applications
We employ a method of femtosecond laser fragmentation of preliminarily prepared water-dispersed microcolloids to fabricate aqueous solutions of ultrapure bare Si-based nanoparticles (Si-NPs) and assess their potential for biomedical applications. The nanoparticles appear spherical in shape, with low size dispersion and a controllable mean size, from a few nm to several tens of nm, while a negative surface charge (−35 mV ± 0.10 according to z-potential data) provides good electrostatic stabilization of colloidal Si-NP solutions. Structural analysis shows that the Si-NPs are composed of Si nanocrystals with inclusions of silicon oxide species, covered by a SiOx (1 < x < 2) shell, while the to…
Femtosecond laser fragmentation from water-dispersed microcolloids: toward fast controllable growth of ultrapure Si-based nanomaterials for biological applications
International audience; An ultrashort laser-assisted method for fast production of concentrated aqueous solutions of ultrapure Si-based colloidal nanoparticles is reported. The method profits from the 3D geometry of femtosecond laser ablation of water-dispersed microscale colloids, prepared preliminarily by the mechanical milling of a Si wafer, in order to avoid strong concentration gradients in the ablated material and provide similar conditions of nanocluster growth within a relatively large laser caustics volume. We demonstrate the possibility for the fast synthesis of non-aggregated, low-size-dispersed, crystalline Si-based nanoparticles, whose size and surface oxidation can be controll…
Silicon Nanocrystals Produced by Nanosecond Laser Ablation in an Organic Liquid
Small (3−5 nm in diameter following HRTEM images) Si nanocrystals were produced in a two-stage process including (1) nanosecond laser ablation of a Si target in an organic liquid (chloroform) that results in formation of big composite polycrystalline particles (about 20−100 nm average diameter) and (2) ultrasonic post-treatment of Si nanoparticles in the presence of HF. The post-treatment is responsible for disintegration of the composite Si particles, release of small individual nanocrystals, and reduction of their size due to HF-induced etching of Si oxide. The downshift and broadening of the ∼520 cm−1 Raman phonon band of the small Si nanocrystals with respect to the bulk Si Raman band i…