Photoluminescent Si-based nanocrystals prepared by pulsed laser ablation in low-pressure helium-nitrogen mixtures for biomedical applications

摘要

Nanocrystalline silicon (Si) films were synthesized by nanosecond laser ablation of crystalline Si targets in low-pressurehelium (He) and nitrogen (N_2) gas mixtures. Photoluminescence (PL) spectra of the prepared samples were found todepend on the He/N_2 ratio in the gas mixture. The ablation pure He atmosphere allowed us to prepare Si nanocrystals(NCs) exhibiting a PL band in red-near-IR range, while samples prepared in the presence of N_2 exhibited a strong PLband with maximum in the green-yellow region. Such a modification of PL properties can be explained by the presenceof amorphous Si oxynitride (a-SiN_xO_y) on the surface of Si-NCs. Structural studies of the prepared samples by means ofthe scanning electron microscopy revealed different morphology for Si-NCs produced under different gas mixtures.After treating of the films by ultrasound and dispersing in water, Si-NCs can be used as novel biodegradable markers forbioimaging, while the observed spectral tailoring effect makes possible an adjustment of the PL emission of suchmarkers to a concrete bioimaging task.