Heavy-metal-free semiconductor material like Silicon Nanoparticle (Si-NPs) is attracting scientists because of their diverse applications in biomedical field. In this work, pulsed laser ablation of silicon in aqueous solution is employed to generate Si-NPs in one step avoiding use of chemical precursors. Characterization by absorption, electron and photoluminescence analysis proves the generation of luminescent Si-NPs. The productivity rate of Si-NPs is investigated by Inductively Coupled Plasma Spectrometry. Furthermore, Si-NPs quantum yield and confocal microscopy studies corroborate the potential use of these biocompatible Si-NPs for imaging applications.

A picosecond laser ablation approach has been developed for the synthesis of ligand-free AuAg bimetallic NPs where the relative amount of Ag is controlled in situ through a laser shielding effect. Various measurements, such as optical spectroscopy, transmission electron microscopy combined with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry, revealed the generation of homogenous 15 nm average size bimetallic NPs with different compositions and tunable localized surface plasmon resonance. Furthermore, ligand-free metallic nanoparticles with respect to chemically synthesized nanoparticles display outstanding properties, i.e. featureless Raman background spectrum, which is a basic requirement in many plasmonic applications such as Surface Enhanced Raman Spectroscopy. Various molecules were chemisorbed on the nanoparticle and SERS investigations were carried out, by varying the laser wavelength. The SERS enhancement factor for AuAg bimetallic NPs shows an enhancement factor of about 5.7 × 10⁵ with respect to the flat AuAg surface.

Biofunctionalized silicon quantum dots were prepared through a one step strategy avoiding the use of chemical precursors. UV-Vis spectroscopy, Raman spectroscopy and HAADF-STEM prove oligonucleotide conjugation to the surface of silicon nanoparticle with an average size of 4 nm. The nanoparticle size results from the size-quenching effect during in situconjugation. Photoemissive properties, conjugation efficiency and stability of these pure colloids were studied and demonstrate the bio-application potential, e.g. for nucleic acid vector delivery with semiconducting, biocompatible nanoparticles.