Optical properties of dextran-stabilized silicon nanoparticles in aqueous medium

Abstract

Silicon nanoparticles (Si-NPs) with initial sizes of the order of 100 nm were prepared by femtosecond laser
ablation-fragmentation of microcrystalline silicon in water followed by drying and resuspending in water
or in aqueous solutions of dextran. The prepared aqueous suspensions of Si-NPs without dextran and with
dextran coating were investigated by means of the scanning electron microscopy, dynamic light scattering
and optical absorption spectroscopy in the spectral range from 250 to 800 nm. The optical absorption of
uncoated Si-NPs in an aqueous medium with different pH-level varied from 4 to 8 was found to decrease
with time because of a process of the dissolution of those NPs in water. The dissolution rate depended
nonmonotonically on the solution acidity (pH level) and the corresponding times were in the range from 50
to 180 hours. The addition of dextran into the solution was found to significantly decrease the dissolution
rate of Si-NPs to 300 hours because of the coating of NPs with a polymer shell. The obtained results can
be useful to develop new biomedical technologies involving Si-NPs as stabilized theranostics (therapy and
diagnostics) agents.

Key words: nanoparticles, dextran, biopolymer, optics, absorbance.