Synthesis and Characterization of Selenium Nanoparticles

SeNPs were prepared via a reduction of sodium selenite by ascorbic acid and stabilized by polysorbate 20. Briefly, 30 mg of Na₂SeO₃.5H₂O was added to 90 mL of Milli-Q water. Ascorbic acid (10 mL, 56.7 mM) was added dropwise to sodium selenite solution with vigorous stirring.10 µL of polysorbate were added after each 2 ml of ascorbic acid. Selenium nanoparticles were formed after the addition of ascorbic acid. This can be visualized by a color change of the reactant solution from clear white to clear red. All solutions were made in a sterile environment by using a sterile cabinet and double distilled water. Selenium nanoparticles were then collected by centrifuging the solution at 12000 rpm. The pellet was resuspended in sterile double distilled water before use in bacteria experiments. Selenium contents of nanoparticles were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES, model Vista-Pro from Varian).