Green synthesis has recently attracted extensive attention from scientists all over the world for the production of metal nanoparticles. Selenium nanoparticles (Se NPs) have been demonstrated as a suitable supplement nutrient for the replacement of selenium ions in terms of safety and efficiency. This work presented a friendly and facile approach to synthesize the Se NPs using polyphenols content in the Cleistocalyx operculatus (CO) leaves extract. The synthesizing conditions were optimized to obtain the Se NPs with uniform distribution and shape. The prepared Se NPs were well-characterized using scanning electron microscopy, X-ray diffraction, energy diffractive spectroscopy, and Fourier-transform infrared spectroscopy. The resultant Se NPs were in spherical shape with the particle size in a range from 50–200 nm. The antimicrobial properties of Se NPs were investigated against Echerichia coli and Staphylococcus aureus, which showed reasonable activity. The acute oral toxicity of Se NPs in mice was also studied. The result indicated that Se NPs exhibited lower toxicity than that of SeO₂ with the lethal concentration (50% death of mice) of 7.75 mg kg⁻¹_.

Selenium element is considered as one of the most important micronutrients for many biological systems. It has been well demonstrated that Se nanoparticles (Se NPs) express greater bioavailability, biocompatability, and less toxicity than that of Se in ion form. In this work, the Se NPs were facilely fabricated by a one-step plasma process in the ethanol–water solution mixture. The as-prepared Se NPs were well characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectroscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDX). The prepared Se NPs were a light red color with a spherical shape and particle size in the range of 100–200 nm. The average diameter of the Se NPs calculated from the ImageJ software and TEM image was approximately 154 nm. The EDX results showed that the Se NPs prepared by the plasma process in the solution were highly pure and stable. The acute oral toxicity of the obtained Se NPs toward mice was also studied, which revealed that the Se NPs were safe for the human body. The mechanism for the formation of Se NPs from the Se ions under the solution plasma condition was also studied and discussed.