Walnut leaf extract-based green synthesis of selenium nanoparticles via microwave irradiation and their characteristics assessment

Abstract

Selenium nanoparticles (Se NPs) have predominant characteristics compared to that in their bulk usage due to their high surface-to-volume ratio. The walnut (Juglans regia L.) leaf extract containing different bioactive compounds that act as reductant and stabilizing agents has been used for the green synthesis of the Se NPs. Influences of two synthetic variables, namely, the amount of selenium salt solution ranging from 15 to 25 mL and the amount of walnut leaf extract ranging from 1 to 5 mL, on broad emission peak (λ max) and absorbance of colloidal solutions having Se NPs were evaluated via the response surface methodology. Obtained results indicated that using microwave radiation (800 W for 4 min) and 5 mL of walnut leaf extract and 15 mL of selenium salt solution, Se NPs with λ max, absorbance, particle size, polydispersity index, and zeta potential values of 375 nm, 3.65% absorbance unit (a.u.), 208 nm, 0.206, and -24.7 mV were synthesized, which had high bactericidal activity toward Escherichia coli and Staphylococcus aureus. The transmission electron microscopy analysis also indicated that spherical and monodispersed Se NPs with a mean particle size of 150 nm were formed using the walnut leaf extract.