Extracellular synthesis of cuprous selenide nanospheres by a biological-chemical coupling reduction process in an...

Biosynthesis of metal nanoparticles represents a clean, eco-friendly and sustainable "green chemistry" engineering. Lately, a number of metal selenides were successfully synthesized by biological methods. Here, cuprous selenide (Cu₂ Se) nanospheres were prepared under mild conditions by a novel biological-chemical coupling reduction process. The simple process takes place between EDTA-Cu and Na₂ SeO₃ in presence of an alkaline solution containing NaBH₄ and a selenite-reducing bacteria, Pantoea agglomerans. It is noteworthy that the isolated Pantoea agglomerans and Cu⁺ ions, where the latter are obtained from reducing Cu²⁺ ions by NaBH₄ , play a key role, and Cu⁺ ions not only can promote the generation of Se^2- ions as a catalyst, but also can react with Se^2- ions to form Cu₂ Se. XRD pattern, SEM, and TEM images indicated that Cu₂ Se nanoparticles were tetragonal crystal structure and the nanospheres diameter were about 100 nm. EDX, UV-vis, and FTIR spectra show that the biosynthesized Cu₂ Se nanospheres are wrapped by protein and have a better stability. This work first proposes a new biosynthesis mechanism, and has important reference value for biological preparation of metal selenide nanomaterials. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1264-1270, 2016.