Controllable biosynthesis and characterization of α-ZnS and β-ZnS quantum dots: Comparing their optical properties

The controllable biosynthesis of alpha-ZnS and beta-ZnS quantum dots by Clostridiaceae sp. using different concentration of hydroxypropyl starch as dispersant are demonstrated. The structure and properties are characterized by XRD, TEM, HRTEM, UV-Vis and fluorescence spectra, and so on. The results indicate that the alpha-ZnS quantum dots with wurtzite structure and diameter of 8 +/- 2 nm were attained under low dose of hydroxypropyl starch, while high dose obtained the beta-ZnS quantum dots with sphalerite structure and diameter of 4 + 1 nm. The UV Vis absorption of beta-ZnS quantum dots have an evident red shift compared with alpha-ZnS quantum dots, and the as-biosynthesized beta-ZnS quantum dots have a stronger fluorescence activity than alpha-ZnS quantum dots. This work displays a simple biosynthetic method to control the crystal structure and particle size of metal sulfide nanoparticles under mild conditions. (C) 2016 Elsevier Ltd. All rights reserved.