An experimental and theoretical study on photoluminescence of Ce3+-doped ZnS quantum dots and their application in Aspergillus oryzae

Abstract

ZnS and ZnS:3.125%Ce3+ (ZSC) quantum dots (QDs) were synthesized by a low-temperature solid-phase method. The crystal structure, photoluminescence (PL) properties of ZSC QDs, and their effects on the growth and kojic acid production of Aspergillus oryzae (A. oryzae) were investigated. It is found that both QDs have a cubic blend structure with the average particle size ranging of 2.75–6.14 nm. Ce3+ doping not only increases the band gap of ZnS QDs from 3.43 to 3.48 eV, but also increases the PL intensity by about 2.23 times, which is due to the fact that the electron carrier concentration is improved, and then the rate of radiative recombination is increased. The integral emission intensity, biomass, extracellular proteins yield, and kojic acid production of A. oryzae cultured with ZSC (ZnS) QDs are about 4.31 (3.23), 1.61 (1.20), 1.12 (1.09), and 2.99 (1.68) times higher than that of medium without QDs, respectively.