Efficient Photoluminescence of Mn2+-Doped ZnS Quantum Dots Sensitized by Hypocrellin A

Abstract

Mn2+-doped ZnS semiconductor quantum dots reveal remarkably intense photoluminescence with the 4T1(4G) f6A1(6S) transition. In this study, following growth doping technique, Mn2+-doped ZnS quantum dots (ZnS:Mn2+ QDs) with high-quality optical properties and narrow size distribution were synthesized successfully. The dopant emission has been optimized with various reaction parameters, and it has been found that the percentage of introduced dopant, reaction temperature, and time as well as the pH of a reaction mixture are key factors for controlling the intensity. Photoluminescence emission (PL) measurements of ZnS:Mn2+ QDs show Mn2+ d-d orange luminescence along with band-edge blue luminescence. Moreover, the electron transfer from singlet states of hypocrellin A (HA) to colloidal ZnS:Mn2+ QDs has been examined by absorption spectra and fluorescence quenching. The absorption spectrum gave an evidence of the increases in the extinction coefficient and the red-shift of the absorption maxima in the absorption spectra of HA in the presence of ZnS:Mn2+ QDs, demonstrating the occurrence of surface interactions between the sensitizer and the particle surface. Fluorescence quenching by ZnS:Mn2+ QDs also suggested that there were a complex association between HA and ZnS:Mn2+ QDs, which was necessary for observing the heterogeneous electron-transfer process at the interface of sensitizer-semiconductor.