The effect of photo-irradiation on the optical properties of thiol-capped CdTe quantum dots.

In this report, the effect of photo-irradiation on the optical properties of thioglycolic acid (TGA) capped CdTe QDs was investigated. The photo-irradiation led to an increase in the photoluminescence (PL) efficiency of TGA-capped CdTe QDs with a low quantum yield under both the open air and nitrogen atmosphere. The photo-irradiation caused a blue-shift of PL peak under the open air and almost no change of PL peak position under the nitrogen atmosphere. The XPS study revealed the oxidation of the unpassivated surface of the Te atoms which mainly contributed to the observed optical property changes for CdTe QDs photo-irradiated under the open air. While for the CdTe QDs photo-irradiated under the nitrogen atmosphere, the decomposition of TGA led to the release of sulphur which formed a CdS shell on the CdTe core, resulting in an enhanced PL efficiency.