On the generation of free radical species from quantum dots

The generation of radical species in aqueous solution by photoirradiation of CdS, CdSe, and CdsE/ZnS quantum dots (QD), was investigated. Two independent methods such as EPR spectroscopy and a radical-specific highly sensitive fluorimetric assay was used to measure and identify any photogenerated radical species. CdS QDs were synthesized in a reverse-micellar medium while the CdSe QDs were synthesized according to the method of Peng and Peng. The CdSe QDs were then coated with hexamethyl-disilathiane and diethylzinc to produce CdSe/ZnS QDs. A fluorescence spectroscopy assay based on the specific trapping of hydroxyl radical by terepthalate anions was used to verify the hypothesis drawn from the EPR data. It was found that semiconductor quantum dots produce free radicals upon UV irradiation in aqueous solution with two independent methods. The results show that with two independent methods that semiconductor quantum dots produce free radicals upon UV radiation in aqueous solutions.