Charge transfer dynamics of the CdTe quantum dots fluorescence quenching induced by ferrous (II) ions

Size dependence of glutathione capped CdTe quantum dots (GSH-CdTe QDs) on the sensitivity and selectivity in the fluorometric detection of ferrous (II) ions (Fe2+) has been systematically investigated. Smaller-size QDs show higher sensitivity in the detection of Fe2+, resulting in higher quenching efficiency and red shift of the fluorescence peak of QDs. Stern-Volmer plots indicate that the charge transfer model can be employed to account for the observed fluorescence quenching effect. Fe2+ is bound to the surface of QDs by GSH and excited electrons are transferred from QDs to Fe2+, which facilitates a nonradiative recombination process and a decrease in the PL efficiency. In addition, the results from time resolved photoluminescence and a confocal scanning fluorescence microscope have shown that smaller-size QDs have a faster decrease in the fluorescence lifetime compared with that of larger-size QDs with Fe2+ addition, suggesting that the fast charge transfer in smaller-size QDs should be responsible for the observed fluorescence quenching effect. This Letter provides a comprehensive understanding of the mechanism of the fluorescence for the CdTe QDs quenched by Fe2+. Published under license by AIP Publishing.