Fluorescence Quenching of CdTe Quantum Dots with Co (III) Complexes via Electrostatic Assembly Formation

The photoluminescence quenching of CdTe QDs in the presence of three different Co (III)-complexes is studied to elucidate the role of interactions between functional groups of positively charged cysteamine capped CdTe QDs and negatively charged Co (III) complexes bearing carboxylic groups. The steady state and time resolved spectroscopy has been used to investigate the mechanism of quenching. After detailed analysis, it is concluded that quenching is contributed by both static as well as dynamic processes. The static contribution has been assigned to the electrostatic assembly formation via ionic interactions between the amine functional groups of positively charged cysteamine capped CdTe QDs and carboxylic acid groups of negatively charged complexes. The electrostatic interactions were confirmed by zeta potential measurement as well as from effect of salt addition. These studies have implications in designing donor/acceptor pairs having complementary functional groups for efficient optoelectronic devices or photocatalytic systems.