CdTe quantum dots photoluminescence quenching induced by EDTA for the determination of Calcium ions

Abstract

In this work a fluorometric approach for the selective detection of calcium by using CdTe nanocrystals, was developed. The chemosensor interacted not with the metal, but with a ligand that also bind the metal. The fluorescence response was modulated by the extension of the competitive metal-ligand binding, and therefore the amount of free ligand. CdTe quantum dots (QDs) with different capping layers were evaluated, as the QDs surface chemistry and ligand nature affected recognition, thus the magnitude of the ensuing fluorescence quenching [1]. The developed procedure was automated by using a multi-pumping flow system. Upon optimization, Thioglycolic acid (TGA) and EDTA were selected as capping and ligand, respectively, providing a linear working range for calcium concentrations between 0.80 – 3.20 mg L−1, and a detection limit of 0.66 mg L−1. A quenching mechanism relying on nanocrystal destabilization upon detachment of surface Cd by the ligand was proposed.