Microwave-assisted synthesis of water soluble thiol capped CdSe/ZnS quantum dots and its interaction with sulfonylurea herbicides.

A simple and fast procedure for water solubilization of CdSe/ZnS quantum dots (QDs) using microwave irradiation (MW) has been optimized. The CdSe/ZnS QDs were synthesized in organic media and water solubilization was achieved by replacing the initial hydrophobic ligands (TOPO and TOP) with hydrophilic heterobifunctional thiol ligands, such as L-cysteine (L-Cys), 3-mercaptopropionic acid (3-MPA) and cysteamine (CTAM). The use of MW irradiation allowed carrying out the modification of the surface thiol of QDs in a simple and fast way (only 40 s was required). Different optimization studies based on activation-time, irradiation-time, concentration of ligands, pH and lifetime fluorescent properties were carried out in order to obtain the best results for the solubilization of QDs. By the proposed method, the resulting water-soluble QDs exhibit a strong fluorescence emission at about 590 nm, with a high and reproducible photostability and acceptable yields. With the aim of contributing to exploiting the advantages of synthetized QDs from an analytical point of view, the different behavior with sulfonylurea herbicides (SUHs) were studied.