Improved sensing performance from methionine capped CdTe and CdTe/ZnS quantum dots for the detection of trace amounts of explosive chemicals in liquid media

Abstract

Water soluble methionine functionalized CdTe quantum dots (QDs) and CdTe/ZnS core–shell QD samples have been prepared by a reflux condensation method and have been used to detect explosive chemicals, such as dinitrotoluene (DNT), nitrotoluene (NT) and nitrobenzene (NB) in liquid media. Meisenheimer complex formation between the QD surface attached methionine and aromatic explosive molecules has helped to detect them selectively via a fluorescent quenching process. Fluorescence quenching occurred because of the transfer of excited electrons from QD to the explosive molecules. Depending upon the number of nitro groups present on the explosive molecule, the quenching efficiency of different analytes varied. Due to surface passivation and inductive effects, the methionine capped CdTe/ZnS core–shell quantum dot sample resulted in the maximum quenching constant.