Chiral and Bright Green Fluorescent MXene Quantum Dots as “On/Off/On” Nanoprobe for the Selective and Ultrasensitive Detection of Hypochlorite and Glutathione

MXene quantum dots (MQDs) exhibit excellent optical properties and good biocompatibility, making them promising materials for sensing and biomedical applications. We report the synthesis of bright green emissive chiral MQDs (C-MQDs) with the highest fluorescence quantum yield of 59% by using a simple solvothermal method. The synthesized C-MQDs exhibited a maximum emission at 495 nm upon excitation at 400 nm. Notably, the fluorescence intensity of the C-MQDs was strongly reduced after the addition of hypochlorite (ClO – ) ions. Mechanistic studies indicated that this quenching occurred through a static quenching process, resulting from the formation of a nonfluorescent complex between ClO – ions and the surface functional groups of the C-MQDs. Surprisingly, the fluorescence was restored after the addition of glutathione (GSH) to the C-MQDs-ClO – complex, as GSH reduced the ClO – ions. As a result, the fluorescence “on/off/on” behavior of the C-MQDs was used to detect ClO – and GSH with very good limit of detection (LOD) as 33 and 50 nM, respectively. Furthermore, the analytes were successfully detected inside living cells, demonstrating the probe’s capability for intracellular sensing applications. Moreover, ClO – ions were detected in real water samples with a very good recovery, even in the presence of other contaminants. These results demonstrate that such a nanoprobe has great potential in therapeutic applications.