Facile Synthesis of Water-Soluble WS2 Quantum Dots for Turn-On Fluorescent Measurement of Lipoic Acid

A facile and eco-friendly approach for the synthesis of water-soluble WS 2 quantum dots (QDs) was developed via ultrasonication and a hydrothermal process from bulk WS 2 . In this strategy, the dispersity of bulk WS 2 in aqueous phase was improved with the aid of a surfactant (hexadecyltrimethylammonium bromide, CTAB), which could shorten the exfoliation time and improve the exfoliation efficiency to form layered WS 2 nanosheets. Through hydrothermal treatment, the nanosheets were further scissored into QDs with high quality. The QDs show excellent features with narrow size distribution, good water solubility, and stable fluorescence. We find that the fluorescence of WS 2 QDs can be quenched by Fe 3+ through photoinduced electron transfer, and a wide detection linear range for Fe 3+ is acquired. It indicates that WS 2 QD can be used as a “turn-off” probe for Fe 3+ . In the presence of lipoic acid (LA), the fluorescence was recovered due to the stronger interaction between LA and Fe 3+ than WS 2 QDs. A “turn-on” sensor for LA was developed with a linear range from 1 to 10 μM and a detection limit of 0.59 μM. The strategy might be suitable for the facile synthesis of other water-soluble transition metal dichalcogenide QDs. It is expected that the water-soluble QDs have great potential applications in biological system.