Molybdenum disulfide quantum dots as a photoluminescence sensing platform for 2,4,6-trinitrophenol detection

Transition metal chalcogenides, especially molybdenum disulfide (MoS2), have recently attracted wide attention from researchers as graphene-analogous materials. However, until now, little literature has reported the synthesis of photoluminescent MoS2 materials and their applications in analytical chemistry. We herein presented a facile bottom-up hydrothermal route for the synthesis of photoluminescent MoS2 quantum dots (QDs) by using sodium molybdate and cysteine as precursors. The prepared MoS2 QDs were characterized by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and UV-vis spectroscopy. The MoS2 QDs were then used as photoluminescent probes to construct a photoluminescence (PL) quenching sensor for detection of 2,4,6-trinitrophenol (TNP). The TNP sensor presented a wide linear range from 0.099 to 36.5 μM with a high detection limit of 95 nM. Furthermore, the sensor displayed a high sensitivity toward TNP over other structurally similar compounds like 2,4,6-trinitrotoluene, p-chlorophenol, phenol, and 2,6-di-tert-butyl-4-methylphenol. To understand the origin of the high sensitivity, we assessed the emission wavelength-dependent PL quenching behavior of MoS2 QDs by the above five compounds using Stem-Volmer equation in detail. The results showed that the novel approach we put forward can satisfactorily explain the interaction mechanisms between MoS2 QDs and the five compounds, and the high sensitivity for TNP very likely originated from a combination of the PL resonance energy transfer, electronic energy transfer, and electrostatic interactions between MoS2 QDs and TNP. Finally, the sensor was successfully applied for detection of TNP in water samples and test papers.