Polychromatic fluorescent MoS2 quantum dots: fabrication and off–on sensing for fluorine ions in water

Recently, MoS2 quantum dots (QDs) have receive widespread attention as a promising luminescent material. However, so far, little effort has been made on the multicolor emission of MoS2 QDs. Herein, an in situ iodine doping strategy is presented and used to synthesize tunable-photoluminescent (PL) MoS2 QDs. By fine iodine doping, the PL of the MoS2 QDs (I-MoS2 QDs) can be tuned in the range from 423 nm to 529 nm, which exceeds the as-reported emission wavelength range. Studies using controlled experiments and density functional theory (DFT) reveal that the change in electronic state of MoS2 QDs is responsible for the changing PL due to iodine doping. As-synthesized I-MoS2 QDs combined with Fe3+ is developed as a "turn-off-on" fluorescence sensor for F- ions in water. The fluorescence probe has a fine linear response to F- ions in the concentration range of 2.5-80 μM, and the limit of detection is 1.4 μM (S/N = 3).