Synthesis of MoS2 Quantum Dots Uniformly Dispersed on Low Dimensional MoS2 Nanosheets and Unravelling its Multiple Emissive States

We demonstrate a simple and green route for the synthesis of MoS2 quantum dots (QDs) of size 1-4 nm dispersed uniformly over the mono and bilayered, low dimensional MoS2 sheets, referred as MoS2 quantum dots dispersed over nanosheets (MoS2 QDNS). The synthesis was accomplished by the high temperature hydrothermal reaction of bulk MoS2 in aqueous NaOH. The MoS2 QDNS displays luminescence emission spanning a large portion of the UV and visible region of electromagnetic spectrum, envisaged to stem from both QDs and the nanosheets. A detailed photophysical characterization including time resolved fluorescence were carried out to unfold the origin of photoluminescence (PL) emission from this hybrid nanostructure. Our studies reveal that, blue and red portion of the emission are solely from QDs and the nanosheets, respectively. Whereas intermediate segment of the emission hail from the synergistic contribution of QDs and nanosheets. The MoS2 QDNS, manifests excellent stability, retained its characteristic morphology and PL even after several months. Finally, the excellent pH responsive PL emission of MoS2 QDNS makes them a promising candidate for biological and environmental applications.