Salt assisted sonochemical exfoliation and synthesis of highly stable few-to-monolayer WS₂ quantum dots with tunable optical properties

As a 2D material, few to monolayer WS₂ have seen much research interest due to its strong excitonic effects, which will affect the optical and optoelectronic properties. In this study, we report synthesis of highly stable few-to-monolayer quantum dots of tungsten disulfide (WS₂) and its analysis. A facile method in which salts such as sodium hydroxid, sodium chloride, ammonium hydroxide and lithium hydroxide assisted sonochemical exfoliation of bulk WS₂ powder has been employed in N-Methyl-2-pyrrolidone for 2 h. Resultant WS₂ quantum dot nanosheets were characterized by the XRD, DLS, TEM, HRTEM, Raman and UV–Visible Spectroscopy to amass structural, morphological and optical properties. Salts promoted the exfoliation processes and the prepared few-to-monolayer WS₂ quantum dot have a lateral size of 3 ± 0.5 nm and better yield in comparison to WS₂ quantum dots in N-Methyl-2-pyrrolidone. Further the Raman and UV–Vis. analysis reiterate the successful exfoliation mechanism which consumes less time and the WS₂ quantum dots show blue shift with an excitonic band gap of 2.7 eV.