Facile synthesis of photoluminescent MoS2 and WS2 quantum dots with strong surface-state emission

Abstract

Transition metal dichalcogenides quantum dots (QDs), especially molybdenum disulfide (MoS2) and tungsten disulfide (WS2) QDs, have attracted great attention as a potential candidate for the application of fluorescent materials. However, the photoluminescence quantum yield (PLQY) of these QDs is still very low, which severely limits their availability for practical applications. Here, we present a simple and green strategy to synthesis highly photoluminescent MoS2/WS2 QDs using femtosecond laser ablation of raw MoS2/WS2 powders in solution. The as-prepared MoS2/WS2 QDs exhibit intense and excellent photostability photoluminescence in blue region with a satisfying PLQY of 22.5%. By detailed characterization and spectroscopic study, we find that abundant surface functional groups, such as C–O, CO, and C–N, can efficiently introduce new surface-state emission centers and result in their intense fluorescent emission. A simplified energy level and electron transition diagram has been proposed to help understand the surface-state emission mechanism.