Discovery of natural water-dispersible MoS2 quantum dots in bulk powder

Abstract In contrast to laborious efforts to gain quantum dots (QDs) of two-dimensional (2D) layered materials, less attention has been given to the discovery of natural QDs present in the powder sample. In this study, we discovered that a considerable quantity of natural QDs are present in 2D powders and demonstrated a simple way to obtain MoS2 QDs from a bulk powder without any chemical and severe ultrasonication. The natural MoS2 QDs were obtained by filtering the MoS2 powders dispersed in ethanol. The separated QDs resulted in a stable blue suspension in deionized water which exhibited the absorption spectra at a wavelength of 320 nm, supporting that MoS2 QDs were successfully separated from the bulk powder. And, the maximum photoluminescence intensity appeared in the ultraviolet region under the excitation of 320 nm. Also, the doping effect of MoS2 QDs on MoS2 flakes led to the enhancement of photoluminescence spectra due to a hole carrier from MoS2 QDs. Our finding paves the way to explore natural QDs from a powder sample of other 2D materials.