Preparation of Transition Metal Disulfide Nano-dots via Hydroxyl Radicals-mediated Cutting Metal-Sulfur Bonds.

Abstract

The preparation of low-dimensional transition metal disulfides (MS2, M = Mo, W) via ultrasonication-assisted liquid-phase exfoliation from mineral bulk-MS2 is proven to be advantageous in terms of sulfurizing reagent-free conditions and operational safety. Nevertheless, mechanical energy input is insufficient to effectively cut metal-sulfur bonds to form small-sized MS2 nano-dots. Herein, we develop an innovative strategy based on hydroxyl radicals-mediated cutting metal-sulfur bonds to prepare MS2 nano-dots with lateral dimension of 10 nm and height of 2 nm, through ultrasonication treatment of bulk-MS2 in the presence of a mixture of ammonium citrate/N-Methylpyrrolidone ((NH4)3CA/NMP). A pivotal aspect of this strategy is the in-situ generation of hydroxyl radicals from citrate ions (CA3-), which can effectively cut metal-sulfur bonds of the submicron-sized sheet that was as-exfoliated by NMP. Furthermore, the introduced CA3- adsorbs onto the surfaces of MS2 nano-dots, preventing their re-aggregation in the disperse system. This work provides a facile strategy for the direct preparation of metal disulfide nano-dots from their bulk-minerals.