Layered Sulfur Nanosheets Prepared by Assembly of Sulfur Quantum Dots: Implications for Wide Optical Absorption and Multiwavelength Photoluminescence

Preparation, characterization, and optical properties of layered sulfur nanosheets (S-NSs) from natural sublimed sulfur were reported in this work. Few-layered S-NSs were prepared by a developed liquid-phase method including three steps: (1) forming sulfur quantum dots from natural sublimed sulfur; (2) forming multilayered nanosheets by assembling sulfur quantum dots through the hydrothermal method; and (3) sonication exfoliation of the multilayered S-NSs. The thinnest S-NSs (sulfurene) with a 0.84 nm thickness were obtained by the developed method. The obtained S-NSs showed wide-range absorption from ultraviolet to the visible region, multiwavelength photoluminescence, and superb water dispersibility and stability over two months in air. A reduction current peak was observed at -1.2 V (vs Ag/AgCl, Sat. KCl) on a fluorine-doped tin oxide electrode in 0.010 M HCl containing S-NSs, which is attributed to the reduction from S-0 to S2- of the S-NSs. These alternative two-dimensional (2D) nanosheets of S-NSs with good stability and water dispersibility will provide opportunities for the research fields of visible-light-active photocatalysis and optical sensing.