A novel kind of quantum dots, sulfur quantum dots (S dots), is synthesized by simply treating sublimated sulfur powders with alkali using polyethylene glycol-400 as passivation agents. The synthesized S dots exhibit excellent aqueous dispersibility, eminent photostability and temperature dependent photoluminescence (PL). An "assemble-fission" mechanism is proposed for the S dots formation in which "assembling" and "fission" are involved and contest each other. The ultimate morphologies of the S dots are dependent on the balance of the two forces. Guided by the assemble-fission mechanism, weakening the assembling effect is beneficial for obtaining monodisperse S dots, which can be achieved by pretreating of sulfur powder with nitric acid. PL wavelength of the S dots has been successfully tuned between green and blue light (from 550 to 440 nm) by simply controlling reaction time. A satisfactory quantum yield of 3.8% is obtained. Significant electrochemiluminescence of the S dots is observed in an annihilation reaction. Chemiluminescence from the S dots has been observed by direct oxidation. Taking advantage of unique and inherent antimicrobial activity of the sulfur particles, it is believed that this new emerging luminescent nanomaterial is highly promising in the development of new types of optoelectronic devices and tracer for live cells, in vivo imaging and diagnostics.

Inspired by graphene nanosheets, one kind of two-dimensional (2D) layered nanomaterials, sulfur nanosheets (S-NSs), were prepared by direct sonication exfoliation of the sublimed sulfur suspended in an aqueous solution containing bovine serum albumin (BSA). The prepared S-NSs showed a wide range of absorption properties from ultraviolet to the visible region, distinct multiwavelength photoluminescence (PL), and a significant electrochemiluminescence (ECL) phenomenon during potential cycled scanning or potential pulse step. Moreover, the S-NSs were found to have superb stability over 2 months in air and the strong ability to be a visible-light-active element photocatalyst. The prepared S-NSs will potentially be applied in the field of photocatalysis, sensors, optoelectronics, and transistors.

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 S0 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.

A novel sensor based on Ag2S/chitosan films was prepared via a coordination-driven self-assembled method. Experiments demonstrated that Ag2S was inert to chitosan film. Structural, and sensing property studies were realized by FTIR, DSC, SEM, and fluorescence analysis. DSC showed good crystallization after manipulation, showing that the Ag2S QDs were uniformly distributed in the film, leading to a good fluorescence property. The fluorescence of the films was selective to benzaldehyde. The linear detection on benzaldehyde concentration by the fluorescence method can be established was from 0 to 108 mg/L. The films could be quenched because of the electron transfer between benzaldehyde and Ag2S QDs. It would therefore be developed as an optical sensor.

A novel sensor based on Ag2S/chitosan films was prepared via a coordination-driven self-assembled method. Experiments demonstrated that Ag2S was inert to chitosan film. Structural, and sensing property studies were realized by FTIR, DSC, SEM, and fluorescence analysis. DSC showed good crystallization after manipulation, showing that the Ag2S QDs were uniformly distributed in the film, leading to a good fluorescence property. The fluorescence of the films was selective to benzaldehyde. The linear detection on benzaldehyde concentration by the fluorescence method can be established was from 0 to 108 mg/L. The films could be quenched because of the electron transfer between benzaldehyde and Ag2S QDs. It would therefore be developed as an optical sensor.