Hydrogen Peroxide Assisted Synthesis of Highly Luminescent Sulfur Quantum Dots

Abstract

An H 2 O 2 -assisted top-down approach is used to synthesize brightly luminescent, color-tunable sulfur quantum dots (SQDs), with aphotoluminescence quantum yield of up to 23 %. The formation of SQDs involves dissolution of bulk sulfur powder into small particles in an alkaline environment in the presence of polyethylene glycol, followed by H 2 O 2assisted etching of polysulfide species,which has the advantage of the passivation of surface states.T his synthetic strategy allows us to simultaneously control the final sizeo fS QDs,t o tune their emission color,a nd to improve their emission quantum yield by eliminating surface traps.Down-conversion white light emitting diodes were also fabricated using blue emissive SQDs and orange emissive copper nanoclusters,with CIE color coordinates of (0.33, 0.32) and ah igh color rendering index of 91. The water-soluble,h ighly luminescent SQDs are promising luminescent materials that can be produced from abundant precursor materials.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Negatively Charged Sulfur Quantum Dots for Treatment of Drug-Resistant Pathogenic Bacterial Infections

“…The results indicated the trend that the smaller the particle size, the stronger the fluorescence of PSS-SQDs. It is worth noting that the PSS-SQDs could be obtained within 12 h using either an oil bath or a Teflon vessel (hydrothermal method) at 70 °C (Figures S10–S12), where the reaction time was greatly shortened compared with previous reports on the synthesis of polyethylene glycol-stabilized SQDs (PEG-SQDs, at least 72 h). , …”

“…It is worth noting that the PSS-SQDs could be obtained within 12 h using either an oil bath or a Teflon vessel (hydrothermal method) at 70 °C (Figures S10−S12), where the reaction time was greatly shortened compared with previous reports on the synthesis of polyethylene glycol-stabilized SQDs (PEG-SQDs, at least 72 h). 18,19 Transmission electron microscopy (TEM) and atomic force microscopy (AFM) imaging shows that the average size of SNPs is ∼8 nm (Figures S13 and S14). After being treated by H 2 O 2 , monodispersed SQDs with the size as small as ∼2 nm were obtained (Figure 1a,b).…”

“…The only survived peak at 220 nm is ascribed to the n → σ* transition of nonbonding electrons of S. 19 It means that not only the size decreases but also surface state changes after the etching of PSS-SNPs by H 2 O 2 , similar to the results reported by Wang and co-workers. 18 Moreover, X-ray photoelectron spectroscopy (XPS) shows that the PSS-SQDs are composed of C, O, and S (Figure S17). The high content of C and O verifies the existence of PSS on the surface of SQDs.…”

“…As expected, the as-prepared PSS-SNPs and PSS-SQDs are both negatively charged with ζ-potential On the basis of the above results, an alkali fission and H 2 O 2assisted oxidative etching mechanism for the synthesis of PSS-SQDs is proposed, which is similar to that of the top-down prepared PEG-SQDs. 18,19 In an alkaline environment, sulfur powder can be dissolved into aqueous solution by splitting bulk sulfur into nanoscale particles and forming a mass of S 2− / SO 3 2− (eq 1). Negatively charged PSS is capped on the surface of the particles and can stabilize them from aggregation due to strong electrostatic repulsion.…”

Efficient Conversion of Elemental Sulfur to Robust Ultrabright Fluorescent Sulfur Quantum Dots Using Sulfur-Ethylenediamine Precursor

“…Since the pioneering work on direct synthesis of sulfur quantum dots (SQDs) from S by an assembly fission method in 2018, as a novel metal-free fluorescent dots, SQDs have attracted increasing interest due to their unique properties. − However, the disadvantages of long reaction time, low photoluminescence quantum yield (PLQY), and very low S-to-SQDs conversion efficiency (CE) (lower than 1%) seriously hinder the real applications of SQDs. − To overcome these limitations, we and other groups have developed a variety of approaches, such as O 2 acceleration, − H 2 O 2 or ions assisted synthesis, − hydrothermal synthesis, − ultrasonication treatment, microwave reaction, and a mechanochemical technique to synthesize fluorescent SQDs. Despite impressive progress has been made in the past three years, neither the PLQY of SQDs nor the S-to-SQDs CE can meet the requirements of practical applications.…”