Highly fluorescent sulfur quantum dots could be rapidly and massively synthesized from inexpensive elemental sulfur under a pure O2 atmosphere.

The direct utilization of abundant and cheap elemental sulfur (S) to synthesize sulfur quantum dots (SQDs) with satisfactory yield and photoluminescence quantum yield (PLQY) remains a big challenge. Here, we report a simple and effective method for mass-producible synthesis of ultrabright fluorescent SQDs based on one-pot solvothermal treatment of S-ethylenediamine (S-EDA) solution. The PLQY of synthesized SQDs and the corresponding S-to-SQDs conversion efficiency (CE) can reach as high as 87.8% and 15.9%, respectively, both of which are the highest values to date. In addition, the SQDs simultaneously show good water solubility, superior storage stability, stable fluorescence against ionic strength variation and pH change, and low toxicity, which enable them promising for numerous applications such as fabrication of fluorescent polymer composite and ink. Furthermore, SQDs also present strong two-photon emission, and their use for two-photon fluorescence imaging is reported here for the first time. This work thus highlights enormous opportunities not only for bringing SQDs from laboratory research to real applications but also for the value-added utilization of S resource.

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The development of low-cost adsorbent with excellent adsorption property remains a big challenge. Herein, the functionalization of natural peach gum polysaccharide (PGP) with multiple amine groups for the removal of toxic Cr(VI) ions from water was studied. The obtained PGP-NH 2 gel exhibited high-removal efficiency (>99.5%) toward Cr(VI) ions, especially with relatively low initial concentration of Cr(VI) ions (≤250 mg/L). The influences of pH, ionic strength, contact time, initial concentration, and temperature on the adsorption of Cr(VI) ions were systematically investigated. The PGP-NH 2 gel showed rapid adsorption rate and could reach adsorption equilibrium within about 40 min. The Cr(VI) ion uptake process could be described by pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of PGP-NH 2 gel could reach 188.32 mg/g. Thermodynamic investigation results indicated the spontaneous and exothermic characteristic of the uptake process. Moreover, the PGP-NH 2 gel also exhibited favorable reusability, and 135.52 mg/g of adsorption capacity was retained even after being reused for five times. Considering its low cost and superior uptake property, the PGP-NH 2 gel holds a great promise for employing as an adsorbent to treat Cr(VI) ion-containing wastewater.

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