One-Pot Synthesis of Fluorescent Guanidyl Sulfur Quantum Dots for Antibacterial and Antioxidant Performance

Sulfur quantum dots (SQDs) hold immense promise for a wide range of applications due to their unique properties. However, the large-scale production of high-performance SQDs from readily available elemental sulfur remains a significant challenge. Herein, we report a simple yet effective approach to synthesizing highly fluorescent guanidyl SQDs (G-SQDs) with abundant guanidine groups on their surface. By employing a one-pot solvothermal process on an elemental sulfur-ethylenediamine mixture, using arginine as a stabilizer, we achieved a remarkable 12.7% conversion rate from elemental sulfur to G-SQDs. The resulting G-SQDs exhibit small and uniform size, excellent aqueous dispersibility, a high photoluminescence quantum yield of 60.2%, and low cytotoxicity. The presence of guanidine groups significantly enhances their antibacterial and antioxidant activities, making G-SQDs highly effective against both Gram-positive (e.g., S. aureus) and Gram-negative bacteria (e.g., E. coli). Moreover, their ABTS radicals scavenging efficiency is superior to that of other SQDs. These exceptional properties render G-SQDs highly suitable for applications in cell imaging, antibacterial treatments, and food preservation, as demonstrated in this study. Given their simple synthesis and superior performance, this work not only provides a cost-effective route for the production of high-performance SQDs but also promotes the efficient utilization of elemental sulfur resources.