Enhanced UV Protection, Heavy Metal Detection, and Antibacterial Properties of Biomass-Derived Carbon Dots Coated on Protective Fabrics

Carbon dots (CDs) were simply prepared from charcoal by hydrothermal processing at 180 degrees C for 15 h without any chemicals. The as-prepared CDs with an average diameter of 5 +/- 6 nm exhibited a predominant absorption peak at 290 nm, corresponding to the n to pi* transition of the oxygen functional groups (C=O) and the free amine functional groups (-NH2). The resulting CDs were then incorporated into cotton and polyester by facile ultrasonication for 1 h. The obtained CD-coated fabrics were first evaluated for their UV-blocking capability and then for their antibacterial properties against two model pathogens: Gram-negative E. coli and Gram-positive S. aureus. Both cotton and polyester showed no UV protection at 280 or 380 nm; conversely, cotton or polyester decorated with CDs exhibited a UV blocking ratio of 82-98%. The CD-coated fabrics showed 100% antibacterial activities against E. coli and S. aureus, whereas the pristine fabrics showed no effect. The CDs/fabrics could adsorb Hg2+ and Fe3+, resulting in a drastic fluorescence quenching. As such, this distinct feature was exploited for the removal and detection of these two ions with the limits of detection of 55and 72 mu M, respectively.