Green synthesis of fluorescent carbon dots/silver nanoparticles with enhanced antibacterial activity

Eco-friendly nanostructures are promising technological prototypes given the minimal environmental impact and the outstanding properties of nanoparticles for several applications. Carbon dots are essential for nanomedicine, drug delivery, bioimaging, and antibacterial activity, while metal nanoparticles are versatile building blocks in related areas. Herein, the association of silver nanoparticles/carbon dots prepared from lemon and onion extract is explored in producing complexes characterized by XRD pattern, FTIR, SEM images, and fluorescence assays. The combination of nanostructures preserves the intrinsic fluorescence of carbon dots, opening the possibility for use as fluorescent markers while reinforcing the combined antibacterial of components (silver nanoparticles and carbon dots). As a result, the best antibacterial performance was observed for the system composed of carbon dots and silver nanoparticles with relevant antibacterial activity against S. aureus (experiments in triplicate). After six hours of treatment, the log reduction in the viable cells was 3.2 log (colony forming units/mL—CFU/mL). In addition, the potential of the compound applied as an antibiofilm agent was observed with a reduction in 5.3 log (CFU/mL) against biofilm-forming S. aureus. These results confirm the promising application of synthesized composite against planktonic and biofilm forms of S. aureus, offering a hopeful outlook for the future of antibacterial research.