Green synthesis of <i>Sapindus mukorossi</i> -mediated carbon quantum dots for therapeutic and photocatalytic applications

We report the first fabrication of S. mukorossi seed extract-mediated CQDs by a hydrothermal approach. Phytochemical analysis and GC-MS of seed extract divulged the involvement of carbohydrates, alcohols, and various esters as precursors. UV-vis spectrum revealed absorbance peaks at 210 and 275 nm while FTIR and XPS depicted functional groups. Zetasizer measured potential as -11.9 ± 0.48 mV and XRD affirmed the amorphous nature. SEM-EDX validated the irregular surface morphology and presence of carbon and oxygen. CQDs inhibited the growth of MRSA (21 mm), P. aeruginosa (18 mm), S. aureus (14 mm), and A. baumannii (10 mm). Their antibacterial potential was superior to that of the seed extract and some antibiotics. CQDs asserted synergy with some antibiotics by a modified disk-diffusion method. Antioxidant and anti-inflammatory activities of CQDs were appraised by DPPH and BSA assays, and evidenced by IC50 values of 340 µg/mL and 65 µg/mL, respectively. Photoactive CQDs degraded methyl red (η = 58.6%), crystal violet (η = 41.9%), malachite green (η = 29.4%), and methylene blue (η = 8.6%) in 150 min, and Ciprofloxacin (η = 14.4%) and Metronidazole (η = 12.8%) in 60 min. This study highlights that the distinctive phytochemical makeup of green extract can serve as a lucrative route for the production of innovative nanomaterials with considerable biological and photocatalytic qualities.