Waste-derived high-yield biocompatible fluorescent carbon quantum dots for biological and nanofertiliser applications

Petroleum coke and kitchen tea residues are solid waste containing significant carbon contents. In this novel work, we have efficiently fabricated high quantum yield fluorescent carbon quantum dots (CQDs) from petroleum coke (Pet coke/PC) and kitchen tea residues (KTR) by using a simple and environmentally friendly process of chemical oxidation induced by ultrasonic energy. The average particle dimension of the fabricated PC-CQDs and KTR-CQDs are 6 nm and 4.5 nm, respectively revealing highly water-soluble possessing excitation-dependent fluorescence with a maximum photoluminescent quantum yield of 55.14 %. The cell-biology studies demonstrated their excellent biocompatibility with anti-cytotoxic, no significant reactive oxygen species (ROS) generation, and are non-genotoxic behaviors. Certain free radical scavenging activity was also observed, representing the presence of sensible antioxidant properties in the waste-derived CQDs. In addition, KTR-CQDs possesses excellent antibacterial properties against different bacterial strains. Further, the phytological investigation with Stevia rebaudiana plants demonstrates the promising potential of waste-derived CQDs to serve as a nanofertilizer, thereby enhancing plant growth. This study opens up a new avenue for gainful and sustainable utilization of industrial waste.