Landscaping sustainable conversion of waste plastics to carbon dots and enormous diversity in O2 harvesting, hypoxia, autophagy

Abstract

Recent discoveries using polyethylene-derived carbon dots (CD) not only offer tangible ways of mitigating plastics pollution but also open tremendous application prospects. Using their massive aerial-oxygen-harvesting properties, oxidation reactions can be accomplished with equal efficiencies in air and in oxygen, enabling the use of free air as oxidants, while their ability to self-eliminate or ‘autophagy’ enables easy disposal. Light-induced ‘hypoxia’ in them can provide for programmable oxygen concentrations within a solution. However, utilizing different waste plastics as feedstock and the tunability of the emergent properties has remained unexplored. Herein, we show that CDs can be obtained from ten of the most abundant plastic wastes with 100% conversion efficiencies, and recovered as powders for easy transportation and storage. We further establish that O2 harvesting ability and the magnitude of hypoxia in CDs are highly structure-dependent and rationally controllable. O2 enrichment can be tremendously modulated in the as-synthesized CDs within a 405–830 μM range where the ratios of strongly and weakly bound oxygen molecules vary between 1.46 and 3.14. Moreover, hypoxia can be adjusted in the 82–266 μM range with 30 min of light exposure while autophagy follows a pseudo-first-order kinetics with effective disappearances from a solution spanning from two days to months.