Upcycling of cotton waste to functional carbon dots: Photocatalysis and antibacterial action under vis-NIR light

Carbon dots are fluorescent nanomaterials with interesting optical properties and good biocompatibility that can be fabricated from many carbon sources. In the present work, we have produced carbon dots from non-woven cotton waste, following an ecological strategy, easy to scale up. The fabricated carbon dots possess strong photoluminescence (PL), they are chemically very stable and biocompatible. We have investigated their photocatalytic properties under visible–near IR light irradiation, and consequently their antibacterial properties under these conditions, using as a model cell the Gram-negative bacteria Escherichia coli (E.coli). Finally, we have fabricated a proof-of-concept paper sensor by functionalizing lab filter paper with the produced carbon dots, using poly(vinyl alcohol) as binder. The analysis of digital photographs of the paper sensors under UV light reveals a quenching of the photoluminescence of the carbon dots in the presence of E. coli, extending the potential applications of carbon dots to paper-based bacterial sensors.