Luminescent carbon dots obtained from polymeric waste

Here a sustainable approach for the bottom-up fabrication of luminescent carbon dots (CDs) through a green synthetic route by using polymeric waste as a single precursor material is developed. Polylactide has been selected as a carbon-containing model polymeric waste because of its remarkable presence in the packaging field and its associated "white-pollution". Spherical CDs with diameters of 3 nm have been synthesized through a one-pot hydrothermal reaction of water-dissolved polylactide oligomers (M-n = 1.200-1.900 g mol(-1)) at mild temperatures. Chemical, structural, morphological and optical properties of the synthesized CDs have been studied. Results reveal that CDs consist of a carbonaceous nucleus having a sp(2) conformation with carboxyl and hydroxyl surface groups, making it dispersible in polar media. The optical features of obtained CDs depend on reaction conditions (time and temperature) and on the insertion of nitrogen groups within the CD structure. A proof of concept study of the application of the proposed approach for the production of luminescent CDs from commercial PLA lids for paper hot cups is also provided. The route here reported provides novel cues for a catalyst-free and organic-solvent-free industrial-scale fabrication of photoluminescent nanomaterials from actual polymeric waste as a viable non-toxic and cheap alternative to quantum dots and rare earth based nanophosphors. (C) 2020 Elsevier Ltd. All rights reserved.