Phosphorus- and nitrogen-codoped carbon dots (PN-CDs) catalyze Vis-NIR-light-induced photoATRP

Abstract

Recently, carbon dots (CDs) have been recognized to be efficient catalysts for photo-activated reversible deactivation radical polymerization (RDRP) under visible light. However, the use of CDs to catalyze near infrared (NIR)-light-induced RDRP remains a challenge. Here, we prepared phosphorus- and nitrogen-codoped carbon dots (PN-CDs) with citric acid, L-tryptophan and diammonium hydrogen phosphate as the precursors. Compared with nitrogen-doped CDs, the absorption spectrum of the PN-CDs extended from the UV/visible region to the NIR after the introduction of the P atoms. The PN-CDs were used as the catalyst for photo-induced atom transfer radical polymerization (photoATRP). In addition to the predicted catalytic ability under irradiation with visible light, the PN-CDs exhibited unexpectedly high efficiency to catalyze polymerization under NIR (NIR-ATRP). The livingness of the NIR-ATRP was confirmed by the polymerization kinetics, chain extension and “on–off” light experiments; the versatility of the system was demonstrated using different monomers and solvents. Owing to the good penetration of NIR, the polymerization could be performed in the presence of an opaque barrier (i.e., pork skin). A crosslinked polymer gel was achieved by penetrating NIR-ATRP and showed photoluminescence properties and good deep-layered healing ability, demonstrating the potential of the PN-CD-catalyzed NIR-ATRP method in practical application.