Light-driven “on-demand synthesis” of N/Br-codoped polymeric carbon dots as dual-mode photoinitiator for intrinsically fluorescent polymers

The development of metal-free photocatalysts operating under low-energy light remains a challenge, especially those obtainable via sustainable pathways. While carbon dots (CDs) are a promising biocompatible platform, their conventional synthesis via energy-intensive methods (e.g., hydrothermal, pyrolysis) hinders scalable application. Herein, we report a straightforward, light-induced strategy to obtain N,Br-codoped polymeric CDs (N/Br-PCDs). Irradiation of glycine (Gly) and phenacyl bromide (PAB) under 365 nm light at room temperature yields N/Br-PCDs with an average diameter of ∼4 nm. PAB acts as the photochemical precursor, providing both the carbon framework and the bromine species responsible for a heavy-atom effect, which facilitates efficient intersystem crossing (ISC), indicated by a shortened fluorescence lifetime (∼2.5 ns) to populate the reactive triplet states necessary for photoredox processes. N/Br-PCDs function as efficient dual-mode photoinitiators, initiating the radical polymerization of acrylates/acrylamides (HEA/NIPAM) as Type I photoinitiators, and catalyzing the cationic polymerization of vinyl ethers (IBVE) and epoxides (CHO), when combined with diphenyliodonium salt under visible light. A practical “on-demand synthesis” strategy is demonstrated, where the polymerization occurs in-situ within the crude reaction mixture. This work not only clarifies the structural paradigm of polymeric carbon dots but also presents a highly adaptable platform for advanced light-driven manufacturing.