Achieving Matrix-Free Self-Protective Room-Temperature Phosphorescence from Polymer-Derived Carbon Dots for Optical Applications

Abstract Room-temperature phosphorescence (RTP) carbon dots (CDs) are highly promising for optoelectronic applications but typically rely on external matrices to achieve high efficiency and long-lived emission. Herein, we address this limitation by designing matrix-free self-protected RTP CDs (CDsT) via one-step hydrothermal treatment of a polymer, poly(acrylamide-co-N-acryloylcarbazole). Such molecular design affords a dual-enhancement mechanism. Specifically, nitrogen atoms strengthen spin-orbit coupling, thereby facilitating intersystem crossing and efficient population of triplet excitons. Meanwhile, extensive hydrogen bonding between amide and amino groups restricts the intramolecular motions, significantly suppressing the nonradiative decay. Consequently, the cross-linked CDs exhibit blue fluorescence and bright green RTP. Elevating the reaction temperature from 120 to 220 °C progressively enriches C═N–C and C═O functional groups, which remarkably prolongs the phosphorescence lifetime from 446 to 761 ms. These optical properties provide possible promise in 3D dynamic information encryption and time-delayed ligh-emitting diodest, providing a new paradigm for designing advanced self-protective RTP nanomaterials.