Engineering triplet emissive centers in self-protective carbonized polymer dots for multicolor room-temperature phosphorescence from visible to near-infrared.

Multicolor room-temperature phosphorescence (RTP), particularly with long-wavelength emission, remains highly challenging in self-protective organic luminescent systems. Herein, we report a facile strategy for engineering triplet emissive centers in self-protective carbonized polymer dots (CPDs) through pH-regulated synthesis. By simply adjusting the pH of the precursor solution while keeping the precursor composition unchanged, a series of CPDs exhibiting tunable RTP from green to near-infrared were obtained, denoted as G-CPDs (540 nm), Y-CPDs (580 nm), and R-CPDs (710 nm). Systematic spectroscopic and structural investigations reveal that pH regulation governs the formation of distinct triplet emissive centers, thereby enabling precise control over RTP color. These findings provide important mechanistic insights into the structural origin of color-tunable phosphorescence in CPDs. This work not only demonstrates visible-to-near-infrared multicolor RTP in a self-protective system, but also offers a versatile platform for the rational design of advanced organic phosphorescent materials.