One-pot synthesis of carbon dots confined in CaSiO3 for efficient phosphorescence with excitation-dependent emission in aqueous environments

Phosphorescent carbon dots (CDs) capable of excitation-dependent excitation and stable emission in aqueous environments remain fundamentally challenging due to inefficient intersystem crossing and rapid triplet deactivation. Herein, we report a confinement-enabled strategy to regulate excited-state dynamics by integrating malic acid/ethylenediamine-derived CDs within a CaSiO 3 matrix (MA/EA-CDs@CaSiO 3 ) via a one-pot in situ formation strategy. We show that the rigid inorganic framework, together with Ca 2+ -induced local electric fields, synergistically suppresses nonradiative relaxation and facilitates intersystem crossing, leading to efficient stabilization of triplet excitons. As a result, the composites exhibit pronounced visible-light-excitable phosphorescence with quantum yields up to 23.78% in the solid state and ∼10% under 395 nm excitation. Notably, the confined structure preserves long-lived emission even in aqueous environments, indicating effective protection of triplet states against oxygen and solvent-induced quenching. Beyond performance, this work elucidates how inorganic confinement and local coordination environments cooperatively regulate excited-state processes in carbon-based luminophores. The design strategy established in this work provides a generalizable framework for constructing aqueous-compatible phosphorescent systems and advancing the fundamental understanding of room-temperature phosphorescence in hybrid materials.