Carbon Dots Confined in Silica Nanoparticles for Triplet-to-Singlet Föster Resonance Energy-Transfer-Induced Delayed Fluorescence

Room temperature afterglow (RTA) carbon dots (CDs) are supposed to provide a promising alternative to inorganic and purely organic phosphors whose toxicity and high cost are always a major concern. However, it remains a formidable challenge to realize tunable and water-processable RTA from CDs. In this work, a strategy is proposed to achieve tunable and water-processable RTA from CDs with triplet-to-singlet Föster resonance energy-transfer-induced delayed fluorescence (TS-FRET DF). This strategy is realized by just mixing room temperature phosphorescence CDs with green emission confined in silica nanoparticles (GCDs@SiO₂) as the energy donors with FRET-matched orange-emissive CDs (OCDs) as the energy acceptors in aqueous solution. The TS-FRET DF of GCDs@SiO₂–OCDs can be tuned from green to orange by the amount of OCDs, pH, and organic solvents, respectively. Finally, GCDs@SiO₂–OCDs with interesting room temperature water-processable TS-FRET DF can be successfully used in information security and fingerprint recognition.