Cascade energy transfer endows phosphorescent carbon dots-based films with tunable and broadband afterglow for fingerprint recognition and anticounterfeiting

Room-temperature phosphorescence (RTP) carbon dots (CDs) have attracted extensive attention due to their afterglow properties and promising potential in optical information and encryption fields. However, achieving tunable and broadband RTP CDs-based afterglow materials remains a great challenge for practical applications. Herein, we constructed broadly tunable afterglow CDs-based hybrid systems by employing cascade Förster resonance energy transfer (FRET) for fingerprint recognition and anticounterfeiting. The as-prepared CDs composites exhibit excellent green RTP properties with a quantum yield of 21.7 % and a lifetime of 1.05 s. Combination of the RTP CDs as the energy donor and Sulforhodamine 101 (SR101), Rhodamine B or Rhodamine 6G as the acceptor in polyvinyl alcohol (PVA) film, the afterglow spectrum of RTP CDs/dye/PVA film is markedly extended to the red region through an efficient triplet-singlet FRET. The sequential incorporation of SR101 and Oxazine 170 with RTP CDs further broadens the afterglow spectrum of CDs/SR101/Oxazine170/PVA film covering from green to near-infrared regions due to the cascade relayed FRET. The flexible FRET configuration of highly emissive RTP CDs with various dye acceptors endows the CDs/dyes/PVA hybrid films with tunable color and broadband afterglow properties for fingerprint recognition and anticounterfeiting applications.