Promoting the Efficiency of Room-Temperature Phosphorescence by Forming the Composite and Employing It for Fingerprint Detection.

Currently, carbon dots (CDs) with room-temperature phosphorescence (RTP) show bright prospects in multiple fields, owing to their tunable wavelengths and large Stokes shifts. Howbeit, obtaining the long-lived efficient RTP of CDs still encounters a different kind of challenge. Here, we originally prepared the carbon dots (CDs@β-GPA) with β-guanidinopropionic acid and diethylenetriamine pentamethylene phosphonic acid, and CDs@β-GPA exhibited the obvious green RTP when fixed on filter paper. Importantly, the introduction of boric acid (BA) into the carbon dots resulted in stabilized triplet excitons by forming the composite of CDs@β-GPA/BA through covalent coupling, and the optical band gap was effectively reduced and nonradiative transitions were inhibited, thus leading to a significantly prolonged phosphorescence lifetime of up to 1.35 s. Meanwhile, we also acquired the phosphorescent emission of CDs@β-GPA/BA excited by visible light. This strategy may broaden the approaches to produce a long-lifetime and high-efficiency RTP material. Moreover, CDs@β-GPA/BA was successfully employed in the fields of fingerprint detection and advanced information encryption.