Long-lived and stable aqueous room-temperature phosphorescent carbon dot based composites for optical security

Highly efficient and durable room-temperature phosphorescence (RTP) in aqueous systems is essential to practical applications. Herein, an in-situ host guest strategy is introduced to synthesize cyanuric acid (CA)-derived phosphorescent nitrogen-doped carbon dots (NCDs) composites (NCDs@CA). It reveals that robust hydrogen bonding networks between NCDs@CA and water stabilize triplet excitons, suppress nonradiative decay pathways, and facilitate efficient energy transfer from CA to NCDs. These interactions lead to remarkable improvement with the phosphorescent quantum yield and lifetime increasing to 28.2% (4-fold) and 900.10 ms (6.1-fold), respectively, at 60 wt% water under ambient conditions. NCDs@CA exhibits remarkable water-boosted RTP properties, even in fully aqueous environments with up to 500 wt% water. The outstanding aqueous RTP properties of NCDs@CA indicate promising applications, such as information encryption and advanced portable anti-counterfeiting technology.