Visible light activated time dependent phosphorescence colors from carbon dots based materials

To endow carbon dots (CDs)-based materials with time dependent phosphorescence colors (TDPCs) activated by visible light will benefit high-level data encryption and anticounterfeiting. It needs multiple emission centers of triplet state stabilized by noncovalent bonds. In this work, levofloxacin and ethanolamine were applied to synthesize CDs (LEE-CDs), in which, aromatic moieties and multiple emissive centers were formed by the reaction between fluorinated quinolone moieties and ethanolamine. Melamine (MA) and cyanuric acid (CA) with large π systems were selected as matrices, and urea and biuret without π systems were selected as the comparison matrices. Interestingly, LEE-CDs encapsulated in MA (LEE-CDs@MA) exhibited visible-light-activated TDPCs varying from red to yellow green, while LEE-CDs@CA displayed TDPCs from red to yellow green after excited by visible light, yellow to green after excited by UV light. However, LEE-CDs@Urea and LEE-CDs@Biuret could only generate a single color RTP after excited by visible or UV light. It can be inferred that π-π stacking interactions combining with hydrogen bonds activated the O-related triplet state with a short lifetime, and hydrogen bonds only retained the N-related triplet state in LEE-CDs with a long lifetime and the emissive center of matrices with an intermediate lifetime. Therefore, the dynamic ratio of the RTP emissive bands from the three centers changing over time resulted in TDPCs. •Visible light activated time dependent phosphorescence colors of carbon dots.•π−π stacking interaction activating the mute o-related RTP emission center.•Time dependent phosphorescence colors varying from red to yellow.•Dynamic anti-counterfeiting achieved by time dependent phosphorescence colors.