Color-tunable afterglow carbon dot@zeolite hybrids with efficient room temperature phosphorescence as anti-counterfeiting materials

Carbon dots (CDs) have been widely explored as active components in sensing, catalysis and therapeutics, thanks to their unique traits combining cost efficiency, high biocompatibility, straightforward synthesis and excellent luminescent properties. Although numerous room-temperature phosphorescent (RTP) carbon-dot systems have been reported in recent years, the development of simple, cost-effective, and scalable strategies for preparing RTP carbon-dot composites with tunable emission colors remains of considerable interest. Besides, the fabrication of multicolor phosphorescent CDs remains highly sought after. This work introduces a facile and scalable strategy to produce citric acid-based CDs embedded into zeolites (CA-CDs@zeolite) with long-lived phosphorescence. In comparison with reported protocols to produce similar composites, our method allows for the straightforward preparation of inexpensive phosphorescent CDs@zeolite in only 8 h. By controlling the drying temperature and the amount of citric acid (CA), green and yellow phosphorescence CDs were successfully obtained with a luminescence quantum yield ranging from 2 to 7% and a remarkable phosphorescence lifetime of 141.1 and 335.3 ms, respectively. Moreover, upon addition of urea into CA-CDs@zeolite CA₅₀₀U-CDs@zeolite were generated, which displayed bright fluorescence and a luminescence quantum yield of 10%. The different CD containing zeolitic composites were used to build colored patterns for applications in anti-counterfeiting.