Abstract
Photo-stimulation responsive room temperature phosphorescence (RTP) carbon dots (CDs) have potential applications in advanced dynamic information encryption and anti-counterfeiting. However, the development of photo-responsive long-wavelength RTP CD materials with excellent reversibility and water resistance, as well as CD materials with both photo-induced fluorescence discoloration and photo-responsive reversible RTP properties, remains a challenge. Here, pyrene, which has a large conjugated structure, and 4-(1,2,2-triphenylvinyl)benzaldehyde, which has a tetraphenylethylene structure, were selected as the main raw materials to synthesize two CDs. Then, by introducing a PMMA matrix, reversible photo-responsive long-wavelength red RTP emission with a lifetime of 257 ms from a CD-based composite is realized for the first time, and the combination of photo-induced fluorescence discoloration and photo-responsive reversible yellow RTP with a lifetime of 287 ms is realized. Importantly, photo-responsive reversible RTP has excellent water resistance. The fluorescence discoloration was caused by photocyclization under long-term UV irradiation due to the presence of the tetraphenylethylene structure. The rigid environment provided by the PMMA matrix and the hydrogen bonds formed between the PMMA and CDs promote the generation of RTP. The photo-responsiveness of RTP is caused by the conversion of molecular oxygen (3O2) to singlet oxygen (1O2) under continuous UV irradiation. It is filled with 3O2 again after being placed in air to inactivate the RTP, thus achieving reversible RTP behavior. Owing to their excellent photo-responsive properties and water resistance, these materials have the potential to achieve repeatable dynamic information encryption and multilevel pattern anti-counterfeiting while also broadening the range of applications in water environments.
Published Version
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