Excitation-dependent organic phosphors exhibiting different luminescence colors for information anti-counterfeiting

The development of organic phosphors with excitation-dependent luminescence color is tremendously challenging for organic room temperature phosphorescent (ORTP) systems. Herein, we designed and synthesized a series of novel ORTP materials based on pyranone. Under the excitation of 254 nm, the materials exhibited the rare phenomenon of emitting almost pure phosphorescence, whereas strong cyan photoluminescence and weak green phosphorescence were observed upon exposure to 360 nm excitation light. Experiment analysis and theoretical calculations demonstrate that the regulation of luminescent color is attributed to the different transition process of excitons from singlet excited states (S1 and S2) to triplet excited states (T1) under various excitation wavelengths. The materials still can maintain the crystalline state under various extreme conditions (ground, recrystallization, high pressure), thereby maintaining the ORTP properties. In addition, the ORTP properties of the materials are very stable to water/heat/light/air. Taking advantage of the multiple luminescence colors, excellent crystallinity and stability, these phosphors can be developed as an advanced anti-counterfeiting ink for printing and hand-painting on a wide range of media, showing an extremely ideal application prospect.