Enabling Visualized Time‐Resolved Dynamic Discoloring Afterglow from Carbon Dots by Engineering Luminescent Centers and Trap‐States for Security Applications

Abstract Luminescent materials with time‐resolved dynamic discoloring afterglow (TDDA) hold significant potential for applications in anti‐counterfeiting and data encryption. However, the afterglows coming from organic systems are usually unidentifiable due to their shorter durations (less than 10 s). Achievement of long‐lasting and visually discernible TDDA remains highly desirable but challenging. In this work, the TDDA duration is successfully extended from less than 10 s to minutes by engineering the luminescent centers of carbon dots (CDs) and introducing deep trap‐states in a composite of CDs and carbon nitrides (CNs) (named Y‐CDs@CN). It is confirmed that the regulation of luminescent centers in CDs containing both C═N and C═O bonds is responsible for the color changes during TDDA from yellow to green. Moreover, the generation of deep trap states is found to be significant for prolonging the afterglow duration to minutes level through converting room temperature phosphorescence into long persistent luminescence, thus making the entire dynamic discoloring process being easily recognized to naked eyes. Furthermore, the afterglow of Y‐CDs@CN can also be excited by blue light and even using white light of a cell phone. To harness these characteristics, potential applications of Y‐CDs@CN for portable anti‐counterfeiting and multidimensional information encryption are primarily investigated.