Achieving tunable time-dependent delayed emission color via dynamic competition between the matrix and carbon dots for anti-counterfeiting and multidimensional encryption

Delayed emission (DE) materials with tunable lifetime and wavelength can provide more modes of anti-counterfeiting and information encryption for improving security levels. It is both attractive and challenging to create carbon-based materials with dynamic DE colors through multiple luminescence centers. Herein, we have developed a composite material (BA@CDs) with tunable lifetimes and variable DE colors ranging from blue to orange by heating treatment method. Surprisingly, the delayed luminescence emission of BA@CDs can last up to 11 s, and then a color change occurs within 2 s. By utilizing various analysis methods, the origin of this long lifetime DE property is investigated, revealing the significant role played by two distinct phosphorescent emission centers. The dynamic competition and energy transfer (ET) process between the two emission centers reveal an interaction between the host matrix and N, S-CDs, indicating a significant interplay between them. This tunable phosphorescent material further demonstrates its advantages in anti-counterfeiting and information encryption.