Ultra-wide time-dependent phosphorescence color of carbon dots via a synergistic strategy of dual confinement structures constructing multiple luminescent centers†

Phosphorescent materials with time-dependent phosphorescent color (TDPC) output have significant potential for applications in advanced optical information encryption. However, the effective construction of TDPC composites compatible with multiple phosphorescent emission centers to achieve wider phosphorescent colors evolving over time in a single material system remains a huge challenge. Here, ultra-wide TDPC composites with time-dependent color evolution were realized for the first time in a single system by exploiting the synergistic effect of a doubly confined structure. Utilizing organosilanes to pretreat the reactive precursor, combined with a boric acid (BA) matrix, the composite (Si-CDs@B₂O₃) was prepared by direct calcination. Our results reveal that the Si-CDs@B₂O₃ composite has significant ultra-wide TDPC properties, with the phosphorescent emission shifting from red to orange, yellow, green, and cyan blue. Characterization analysis reveals the important role of organosilanes in achieving ultra-wide TDPC properties. It also demonstrates that the red phosphorescence originates from the interaction of CO on the surface of CDs with the BA matrix, while the blue phosphorescence originates from the intrinsic emission of B–O bonds in the BA matrix. The distinctive dynamic room-temperature phosphorescence properties of the Si-CDs@B₂O₃ composite were leveraged to develop a strategy for its use in information encryption on a precise time scale.