Carbon Dots-Inked Paper with Single/Two-Photon Excited Dual-Mode Thermochromic Afterglow for Advanced Dynamic Information Encryption.

Achieving thermochromic afterglow (TCAG) in a single material for advanced information encryption remains a significant challenge. Herein, TCAG in carbon dots (CDs)-inked paper (CDs@Paper) was achieved by tuning the temperature-dependent dual-mode afterglow of room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). The CDs were synthesized through thermal treatment of levofloxacin in melting boric acid with post-purification via dialysis. CDs@Paper exhibited TCAG and excitation-dependent afterglow color properties. The TCAG of CDs@Paper exhibited dynamic color changes from blue at high temperatures to yellow at low temperatures by adjusting the proportion of the temperature-dependent TADF and phosphorescence. Notably, two-photon afterglow in CDs-based afterglow materials and time-dependent two-photon afterglow colors were achieved for the first time. Moreover, leveraging the opposite emission responses of phosphorescence and TADF to temperature, CDs@Paper demonstrated TCAG with temperature-sensing capabilities across a wide temperature range. Furthermore, a CDs@Paper-based 3D code containing color and temperature information was successfully developed for advanced dynamic information encryption. This article is protected by copyright. All rights reserved.