Visible Light-Activated Dual-Mode Afterglow Emission in Chlorine-Doped Carbon Dot-Based Composite for Advanced Information Encryption

Carbon dot (CD)-based long-afterglow luminescent materials have attracted widespread attention owing to their unique luminescent properties, eco-friendliness, and extensive application prospects. However, the development of visible light-activated long-lived afterglow based on CD materials remains considerably challenging. Herein, a CD-based composite (Cl-CD@BA) with visible light-activated afterglow was synthesized via thermal treatment of Cl-CD and boric acid (BA). The Cl-CD@BA composite demonstrated room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) dual-mode afterglow emission. Notably, a green TADF emission peak at 525 nm (with 193 ms) could be observed by the naked eye for over 6 s after the composite was excited by white light from a mobile phone flashlight. Furthermore, a concept of information encryption using the Cl-CD@BA composite was proposed through inkjet printing technology, indicating the considerable potential of CD-based afterglow materials in advanced information encryption applications.