Dual-Mode Responsive Dynamic Afterglow Color in Carbon Dots and Carbon Nitride Composite for Advanced Optical Information and Temperature Sensors

Abstract

Responsive dynamic afterglow carbon dot (CD) materials, which can continuously emit light of dynamically varying color after excitation cessation, promise broad applications in advanced information encryption and related fields. However, as most reported CD-based afterglow systems still exhibit single-variable-responsive color evolution, their applicability to information encryption and complex environments is limited. Herein, this study reports a CD-based composite with a dual-mode responsive dynamic afterglow color. A fluorine (F)-doping strategy modulated the band gap of the CDs and created triplet emission centers. Subsequently, a simple microwave treatment embedded the F-doped CDs (FCDs) into a carbon nitride matrix through covalent bonds, effectively promoting triplet emission. The resulting FCD composite emits a dynamic afterglow with time- and temperature-dependent response characteristics. Multiple triplet energy levels generate room-temperature phosphorescence and thermally activated delayed fluorescence. The distinct emission wavelengths and lifetimes of these two processes endow the FCD composite material with dually responsive afterglow in the blue-to-green spectral region, which can be exploited in advanced optical information encryption and temperature sensing.