Composite Carbon Dot Materials with Long Room Temperature Phosphorescence in Solid and Liquid Environments for Encryption Technologies and Biological Detection

This study presents an innovative approach to design room temperature phosphorescent (RTP) carbon dot composites with ultralong afterglow lifetimes in both solid and liquid states. The proposed carbon dot composites, namely, L-NCDs-BA (solid) and L-NCDs-SiO2 (liquid), were synthesized through a straightforward hydrothermal method. The solid composite achieved an afterglow lifetime of 1.63 s, while the liquid composite demonstrated a notable afterglow of 1.30 s. These values surpass most reported nonmetallic RTP materials to date. Morphological and structural analyses confirmed effective encapsulation within a boric acid matrix and a silica framework, providing protection against quenching factors. The composites displayed excitation-dependent fluorescence emission, allowing for color-tunable fluorescence. Applications in information encryption and biological detection were explored, showcasing potential in anticounterfeiting and selective sensing of L-NCDs carbon dot composites. This study provides a comprehensive exploration of the structure, photophysical properties, and applications of ultralong-lived RTP carbon dot composites. The synthesized materials offer promising avenues for advanced optoelectronic devices, anticounterfeiting technologies, and selective biological detection systems.