A ratiometric fluorescent platform based on nitrogen-doped carbon dots for simultaneous detection and discrimination...

Chloramphenicol (CAP) and chlorogenic acid (CGA) are often co-applied due to their synergistic antibacterial effect, leading to their coexistence in food and environmental samples and raising concerns about potential cumulative risks. Therefore, a method for their concurrent detection is urgently needed. Herein, a dual-excitation ratiometric fluorescence sensing platform constructed from nitrogen-doped carbon dots (N-CDs) is developed for simultaneous detection and discrimination of CAP and CGA. The N-CDs are synthesized hydrothermally from carbamide and 5-aminoisophthalic acid, exhibiting strong blue emission at 405 nm under excitation wavelengths of 287 nm and 345 nm. Upon exposure to CAP, the excitation at 287 nm is selectively quenched via the localization of inner filter effect, while the excitation response at 345 nm remains unchanged, affording a limit of detection (LOD) of 81 nM over 0.27-80 μM. In contrast, CGA quenches both excitation peaks through static quenching and inner filter effect, achieving a LOD of 93 nM within 0.31-50 μM. Leveraging these distinct quenching responses, linear discriminant analysis together with hierarchical cluster analysis are utilized to discriminate CAP and CGA within mixed samples. In addition, a smartphone-assisted sensing strategy is constructed for the visual and on-site quantitative analysis of CAP and CGA, which exhibits favorable recovery rates in real samples. Therefore, this work presents a reliable dual-excitation ratiometric sensing method for CAP and CGA, demonstrating strong potential in food safety and environmental monitoring.