A Double-Excitation Intrinsically Dual Emissive Carbon Dot Platform Enables Multi-Channel Sensitive Detection and Imaging of Common Pesticides in Live Models

Carbon dot sensors often couple one excitation condition to one analyte and one output, limiting information from a single probe. Here, we report intrinsically dual-emissive carbon dots (De-CDs) whose two excitation windows partition complementary sensing functions. Under 365 nm excitation, Hg2+ quenches the 450 and 680 nm emissions and clothianidin restores them, enabling sequential on-off-on determination by ratiometric fluorescence and a complementary UV−Vis response at 441 nm. The fluorescence channel quantified Hg2+ over 0.0116−12 μmol L−1 (LOD = 0.0116 μmol L−1), while clothianidin showed piecewise calibration up to 45 μmol L−1 (LOD = 0.0031 μmol L−1); UV−Vis LODs were 0.0095 and 0.0010 μmol L−1. The dual-channel design enables simultaneous utilization of fluorescent and UV wavelengths, thereby reducing interference and enhancing selectivity during detection. Under 420 nm excitation, a red-emission redistribution quantified Zn2+ over 0.0157−3.5 μmol L−1 (LOD = 0.0157 μmol L−1) and provided a zineb calibration over 0.0102−9 μmol L−1 (LOD = 0.0102 μmol L−1). Hg2+ forms ground-state complexes causing fluorescence quenching, and clothianidin competitively displaces Hg2+ to restore fluorescence (“On-Off-On”). In contrast, Zn2+ induces chelation-enhanced fluorescence by restricting intramolecular motion and suppressing non-radiative decay. Measurements in soil, river water, and fruit agreed with ICP-AES, LC−MS, or GC. Excitation-dependent responses were further demonstrated in HepG2 cells, zebrafish, mice, and rice seedlings. This carbon-dot scaffold separates sensing tasks by excitation wavelength and integrates complementary readouts with multiscale imaging. This multifunctional platform integrates environmental, common foods monitoring and bioimaging for synchronous analysis of multiple pollutants.