Carbon Dots Dually Doped with Fe and Co for Visual Detection of H₂O₂ and Glutathione

Hydrogen peroxide (H 2 O 2 ) and glutathione (GSH) have been reported to be associated with a variety of diseases. Therefore, the accurate and rapid determination of H 2 O 2 and GSH was very important. The traditional assay was the colorimetric method, which suffered from the bottleneck of single-mode analysis. In this work, we designed a dual-mode fluorescence and colorimetric sensor for detecting H 2 O 2 and GSH based on bifunctional Fe, Co-CDs, which possessed peroxidase (POD)-mimetic activity and fluorescence property. Concretely, the Fe, Co-CDs catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product (oxTMB) with the help of H 2 O 2, which could be inhibited by GSH. Meanwhile, the fluorescence of Fe, Co-CDs weakened with increasing oxTMB, realizing the fluorescence analysis of H 2 O 2 and GSH. In fluorescence and colorimetric sensors, the detection limit (LOD) of H 2 O 2 could reach as low as 0.54 μM and 0.81 μM, as well as the LOD of GSH was 0.39 and 0.61 μM, respectively. Besides, the smartphone-assisted hydrogel sensor was developed for on-site detection of GSH via color change. This study not only designed a dual-mode sensor for dual-target detection but also provided insights for further exploration of multifunctional nanozymes.