Iron-doped carbon dot nanozymes with fluorescence and enzyme-like activity as dual-mode sensor for the detection of tetracycline.

Carbon dot nanozymes (CDNEs) hold great potential for constructing multi-modal analysis system, yet their practical applications remain constrained by the poor tunability of fluorescence and catalytic activity. In this study, we developed a novel CDNEs with good blue fluorescence and enzyme-like characteristic by directly doping iron ions during the synthesis of carbon dots. The partial reduction of Fe(III) to Fe(II) during the reaction and their coordination via FeO or FeN bonds endowed the CDNEs with high enzyme-like activity, which efficiently catalyzes the generation of reactive oxygen species (ROS) from HO. Based on the effects of tetracycline (TC) on the fluorescence signal and enzymatic activity of CDNEs, a dual-mode analysis system of TC utilizing both fluorescence and absorption was constructed. The proposed spectral-response method possess high sensitivity and selectivity, and the limit of detection can reach 20 nM. Moreover, a scanometric analysis mode also was developed based on the visually observable color change, which was suitable for the rapid on-site and high throughput detection of TC in real water samples with the recoveries of 90.2%-108.6%. This study offers a potent strategy for monitoring antibiotic pollution and facilitate the application of functionalized CDNEs in environmental and biomedical fields.