Research progress and applications of iron-based nanozymes in colorimetric sensing of agricultural pollutants

Natural enzymes are highly valued for their efficient specificity and catalytic activity. However, their poor stability, environmental sensitivity, and costly preparation restrict their practical applications. Nanozymes are nanomaterials with superior catalytic properties that compensate for natural enzyme deficiencies. As one of the earliest developed nanozymes, iron-based nanozymes have diverse morphological structures and different simulated catalytic properties, showing promising potential for agricultural pollutant sensing. Compared with traditional detection methods, the colorimetric method based on nanozymes has the characteristics of simplicity, rapidity, and visualization, which can be used for immediate and rapid on-site detection. In this review, the catalytic types of iron-based nanozymes, such as peroxidase-like, oxidase-like, catalase-like, and superoxide dismutase-like activities, and the corresponding catalytic mechanisms are presented. The classification of iron-based nanozymes based on various structures is then discussed. Furthermore, this review focuses on the current status of iron-based nanozymes for the colorimetric detection of common agricultural pollutants, including heavy metal ions, nonmetal ions, pesticides, and pharmaceutical and personal care products. Finally, the current research status and development direction of iron-based nanozymes in sensing applications are summarized and prospected.