Engineering "three-in-one" fluorescent nanozyme of Ce-Au NCs for on-site visual detection of Hg²

Hg²⁺ contamination poses a serious threat to the environment and human health. Although gold nanoclusters (Au NCs) have been utilized as fluorescence probes or colorimetric nanozymes for performing Hg²⁺ assays by using a single method, designing multifunctional nanoclusters as fluorescent nanozyme remains challenging. Herein, Ce-aggregated gold nanoclusters (Ce-Au NCs) were reported with "three in one" functions to generate strong fluorescence, excellent peroxidase-like activity, and the highly specific recognition of Hg²⁺ via its metallophilic interaction. A portable fluorescence and colorimetric dual-mode sensing device based on Ce-Au NCs was developed for on-site visual analysis of Hg²⁺. In the presence of Hg²⁺, fluorescence was effectively quenched and the paper-based chips gradually darkened from green till they became completely absent, while peroxidase-like activity was significantly enhanced. Two independent signals were captured by one identification unit, which provided self-validation to improve reliability and accuracy. Therefore, this work presents a simple synthesis of a multifunctional fluorescent nanozyme, and the developed portable device for on-site visual detection has considerable potential for application in the rapid on-site analysis of heavy metal ions in the environment.