Hollow FeNi Prussian blue nanocages with enhanced peroxidase-mimicking activity for colorimetric detection of mercury ions and L-cysteine

Despite extensive research into nanozymes, developing highly active catalysts with broad application potential remains a significant challenge. In this study, we synthesized hollow FeNi Prussian blue analog (H-FeNi PBA) nanocages through a straightforward chemical etching method, using FeNi PBA nanocubes as precursors. The resulting H-FeNi PBA nanocages exhibited enhanced peroxidase-mimetic activity, attributed to their increased specific surface area, pore volume, and Fe 2+ content. Leveraging this activity, we developed a novel colorimetric sensing platform for the detection of mercury ions (Hg 2+ ) and L-cysteine (Cys). The platform operates based on the peroxidase-mimetic activity of H-FeNi PBA nanocages, the inhibitory effect of Cys on this activity, and the restoration of activity through the specific complexation between Cys and Hg 2+ . After optimization, the platform demonstrated wide linear detection ranges (0.1–42 μM for Hg 2+ and 1–64 μM for Cys) and low detection limits (0.035 μM for Hg 2+ and 0.24 μM for Cys). The method was successfully applied to detect Hg 2+ and Cys in real samples, showcasing its potential for environmental monitoring and biomedical applications. This work not only provides a simple strategy for synthesizing highly active nanozymes but also highlights their potential in biosensing and catalysis.