Rational design of a o-phosphoethanolamine-functionalized sheet-like nanozyme enables target-induced crosslinking for sensing Cr3+

Background Trivalent chromium (Cr 3+ ), a relatively environmentally benign and biologically beneficial species of chromium, is widely applied in manufacturing processes as well as in the food and healthcare industries. Exploring a convenient, dependable, and sensitive method for Cr 3+ monitoring becomes practically important for ensuring environmental health and food safety. Results In this study, a o -phosphoethanolamine-functionalized, sheet-like manganese-based nanozyme (OPA@MnT) with excellent oxidase-like activity was designed for sensitive and selective Cr 3+ sensing based on target-induced nanozyme crosslinking. The OPA functional group and nanosheet structure enable specific coordination with Cr 3+ via nitrogen and oxygen donors, triggering aggregation of OPA@MnT and a reduction in active oxygen vacancies, both of which effectively suppress its catalytic activity. Based on this mechanism, a facile colorimetric sensing strategy was established, exhibiting a wide linear detection range (0.25–10 μM), a low detection limit (0.15 μM), and selectivity against potential interfering species. The method was successfully applied to environmental water and dietary supplement samples, showing good agreement with standard ICP-MS measurements. Significance Our work provides a simple, sensitive, and reliable strategy for Cr 3+ monitoring with promising applications in environmental analysis and food safety assessment. Moreover, the elucidated interaction mechanism between metal ions and nanozymes offers valuable insights for the rational design of nanozyme-based sensing platforms for broader analytical applications.