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

Trivalent chromium (Cr³⁺), 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 Cr³⁺ monitoring becomes practically important for ensuring environmental health and food safety.

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 Cr³⁺ sensing based on target-induced nanozyme crosslinking. The OPA functional group and nanosheet structure enable specific coordination with Cr³⁺ 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.

Our work provides a simple, sensitive, and reliable strategy for Cr³⁺ 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.