Defect-rich CeO _{2− x} nanosheets as efficient oxidase nanozymes for colorimetric Hg ²⁺

Defective, oxygen vacancy-rich CeO _{2− x} nanosheets were prepared. CeO _{2− x} nanosheets exhibit superior oxidase-mimic activity, enabling oxidant-free oxidation of chromogenic substrates. The material was successfully applied for highly sensitive naked-eye Hg ²⁺ detection and dye degradation.