Channel Effect Enhancing Hg ²⁺ Adsorption to Modulate d ‐Orbitals of the Active Centers for Regulating Enzymatic Activity

Nanozymes have shown great promise in detecting heavy metal pollution (specifically Hg 2+ ), while their development and application are usually hindered by vague catalytic mechanism. Herein, NiCo 2 O 4 nanosheets supported Pd nano (Pd@NiCo 2 O 4 ) with controllable morphologies were constructed by a surfactant‐oriented strategy. Taking advantage of the anionic property of sodium dodecyl sulfonate (SDS), the surface of SDS‐NiCO 2 O 4 nanosheets ( S ‐NiCo 2 O 4 ) exhibits channel features. Compared with the CTAB‐directed Pd@NiCo 2 O 4 ( C ‐Pd@NiCo 2 O 4 ), the channel effect of S ‐Pd@NiCo 2 O 4 can more easily adsorb catalysed substrates (TMB), resulting in a red shift of the absorbance. This can switch the enzymatic activity from bifunctional performance (OXD and POD) to monofunctional activity (OXD). Significantly, the channel effect of S ‐Pd@NiCo 2 O 4 enhances the adsorption of Hg 2+ , which suppresses the formation of Pd‐Hg alloy and promotes the formation of HgO. The formation of Pd–Hg alloy in C ‐Pd@NiCo 2 O 4 , enhances enzymatic activity by facilitating electron transfer through d – d orbital interactions. In contrast, the Hg–O interaction can modulate the d ‐band structure of S ‐Pd@NiCo 2 O 4 to reduce its enzymatic activity. Therefore, the S ‐Pd@NiCo 2 O 4 can overcome negative effects (high endogenous H 2 O 2 disturbing the fluorescence signal of C ‐Pd@NiCo 2 O 4 for Hg 2+ detection) of complex TME to visually detect Hg 2+ in cancer cells.