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

ABSTRACT

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.