Al3+ Cofactor Evoking Iron Porphyrin-AuNP Hybrids as Oxidase-Mimicking Nanozymes with Prominent Catalytic Efficiency in a Broad pH Range

Nanomaterial-based artificial enzymes (nanozymes) have great potential for boosting their intrinsic activities to narrow the gaps against natural enzymes. Different from natural enzymes, nanozymes usually cannot work efficiently under physiological pH, which limits their application in environmental and biological fields. Here, we proposed that the originally futile tetrakis (4-carboxyphenyl) iron porphyrin (FeTCPP) compounds in the FeII-TCPP-Au nanoparticle (FeII-TCPP-AuNP) hybrid are functionalized to serve as critical active sites involved in cytochrome P450 to greatly boost the oxidase-mimicking activity by an Al3+ cofactor at neutral pH. The microenvironment around FeTCPP can be chemically optimized to provoke the oxidase-mimicking activity with 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate with the help of Al3+. The activity-provoking ability of the system is tunable by changing the concentrations of Al3+, the strong ligand F–, and temperature. Based on this, the selective and sensitive colorimetric sensor of Al3+ based on nanozymes was first developed. The novelty of the present work is not only a new means to develop iron porphyrin nanozymes with superior oxidase-mimicking activity at neutral pH but is also the first example that hard acid Al3+ can serve as a robust and efficient cofactor to synergize the catalytic performance of nanozymes. Therefore, this study provides some enlightenment about the integration of artificial cofactors in biomimetic chemistry and expands the application of nanozymes in environmental fields.