Nanozyme Rich in Oxygen Vacancies Derived from Mn-Based Metal–Organic Gel for the Determination of Alkaline Phosphatase

Vacancy engineering as an effective strategy has been widely employed to regulate the enzyme–mimic activity of nanomaterials by adjusting the surface, electronic structure, and creating more active sites. Herein, we purposed a facile and simple method to acquire transition metal manganese oxide rich in oxygen vacancies (OVs-Mn2O3-400) by pyrolyzing the precursor of the Mn(II)-based metal–organic gel directly. The as-prepared OVs-Mn2O3-400 exhibited superior oxidase-like activity as oxygen vacancies participated in the generation of O2•–. Besides, steady state kinetic constant (Km) and catalytic kinetic constant (Ea) suggested that OVs-Mn2O3-400 had a stronger affinity toward 3,3′,5,5′-tetramethylbenzidine and possessed prominent catalytic performance. By taking 2-phospho-l-ascorbic acid as the substrate, which can be converted into reducing substance ascorbic acid in the presence of alkaline phosphatase (ALP), OVs-Mn2O3-400 can be applied as an efficient nanozyme for ALP colorimetric analysis without the help of destructive H2O2. The colorimetric sensor established by OVs-Mn2O3-400 for ALP detection showed a good linearity from 0.1 to 12 U/L and a lower limit of detection of 0.054 U/L. Our work paves the way for designing enhanced enzyme-like activity nanozymes, which is of significance in biosensing.