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-Mn 2 O 3 -400) by pyrolyzing the precursor of the Mn(II)-based metal-organic gel directly. The as-prepared OVs-Mn 2 O 3 -400 exhibited superior oxidase-like activity as oxygen vacancies participated in the generation of O 2 •- . Besides, steady state kinetic constant ( K m ) and catalytic kinetic constant ( E a ) suggested that OVs-Mn 2 O 3 -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-Mn 2 O 3 -400 can be applied as an efficient nanozyme for ALP colorimetric analysis without the help of destructive H 2 O 2 . The colorimetric sensor established by OVs-Mn 2 O 3 -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.