Heteroatom-doped Co-MOF derivative enhancing immobilization and activity of two enzymes for small-molecules electrochemical determination

The enzyme immobilization and catalytic properties of metal-oxide framework (MOF) derivatives can be complemented by the synergistic effects associated with the doping of heteroatoms. Herein, the MOF derivative Ni-doped Co/CoO/NC was prepared under nitrogen by pyrolysis of bimetallic Ni-Co-Zeolitic Imidazolate Framework (ZIF). The introduction of defect sites in the cobalt oxide structure by nickel and the strong metal electron synergistic effect improved the conductivity of prepared composite. Afterward, myoglobin (Mb) and acetylcholinesterase (AChE) were immobilized respectively on carbon paste electrode (CPE) modified by Ni-doped Co/CoO/NC and conductive film to construct electrochemical sensors. The electrochemical behavior of small molecules including hydrogen peroxide (H2O2), nitrite (NO2–) and organophosphate pesticides (OPs) was investigated via various electrochemical methods. Constructed H2O2 and NO2– sensors have good linearity in the range of 4 × 10−6-1.5 × 10−3 M and 8 × 10−7-1.05 × 10−3 M, 1.05 × 10−3-2.05 × 10−3 M with limits of detection of 1.5 × 10−6 M and 3.0 × 10−7 M, respectively. The linear range of the OPs sensors was 5.0 × 10−12-5.0 × 10−8 g.m−1 for methyl parathion and 1.0 × 10−13-1.0 × 10−10 g.mL−1 for paraoxon, respectively. And detection limits are 1.8 × 10−12 g.mL−1 (S/N = 3) for methyl parathion and 4.6 × 10−14 g.mL−1 for paraoxon. By extension, heteroatom-doped MOF derivatives offer potential new function as electrode modifier for biosensors.