The peroxidase and oxidase-like activity of NiCo2O4 mesoporous spheres: Mechanistic understanding and colorimetric biosensing

•NiCo2O4 MS were found to possess the peroxidase and oxidase-like activity.•The peroxidase-like activity of NiCo2O4 MS was stemmed from not only ·OH but also 1O2.•The oxidase-like activity may stem from NiCo2O4 MS′ oxidation rather than ·OH and 1O2.•A colorimetric detection tool is designed for glucose determination in serum samples.

The synthesized NiCo2O4 mesoporous spheres (MS) displayed intrinsic peroxidase and oxidase-like activity were firstly reported. The catalytic mechanism of the oxidase-like activity of NiCo2O4 MS was analyzed in detail using the electron spin resonance (ESR) method. It is found that NiCo2O4 MS could directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) but did not produce 1O2 and ·OH. And the mechanism of the peroxidase-like activity of NiCo2O4 MS was also verified that the oxidation of TMB stemmed from not only ·OH but also 1O2. Based on the NiCo2O4 MS showed excellent peroxidase-like activity over a broad temperature range, especially at normal body temperature, a detection tool was designed for glucose determination in diabetics' serum samples. And this detection method based on NiCo2O4 MS gave a lower limit of detection than the method using Co3O4 NPs and NiO NPs, as the single-component oxides of NiCo2O4. Our study may open up the possibility to make a great influence on the next generation of enzyme mimetics system.

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