Cobalt oxyhydroxide nanoflakes with intrinsic peroxidase catalytic activity and their application to serum glucose detection.

Cobalt oxyhydroxide (CoOOH) nanoflakes, an emerging type of two-dimensional nanomaterial, show great potential for use in molecular detection. Previous assays utilizing such materials have largely been based on their outstanding fluorescence quenching ability and oxidizing power. Herein, we report the intrinsic peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanoflakes, and we show how this activity can be employed for glucose detection. We found that, in the presence of hydrogen peroxide (H2O2), the nanoflakes accelerated the conversion of peroxidase substrates such as 3,3',5,5'-tetramethylbenzidine (TMB) into colored products. By combining the CoOOH nanoflakes with the biological enzyme glucose oxidase (GOx), we developed a colorimetric method for the detection of glucose within the concentration range 5.3-500 μM. The proposed method was applied to detect elevated blood glucose levels in diabetic patients, and the intense color change induced by elevated glucose levels was found to be readily apparent to the naked eye, proving the utility of our assay for point-of-care testing. Graphical abstract The intrinsic peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanoflakes was exploited to enable the direct visualization of elevated glucose levels in sera from diabetic patients.