PB@Co3O4 nanoparticles as both oxidase and peroxidase mimics and their application for colorimetric detection of glutathione

Abstract

Co₃O₄-modified Prussian blue (PB) nanocubes (PB@Co₃O₄) were prepared by a simple water-bath method with CoCl₂ as the Co source. TEM, SEM, XRD and XPS results indicated the uniform distribution of island-like spinel-phase Co₃O₄ nanoparticles (NPs) on the surfaces of the PB nanocubes (∼200 nm). The PB@Co₃O₄ NPs exhibited both intrinsic oxidase- and peroxidase-like activities and were observed to rapidly oxidize the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) with or without hydrogen peroxide at acidic pH values. In contrast, PB nanocubes or Co₃O₄ NPs alone could not efficiently oxidize TMB without H₂O₂. The enzyme-like activity of PB@Co₃O₄ NPs was also influenced by the working pH and temperature. Based on the oxidase-like activity of PB@Co₃O₄ NPs, a facile colorimetric biosensor for detection of glutathione was successfully fabricated, and displayed a linear range of 0.1 to 10 μM (R = 0.9740) and limit of detection of 0.021 μM (S/N = 3). These results demonstrate the potential applications of PB@Co₃O₄ NPs in bioanalysis and biodetection.