Peroxidase mimetic activity of porphyrin modified ZnFe2O4/reduced graphene oxide and its application for colorimetric detection of H2O2 and glutathione

Artificial nanoenzymes which can overcome some drawbacks of natural enzymes is a challenging topic in the biosensor field. Herein, we demonstrated 5, 10, 15, 20-tetrakis (4-carboxylpheyl)-porphyrin modified magnetic ZnFe 2 O 4 nanoparticles loaded on the surface of reduced graphene oxide (Por-ZnFe 2 O 4 /rGO), which exhibited intrinsic peroxidase-like activity and rapidly oxidized the peroxidase substrate 3, 3′, 5, 5′-tetramethylbenzidine (TMB) into a blue product (OxTMB) distinguished by naked eyes. Interestingly, by comparative study of different nanomaterials ZnFe 2 O 4 nanoparticles, ZnFe 2 O 4 /rGO and Por-ZnFe 2 O 4 , Por-ZnFe 2 O 4 /rGO was proved to possess the highest peroxidase-like activity. Electron spin resonance (ESR) verified the catalytic activity of Por-ZnFe 2 O 4 /rGO for H 2 O 2 was due to hydroxyl radical from decomposition of H 2 O 2 . Temperature and pH strongly affected the peroxidase-like activity of Por-ZnFe 2 O 4 /rGO nanocomposites. Under optimal conditions (pH = 4, 40 °C), the constructed sensor based on the catalytic activity of the Por-ZnFe 2 O 4 /rGO could be conveniently used for colorimetric detection of H 2 O 2 in the range of 0.7–30 μM with the detection limit of 0.54 μM. Moreover, the colorimetric sensor based on Por-ZnFe 2 O 4 /rGO exhibited a good linear response to glutathione (GHS) in the range of 2–40 μM with a low detection limit of 0.76 μM. The detection of GHS can be easily realized through the obvious color change by naked eyes without any complicated instrumentation.