Graphite nanosheet-based composites for mediator-free H2O2 biosensor

Abstract

Graphite nanosheet (GNS)–Nafion composites were prepared for the immobilization of hemoglobin (Hb) to construct a mediator-free H₂O₂ biosensor. Scanning electron microscopy (SEM), UV-vis spectroscopy and Fourier transform infrared spectroscopy were used to characterize the Hb–GNS–Nafion composite film. Due to good biocompatibility of the composite film, immobilized Hb retained its native structure. The Hb–GNS–Nafion composite film-modified electrodes showed direct electrochemistry with a fast electron-transfer rate (6.63 s⁻¹) and high electrocatalytic activity to the reduction of hydrogen peroxide (H₂O₂). The resulting biosensor exhibited a high sensitivity of 412.7 mA M⁻¹ cm⁻², a low detection limit of 2.0 × 10⁻⁷ M, and a small apparent Michaelis–Menten constant of 37 µM. These results were comparable or superior to the biosensors based on the carbon nanofiber (CNF)- and carbon nanotube (CNT)-based biosensors. Due to the lower cost of GNSs, the GNS-based composite can combine with other redox proteins and widely apply in mediator-free biosensors, bioelectronics and biofuel cells.