Graphite nanosheet-based composites for mediator-free H2O2 biosensor

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 x 10(-7) M, and a small apparent Michaelis-Menten constant of 37 mu M. 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.