An amperometric glucose biosensor based on the immobilization of glucose oxidase on the ZnO nanotubes

A glucose biosensor is fabricated with immobilization of glucose oxidase onto ZnO nanotube arrays by cross-linking method. The ZnO nanotube arrays are synthesized by chemical etching of ZnO nanorods that are electrochemically deposited on the Au surface. Morphology and structure of ZnO nanotubes are characterized by FESEM, HRTEM and XRD. Fourier-transform infrared spectroscopy reveals that the glucose oxidase immobilized on the ZnO nanotubes retains its native conformation. The biosensor has a wide linear range for the detection of glucose from 50 μM to 12 mM (a correlation coefficient of 0.998) with 3 s response time. The sensitivity of the biosensor is found to be 21.7 μA/mM cm2. Moreover, its experimental detection limit is 1 μM (S/N = 3) and the apparent Michaelis–Menten constant is calculated to be 19 mM. The anti-interference ability and long-term stability of the biosensor are also assessed. Compared with the biosensors based on the nanorod and flat structure, the proposed biosensor shows expanded linear range and sensitivity. All these results demonstrate that ZnO nanotube can provide a promising material for the biosensor designs and other biological applications.