Effects of morphology of nanostructured ZnO on direct electrochemistry and biosensing properties of glucose oxidase

An amperometric glucose biosensor based on the direct electron transfer (DET) of glucose oxidase (GOx) was developed and the enhanced catalytic current in presence of substrate was used to quantify glucose. GOx was adsorbed onto nanostructured ZnO modified indium tin oxide (ITO) electrodes. The goal of this work was to study the effects of morphology of nanostructured ZnO on DET of GOx and the sensor’s analytical properties. Nanostructured ZnO materials including nanorods (NRs) and nanoplates (NPs) were electrochemical deposited onto ITO and were characterized using scanning electron microscopy and X-ray diffraction. Through adjusting the precursor of Zn ions, electrolytes and controlling deposition charge (Q, in Coulomb, C), different nanostructured ZnO with different size, shape and deposition density were obtained. GOx was adsorbed onto nanostructured ZnO via layer-by-layer assembling to form GOx and polylectrolyte multilayer films. Compared to bare ITO or ITO deposited with nanostructured ZnO with other morphologies, GOx immobilized onto ZnO NRs arrays (Q = 0.1 C) gave higher current signals, exhibited reversible DET (ks, 2.16 s−1), wide linear range (from 0.1 to 9 mM) with the limit of detection of 1.94 μM and low apparent Michaelis–Menten constant (KMapp, 3.12 mM).