Electrocatalytic Properties of ZnO Thin Film Based Biosensor for Detection of Uric Acid

A novel uric acid biosensor employing ZnO thin film as matrix is developed using pulsed laser deposition technique. The dependence of electrocatalytic properties of ZnO thin films on the ZnO processing pressure during growth is studied. It has been observed that the growth kinetics of ZnO matrix play a critical role in governing the electron transfer characteristics of ZnO thin film based biosensors. It is found from the cyclic voltammetric measurements that the peak oxidation current of ZnO/ITO/glass electrode increases with a rise in pressure of ambient gas from 1 to 100 mT and is maximum (548 µA) for ZnO thin film based electrode prepared in an oxygen ambient of 100 mT. The variation in peak current with change in processing pressure is attributed to the change in surface properties, which largely depends on the mean free path and kinetic energy of ablated species arriving at the substrate. The optimized ZnO thin film (100 mT) offers high surface coverage (9.74 × 10^–9 mol/cm²) during immobilization of uric acid resulting in a sensitivity of 122 µA/(mM-cm²). In addition, the prepared ZnO based biosensor exhibit high affinity towards detection of uric acid (Km~0.07 mM), low limit of detection (0.01 mM) along a storage stability of more than 20 weeks. Thus, the present work suggests an important role of plume kinetics for the fabrication of ZnO thin film based biosensors.