Highly sensitive hydrogen peroxide biosensors based on TiO2 nanodots/ITO electrodes

Abstract

Uniformly dispersed and size-controllable TiO₂ nanodots (TN) were directly synthesized on indium-tin-oxide (ITO) electrodes and were further utilized to immobilize horseradish peroxidase (HRP) enzyme and facilitate direct electron transfer for construction of a hydrogen peroxide (H₂O₂) biosensor. The enzyme adsorption ability of TN/ITO electrodes were investigated using a UV–vis spectrometer, and the results indicated that TiO₂ nanodots possess better enzyme adsorption ability than TiO₂ film, and this ability could be further improved by varying the mean diameter of the nanodots from 30 nm to 79 nm. The sensitivity of the H₂O₂ biosensors based on Nafion/HRP/TN/ITO electrodes was significantly increased by adjusting the dimension of TiO₂ nanodots on the modified electrode and the sensitivity differences among these electrodes are in accord with their enzyme adsorption ability. TiO₂ nanodots with the largest diameter (79 nm) on a ITO electrode had the best enzyme adsorption ability and biosensor performance with a high sensitivity of 1176 μA mM⁻¹ cm⁻² as well as a wide linear range of 1–780 μM. These results show that well-dispersed, high surface area and high curvature TiO₂ nanodots could be a promising material for protein adsorption and fabrication of electrochemical biosensors.