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

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 mu A mM(-1) cm(-2) as well as a wide linear range of 1-780 mu M. 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