TiO2-Based Thick Film pH Sensor

Miniaturized electrochemical pH sensors are increasingly in demand for applications such as online monitoring of water quality and health monitoring. The metal oxides are the best candidates for sensing electrodes of such sensors as they offer high chemical stability. In this paper, we present a novel approach to obtain interdigitated conductimetric pH sensor using screen printing of TiO2 thick film on an alumina substrate. The microstructural and crystalline properties of the TiO2 sensitive film were examined with scanning electron microscopy and Raman spectroscopy. The impedance spectroscopic studies of the fabricated thick film sensor were carried out in the frequency range of 5-20 kHz for the test solutions in the pH range of 4-10 and it was observed that the impedance of the film is distinctly dependent on pH. Using the measured impedance data, we have also proposed an equivalent RC network model for the fabricated pH sensor. The physical meaning of the model parameters was determined by electrochemical impedance spectroscopic analysis, and through statistical analysis it was found that all parameters are distinctly pH-dependent.