Mixed metal oxide films as pH sensing materials.

Abstract  Due to the demand for accurate, reliable and highly sensitive pH sensors, research is being pursued to find novel materials to achieve this goal. Semiconducting metal oxides, such as TiO, SnO and SnO2 and insulating oxides such as Nb2O5 and Bi2O3, and their mixtures in different proportions are being investigated for this purpose. The films of these materials mixtures are used in conjunction with an interdigitated electrode pattern to produce a conductimetric/capacitive pH sensor. The advantages of this approach include straightforward manufacturing, versatility and cost-effectiveness. It was noted that upon contact with a solution, the electrical parameters of the films, such as resistance etc., change. The correlation of these changes with pH values is the basis for the proposed system development. The ultimate goal is to find materials composition, which would have the highest sensitivity towards the pH level of the solutions. It was found that the materials that produced the highest sensitivity either had a long response time or were unstable over a wide pH range. Those exhibiting lower sensitivities were found to be more stable over a wide pH range. All oxide films tested demonstrated a change in electrical parameters upon contact with buffers of known pH value. [ABSTRACT FROM AUTHOR]