Investigation of tin oxides as sensing layers in conductimetric interdigitated pH sensors

Due to the increasing demand for accurate, reliable and highly sensitive pH sensors, research is ongoing to find new materials and methods to achieve this goal. An approach that shows promise in the pH-sensing field is the conductimetric pH sensor. It has the advantage of simpler construction over its potentiometric counterpart and may prove less expensive in mass production. It also meets the criteria for possible future miniaturization.This work attempts to qualify tin oxides (SnO and SnO2) as sensing materials in conductimetric interdigitated pH sensors. Both materials are tested over a range of frequencies that cover all major operating areas of the devices. Sensors are subjected to testing with pH buffers in the range pH 2–11, and all changes in their electrical parameters are recorded.It was found that SnO and SnO2 operated at low frequencies produces the best response to pH change. Tests produced a notable increase in conductance for both materials, and the magnitude of the increase in conductance is directly related to the pH of the test solution.No meaningful relationship was observed for either material at higher frequencies.