Electrochemical interdigitated conductimetric ph sensor based on RuO2 thick film sensitive layer

Metal oxide based electrochemical pH sensors are an alternative to the glass pH sensor, exhibiting many potential advantages in industrial and laboratory applications. In particular, thick film based pH sensors are promising devices for a next generation of wireless sensors for online monitoring of water pollution. So far, there have been many solid state materials used for pH sensor fabrication, among which RuO₂ based sensitive material stands out due to its excellent sensitivity and high accuracy. In potentiometric measurements, the RuO₂ based pH sensor exhibited excellent sensing performance with sensitivity close to the theoretical Nernstian value. In this work, an interdigitated conductimetric pH sensor based on RuO₂ sensitive layer was fabricated by screen printing technology on an alumina substrate. The RuO₂ sensitive layer was deposited on the top of the interdigitated Ag electrode. The impedance spectroscopic studies carried out in the frequency range of 10 mHz - 2 MHz revealed a decrease in the sensor resistance when it was exposed to the test solutions with increasing pH value. The relative change in conductance was found to be almost linear function of pH in the range of 3-11 at 1 kHz. The conductimetric pH sensors can be used for fabrication of low cost miniaturized sensors based on monitoring of the variation of electrical parameters as a function of pH of test solutions.