Morphology and sensing characteristics of nanostructured RuO2 electrodes for integrated water quality monitoring sensors

Nanostructured RuO2 sensing electrodes (SE) for water quality sensors were prepared on platinized alumina substrates. Their morphology was analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results show that morphology and surface compositions of RuO2-SEs are sensitive to superoxide oxygen ions (O2-). Sensing properties of RuO2-SEs were investigated for potentiometric detection of dissolved oxygen and pH at temperatures from 9 to 30 °C. Sensor was capable to measure dissolved oxygen from 0.6 to 8.0 ppm and from 2 to 13 pH, respectively. The measurement results show very good linearity and an excellent reproducibility was obtained. Nernstian slope was 58 mV/pH at 23 °C for the RuO2-SEs. Although RuO2 film SEs have shown very good response time to the pH changes, which was within 1–2 s at temperature 23 °C, as water temperature cooled down, the sensor response time increased and was about 8–10 min at a temperature of 9 °C.