Highly-Sensitive Nanostructured Sensor System Based on RuO Sensing Electrode for Water Quality Monitoring

Abstract

Sensor system based on nanostructured RuO sensing electrode (SE) was fabricated and examined for pH and dissolved oxygen (DO) detection in water at a temperature range of 9-35°C. The electromotive force (emf) response at these temperatures was linear to the logarithm of pH (from 2.0 to 13.0 pH) and DO concentrations in the range from 0.6 to 8.0 ppm (log[O2], -4.71 to -3.59) at a neutral pH. In was also found that the response/recovery time of the sensor to DO changes is sluggish as the water temperature cools down. Sensor response time, T90, to the different DO increased from 8 min at a temperature of 23°C to about 30 min at a temperature of 9°C. The slope was -41 mV per decade for the RuO -SE at 8.0 pH and it was closely followed the Nernst equation. However, it was found that in strong alkaline solutions sensor emf is a mixed-potential of fast and slow electrochemical reactions involving O2 -, RuO4 2- and OH- ions. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX) and impedance spectroscopy techniques were used to examine the morphology, crystalline structure and electrochemical behaviour of the nanostructured RuO -SEs, respectively. Characterization analysis revealed that RuO2-SE consist of RuO2 nano-particles in the range of 100-650 nm homogeneously distributed across SE. Keywords: nanostructures, potentiometric sensors, ruthenium oxide, dissolved oxygen, pH