Potentiometric solid-state sensor for DO measurement in water using sub-micron Cu(0.4)Ru(3.4)O(7) + RuO(2) sensing electrode

The dissolved oxygen (DO) sensing electrode (SE) concept utilizing sub-micron-sized ruthenium oxide (RuO2), doped with other nanostructured oxides, has been extended to investigate the possibility of employing copper (II) oxide (Cu2O) as a dopant in order to improve sensor's characteristics and meet long term antifouling needs for SEs. In this work, a thin-film SE made of RuO2 was constructed on the alumina sensor substrate, and a range of dopants and their concentrations was added to it in order to optimize SE properties. The Cu2O-doped RuO2 SE had shown a linear response to DO between 0.5 and 8.0ppm at various temperatures, with two sensitivity maxima of 47.4 and 46.0mV per decade for Cu2O concentrations of 10 and 20 mol%, respectively. The maximum sensitivity for Cu0.4Ru3.4O7 +RuO2-SE was obtained at a dopant concentration of 10%. Selectivity measurements revealed that the presence of Ca2+, Mg2+, Li+, Na+, NO3-, PO4 3-, SO4 2-, F-, K+ and Cl- in the solution had no significant effect on the sensor's emf. The sensor allows overcoming the problem of an insufficient selectivity of semiconductor-based water sensors. It was also found that the doping of RuO2-SE by Cu2O allowed it to function at full capacity in a natural outdoor water body with no obvious effects of biofouling.