On-chip electrochemical detection of dissolved oxygen: Eliminating the requirement for a permeable selective membrane

Membrane-free electrochemical dissolved oxygen sensors were developed using micro interdigitated electrode arrays. The optimised sensor for detection of dissolved oxygen should contain a gold generator electrode to produce hydrogen peroxide, and a platinum collector electrode for the subsequent detection. The microfabrication process required platinum electrodeposition onto one comb of a gold interdigitated array. The deposition also decreased the inter-electrode gap and increased the collection efficiency. The dual metal IDE was then used to sense dissolved oxygen in water. A pre-treatment step was also required to improve the sensitivity of platinum to hydrogen peroxide ensuring a clean, reproducible surface for each test. The developed sensor accurately detected oxygen concentrations between 0 and 9 ppm, with a sensitivity of 1.59 nA/ppm and an LOD of 0.36 ppm. The detection of oxygen was also tested in the presence of unknown interferents, in estuarine river water, and with known interferents. It was found that the magnitude of hydrogen peroxide oxidation was generally unaffected by the presence of interferents, indicating a potential for interferent free oxygen detection without the requirement of oxygen permeable membranes.