Hydrogen Peroxide Detection at Electrochemically and Sol‐Gel Derived Ir Oxide Films

Ir oxide (IrOx) films, formed electrochemically on bulk Ir metal (Ir/IrOx) and also on sol‐gel (SG) derived non‐silica based nanoparticulate Ir, have been studied as material useful for the detection of hydrogen peroxide, with possible application as a glucose biosensor. H₂O₂ reduction and oxidation on Ir/IrOx and SG‐derived IrOx films, deposited on various substrates such as Pt, Ir and GC, have been compared to the H₂O₂ behavior at the bare substrate. It was found that H₂O₂ reduction proceeds on the underlying electrode substrate, while H₂O₂ oxidation is independent of the nature of the substrate, therefore occurring via the IrOx film. The reactivity of IrOx towards H₂O₂ oxidation is similar to that seen at Pt, although IrOx has the additional advantages of excellent stability, insensitivity to common interfering substances, biocompatibility and a linear range of detection, up to at least 12 mM H₂O_2. At micromolar concentrations of H₂O₂, a second mode of detection, involving the catalyzed growth of IrOx films at Ir substrates, can be employed. These two methods of H₂O₂ analysis (oxidation/reduction and enhanced IrOx growth) can also be employed for glucose detection using IrOx‐based glucose biosensors.