Temperature-controlled chemical bath deposition of iridium oxide via pre-coordinated hexahydroxyiridate (III) complexes for high-sensitivity pH sensing

We developed an aqueous solution-based approach to deposit iridium oxide thin films on transparent and flexible substrates, including indium tin oxide (ITO) glass and mica, for pH sensing applications. Building on our earlier work employing chemical bath deposition (CBD), we addressed the challenges of achieving reproducible deposition rates using a consistent iridium precursor. In this study, we refined the CBD process by introducing a pre-coordination step and implementing precise temperature control, resulting in significantly improved film quality and process stability. The optimized iridium oxide films demonstrated a high charge storage capacity of 32.4 mC/cm² and a superior pH sensitivity of 79.4 ± 2.3 mV/pH. Moreover, the films maintained excellent electrochemical stability and mechanical integrity after 10,000 bending cycles, without observable cracking or delamination. These findings underscore the potential of chemically deposited iridium oxide films as robust, flexible platforms for biomedical pH sensing applications.