Integrated pH and Sodium Sensor Array Based on Iridium Oxide Film

We have developed a sensor array consisting of an iridium oxide (IrO x ) electrode for pH measurement, an iridium oxide based ion-selective sensor for sodium detection, and two silver chloride (AgCl) reference electrodes. The planar sensor array was fabricated on a flexible substrate with simple fabrication processes. The iridium oxide sensing film was synthesized by the sol-gel process. The sodium sensor was fabricated by deposition of a sodium-selective membrane on the iridium oxide film. The silver chloride reference electrodes were made by printing. The sensor array was tested in standard pH buffer solutions with or without the existence of sodium. In both scenarios, a promising sensitivity of 61.46 mV/pH in the pH ranges from acid to alkaline at the room temperature was achieved. The potential increases induced by the sodium interference were calibrated by the sodium sensor. The calibrated results show excellent pH responses with minimum interference. The pH and sodium sensor array demonstrates a unique capability to provide accurate pH detection in the environment containing sodium interference.