Fabrication of integrated solid state electrode for extended gate-FET pH sensor

To realize the miniaturization of an extended gate field effect transistor (EGFET) based sensor, an all solid state phase electrodes are needed. This paper presents the facile fabrication of an integrated solid state electrode (ISSE) consisting a solid state silver/silver chloride (Ag/AgCl) reference electrode (RE) and ZnO nanostructures sensing electrode (SE) on a single 2 × 2 cm² indium tin oxide (ITO) substrate. The RE and SE was fabricated by thermal evaporation (TE) and simple immersion process respectively. The ISSE was then tested by applying it to an EGFET pH sensor setup and compared with commercialized Ag/AgCl RE; and it was found that the sensor sensitivity for both electrodes are comparable (commercial RE: 52.4 mV pH⁻¹, ISSE: 53.4 mV pH⁻¹). (paper)