A Flexible Ruthenium Oxide Electrodeposited SPCE Sensor for Stable Detection of Wide-Range pH Enhanced by Annealing

A low-cost flexible miniaturized pH sensor was developed by cyclic-voltammetry (CV) electrodeposition of ruthenium oxide (RUO
2
) on the surface of screen-printed carbon electrode (SPCE) on PET substrate. By using a post atmospheric anneal treatment at a low temperature of 90°C for 30 mins, the prepared sensor could detect a wide-range pH with stable potential responses. The measured open-circuit potential (OCP) results demonstrated that the good linear pH range was from 3 to 13 with a sensitivity of 51.17 mV/pH. The morphologies, composition and capacitance of modified SPCEs were characterized with SEM, XRD and electrochemical tests. For on-site fast determination of analyte pH, a smartphone-based analyzer was developed by using a mini potentiostat IC chip.