Wireless Zinc Oxide Based pH Sensor System

In this study, prior to the growth of ZnO nanorods (NRs), a 100 nm-thick ZnO seed layer was deposited by RF magnetron sputtering on a glass substrate. Subsequently, ZnO NRs were grown on ZnO seed layers via the hydrothermal method at 90°C for 6 h and annealing at 400°C. By using a Pt electrode as reference electrode, the potentiometric method was used to measure the potential difference between the two ends, and an operation amplifier (OPA) was employed as the readout circuit. The sensor and reference electrode were placed in a buffer solution of different pH values (4, 6, 8, and 10) for potentiometric analysis. Results showed that the average sensitivity of the ZnO NR sensor was ∼4.4 × 10−2 V/pH, and linearity was ∼0.98. The Arduino Uno was used to collect data, and the XBee module was utilized for wireless transmission. The computer side used the C# program to present the user interface, display the measurement results, and realize a wireless sensing network.