PERFORMANCE OF pH SENSOR ELECTRODE BASED ON ZnO NRs ON FTO-GLASS SUBSTRATE

In this work, ZnO nanorods (ZnO NRs) were successfully synthesized on FTO-glass via hydrothermal technique. Two steps were followed to grow ZnO NRs. In the first step, the seed layer of ZnO nanocrystals was deposited by using a drop cast method. The second step was represented by the hydrothermal growth of ZnO NRs on a pre-coated FTO-glass with the seed layer. The hydrothermal growth was conducted at 90 degrees C for 2 h. The resulted structure, morphology and optical properties of the produced layers were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) and UV-visible spectrophotometer, respectively. The analysis confirmed that the ZnO NRs grown by the hydrothermal method have a hexagonal crystal structure which was grown randomly on the FTO surface. The crystallite size was recorded 50 nm and a slight microstrain (0.142%) was calculated. The bandgap was found to be in the range of 3.14-3.17 eV. The ZnO NRs have a high density and large aspect ratio. A pH sensor with high sensitivity was fabricated using a two-electrode cell configuration. The ZnO NRs sensor showed the sensitivity of -59.03 mV/pH, which is quite promising and close to the theoretical value (-59.12 mV/pH).