In this study, the hydrothermal method was used for growing and characterizations of Titanium Dioxide (TiO2) nanorods on the Fluorine-doped Tin Oxide (FTO) coated glass substrate at some different preparation conditions of the hydrothermal process at a constant reaction time. The hydrothermal growth temperature, precursor solution of Titanium Tetra Chloride (TiCl4), hydrochloric acid (HCl) concentration, and annealing temperature effect on the growth characteristics of TiO2 nanorods synthesized over a 6-hour reaction time were studied. The effect of acidity (HCl concentrations) of grew TiO2 nanorods structure on FTO substrate is optimized, resulting in a well-aligned vertical array of nano-parallelepiped and flowerlike shape.
The crystal structures, morphology, chemical composition, and the size distribution of the prepared TiO2 nanorods were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM) images, respectively. For electrical properties, the low specific contact resistance of (128.5734 Ω.cm2) at a room temperature for (Al/TiO2) contact was obtained, which confirmed the thermal stability of the contact. Under strong acidic condition, the structural and morphological studies showed that the rutile TiO2 nanorods shape is the predominant phase with growth well of aligned vertical array of parallelepiped for nanorods.
Afterward, TiO2 nanorods for EGFET based pH sensor was synthesized. In the wide sensing range of pH (2–12), optimized TiO2 nanorods as a sensing membrane for EGFET pH-sensor exhibited higher (Super-Nernstian) sensitivity and linearity of 2.0 (µA)0.5/pH, 98.98 % and 78.25 mV/pH, 99.27 % of saturation, and linear regions, respectively. Flower-shaped like TiO2 nanorods synthesized under the same conditions, on the other hand, showed a slight decrease in sensitivity and linearity, with sensitivity and linearity of 1.44 (µA)0.5/pH, 99.51.8 % and 60.96 mV/pH, 96.18 % of saturation and linear regions, respectively. This occurred due to the excellent growth TiO2 nanorods’ higher surface-to-volume ratio, as confirmed in the structure and surface morphology photographs. Furthermore, the repeatability of the TiO2 nanorods EGFET pH-sensor was calculated using the output voltage versus sensing time characteristics, and it was found to be 0.23 %, indicating good repeatability, stability, and reliability. Moreover, a lower obtained hysteresis value of 9.1 mV was also supporting the good performance of the TiO2 nanorods EGFET pH-sensor. Based on the above results, the TiO2 nanorods EGFET based pH sensor is a good choice for detecting hydrogen ions in various liquids. As an outcome, the results clearly indicated that the synthesized TiO2 nanorods EGFET pH-sensor has the potential to be used as chemical and biological sensors in the future.