Preparation and characterization of the titanium dioxide thin films used for pH electrode and procaine drug sensor by sol–gel method

We used titanium dioxide (TiO2) as the sensing layer of an ion selective pH sensor electrode, and as the substrate for a procaine drug sensitive membrane sensor. The TiO2 thin films were prepared using sol–gel spin coating technology. We adopted the Ti(OC4H9)4 as the precursor, and added an ethanol solute to obtain the TiO2 sol. The sol–gel was spun coated onto the indium tin oxide (ITO) substrate. The drug sensitive membrane was coated on the TiO2 film. We then measured the IDS–VG curves of the TiO2 ion selective electrode (ISE) pH sensor in pH buffer solutions that had different pH concentrations using a Keithley 236 Semiconductor Parameter Analyzer instrument. The procaine concentration was measured from 10−2 M to 10−6 M with the drug sensitive membrane using a HP 34401A Digital Multimeter. We prepared the TiO2 ISE pH sensor and obtained a high pH sensitivity of 58.73 mV/pH. Uniform TiO2 films surface structures, with an average roughness (Ra) of 10.211 nm and root mean square roughness (Rms) of 13.01 nm were obtained. The drift effect of the titanium dioxide ion selective pH sensor electrode is 1.97 mV h−1. The sensitivity of the procaine drug sensor is 55.03 mV pC−1 between 1.0 × 10−2 mol L−1 and 1.0 × 10−6 mol L−1 procaine concentrations. The detection limit is 5.0 × 10−6 mol L−1. The response time to reach 90% output voltage is 16 s. Forty seconds are required to reach 95% output voltage. The procaine drug sensor 1 × 10−3 mol L−1 drift test is 3.64 mV h−1 and the variation in output voltage of the repeated measurement is less than 7.4 mV.