A super-hydrophilic pH-sensitive electrode with a porous TiO₂ thin film is proposed in this work and fabricated using the chemical etching method. In total, 30 groups of porous TiO₂ thin film were obtained by immersing a Ti sheet in NaOH, with the solution concentration ranging from 0.5–4 M and the reaction time ranging from 15–240 min. SEM, XRD, XPS, and a contact angle meter were used to investigate the influence of the chemical etching parameters on the morphology, composition, and wettability of the fabricated electrodes. The chemical etching parameters were found to have a significant influence on the specific surface area and the component of the films, which strongly affected the wettability and pH sensing characteristics of the electrodes. The electrode obtained with a solution concentration of 1 M and reaction time of 120 min is the ideal product because of its excellent wettability, with a contact angle of 5.46°, and good pH sensing characteristics in pH buffer solutions. The electrode also showed good stability regarding its wettability and pH sensing properties during storage and utilization.

A solid thin film Ag/AgCl reference electrode modified by polydopamine (PDA) was developed in order to present a stable and fixed reference potential in solution. The reference electrode consists of a silver film, an AgCl layer and a PDA-modified film. The bare Ag/AgCl reference electrode, Nafion-modified Ag/AgCl reference electrode, PDA-modified Ag/AgCl reference electrode and Nafion-PDA-modified Ag/AgCl reference electrode were fabricated respectively. The sensitivity of these reference electrodes in KCl solution was measured, and the PDA-modified reference electrode had a sensitivity of 2.1 mV/pCl. Then the stability and reversibility were tested in different solutions in buffer and cyclic voltammetric characteristics was also investigated. The results showed that the reference electrode modified by PDA was stabled in PBS solution within a month, with a standard deviation of 1.4 mV. The response potential of electrode modified by PDA always recovers to a relatively stable potential and the deviation is less than 5 mV in different pH buffer solutions. The PDA-modified reference electrode also showed minimal drift over 50 cyclic voltammetry tests compared to other reference electrodes. The reference electrode modified by PDA has good reproducibility, and the sensitivity of the sensor composed of the self-made electrode is close to that of the commercial reference electrode.