A novel miniaturized pH potentiometric electrode based on a nano bismuth oxide film deposited on a fluorine doped nano tin oxide glass substrate

A novel thin film of bismuth oxide (Bi2O3) deposited on a fluorine doped tin oxide glass substrate (FTO), using a spray pyrolysis technique, was prepared and used as a pH sensing membrane. The deposited Bi2O3 film was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Film prepared by pyrolysis at 550 °C displayed a tetragonal β-phase of Bi2O3 with a porous structure, high roughness surface and nano cracks. The fabricated Bi2O3/FTO film was used as a miniaturized potentiometric electrode for monitoring a wide range of pH (pH 2 – 12) in aqueous solutions. The electrode exhibited an ideal near-Nernstian response (slope of −60.2 ± 0.3 mV/decade), high potential stability, mechanical durability and good selectivity toward some common interfering cations and anions, supporting its applicability for quality control/quality assurance purposes. The performance characteristics of the electrode and validation measurements, according to the standard methods, were evaluated. The Bi2O3/FTO-based electrode was satisfactorily used for monitoring the pH of some real water, beverages and fruit juice samples and the results compared fairly well with data obtained by the conventional pH glass electrode.