Characterization and application of a new pH sensor based on magnetron sputtered porous WO3 thin films deposited at oblique angles

• A solid-state pH sensor based on WO3 amorphous thin film electrode is reported.
• Cyclic voltammetry and XRD confirmed the amorphous nature of tungsten.
• Potentiometric response of the WO3 electrode revealed a quasi-Nernstian behavior.
• The interference of the most common ions (Li+, Na+, K+ and NH4+) was negligible.
• A full solid state pH sensor is developed.

In this communication we report about an outstanding solid-state pH sensor based on amorphous nanocolumnar porous thin film electrodes. Transparent WO3 thin films were deposited by reactive magnetron sputtering in an oblique angle configuration to enhance their porosity onto indium tin oxide (ITO) and screen printed electrodes (SPE). The potentiometric pH response of the nanoporous WO3-modified ITO electrode revealed a quasi-Nernstian behaviour, i.e. a linear working range from pH 1 to 12 with a slope of about −57.7 mV/pH. pH detection with this electrode was quite reproducible, displayed excellent anti-interference properties and a high stable response that remained unaltered over at least 3 months. Finally, a pH sensor was developed using nanoporous WO3-modified screen printed electrode (SPE) using a polypyrrole-modified Ag/AgCl electrode as internal reference electrode. This full solid state pH sensor presented a Nernstian behaviour with a slope of about −59 mV/pH and offered important analytical and operation advantages for decentralized pH measurements in different applications.

Figure optionsDownload as PowerPoint slide