The New Reliable pH Sensor Based on Hydrous Iridium Dioxide and Its Composites

Area of Science:

• Electrochemistry
• Materials Science
• Sensor Technology

Background:

• Development of reliable sensors for accurate pH determination is crucial in various scientific fields.
• Solid-contact ion-selective electrodes require robust and stable materials for optimal performance.
• Hydrous iridium oxide (hIrO2) shows potential for electrochemical applications but requires optimization for sensor development.

Purpose of the Study:

• To design and evaluate novel solid-contact layers for pH-selective electrodes using hydrous iridium oxide and its composites.
• To investigate the impact of incorporating carbon nanotubes and conducting polymers into hIrO2-based materials on sensor performance.
• To present a universal approach for developing high-performance solid-state ion-selective sensors.

Main Methods:

• Preparation of three different hIrO2-based materials: standalone hIrO2, hIrO2-carbon nanotubes composite, and a triple composite (hIrO2-carbon nanotubes-poly(3-octylthiophene-2,5-diyl)).
• Fabrication of pH-selective electrodes utilizing these materials as solid-contact layers with a polymeric membrane.
• Characterization of sensor performance, including potentiometric response, linear range, stability, electrical capacitance, and wetting properties.

Main Results:

• The addition of functional materials significantly improved sensor performance compared to standalone hIrO2.
• Carbon nanotubes increased the electrical capacitance of the sensor up to 400 µF.
• The conducting polymer enhanced material wetting properties and potentiometric response stability.
• Electrodes with hIrO2-based materials exhibited a linear pH response from 2 to 11.
• The triple composite material demonstrated the most stable potentiometric response with the lowest potential drift (0.036 mV/h).

Conclusions:

• Composite materials incorporating hydrous iridium oxide, carbon nanotubes, and conducting polymers offer a superior approach for developing reliable pH sensors.
• The synergistic effects of the composite components lead to enhanced electrical properties, improved stability, and a wider linear response range.
• This study presents a versatile strategy for designing advanced solid-state ion-selective electrodes with tailored functionalities.