Stability of the inner polyaniline solid contact layer in all-solid-state K+-selective electrodes based on...

Area of Science:

• Electrochemistry
• Spectroscopy
• Materials Science

Background:

• Solid contact (SC) layers in ion-selective electrodes (ISEs) are crucial for performance.
• Polyaniline (PANI) is a common electrically conducting polymer used in SCs.
• Understanding SC stability is vital for developing reliable ISEs.

Purpose of the Study:

• To present a UV-visible spectroscopy method for evaluating the stability of polyaniline (PANI) SC layers in all-solid-state ISEs.
• To investigate the influence of plasticized poly(vinyl chloride) (PVC) membrane composition and sample solution pH on PANI SC stability.
• To provide a tool for optimizing SC and membrane combinations for ISEs.

Main Methods:

• Electrochemical deposition of PANI on glassy carbon or tin oxide-coated quartz.
• Deposition of a K+-selective plasticized PVC membrane (ISM) on the PANI layer.
• UV-visible spectroscopy to monitor PANI stability under varying conditions.
• Electrochemical characterization of K+-selective ISEs.

Main Results:

• Short-term stability of the PANI SC layer is good across different membrane types and pH values (2, 6, 9).
• The plasticized PVC membrane effectively shields the pH-sensitive PANI layer.
• Long-term stability of the PANI SC layer varies significantly with membrane composition.
• Water uptake and OH- ion permeability of the PVC membrane are critical factors for PANI SC stability.
• The studied solid contact K+-selective electrodes exhibited a Nernstian response (58.2 ± 0.1 mV/log aK).

Conclusions:

• The developed UV-visible spectroscopy method is effective for studying PANI SC stability in ISEs.
• PVC membrane composition must be carefully selected to ensure long-term PANI SC stability, potentially differing from conventional ISE requirements.
• This research offers a pathway for designing more robust and stable solid contact ISEs.