Ionic liquid/poly(ionic liquid) membranes as non-flowing, conductive materials for electrochemical gas sensing

Area of Science:

• Electrochemistry
• Materials Science
• Sensor Technology

Background:

• Volatile electrolytes in amperometric gas sensors pose risks.
• Ionic liquids (ILs) offer tuneable properties but can leak.
• Membrane-free designs require stable IL-based electrolytes.

Purpose of the Study:

• To develop stable, non-flowing membranes for amperometric gas sensors.
• To investigate the use of ionic liquid/polymer mixtures as sensor membranes.
• To optimize the IL/poly(IL) ratio for sensor performance.

Main Methods:

• Mixing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) with poly(diallyldimethylammonium bis(trifluoromethylsulfonyl)imide) (poly[DADMA][NTf2]).
• Fabricating miniaturised, planar electrode devices with varying IL/poly(IL) ratios (e.g., 60/40 wt%).
• Evaluating membrane robustness, conductivity, and electrochemical performance for O2, SO2, and NH3 using voltammetry.

Main Results:

• The 60/40 wt% IL/poly(IL) membrane demonstrated excellent robustness and non-flowing characteristics.
• Gas sensing responses for O2, SO2, and NH3 were highly reproducible.
• While sensitivity decreased slightly, electron transfer kinetics and limit of detection improved for O2 and SO2.

Conclusions:

• IL/poly(IL) composite membranes offer a robust solution for membrane-free amperometric gas sensors.
• These 'designer' materials enhance sensor stability and electrochemical properties.
• The developed membranes show significant potential for next-generation gas sensing applications.