A miniature chemiresistor sensor for carbon dioxide

• Poly(ethyleneimine) functionalized polyaniline nanothin film miniature chemiresistor CO2 sensor.
• Detection by CO2–amines reactions of acid–base, dissolution and base-catalyzed hydration.
• pH change from acids and carbamates produced and detected by polyaniline nanothin film.
• Sensor was accurate, precise, highly sensitive and selective.
• Suitable for portable multi-analyte breath analysis and environmental monitoring detector.

A carpet-like nanostructure of polyaniline (PANI) nanothin film functionalized with poly(ethyleneimine), PEI, was used as a miniature chemiresistor sensor for detection of CO2 at room temperature. Good sensing performance was observed upon exposing the PEI–PANI device to 50–5000 ppm CO2 in presence of humidity with negligible interference from ammonia, carbon monoxide, methane and nitrogen dioxide. The sensing mechanism relied on acid–base reaction, CO2 dissolution and amine-catalyzed hydration that yielded carbamates and carbonic acid for a subsequent pH detection. The sensing device showed reliable results in detecting an unknown concentration of CO2 in air.

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