Fabrication and Characterization of IrO2-Based Microsensors for Fast Detection of Carbon Dioxide

A pair of closely spaced IrO2 electrodes covered by a polymer film is employed as a new solid-state microsensor for CO2 gas at 1 atm and room temperature. Its function is based on IrO2 sensitivity to the pH-lowering effect produced by CO2 equilibration in the polymer film. This sensitivity is made “asymmetric” by leaving one IrO2/polymer “masked” to CO2 gas exposure. The potential difference is measured and found to be reversible and reproducible for the concentration determination of CO2 between ∼0.1–100% CO2 in N2. Since the microsensor shows fast response, it can also be employed in transient flow-injection experiments for the volumetric analysis of CO2. When calibrated carefully and used with care, the new microsensor based on IrO2 is capable of measuring either the concentration or volume of CO2 with high precision and negligible baseline drift.