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 fur CO2 gas at 1 atm and roo m temperature. Its function is based on IrO2 sensitivity to the pH-low ering effect produced by CO2 equilibration in the polymer film. This s ensitivity 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 similar to 0.1-100% CO2 in N-2. Since the microsensor shows fast response, it can also be employed in transient flow-injecti on experiments for the volumetric analysis of CO2. When calibrated car efully and used with care, the new microsensor based on IrO2 is capabl e of measuring either the concentration or volume of CO2 with high pre cision and negligible baseline drift.