Fast Responding Amperometric CO Microsensor with Ionic Liquid-Aprotic Solvent Electrolytes.

Knowledge about the microscale distribution of CO is essential in many environmental and technical settings, and electrochemical CO sensing may be optimized to yield such information. The performance of a Clark-type CO sensor was greatly improved by adding 20% dimethylformamide (DMF) to the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA) previously used as an electrolyte. The addition of DMF resulted in a much faster response to increasing (95% response of about 100 s) or decreasing CO concentration, a negligible interference from low concentrations of NO, and a signal temperature dependence similar to that of O microsensors. The use of 80% EMIM-DCA/20% DMF as an electrolyte leads to CO reduction at -0.72 V (vs standard hydrogen electrode), reducing the overpotential by 0.2 V as compared to the use of 100% EMIM-DCA. The CO microsensor has a calculated limit of detection of 0.5 Pa CO, and sensors optimized for high sensitivity exhibited a linear response within the range of 0-4.6 kPa (0-1.7 mM) CO. A set of four sensors exhibited no noticeable change of zero current and CO sensitivity during 4 months of continuous polarization.