Ionic Liquid Based Polymer Electrolytes for NO2 Electrochemical Sensors

Amperometric NO2 sensors with a new type of printed solid polymer electrolyte and printed carbon working electrodes were developed. The electrolytes consisted of the ionic liquids 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [EMIM][N(Tf)(2)], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][CF3SO3], and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4], which were immobilized in a poly(vinylidene fluoride) (PVDF) matrix. The analyte, gaseous nitrogen dioxide, was detected by reduction at -500 mV vs. the platinum pseudoreference electrode. The sensors showed linear behavior over the whole tested range, i.e., 0-5 ppm, and their sensitivities were in the order of hundreds of nanoamperes per one ppm of NO2. The sensor sensitivity was influenced by the electrical conductance of the electrolyte; the higher the conductance, the greater the sensor sensitivity. The rise/recovery times were of the order of tens of seconds. The use of screen printing technology for the preparation of the solid electrolyte and the carbon working electrode simplifies sensor fabrication without a negative effect on sensor performance.