When Nanoparticles Meet Poly(Ionic Liquid)s: Chemoresistive CO2 Sensing at Room Temperature

Tetraalkylammonium-based poly(ionic liquid)s (PILs) are able to absorb particularly large amounts of CO2; thus are considered up-and-coming materials in applications ranging from sensing, separation, to storage of CO2. To meet the requirements of practical usage, their chemical activity has to be combined with other functionalities, for example, by fabricating composite materials. Poly[(p-vinylbenzyl) trimethylammonium hexafluorophosphate] and La2O2CO3 nanoparticles-both of which are intrinsically insulating materials-are utilized as building blocks, taking full advantage of the electrostatic interaction at their interface to boost the overall conductivity of composites at room temperature. To rationalize this unique behavior, the charge transport mechanism is studied using impedance spectroscopy. It is found find that, for the composites with La2O2CO3 content of 60-80 wt%, the interfacial effect becomes dominant and leads to the formation of conduction channels with increased mobility of [PF6]-anions. These composites show further increase of the conductivity when exposed to pulses of CO2 between 150 and 2400 ppm at room temperature in a relative humidity of 50%. This work therefore provides a simple strategy to achieve an enhancement of the electrical properties required for the utilization of PILs-based CO2 sensors, but in the future this concept can be easily extended to other electronic devices