Towards low cost and low temperature capacitive CO2 sensors based on amine functionalized silica nanoparticles

Hybrid materials based on inorganic particles and an organic polymer were developed and used as an efficient sensing material for carbon dioxide (CO2). The sensing material consists of fumed silica that is functionalized with an organic polymer, polyethylenimine, by means of the impregnation method. The organic polymer is effectively immobilized around the silica nanoparticles and confirmed by infrared spectroscopy. Thermogravimetric analysis proves the thermal stability of the sensing material. CO2 capacitive sensors operating at temperatures lower than 70 °C were fabricated by depositing a thin layer of hybrid sensing material on interdigitated gold electrodes. Impedance spectroscopy explored the sensing capability of the hybrid organic-inorganic material towards CO2 in the presence of different relative humidity levels, as well as its stability and reversibility. This strategy to couple organic and inorganic materials as a sensing layer for CO2 paves the way for the design of a low-cost CO2 sensor.