Flame-Made La(2)O(3)-Based Nanocomposite CO(2) Sensors as Perspective Part of GHG Monitoring System

Continuous monitoring of greenhouse gases with high spatio-temporal resolution has lately become an urgent task because of tightening environmental restrictions. It may be addressed with an economically efficient solution, based on semiconductor metal oxide gas sensors. In the present work, CO(2) detection in the relevant concentration range and ambient conditions was successfully effectuated by fine-particulate La(2)O(3)-based materials. Flame spray pyrolysis technique was used for the synthesis of sensitive materials, which were studied with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) and low temperature nitrogen adsorption coupled with Brunauer–Emmett–Teller (BET) effective surface area calculation methodology. The obtained materials represent a composite of lanthanum oxide, hydroxide and carbonate phases. The positive correlation has been established between the carbonate content in the as prepared materials and their sensor response towards CO(2). Small dimensional planar MEMS micro-hotplates with low energy consumption were used for gas sensor fabrication through inkjet printing. The sensors showed highly selective CO(2) detection in the range of 200–6667 ppm in humid air compared with pollutant gases (H(2) 50 ppm, CH(4) 100 ppm, NO(2) 1 ppm, NO 1 ppm, NH(3) 20 ppm, H(2)S 1 ppm, SO(2) 1 ppm), typical for the atmospheric air of urbanized and industrial area.