Enhanced CO2-sensing response of nanostructured cobalt aluminate synthesized using a microwave-assisted colloidal method

Blue powders of nanostructured cobalt aluminate were synthesized using a microwave-assisted colloidal method applied in a non-aqueous medium, using dodecylamine as a surfactant. X-ray diffraction, UV-vis, and Raman measurements showed that single-phase CoAl2O4 was obtained when a calcination temperature of 800 degrees C was used. Extensive porosity was observed in the powders using scanning electron microscopy. Transmission electron microscopy studies showed that irregular-shaped nanoparticles with an average size of 9 nm were obtained. The gas-sensing properties were measured on thick films prepared using CoAl2O4 powder. The sensing response at different frequencies was determined by measuring the magnitude of the impedance (14) in air, and CO2. The results showed that the cobalt aluminate material produced here could be used to detect concentrations of 50 and 100 ppm of carbon dioxide at temperatures of 200-250 degrees C with a response time of between 5 and 15 s. Better recovery times (11-25 s) and a reproducible dynamic response were also achieved. (C) 2015 Elsevier B.V. All rights reserved.