Preparation of CuO thin films on porous BaTiO3 by self-assembled multibilayer film formation and application as a CO2 sensor

CuO thin films were prepared by decomposition of self-assembled multibilayer films as a molecular template. The CO2 sensing property of the resultant films on porous BaTiO3 was investigated as a capacitive type sensor. Self-assembled bilayer films of a few 1000 layers thickness can be readily obtained by casting an aqueous suspension composed of dimethyldihexadecylammonium bromide (DC1-16), Cu(CH3CO2)2, hexadecylethylenediamine and PVA. Cu2+ ions associated with two hexadecylethylenediamine molecules were arranged in the hydrophobic layer of the multibilayer film. Rapid heating to the combustion temperature of DC1-16 was desirable for removing organic molecules in the multibilayer template. Thin CuO films can be obtained by calcination above 573 K. The resultant films were porous and consisted of fine particles. The capacitance of the films on the BaTiO3 porous substrate exhibited a high sensitivity to CO2, (twice that of a conventional mixed oxide capacitor of CuO-BaTiO3), increasing with increasing CO2 concentration in the range from 100 ppm to 50% at 873 K. It was concluded that CuO thin films on BaTiO3 are appropriate capacitive type CO2 sensors. 18 refs.