No 1, Vol. 4, 2003 


Marie-Isabelle Baraton and Lhadi Merhari


When applied to the study of semiconducting nanosized particles, Fourier transform infrared spectroscopy allows the simultaneous analysis of the chemical reactions occurring at the nanoparticle surface and the resultant variations of the electrical conductivity. This technique has been used to compare the sensing potentiality of three semiconductors (tin oxide, indium oxide and tungsten oxide nanoparticles) before they are integrated in the fabrication process of actual gas sensors. It has been found that the sensitivity to CO of tin oxide and indium oxide nanoparticles is fairly good whereas that of tungsten oxide is quasi nil. However, tungsten oxide, like indium oxide, is very sensitive to oxygen and reducing treatments. The presence of humidity irreversibly affects the response of tin oxide to CO and oxygen, whereas that of indium and tungsten oxides to both gases seems to be relatively independent from the moisture content. It is generally observed that a higher operating temperature leads to a more stable baseline and a faster response. Moreover, the formation of surface carbonate groups observed in several cases under CO adsorption does not imply a larger response, thus confirming that the carbonate formation is not a significant factor in the CO detection mechanism.

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