Nanocomposites and nanomaterials

Nanomaterial based on SnO2 with Co and Sb additives - perspective material for H2 semiconductor sensors
Fedorenko G.V., Oleksenko L.P., Maksymovych N.P., Matushko I.P., Skolyar G.I., Ripko O.P., Lutsenko L.V. 
Department of Chemistry, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrs’ka str., Kyiv 01601, Ukraine
E-mail: georgf@ukr.net 

Semiconductor sensors based on metal oxides are widely used to determine the presence of toxic and explosive gases in the ambient air. The principle of the sensor operation is based on a change of its electrical resistance in the presence of the analyzed gas. Chemical composition of the sensor sensitive layer and its morphology significantly affect the electronic processes that determine the sensitivities of the sensors to the gas. The use of the nanomaterials as gas sensitive layers of the sensors is promising for increasing the sensitivities of the sensors.
A non-aqueous sol-gel method was used to create the nanosized material in our work. The method allowed to obtain the nanomaterial based on tin dioxide with antimony additives with average particle size 12 nm. Such small sizes were obtained as a result of polymerization of glycolates in the process of synthesis that had led to creation of a three-dimensional grid where ethylene glycol molecules act as bridges between tin and antimony atoms. This structure-forming function contributed to the absence of agglomeration of the material particles during heat treatment of the xerogel, that prevented increasing the sizes of the particles. To increase the sensitivities of the sensors, cobalt oxide, a known catalyst for hydrogen oxidation, was added to the resulting nanomaterial.
The gas sensitive properties of the hydrogen sensors based on SnO2-Sb2O5 semiconductor nanomaterial with the particle size of 5-25 nm obtained by the sol-gel method and then modified by Co3O4 and characteristics of the sensors based on the same material with the particle size of 1-30 μm obtained by the method of co-precipitation of hydroxides of tin and stybium obtained from their chlorides were presented in the work. It was found that the sensor based on nanoscale Co-containing material was more sensitive to H2. The response of the sensor based on the nanosized material was equal to 13.9 in the presence of 500 ppm H2. Elecrical resistance of the sensor created on the base of microcrystalline material had changed in 6.2 times. Improved characterics of the sensor based on the nanosized material were explained by influence of its morphology on the electronic processes occuring on the surface of the gas sensitive layer of the sensor.