Nanotechnology and nanomaterials

Mechanochemical and microwave modification of nanosized SnO2 for creation of hydrogen semiconductor sensor 
Khalameida S.V. 1, Matushko I.P.2, Sydorchuk V.V . 1, Oleksenko L.P.2, Maksymovych N.P.2, Samsonenko M.M .1, Khyzhun O.Yu 3.
1 Institute for Sorption and Problems of Endoecology of the NAS of Ukraine, 13 Gen. Naumova Str, Kyiv-03164, Ukraine. 
E-mail: svkhal@ukr.net
2 Department of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrs’ka str., 64/13,  Kyiv-01601, Ukraine.

3 I.M.Frantsevich Institute for Problems of Materials of the NAS of Ukraine, 3 Krzhyzhanivskogo Str., Kyiv-03680, Ukraine.

Nowdays tin dioxide is one of the most perspective materials to create adsorption semiconductor gas sensors purposed to control air ambient. Since high temperature calcination is a necessary stage for fabrication of the sensors, SnO2 must have a thermostable porous structure. We subjected precipitated SnO2 to mechanochemical and microwave treatments (MChT and MWT) to prevent its sintering. This leads to noticeable increase in the specific surface area for annealed at 450°C samples: from 44 m2/g for initial sample to 60 and 84 m2/g for modified samples. The size of the crystallites determined using XRD and TEM data decreases from 15 nm for the initial sample to 7-10 nm for the samples after MChT and MWT. The aim of the work is to study the effect of MChT and MWT of the material of the gas sensitive layer on the base of SnO2 of adsorption-semiconductor sensors on their sensitivity to hydrogen.
The sensor consisted of a ceramic plate with a heater on one side of the plate and measuring contacts on the opposite side of the plate. The sensitive layers of the semiconductor nanomaterials obtained after the MChT and MWT of SnO2 were placed between the contacts and cobalt oxide, well know catalyst of H2 oxidation, was introduced in the layer. Then the sensors were calcinated at 620 0C in air. It was found that Co-containing sensor created on the base of SnO2 nanomaterial after the microwave treatment had the greater sensor response to hydrogen microconcentration than the sensor based on the material after the treatment in the aqueous medium mechanochemical treatment only. The obtained results are consistent with XPS data and values of the larger specific surface area of the material after MWT of SnO2 (84 m2/g) than after the MChT one (60 m2/g).