Nanocrystalline ZnO(Ga): Paramagnetic centers, surface acidity and gas sensor properties

Nanocrystalline ZnO and ZnO(Ga) samples with different gallium content were prepared by wet-chemical method. Introduction of gallium leads to the increase of amount of weak acid sites such as surface hydroxyl groups. Gas sensing properties toward 0.2-2 ppm H2S and NO2 were studied at 100-450 degrees C by DC conductance measurements. The optimal temperature for gas sensing experiments was determined. Sensor signal toward H2S decreases with increase of Ga concentration. The dependence of ZnO(Ga) sensor signal to NO2 on the gallium content has non-monotonous character, which correlates with the change of conductivity of the samples in air and concentration of paramagnetic donor states. (C) 2013 Elsevier B.V. All rights reserved.