WO3 center dot H2O nanoplates were prepared by the acidification of Na2WO4 center dot H2O and converted into monoclinic WO3 nanoplates by heat treatment. The sizes, morphologies and preferred orientation of the WO3 nanoplates could be controlled by manipulating the acidity of the solution used for the acidification reaction. All of the WO3 nanoplates showed the selective detection of NO2 in the presence of other reducing gases, such as C2H5OH, CH3COCH3, CO, C3H8, and H-2. The gas response, selectivity, and response speed were optimized by varying the morphology of the sensing materials and operation temperature. The WO3 nanoplates with a mean edge size of 192 nm showed the most rapid gas response along with a high response and selectivity to NO2 when operated at 300 degrees C (C) 2010 Elsevier B.V. All rights reserved.