We reported on the synthesis and gas-sensor application of copper oxide particles and plates. CuO particles were prepared by a thermal decomposition method, while CuO plates were obtained by a hydrothermal route. The sensitivity of the as-prepared CuO to NO2 gas and alcohol at varied temperatures was studied systematically. The results revealed that the as-synthesized products had high sensitivity and quick response/recovery time at an operating temperature of 200 degrees C. Furthermore, the CuO plates displayed higher sensitivity to NO2 gas than that of the corresponding particles. This research indicated that CuO plates have potentials in the applications of sensors. (C) 2007 Elsevier Ltd. All rights reserved.