Quantum-sized ZnO was prepared using sol-gel method with zinc acetate dehydrate (Zn(CH3COO)(2)center dot 2H(2)O) and lithium hydroxide monohydrate (LiOH center dot H2O) as raw material. The ZnO particles annealed at different temperature were characterized by means of X-ray diffraction (XRD), Infrared absorption spectroscopy (IR) and UV-vis spectroscopy. The degradation rate of reactive brilliant blue X-BR in aqueous solution was used to evaluate the photocatalytic performance of the quantum-sized ZnO. The experimental results indicated that the photocatalytic property of the ZnO was excellent. The photocatalytic efficiency of quantum-sized ZnO was significantly influenced by the calcining heat. When calcined at 300 degrees C, its size is 6.78 nm and the photocatalytic performance is the best. The degradation rate of reactive brilliant blue X-BR could exceed 90% in 15 min at 35 degrees C, when the concentration of the quantum-sized ZnO was 0.35 mg/L. (c) 2007 Elsevier Ltd. All rights reserved.