ZnO nanopowders with different morphologies were successfully synthesized via hydrothermal method. By using different surfactants and controlling the concentration of surfactant in the reaction mixture, ZnO nanoparticles and nanoplates were obtained at 160 degrees C. The analysis of photoluminescence spectra shows that there exist more oxygen vacancies in the samples with small particle size and rough surface. The as prepared samples are used as photocatalysts for the rhodamine B (RhB) photodegradation, and the results show that ZnO with small particle size is more active for the photocatalytic process. This is attributed to the fact that the smaller particles have larger BET surface area and contain more surface oxygen vacancies, which are considered as stimulative for catalyzing the RhB reaction. The results suggest a positive relationship among particle size, oxygen vacancies and photocatalytic activity for RhB. (C) 2015 Elsevier B.V. All rights reserved.