Rod-like ZnO nanocrystals have been synthesized via art ultrasound-assisted way by the reaction between Zn(CH(3)COO)(2)center dot 2H(2)O and NaOH in the ionic liquid 1-butyl-3-methyl imidazole six hexafluorphosphoric acid salts ([BMIM][PF(6)]) aqueous solution. The products were characterized by XRD, EDX, FESEM, TEM, HRTEM, UV-Vis and PL techniques. The as-prepared ZnO nanorods have a diameter of about 50 nm and a length of 1-2 mu m. A plausible four-step mechanism was proposed to explain the formation of ZnO nanorods. It was found that the lowered ion diffusion velocity in the water-ionic liquid medium could largely contribute to the formation of the ZnO nanorods. The effects of experimental parameters on the formation of the products were also explored. (C) 2011 Elsevier Ltd. All rights reserved.