Novel flowerlike Cu20 micro-nanocrystals were prepared by a greener reductive reaction of cupric acetate monohydrate with ethylene glycol in aqueous solutions of [C8mim]X （X = CI-, Br-, BF4-, PFr-） and [C,,mim][BF4] （n = 4, 6, 8）. The obtained mi- crostructures of Cu2O were characterized by Scanning Electron Microscopy （SEM）, X-ray diffraction （XRD） and Fourier Transform Infrared （FT-IR）. The effects of cations, anions and concentration of the ionic liquids on the morphology of Cu20 were examined in some details. The results suggest that the formation of flowerlike Cu20 was governed by a [Csmim][BF4] controlled reductive reaction mechanism. As one of their applications, the Cu20 nanoparticles were used for the photocatalytic degradation of methylene blue in aqueous solution, and high photocatalytic activity was observed.
