A local ordered structure constructed from solid Cu2O nanocubes was obtained by the radiolytic reduction of Cu(NO3)(2) in a water-in-oil (W/O) microemulsion composed of Triton X-100, n-hexanol, cyclohexane, and water in the presence of ethylene glycol (EG). However, when Triton X-100 was replaced with Brij 56 in the microemulsion, hollow Cu2O nanocubes were synthesized. The addition of toluene into the Brij 56 system could decrease the ratio of hollow nanocubes. It was suggested that the balance between the reduction rate of Cu2+ depending on the yield of hydrated electrons (e(aq)(-)) and the escape rate of the mixed solvent determined their final morphologies. The presence of EG influenced the rigidity of the interface of the microemulsion and thus the above balance, which resulted in the different morphologies of Cu2O nanoparticles in the Brij 56-based microemulsion. (c) 2007 Elsevier Inc. All rights reserved.