A facile, template-free method is reported to prepare Cu2O/Au core-shell nanospheres in aqueous medium at room temperature. In this synthesis, Cu2O nanospheres with definite diameter were first synthesized via the reduction reaction between Cu(NO3)(2) and hydrazine (N2H4). Then, the as-prepared Cu2O nanospheres were employed as nucleation centers for deposition of Au shell, resulting in the formation of core-shell nanospheres. The samples obtained at various stages after the addition of the HAuCl4 were studied by TEM observation. These TEM images revealed that the formation hollow interior space between the core and the shell. In addition, UV-vis spectra results indicated that the optical property of the Cu2O/Au core-shell nanospheres was influenced by the size of the hollow interior spaces between the cores and the shells. (C) 2009 Elsevier B.V. All rights reserved.