Fig. 3(d) is the HRTEM image taken on the specific nanobat-like structure. The clear fringe spacing of 0.25 nm that is perpendicular to the long axis of the nanobat, accords well with the d value of the monoclinic CuO crystal plane, which indicates that the CuO nanobats grew along the [0 1 0] direction. The TEM results fully accord with the XRD and FESEM results.