Figure 9.

(a) High-resolution TEM images of ZnO quantum dots covered by graphene. The graphene shell layer of the ZnO-core quantum dot covered by graphene looks like a single graphene layer. To the right, a magnified image shows the structure of the ZnO core and graphene monolayer. The ZnO petals grow along the [2] direction. (b) Electroluminescence spectra of the fabricated ZnO–graphene quasi-quantum dot LED device with applied voltage from 11 to 17 V. (c) Photograph of light emission at 11, 13, 15 and 17 V applied voltage bias, respectively. Reprinted by permission from [224], copyright 2012 Macmillan Publisher Ltd.