Some Zn1−x Cu x O nanorods display deformed hexagon sections (see Figure 1 (c’)), which may be induced by doping. As seen in Figure 1d, a kind of brush-like

structures appears (at position B). These brushes are randomly assembled by the nanowires. For the sample at position A, the low-magnification SEM image in Figure 1e shows that a large quantity of BYL719 clinical trial micro-cross structures formed. The definition of micro-cross comes from the geometrical similarity to the cross structures. Figure 2a presents the corresponding high-magnification image of such a single micro-cross. We can notice that the micro-cross is a 3D hierarchical structure, which consists of four-folded symmetrical nanorod arrays of 1 μm in length and approximately 350 nm in diameter, together with a nanorod on the central stem having a uniform hexagonal cross section. Four arrayed nanorod branches stand perpendicular to the side surfaces of the central stem. We have also reduced the reaction time to Pevonedistat manufacturer 30 and 5 min in order to observe directly the morphology evolution with the reaction time and get information about the growth process of the micro-cross structures. Under the heating time of 30 min (Figure 2b), the homogenous cross-like structures have also been formed, growing with the length of the four-folded nanorods typically reduced to approximately 450 nm. When the reaction time was 5

min, we could only obtain one-dimensional square-like nanostructures with the edge length of about 200 to 300

nm (Figure 2c), which stands for the early growth stage of the structures. The corresponding EDX analysis shown in Figure 2d indicates that RG-7388 cost the major components of the as-fabricated sample are Zn and Cu, with a small amount of oxygen. Figure 2 SEM and TEM images of Zn 1− x Cu x O samples prepared for different reaction times. (a, b, c) FE-SEM images of Zn1−x Cu x O nanostructures prepared at 750°C for 60, 30, and 5 min, respectively. (d) EDX of the sample prepared at 750°C for 5 min. (e) TEM image, (f) HRTEM image, and (g) SAED Cell press of Zn1−x Cu x O micro-cross structures. Further morphological and structural analysis of the micro-cross structure can be characterized by the HRTEM and selected-area electron diffraction (SAED) techniques. Figure 2e presents the TEM morphology of the individual cross structure, which consists of the nanorod in the central stem, together with the nanorod arrays on the side surface of the core. The central stem is too thick to be detected from the TEM observation. The lattice fringes and the corresponding SAED pattern of the cross-like structure are shown in Figure 2f,g, respectively, which are indicated in Figure 2e with a red square. The lattice spacing of 0.52 nm corresponds to the spacing of [0001] crystal planes of wurtzite ZnO. The above experimental observation reveals that the location of the substrate and reaction time exercise great influences on the morphologies of the products.