Figure  1f shows that the nestlike structure is composed of densely packed layers from the bottom to the top. Every layer consists of four well-edged square nanolaminas with the side length of about 2 μm. At the base of the nestlike structure in Figure  1e, if the concentration of ZD1839 sodium citrate is changed to 0.05 mmol with the deposition time of 5 min, ZnO nests holding the interlaced nanolaminas of ZnO are obtained (Figure  1g,h). The ZnO nanolaminas MK0683 located in the center of ZnO nests are analogy to the flower pistil. Many of these flower pistils show secondary laminas, which have started to grow on the concave of the nests with a slightly different orientation: the secondary

laminas form an angle with the basal plane of the main structure and trend to self-assemble in the center of the nests. With the electrochemical deposition going on, the central cavity of the nest is gradually filled by the nanolaminas to form clew-like structure (Figure  1i,j).

However, the different growth directions for the nest and its pistil are easily recognized from their gap (Figure  1j). Using 0.1 mmol sodium citrate at deposition time of 5 min, the flower-like microstructure of Figure  1d gradually disappeared and transformed into microsphere Apoptosis inhibitor structure with an average diameter of 5 μm (Figure  1k,l). These ZnO microspheres are in fact built from small one-dimensional nanolaminas in a highly close-packed assembly. These nanolaminas are aligned with one another perpendicularly to the more compact ZnO spherical surface. The nanolaminas also served as new nucleation sites for more nanolaminas growth and the eventual development into a well-defined three-dimensional spherical structure. But when further increasing the reaction time to 10 min

and keeping the concentration of sodium citrate certain, nearly all of the ZnO microspheres show large cracks along the equatorial circumference in Figure  1m,n, which may be due to the slightly increased tension of the inner spheres. Figure 1 SEM images of different ZnO microstructures by varying the electrochemical deposition Decitabine chemical structure conditions. (a, b) 0.05 mmol, 1 min; (c, d) 0.1 mmol, 3 min; (e, f) 0.01 mmol, 3 min; (g, h) 0.05 mmol, 5 min; (i, j) 0.05 mmol, 30 min; (k, l) 0.1 mmol, 5 min; (m, n) 0.1 mmol, 10 min. The TEM image of the two typical broken laminas of ZnO from any structure in Figure  1 obtained by ultrasonic treatment for several minutes is shown in Figure  2a. The electron diffraction (ED) pattern (Figure  2b) of these nanolaminas suggests that they have a polycrystalline structure [8]. Figure 2 TEM image (a) and ED ring of laminas of ZnO structures (b). A serials of experiments showed that the existence of citrate ions played a key role in the formation of the ZnO complex microstructures. For the control experiment in the absence of citrate as we previously reported, the products were mainly nanoflowers which were composed of nanorods [26].