Zinc oxide (ZnO) flower-like nanosheets and nanorods were synthesized on a glass substrate with an Al layer by a simple chemical bath method, and their morphology was controlled by adjusting the pH of the solution without the assistance of an additional surfactant. For the 3D nanostructures of the annealed nanosheets, the blue light emission at about 410 nm disappeared, which may be due to the defect of zinc vacancy. The emission of the yellow band at about 550 nm was enhanced, which could have originated from the interstitial oxygen. These results indicate that the concentrations or types of the dominant defects could be changed because of the diffusion of Al substrates during the course of annealing. The as-prepared flower-like nanostructures of nanorods exhibited a high UV emission peak (at about 380 nm). After the samples were annealed, the green emission (at about 500 nm) was also enhanced abnormally, except for the UV emission (at 380 nm), indicating that the crystalline quality could not be improved by annealing for complex nanostructures, except for the top of the structures. Our results present a simple, reproducible, and cost-competitive method to synthesize ZnO three-dimensional flower-like structures and would provide useful information for the fabrication of optoelectronic devices at room temperature.
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