Controlled synthesis and assembly of nanostructured ZnO architectures by a solvothermal soft chemistry process

Controlled synthesis and organization of nanostructured materials using simple and low-cost methods is important in order to exploit their unique properties for practical applications. We describe the results of a systematic study of the solvothermal soft chemical synthesis of novel nanostructured ZnO architectures. Various ZnO nanostructured microspheres and microrod aggregates have been synthesized using Zn(CH ₃COO) ₂ ·2H ₂O in ethylenediamine in the presence of HAuCl ₄· 4H ₂O. In the absence of HAuCl ₄ ·4H ₂O, fibrous and coral-like ZnO rod aggregates are obtained. The morphologies and structures of the obtained ZnO architectures can be tuned by manipulating the relative amounts and the addition sequence of Zn(CH ₃COO) ₂·2H ₂O and HAuCl ₄ ·4H ₂O. The Au(ethylenediamine) ₂ ³⁺ complex, formed from Au ³⁺ by combining with two ethylenediamine molecules, plays a key structuredirecting role in controlling the morphology and structure of the obtained ZnO architectures. All of the nanostructured ZnO architectures can be indexed to the hexagonal wurtzite stricture, and they show variations in the optical absorption properties depending on the distribution and interaction of Au nanoparticles on the ZnO surface. The formation mechanism of the various nanostructured microspheres is also discussed.