Synthesis of ZnO Nanostructures via Sol-gel Method

It is generally believed that the usefulness of ferromagnetic wide band gap semiconductors for spin electronics applications requires the existence of a coupling between ferromagnetic and semi conducting properties. So, ZnO is an important electronic and photonic material because of its wide direct band gap of 3.37 eV. In recent years, in particular, ultraviolet lasing from ZnO nanostructures has been demonstrated at room temperature [1,2], which triggers a wide range of subsequent research in searching for newer synthetic methods. There have been many existing preparative techniques for this material [1-11]. Among them, a vapor-phase transport process with the assistance of noble metal catalysts and thermal evaporation are the two major vapor methods to fabricate one-dimensional ZnO nanostructures (nanorods) with controllable diameters [1-9]. In addition to these techniques, it is well conceived that preparation of ZnO via solution chemical routes provides a promising option for large-scale production of this material. Although they have long been used for ZnO singlecrystal growth [12], wet-chemical approaches still face the problems of polydispersivity and difficulties in bringing the rod diameters down to the sub-100 nm regime [13]. Very recently, single-crystalline ZnO nanorods have been prepared with a modified microemulsion method [13]. Although the regularity of the rod-shape has been significantly improved, the achieved rod diameter is still in the range of 150 nm with that wet-chemical method [13]. Among the reported studies, however, little work has been done with the preparation of ZnO nanopowders. In this work, the sol-gel technique was developed for the formation of ZnO nanostructures. Finally, the magical structure introduced an intermediate structure between two well-known structures as may be of particular interest from both fundamental and applied points of view.