Single-crystalline rocketlike tetrapodal CdS nanorods were synthesized via a one-step seed-epitaxial MOCVD approach by thermal decomposition of Cd(S 2 CNEt 2 ) 2 powders. This bottom-up method uses silver particles to initiate and guide the preferential orientation of the axial nanorods, whereas the epitaxial growth of wurtzite-structured branches occurs on the cubic CdSe seeds. This controlled seedepitaxial method has potential as a general means of forming complex branching structures and may also offer opportunities for applications as building blocks for optoelectronic devices.Significant efforts have been made to control the size and shape of inorganic nanocrystals, because these parameters primarily determine their electronic and optical properties. 1-5 One way to achieve shape control is to enhance anisotropic nanocrystals growth using a liquid medium such as the vapor-liquid-solid (VLS) method. 6 Another common approach is to use surfactants or micelles (regular or inverse) as regulating agents or templates to facilitate anisotropic crystal growth. 7-9 More recently, complicated nanostructures, such as tetrapodlike, hierarchical, dendritic, etc., are highly desired considering their applications as interconnections in the "bottom-up" self-assembly approach toward future nanocircuits and nanodevices. Among them, tetrapodal branched nanostructures are typical because they present promising properties in field emission, mechanical reinforcement of polymer, infrared adsorption, photovoltaic devices, and so on. 10-15 Until now, tetrapodal crystals have frequently occured in several materials such as ZnO, 6 ZnS, 16 ZnSe, 2 CdS, 17 CdSe, 18 and CdTe, 10,19 which are generated through epitaxial growth of wurtzite-structured arms out of the zinc-blende-phased core. 20 In all above cases, however, harsh conditions such as reactions in organic solvents or chemical vapor deposition at high temperatures are normally required. Obviously, seeking new and versatile synthetic routes may be very important.In forming the tetrapodal structure, phase control and switching (nucleation in the zinc blende phase while growing in the wurtzite phase) are key steps. To control these steps, it is necessary to change the nucleation and growth environments and separate the nucleation and growth processes, 21 and the epitaxial growth has long been regarded as the best strategy. Epitaxial growth, however, usually takes place two-dimensionally on a planar substrate; recently, it has been built three-dimensionally on the nanowire surfaces between two materials with the same crystal structure. 22 In addition, the epitaxial growth of wurtzite layers out of a tetrahedral zinc core has been observed before. 23 The growth of these self-assembled nanoarchitectures is based on the crystallographic characteristics. This motivated us to design and fabricate 3D CdS nanoarchitectures. It is well-known that zinc blende CdSe and wurtzite CdS have similar crystal structures and close lattice constants. In accordance with the lattice-matching theory, eff...
