J. Ling et al. /Journal of Solid State Chemistry 178(2005)819-824 30um 5 um 5 um 30u ig. 4. SEM analysis of the compact oxide crust: (a)A three-tiered structure, (b) the exterior, (c) the middle layer and (d) interior of the compact crust by the fine tip. The process is in agreement with the vs experiment is carried out in air atmosphere, the process whisker growth mechanism proposed by Sears [12]. of supplying reactant vapors should be feasible in a Then the nanowires with a uniform diameter growing large scale. We believe the CGva method can be from the same Zno twinned particles will separate at the well extended to other synthetic technology of nano- multiply twinned joints(Fig. 5c). The dendrite nanos- materials tructures in Fig. 5 give a direct evidence for VS growth In summary, a simple CGVa method for producing of nanowires. We believe that the diameter and length of several micro- and nanostructures of Zno in air Zno nanowires can be controlled by the size of twinned atmosphere in a large scale is presented. The partial particles [12] pressure of the reactant metal vapors can be adjusted by It is noteworthy that our reaction process provides a varying the proportion between Zn and Cu. The fast route to synthesize ZnO nanostructures with the presence of Cu actually has a key effect on the control controlled morphology by continually transporting the of the sizes and shapes of the finally synthesized ZnO, so vapors to the reaction area. Furthermore, because the that a confined growth is achieved easily. Given theby the fine tip. The process is in agreement with the VS whisker growth mechanism proposed by Sears [12]. Then the nanowires with a uniform diameter growing from the same ZnO twinned particles will separate at the multiply twinned joints (Fig. 5c). The dendrite nanos￾tructures in Fig. 5 give a direct evidence for VS growth of nanowires. We believe that the diameter and length of ZnO nanowires can be controlled by the size of twinned particles [12]. It is noteworthy that our reaction process provides a fast route to synthesize ZnO nanostructures with the controlled morphology by continually transporting the vapors to the reaction area. Furthermore, because the experiment is carried out in air atmosphere, the process of supplying reactant vapors should be feasible in a large scale. We believe the CGVA method can be well extended to other synthetic technology of nano￾materials. In summary, a simple CGVA method for producing several micro- and nanostructures of ZnO in air atmosphere in a large scale is presented. The partial pressure of the reactant metal vapors can be adjusted by varying the proportion between Zn and Cu. The presence of Cu actually has a key effect on the control of the sizes and shapes of the finally synthesized ZnO, so that a confined growth is achieved easily. Given the ARTICLE IN PRESS Fig. 4. SEM analysis of the compact oxide crust: (a) A three-tiered structure, (b) the exterior, (c) the middle layer and (d) interior of the compact crust. J. Ling et al. / Journal of Solid State Chemistry 178 (2005) 819–824 823