Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyungbuk, Korea 790-784.
Langmuir. 2011 Jan 4;27(1):371-8. doi: 10.1021/la103600c. Epub 2010 Dec 9.
We report a method for synthesizing zinc citrate spheres at a low temperature (90 °C) under normal atmospheric pressure. The spherical structures were amorphous and had an average diameter of ∼1.7 μm. The amorphous zinc citrate spheres could be converted into crystalline ZnO nanostructures in aqueous solutions by heating at 90 °C for 1 h. By local dissolution of the zinc citrate spheres, nucleation and growth of ZnO occurred on the surfaces of the amorphous zinc citrate spheres. The morphologies and exposed crystal faces of the crystalline ZnO nanostructures (structure I: oblate spheroid; structure II: prolate spheroid; structure III: hexagonal disk; structure IV: sphere) could be controlled simply by varying the solution composition (solutions I, II, III, or IV) in which the as-prepared amorphous zinc citrate spheres were converted. The concentration of citrate anions and solution pH played a decisive role in determining the morphologies and exposed crystal faces of the crystalline ZnO nanostructures. On the basis of experimental results, we propose a plausible mechanism for the conversion of amorphous zinc citrate spheres into the variety of observed ZnO structures.
我们报道了一种在低温（90°C）、常压下合成柠檬酸锌球体的方法。这些球形结构为非晶态，平均直径约为 1.7μm。在 90°C 下加热 1 小时，非晶态的柠檬酸锌球体可以在水溶液中转化为结晶 ZnO 纳米结构。通过柠檬酸锌球体的局部溶解，在非晶态柠檬酸锌球体的表面上发生 ZnO 的成核和生长。通过改变转化所得非晶态柠檬酸锌球体的溶液组成（溶液 I、II、III 或 IV），可以简单地控制结晶 ZnO 纳米结构的形貌和暴露的晶面（结构 I：扁球体；结构 II：长球体；结构 III：六方盘；结构 IV：球体）。柠檬酸根阴离子的浓度和溶液 pH 值在决定结晶 ZnO 纳米结构的形貌和暴露晶面方面起着决定性的作用。基于实验结果，我们提出了一个合理的机制，用于解释非晶态柠檬酸锌球体转化为各种观察到的 ZnO 结构。
