Growth Kinetics of ZnO Nanorods: Capping-Dependent Mechanism and Other Interesting Features
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- 作者：Kanishka Biswas ; Barun Das ; C. N. R. Rao
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：February 21, 2008
- 年：2008
- 卷：112
- 期：7
- 页码：2404 - 2411
- 全文大小：421K
- 年卷期：v.112,no.7(February 21, 2008)
- ISSN：1932-7455
文摘
Although the growth of nanocrystals has been investigated by several workers, investigations of the growthof 1-D nanostructures have been limited. We have investigated the growth kinetics of both uncapped andpoly(vinyl pyrollidone) (PVP)-capped ZnO nanorods carefully by a combined use of transmission electronmicroscopy (TEM) and small-angle X-ray scattering (SAXS) which provide direct information on size andshape and compensate for the deficiency of each other. Values of average length and diameter of the ZnOnanorods obtained by TEM and SAXS are comparable. In the presence of the capping agent, the length ofthe nanorods grows faster while the diameter becomes narrower. The length distribution shows periodic changesin the width in the case of the uncapped nanorods, a feature absent in the case of the capped nanorods. In theabsence of the capping agent, we observe the presence of small nanocrystals next to the nanorods after alapse of time. The occurrence of small nanocrystals as well as the periodic focusing and defocusing of thewidth of the length distribution lend support to the diffusion-limited growth model for the growth of uncappedZnO nanorods. Accordingly, the time dependence of the length of uncapped nanorods follows the L3 law asrequired for diffusion-limited Ostwald ripening, while the PVP-capped nanorods show a time dependencewhich is best described by a combination of diffusion and surface reaction with a L3 + L2 type behavior.Collapse of all distribution curves obtained at different times of the reaction into a single universal Gaussianin the case of the PVP-capped nanorods also shows that the growth mechanism is more complex than Ostwaldripening.