Shanbhag Sachin, Tang Zhiyong, Kotov Nicholas A
Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, Florida 32310, USA.
ACS Nano. 2007 Sep;1(2):126-32. doi: 10.1021/nn7000905.
Computer modeling of nanoscale processes provides critical quantitative insights into nanoscale self-organization, which is hard to achieve by other means. Starting from a suspension of Te nanorods, it was recently found that short nanorods (50 nm) self-organized into checkmark-like V-shaped assemblies over a period of a few days, whereas long nanorods (2200 nm) did not. This experimental fact was difficult to explain, and so here we use Brownian dynamics simulations of a dilute suspension of hard spherocylinders to better understand the process of self-organization. With the assumption that close encounters between nanorod tips result in their merger into V-particles, it was found that the ratio of the initial rate of nanorod formation for the short and long rods was 3760. By systematically varying the length and the concentration, we found that the concentration of the nanorods, rather their length, was primarily instrumental in setting the initial rate of checkmark formation. Using a simple kinetic model in conjunction with experimental data, we find that approximately 30,000 close encounters are required on average for a single successful merger. This study gives an important reference point for understanding the mechanism of the formation of complex nanostructured system by oriented attachment; it also can be extended to and provides conceptual leads for other self-organized systems.
纳米尺度过程的计算机建模为纳米尺度的自组织提供了关键的定量见解，而这是通过其他方式难以实现的。从碲纳米棒的悬浮液开始，最近发现短纳米棒（50纳米）在几天时间内自组织成类似对勾的V形聚集体，而长纳米棒（2200纳米）则没有。这一实验事实难以解释，因此在这里我们使用硬球柱体稀悬浮液的布朗动力学模拟来更好地理解自组织过程。假设纳米棒尖端之间的近距离接触会导致它们合并成V形粒子，发现短棒和长棒的纳米棒形成初始速率之比为3760。通过系统地改变长度和浓度，我们发现纳米棒的浓度而非长度，在设定对勾形成的初始速率方面起主要作用。结合实验数据使用一个简单的动力学模型，我们发现单次成功合并平均大约需要30,000次近距离接触。这项研究为理解通过定向附着形成复杂纳米结构系统的机制提供了一个重要的参考点；它也可以扩展到其他自组织系统并为其提供概念线索。
