Sciencotech, 780 Girard Street NW, Washington, DC 20001, USA.
Nanotechnology. 2012 Mar 2;23(8):085701. doi: 10.1088/0957-4484/23/8/085701. Epub 2012 Feb 1.
Why vapor species land on the surface of the nanoparticle seed for nanotube synthesis is a vital question. An investigation has been carried out to find an answer to it. For this, a model of the dipole moment has been developed. A bimetallic alloy (non-alloy, solid solution) exhibiting the shape of a cap has been assumed to function as the nanoparticle seed. Various features of the dipole moment have been examined. The influence of the dipole moment on nanotube synthesis, alignment, chirality, and characteristics has also been studied. Available experiments on the synthesis of carbon nanotubes employing bimetallic catalysts have been compared with the results from calculations. Close correspondence between the two demonstrates that the catalysts may exhibit a dipole moment and have a crucial role in nanotube synthesis and characteristics. The dipole moment has also been employed to determine why some nanotubes grow vertically, while others are bent. Calculated results appear to explain the basic causes for this. These results suggest that the electric field resulting from the dipole moment of catalysts may be important for the vertical alignment of nanotubes. They may attest to the validity of the model and to the existence of a dipole moment in seeds. Although considered for nanotube syntheses, the results may be applicable to other nanomaterials (nanotubes, nanowires, nanodots).
为什么蒸气物种会落在纳米颗粒种子的表面上进行纳米管合成是一个至关重要的问题。已经进行了一项调查以寻找答案。为此，已经开发了偶极矩模型。假设作为纳米颗粒种子的双金属合金（非合金，固溶体）呈现帽的形状。已经检查了偶极矩的各种特征。还研究了偶极矩对纳米管合成、取向、手性和特性的影响。已经将使用双金属催化剂合成碳纳米管的现有实验与计算结果进行了比较。两者之间的紧密对应表明，催化剂可能表现出偶极矩，并在纳米管合成和特性中起着至关重要的作用。偶极矩也被用来确定为什么有些纳米管垂直生长，而有些则弯曲。计算结果似乎解释了这一基本原因。这些结果表明，催化剂偶极矩产生的电场可能对纳米管的垂直取向很重要。它们可能证明了模型的有效性以及种子中偶极矩的存在。尽管这些结果是针对纳米管合成考虑的，但它们可能适用于其他纳米材料（纳米管、纳米线、纳米点）。
