Departamento de Física, CCT, Universidade Federal de Roraima, Roraima, Brazil.
Nanotechnology. 2011 Aug 5;22(31):315708. doi: 10.1088/0957-4484/22/31/315708. Epub 2011 Jul 8.
Diamondoids are hydrogen-terminated nanosized diamond fragments that are present in petroleum crude oil at low concentrations. These fragments are found as oligomers of the smallest diamondoid, adamantane (C(10)H(16)). Due to their small size, diamondoids can be encapsulated into carbon nanotubes to form linear arrangements. We have investigated the encapsulation of diamondoids into single walled carbon nanotubes with diameters between 1.0 and 2.2 nm using fully atomistic simulations. We performed classical molecular dynamics and energy minimizations calculations to determine the most stable configurations. We observed molecular ordered phases (e.g. double, triple, 4- and 5-stranded helices) for the encapsulation of adamantane, diamantane, and dihydroxy diamantane. Our results also indicate that the functionalization of diamantane with hydroxyl groups can lead to an improvement on the molecular packing factor when compared to non-functionalized compounds. Comparisons to hard-sphere models revealed differences, especially when more asymmetrical diamondoids were considered. For larger diamondoids (i.e., adamantane tetramers), we have not observed long-range ordering but only a tendency to form incomplete helical structures. Our calculations predict that thermally stable (at least up to room temperature) complex ordered phases of diamondoids can be formed through encapsulation into carbon nanotubes.
类金刚石是氢终止的纳米金刚石碎片，以低浓度存在于石油原油中。这些碎片以最小的类金刚石金刚烷（C(10)H(16)）的低聚物形式存在。由于其尺寸小，类金刚石可以被封装到碳纳米管中以形成线性排列。我们使用全原子模拟研究了直径在 1.0 和 2.2nm 之间的单壁碳纳米管对类金刚石的封装。我们进行了经典分子动力学和能量最小化计算，以确定最稳定的构型。我们观察到金刚烷、二氢金刚烷和二羟基二氢金刚烷的封装存在分子有序相（例如双螺旋、三螺旋、4 股和 5 股螺旋）。我们的结果还表明，与非功能化化合物相比，二氢金刚烷的羟基官能化可以提高分子堆积因子。与硬球模型的比较显示出差异，尤其是在考虑更不对称的类金刚石时。对于更大的类金刚石（即金刚烷四聚体），我们没有观察到长程有序，但只观察到形成不完全螺旋结构的趋势。我们的计算预测，通过封装到碳纳米管中，可以形成热稳定的（至少在室温下）复杂有序的类金刚石相。
