State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
J Chem Phys. 2011 Sep 28;135(12):124703. doi: 10.1063/1.3638176.
Brownian dynamics simulations are carried out to study the aggregation behavior of polymer-grafted nanoparticles (NPs) in good solvents by using the coarse-grained model derived from the all-atom force field, according to the hierarchical modeling strategy, and here PEG-grafted gold nanoparticles (GNPs) were taken as an example. Generally, grafting PEG to the surface of GNPs is to protect them from aggregation in the solution. However, our results reveal that PEG-grafted GNPs may also aggregate when concentration increases. Our simulations indicate that there exists a critical aggregating concentration (CAC), beyond which the PEG-grafted GNPs will aggregate. We further check the effects of grafting density and the length of grafted chains on the aggregation behavior of the grafted GNPs, and find that there exists an optimized length of grafted chain, at which the system has the maximal CAC. Furthermore, the aggregate size of self-assembled mesostructures formed by the grafted GNPs increases with the concentration. Interestingly, it is observed that the aggregation favors to form linear gold nanowires rather than compact gold nanoclusters, and the corresponding mechanism is also addressed. It is expected that this work would provide useful information for the fabrication of metal nanowires and the surface modification of metal nanoparticles.
采用粗粒化模型并基于分级建模策略，利用从全原子力场导出的模型，对聚合物接枝纳米粒子（NPs）在良溶剂中的聚集行为进行了布朗动力学模拟研究，这里以聚乙二醇（PEG）接枝金纳米粒子（GNPs）为例。通常，在 GNPs 表面接枝 PEG 是为了防止它们在溶液中聚集。然而，我们的结果表明，PEG 接枝的 GNPs 浓度增加时也可能发生聚集。我们的模拟表明，存在一个临界聚集浓度（CAC），超过该浓度后，PEG 接枝的 GNPs 将发生聚集。我们进一步检查了接枝密度和接枝链长度对接枝 GNPs 聚集行为的影响，发现存在一个优化的接枝链长度，在此长度下，系统具有最大的 CAC。此外，由接枝 GNPs 自组装形成的介观结构的聚集尺寸随浓度的增加而增大。有趣的是，观察到聚集有利于形成线性金纳米线而不是致密的金纳米团簇，并且还讨论了相应的机制。预计这项工作将为金属纳米线的制备和金属纳米粒子的表面改性提供有用的信息。
