Principles governing control of aggregation and dispersion of aqueous graphene oxide.
Principles governing control of aggregation and dispersion of aqueous graphene oxide.
复制标题
DOI：
10.1038/s41598-021-01626-3
复制
发表时间：
2021-11-17
影响因子：
4.6
通讯作者：
Coveney PV
中科院分区：
文献类型：
--
作者：
Suter JL;Coveney PV
控制氧化石墨烯（GO）相及其较小类似物石墨烯（氧化物）量子点（GOQD）的结构对于它们的任何广泛预期应用都是至关重要的：用于GO的薄膜或膜应用的纳米颗粒的高度有序排列、用于复合材料的分散纳米颗粒和用于水凝胶的三维多孔排列。在水性环境中，不仅GO薄片的化学组成决定它们的形态;外部因素如pH和共存的阳离子也影响形成的结构。通过使用精确的模型，捕捉表面氧化的异质性和非常大规模的粗粒度的分子动力学，可以模拟GO的行为在现实尺寸的GOQD的GO，导致在水溶液中的各种形态的驱动力被解决。我们发现的形态是由一个复杂的相互作用之间的静电，氢键相互作用。组装的形态可以通过改变氧化程度和pH值来控制。在酸性水溶液中，GO薄片从完全聚集在石墨域上到经由羟基化域之间的氢键部分聚集而变化，导致在高氧化比下形成平面延伸薄片和在低氧化比下形成堆叠。在高pH下，其中边缘羧酸基团被去质子化，静电排斥导致更多的分散，但令人惊讶地仍然观察到各种聚集行为：在石墨区域，通过氢键和“面-边缘”相互作用。钙离子引起额外的聚集，具有更多数量的“面-面”和“边-边”聚集机制，导致不规则的聚集结构。“面-面”聚集机制通过具有羟基化和石墨化区域的不同域的GO薄片而增强，在聚集的薄片上的这些区域之间分别普遍存在氢键和氢键相互作用。这些发现为GO和GOQD的聚集特征提供了解释，并提供了设计自组装和相关应用的定向合成路线的计算方法。
Controlling the structure of graphene oxide (GO) phases and their smaller analogues, graphene (oxide) quantum dots (GOQDs), is vitally important for any of their widespread intended applications: highly ordered arrangements of nanoparticles for thin-film or membrane applications of GO, dispersed nanoparticles for composite materials and three-dimensional porous arrangements for hydrogels. In aqueous environments, it is not only the chemical composition of the GO flakes that determines their morphologies; external factors such as pH and the coexisting cations also influence the structures formed. By using accurate models of GO that capture the heterogeneity of surface oxidation and very large-scale coarse-grained molecular dynamics that can simulate the behaviour of GO at realistic sizes of GOQDs, the driving forces that lead to the various morphologies in aqueous solution are resolved. We find the morphologies are determined by a complex interplay between electrostatic, – and hydrogen bonding interactions. Assembled morphologies can be controlled by changing the degree of oxidation and the pH. In acidic aqueous solution, the GO flakes vary from fully aggregated over graphitic domains to partial aggregation via hydrogen bonding between hydroxylated domains, leading to the formation of planar extended flakes at high oxidation ratios and stacks at low oxidation ratios. At high pH, where the edge carboxylic acid groups are deprotonated, electrostatic repulsion leads to more dispersion, but a variety of aggregation behaviour is surprisingly still observed: over graphitic regions, via hydrogen bonding and “face-edge” interactions. Calcium ions cause additional aggregation, with a greater number of “face-face” and “edge-edge” aggregation mechanisms, leading to irregular aggregated structures. “Face-face” aggregation mechanisms are enhanced by the GO flakes possessing distinct domains of hydroxylated and graphitic regions, with – and hydrogen bonding interactions prevalent between these regions on aggregated flakes respectively. These findings furnish explanations for the aggregation characteristics of GO and GOQDs, and provide computational methods to design directed synthesis routes for self-assembled and associated applications.
登录
查看更多内容
氧化石墨烯的凝胶化研究
影响因子：
3.7
作者：
Bai, Hua;Li, Chun;Shi, Gaoquan
通讯作者：
Shi, Gaoquan
影响因子：
3.3
作者：
Molinero, Valeria;Moore, Emily B.
通讯作者：
Moore, Emily B.
影响因子：
10.9
作者：
Amadei, Carlo A.;Arribas, Paula;Vecitis, Chad D.
通讯作者：
Vecitis, Chad D.
影响因子：
3.9
作者：
Gudarzi, Mohsen Moazzami
通讯作者：
Gudarzi, Mohsen Moazzami
影响因子：
29.4
作者：
Erickson, Kris;Erni, Rolf;Zettl, Alex
通讯作者：
Zettl, Alex