Liu Shuyan, Wu Bin, Yang Xiaoning
State Key Laboratory of Material-Orientated Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology , Nanjing 210009, China.
ACS Appl Mater Interfaces. 2014 Apr 23;6(8):5789-97. doi: 10.1021/am5006095. Epub 2014 Apr 4.
A molecular dynamics simulation was conducted to study the structure and morphology of sodium dodecyl sulfate (SDS) surfactants adsorbed on a nanoscale graphene nanostructure in the presence of an electrolyte. The self-assembly structure can be reorganized by the electrolyte-induced effect. An increase in the ionic strength of the added electrolyte can enhance the stretching of adsorbed surfactants toward the bulk aqueous phase and make headgroups assemble densely, leading to a more compact structure of the SDS/graphene composite. The change in the self-assembly structure is attributed to the accumulation/condensation of electrolyte cations near the surfactant aggregate, consequently screening the electrostatic repulsion between charged headgroups. The role of the electrolyte revealed here provides direct microscopic evidence or an explanation of the reported experiments in the electrolyte tuning of the interfacial structure of a surfactant aggregate on the surface of carbon nanoparticles. Additionally, the buoyant density of the SDS/graphene assembly has been computed. With an increase in the ionic strength of the electrolyte, the buoyant density of the SDS/graphene composite rises. The interfacial accumulation of electrolytes provides an important contribution to the density enhancement. The study will be valuable for the dispersion and application of graphene nanomaterials.
进行了分子动力学模拟，以研究在电解质存在下吸附在纳米级石墨烯纳米结构上的十二烷基硫酸钠（SDS）表面活性剂的结构和形态。自组装结构可通过电解质诱导效应进行重组。添加电解质的离子强度增加可增强吸附的表面活性剂向本体水相的伸展，并使头基密集组装，导致SDS/石墨烯复合材料结构更紧凑。自组装结构的变化归因于电解质阳离子在表面活性剂聚集体附近的积累/凝聚，从而屏蔽了带电头基之间的静电排斥。这里揭示的电解质的作用为碳纳米颗粒表面活性剂聚集体界面结构的电解质调节方面已报道的实验提供了直接的微观证据或解释。此外，还计算了SDS/石墨烯组装体的浮力密度。随着电解质离子强度的增加，SDS/石墨烯复合材料的浮力密度升高。电解质的界面积累对密度增加有重要贡献。该研究对石墨烯纳米材料的分散和应用具有重要价值。
