Study on the Effect of Nanomaterials' Dimensionality on the Synergistic Effect of Surfactant/Nanomaterial and Its Microscopic Mechanism

In this paper, 0D nanoparticles (SiO2 nanoparticles modified by hydroxyl and pentyl active agents), 1D nanotubes (carbon nanotubes modified by carboxyl and pentyl active agents), and 2D nanosheets (graphene nanosheets modified by carboxylic acid chains and pentyl active agents) were constructed after comparative analysis. Then, the microscopic mechanism of different dimensional nanomaterials affecting the performance of surfactants was expounded by molecular dynamics simulation. The results show that only 0D nanoparticles and 2D nanosheets can synergize with the zwitterionic surfactant dodecyl dimethyl carboxyl betaine (BS-12), and the synergistic effect of graphene nanosheets modified with the carboxylic acid chain and pentane active agent is stronger than that of BS-12 alone. After the combination of modified nanoparticles and nanosheets with BS-12, the oil/water interfacial tension was reduced to 13.58 and 4.15 mN/m, respectively. The analysis of the microscopic action mechanism shows that when the modified nanoparticles and nanosheets were added, the total thickness of the oil/water interface layer, the monolayer thickness of the surfactant BS-12, and the interface formation energy of the oil-water system also increased to varying degrees. Second, the cohesive strength of oil molecules in the system (E = -554.98 kcal/mol) was much lower than that in the oil-water system (E = -735.84 kcal/mol) after the modified nanosheets were used in combination with BS-12. Finally, the analysis results of the radial distribution function and the structure of the polar group hydration layer show that the modified nanosheets and BS-12 have strong hydration with water molecules. In general, we studied the interfacial properties of oil-water mixed solutions containing active agent materials. The results show that the graphene oxide nanosheets grafted with carboxylic acid surfactants and alkane surfactants have superior interface properties, which provide a broader prospect for the experiment and practical application of grafted nanomaterials.