State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China.
J Chem Phys. 2011 Nov 28;135(20):204703. doi: 10.1063/1.3661982.
Molecular dynamics simulations have been performed to study the potential of mean force (PMF) between passivated gold nanoparticles (NPs) in supercritical CO(2) (scCO(2)). The nanoparticle model consists of a 140 atom gold nanocore and a surface self-assembled monolayer, in which two kinds of fluorinated alkanethiols were considered. The molecular origin of the thermodynamics interaction and the solvation effect has been comprehensively studied. The simulation results demonstrate that increasing the solvent density and ligand length can enhance the repulsive feature of the free energy between the passivated Au nanoparticles in scCO(2), which is in good agreement with previous experimental results. The interaction forces between the two passivated NPs have been decomposed to reveal various contributions to the free energy. It was revealed that the interaction between capping ligands and the interaction between the capping ligands and scCO(2) solvent molecules cooperatively determine the total PMF. A thermodynamic entropy-energy analysis for each PMF contribution was used to explain the density dependence of PMF in scCO(2) fluid. Our simulation study is expected to provide a novel microscopic understanding of the effect of scCO(2) solvent on the interaction between passivated Au nanoparticles, which is helpful to the dispersion and preparation of functional metal nanoparticles in supercritical fluids.
采用分子动力学模拟方法研究了超临界 CO2（scCO2）中钝化金纳米粒子（NPs）之间的平均力势（PMF）。纳米粒子模型由 140 个原子的金纳米核和表面自组装单分子层组成，其中考虑了两种氟化烷硫醇。全面研究了热力学相互作用和溶剂化效应的分子起源。模拟结果表明，增加溶剂密度和配体长度可以增强 scCO2 中钝化 Au 纳米粒子之间自由能的排斥特征，这与先前的实验结果一致。对两个钝化 NPs 之间的相互作用力进行了分解，以揭示自由能的各种贡献。结果表明，封端配体之间的相互作用以及封端配体与 scCO2 溶剂分子之间的相互作用共同决定了总 PMF。对每个 PMF 贡献进行了热力学熵-能分析，以解释 scCO2 流体中 PMF 的密度依赖性。我们的模拟研究有望为 scCO2 溶剂对钝化 Au 纳米粒子之间相互作用的影响提供一种新的微观理解，这有助于在超临界流体中分散和制备功能性金属纳米粒子。
