Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi 110016, India.
J Chem Phys. 2017 May 7;146(17):174902. doi: 10.1063/1.4982755.
We employ molecular dynamics simulations to study the structure and solvation thermodynamics of thiolated gold nanoparticles of size 1.2 and 1.6 nm with ligand of chain length 8-16 carbons in ethane and propane over a wide range of densities close to the critical isotherm. The Helmholtz free energy is estimated by explicitly calculating the change in entropy and internal energy of solvation, and the effect of density and temperature on fluctuation-driven inherent anisotropy in the ligand corona is characterized. Since the topological variation further accentuates this instantaneous asymmetry in the ligand cloud, the anisotropy with varying surface coverage and chain length is also studied including the solvent contributions to the entropic and energetic metrics. Our results are consistent with the experiment, suggesting a route of obtaining structural insights into solvation thermodynamics that could be useful for understanding the stability of nanoparticle dispersions.
我们采用分子动力学模拟的方法，在接近临界等温线的宽密度范围内，研究了尺寸为 1.2nm 和 1.6nm 的巯基化金纳米粒子在乙烷和丙烷中的溶剂化结构和溶剂化热力学，配体链长为 8-16 个碳原子。通过显式计算溶剂化熵和内能的变化，来估算亥姆霍兹自由能，同时还研究了密度和温度对配体冠层中由涨落驱动的固有各向异性的影响。由于拓扑变化进一步强调了配体云中的这种瞬时不对称性，所以还研究了随着表面覆盖率和链长的变化而产生的各向异性，包括溶剂对熵和能量度量的贡献。我们的结果与实验一致，这为深入了解溶剂化热力学的结构提供了一种途径，可能有助于理解纳米粒子分散体的稳定性。
