ARC Centre of Excellence in Exciton Science, School of Chemistry and The University of Sydney Nano Institute , University of Sydney , Sydney , New South Wales 2006 , Australia.
INM-Leibniz Institute for New Materials , Campus D2 2 , 66123 Saarbrücken , Germany.
Langmuir. 2018 Oct 30;34(43):12982-12989. doi: 10.1021/acs.langmuir.8b02883. Epub 2018 Oct 18.
Inorganic nanoparticle cores are often coated with organic ligands to render them dispersible in apolar solvents. However, the effect of the ligand shell on the colloidal stability of the overall hybrid particle is not fully understood. In particular, it is not known how the length of an apolar alkyl ligand chain affects the stability of a nanoparticle dispersion against agglomeration. Here, small-angle X-ray scattering and molecular dynamics simulations have been used to study the interactions between gold nanoparticles and between cadmium selenide nanoparticles passivated by alkanethiol ligands with 12-18 carbons in the solvent decane. We find that increasing the ligand length increases colloidal stability in the core-dominated regime but decreases it in the ligand-dominated regime. This unexpected inversion is connected to the transition from ligand-dominated to core-dominated agglomeration when the core diameter increases at constant ligand length. Our results provide a microscopic picture of the forces that determine the colloidal stability of apolar nanoparticles and explain why classical colloid theory fails.
无机纳米颗粒核通常涂覆有有机配体以使它们在非极性溶剂中分散。然而，配体壳对整体混合颗粒胶体稳定性的影响还不完全清楚。特别是，不知道非极性烷基配体链的长度如何影响纳米颗粒分散体对聚集的稳定性。在这里，使用小角 X 射线散射和分子动力学模拟研究了在溶剂癸烷中被 12-18 个碳原子的烷硫醇配体钝化的金纳米颗粒和硒化镉纳米颗粒之间的相互作用。我们发现，增加配体长度会增加核心主导区域的胶体稳定性，但会降低配体主导区域的胶体稳定性。这种出人意料的反转与核心直径在恒定配体长度下增加时，从配体主导到核心主导聚集的转变有关。我们的结果提供了决定非极性纳米颗粒胶体稳定性的力的微观图像，并解释了为什么经典胶体理论会失效。
