Monego Debora, Kister Thomas, Kirkwood Nicholas, Doblas David, Mulvaney Paul, Kraus Tobias, Widmer-Cooper Asaph
ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
The University of Sydney Nano Institute, The University of Sydney, Sydney, New South Wales 2006, Australia.
ACS Nano. 2020 May 26;14(5):5278-5287. doi: 10.1021/acsnano.9b03552. Epub 2020 Apr 23.
We report on the colloidal stability of nanoparticles with alkanethiol shells in apolar solvents. Small-angle X-ray scattering and molecular dynamics simulations were used to characterize the interaction between nanoparticles in linear alkane solvents ranging from hexane to hexadecane, including 4 nm gold cores with hexadecanethiol shells and 6 nm cadmium selenide cores with octadecanethiol shells. We find that the agglomeration is enthalpically driven and that, contrary to what one would expect from classical colloid theory, the temperature at which the particles agglomerate increases with increasing solvent chain length. We demonstrate that the inverted trend correlates with the temperatures at which the ligands order in the different solvents and show that the inversion is due to a combination of enthalpic and entropic effects that enhance the stability of the ordered ligand state as the solvent length increases. We also explain why cyclohexane is a better solvent than hexadecane despite the two having very similar solvation parameters.
我们报道了具有链烷硫醇壳层的纳米颗粒在非极性溶剂中的胶体稳定性。利用小角X射线散射和分子动力学模拟来表征纳米颗粒在从己烷到十六烷的线性烷烃溶剂中的相互作用，其中包括具有十六烷硫醇壳层的4纳米金核和具有十八烷硫醇壳层的6纳米硒化镉核。我们发现团聚是由焓驱动的，并且与经典胶体理论所预期的相反，颗粒团聚的温度随着溶剂链长的增加而升高。我们证明这种相反的趋势与配体在不同溶剂中有序排列的温度相关，并表明这种反转是由于焓效应和熵效应的结合，随着溶剂长度的增加，这种效应增强了有序配体状态的稳定性。我们还解释了为什么尽管环己烷和十六烷的溶剂化参数非常相似，但环己烷却是比十六烷更好的溶剂。
