Sarkar M, Riedl J C, Demouchy G, Gélébart F, Mériguet G, Peyre V, Dubois E, Perzynski R
Sorbonne Université, CNRS, PHysico-chimie des Electrolytes et Nanosystèmes InterfaciauX, F-75005, Paris, France.
Département de Physique, Univ. Cergy-Pontoise, 33 bd du port, 95011, Cergy-Pontoise, France.
Eur Phys J E Soft Matter. 2019 Jun 11;42(6):72. doi: 10.1140/epje/i2019-11835-6.
Thermodiffusion properties at room temperature of colloidal dispersions of hydroxyl-coated nanoparticles (NPs) are probed in water, in dimethyl sulfoxide (DMSO) and in mixtures of water and DMSO at various proportions of water, [Formula: see text]. In these polar solvents, the positive NPs superficial charge imparts the systems with a strong electrostatic interparticle repulsion, slightly decreasing from water to DMSO, which is here probed by Small Angle Neutron Scattering and Dynamic Light Scattering. However if submitted to a gradient of temperature, the NPs dispersed in water with ClO counterions present a thermophilic behavior, the same NPs dispersed in DMSO with the same counterions present a thermophobic behavior. Mass diffusion coefficient [Formula: see text] and Ludwig-Soret coefficient [Formula: see text] are measured as a function of NP volume fraction [Formula: see text] at various [Formula: see text]. The [Formula: see text]-dependence of [Formula: see text] is analyzed in terms of thermoelectric and thermophoretic contributions as a function of [Formula: see text]. Using two different models for evaluating the Eastman entropy of transfer of the co- and counterions in the mixtures, the single-particle thermophoretic contribution (the NP's Eastman entropy of transfer) is deduced. It is found to evolve from negative in water to positive in DMSO. It is close to zero on a large range of [Formula: see text] values, meaning that in this [Formula: see text]-range [Formula: see text] largely depends on the thermoelectric effect of free co- and counterions.
在水、二甲基亚砜（DMSO）以及水与DMSO按不同水的比例混合而成的体系中，研究了室温下羟基包覆纳米颗粒（NPs）胶体分散体的热扩散性质，[公式：见原文]。在这些极性溶剂中，带正电的NPs表面电荷赋予体系强烈的粒子间静电排斥作用，从水到DMSO这种排斥作用略有减弱，这通过小角中子散射和动态光散射进行探测。然而，如果施加温度梯度，分散在含有ClO抗衡离子的水中的NPs呈现嗜热行为，而分散在含有相同抗衡离子的DMSO中的相同NPs则呈现厌热行为。在不同的[公式：见原文]下，测量了质量扩散系数[公式：见原文]和路德维希 - 索雷特系数[公式：见原文]作为NP体积分数[公式：见原文]的函数。根据热电和热泳贡献作为[公式：见原文]的函数来分析[公式：见原文]对[公式：见原文]的依赖性。使用两种不同模型评估混合物中抗衡离子和反离子转移的伊士曼熵，推导出单粒子热泳贡献（NP的伊士曼转移熵）。发现其从水中的负值演变为DMSO中的正值。在很大范围的[公式：见原文]值上它接近零，这意味着在这个[公式：见原文]范围内[公式：见原文]很大程度上取决于游离抗衡离子和反离子的热电效应。
