Wu Wenchang, Cui Junwei, Sultan Umair, Gromotka Lukas, Malgaretti Paolo, Damm Cornelia, Harting Jens, Vogel Nicolas, Peukert Wolfgang, Inayat Alexandra, Fröba Andreas P
Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany.
Institute of Chemical Reaction Engineering, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Egerlandstr. 3, 91058 Erlangen, Germany; Institute of Particle Technology, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Cauerstraße 4, 91058 Erlangen, Germany.
J Colloid Interface Sci. 2023 Jul;641:251-264. doi: 10.1016/j.jcis.2023.03.045. Epub 2023 Mar 11.
The applicability of the dynamic light scattering method for the determination of particle diffusivity under confinement without applying refractive index matching was not adequately explored so far. The confinement effect on particle diffusion in a porous material which is relevant for particle chromatography has also not yet been fully characterized.
Dynamic light scattering experiments were performed for unimodal dispersions of 11-mercaptoundecanoic acid-capped gold nanoparticles. Diffusion coefficients of gold nanoparticles in porous silica monoliths were determined without limiting refractive index matching fluids. Comparative experiments were also performed with the same nanoparticles and porous silica monolith but applying refractive index matching.
Two distinct diffusivities could be determined inside the porous silica monolith, both smaller than that in free media, showing a slowing-down of the diffusion processes of nanoparticles under confinement. While the larger diffusivity can be related to the slightly slowed-down diffusion of particles in the bulk of the pores and in the necks connecting individual pores, the smaller diffusivity might be related to the diffusion of particles near the pore walls. It shows that the dynamic light scattering method with a heterodyne detection scheme can be used as a reliable and competitive tool for determining particle diffusion under confinement.
到目前为止，尚未充分探索动态光散射法在不应用折射率匹配的情况下测定受限环境中颗粒扩散率的适用性。对于与颗粒色谱相关的多孔材料中颗粒扩散的限制效应也尚未得到充分表征。
对11-巯基十一烷酸包覆的金纳米颗粒的单峰分散体进行了动态光散射实验。在不使用限制折射率匹配流体的情况下，测定了金纳米颗粒在多孔硅胶整体柱中的扩散系数。还对相同的纳米颗粒和多孔硅胶整体柱进行了应用折射率匹配的对比实验。
在多孔硅胶整体柱内部可以测定出两种不同的扩散率，两者均小于在自由介质中的扩散率，这表明在受限环境下纳米颗粒的扩散过程有所减慢。较大的扩散率可能与颗粒在大部分孔隙以及连接各个孔隙的颈部中扩散略微减慢有关，而较小的扩散率可能与颗粒在孔壁附近的扩散有关。这表明采用外差检测方案的动态光散射法可作为测定受限环境下颗粒扩散的可靠且有竞争力的工具。
