Stabilization mechanisms of nonpolar metal colloids with thin organic shells

薄有机壳非极性金属胶体的稳定机制

• 批准号: 443142444
• 负责人: Professor Dr. Tobias Kraus
• 金额: --
• 依托单位: Leibniz-Institut für Neue Materialien gGmbH (INM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/443142444?language=en
• 关键词: Stabilization; mechanisms; nonpolar; metal; colloids

Nonpolar nanoparticles are an important class of colloids. Syntheses developed in the last two decades yield particles of gold, silver, copper, and other metals and semiconductors. Their cores are covered with organic ligands that render them dispersible in alkanes, aromatics, and other nonpolar solvents. These particles are uncharged and not stabilized by Coulomb repulsion. Recent results from the applicant and other research groups demonstrate, however, that certain combinations of metal core, ligand, and solvent lead to unexpectedly great colloidal stabilities. The results indicate that the stability is due to the molecular structure of the shell. This is in stark contrast to conventional aqueous colloids that are described in DLVO theory.We propose here that nonpolar metal colloids with thin organic shells are stabilized by three mechanisms that have not yet been studied systematically: the entropic contributions of disordered ligand shells; the solvation of the organic shells by solvents that strongly interact on a molecular level; and the intercalation of solute molecules in the ligand shell that provide synergistic stability.This project investigates the proposed mechanisms using gold colloids with core diameters of 1-10 nm. Systematic series are chemically synthesized and covered with strongly bound linear, branched, or kinked (unsaturated) hydrocarbon chains. The resulting colloids are carefully purified and transferred to different solvents and solvent mixtures. The structure of the particles - in particular the density of the shell and its configuration - is assessed quantitatively.The colloidal stability or the dispersions is quantified as a function of concentration using a new technique where a droplet of colloid slowly evaporates during Small-Angle X-ray Scattering. Both particle concentration and agglomeration state are monitored. Thermal stability is measured using temperature-dependent X-ray and dynamic light scattering experiments. The molecular shell structure is analyzed using a combination of thermogravimetry, Raman spectrometry, NMR, optical scattering, and X-ray scattering.All experimental results are compared to detailed Molecular Dynamic simulations that are available in the group of Dr. Asaph Widmer-Cooper in Sydney, Australia. They were refined in previous collaborations between the two groups and will now be used to test the proposed mechanisms of nanoparticle stabilization.

非极性纳米粒子是一类重要的胶体。在过去的二十年里发展起来的合成技术产生了金、银、铜和其他金属和半导体颗粒。它们的核心被有机配体覆盖，这使得它们可以分散在烷烃、芳烃和其他非极性溶剂中。这些粒子不带电荷，也不会因库仑斥力而稳定。然而，申请人和其他研究小组的最新结果表明，金属核、配体和溶剂的某些组合会导致出人意料的极大的胶体稳定性。结果表明，壳层的稳定性与壳层的分子结构有关。这与DLVO理论中描述的传统水溶液胶体形成了鲜明的对比。我们提出，具有薄有机壳层的非极性金属胶体通过三种尚未被系统研究的机制来稳定：无序配体壳层的熵贡献；有机壳层在分子水平上强相互作用的溶剂溶剂化；以及提供协同稳定性的溶质分子在配体壳层中的嵌入。本项目使用核直径为1-10 nm的金胶来研究所提出的机理。系统系列是化学合成的，并覆盖有强结合的直链、支链或扭结(不饱和)碳氢链。生成的胶体经过仔细的提纯，然后转移到不同的溶剂和混合溶剂中。对颗粒的结构--特别是壳层的密度及其构型--进行了定量评估。胶体稳定性或分散性作为浓度的函数被量化，使用了一种新的技术，即胶滴在小角X射线散射过程中缓慢蒸发。同时监测颗粒浓度和团聚状态。用随温度变化的X射线和动态光散射实验测量了其热稳定性。利用热重、拉曼光谱、核磁共振、光学散射和X射线散射等手段对分子壳结构进行了分析，并将所有实验结果与澳大利亚悉尼Asaph Widmer-Cooper博士团队提供的详细分子动力学模拟结果进行了比较。它们在两个小组之前的合作中得到了改进，现在将用于测试拟议的纳米颗粒稳定机制。