Tanaka Jun, Ikeda Seiya, Yoshikuni Nozomu, Mukai Kohki
Graduate School of Engineering Science, Yokohama National Univ., 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
ACS Omega. 2025 Jun 6;10(23):24996-25006. doi: 10.1021/acsomega.5c02599. eCollection 2025 Jun 17.
We report the possibility of classification into single nanosized colloidal quantum dots (CQDs) by membrane filtration by considering the affinity balance between ligands, solvents, and membranes. CQDs are expected to have a wide variety of applications in the near future. To realize the social implementation, efficient process technologies for mass production of CQDs have been eagerly awaited. CQDs are easily agglomerated due to the nanosized colloidal particle, so the surface is usually preserved by ligands. On the other hand, size classification is a matter for CQDs because the optical property is closely related to the size of the particle. Recently, various separation and classification methods using porous membranes have been attempted. However, there are few reports about the membrane filtration of nanosized particles in organic solvents such as CQDs. Therefore, the influence of ligands in organic solvents on membrane filtration has not been researched enough. Lack of basic knowledge has been a hurdle to the widespread use of membrane filtration processes in organic-solvent-based dispersions. In this article, the dispersions of CQDs capped by organic and inorganic ligands in various solvents were examined in detail. In addition, the effects of the ligands and solvents on membrane filtration were also investigated. As a result, the CQDs can exist as clusters in the solvent, which has been conventionally known as a good solvent. Moreover, the size of the clusters changed, depending on the affinity between ligands and solvents. By organizing these results based on the idea of the Hansen solubility parameter, we successfully explained agglomeration in the dispersion or adsorption on the membrane. Furthermore, the Hansen solubility parameter of iodide-ligand CQDs was estimated based on the dispersing test of various solvents, and a new mixed solvent for iodide-capped CQDs was discovered for the first time. The experimental results indicate the possibility of membrane filtration of single nanosized CQDs. Based on this study, we suggest optimal filtration conditions for CQD dispersion.
我们报道了通过考虑配体、溶剂和膜之间的亲和平衡，利用膜过滤将单个纳米级胶体量子点（CQD）分类的可能性。预计CQD在不久的将来会有广泛的应用。为了实现其社会应用，人们急切期待用于大规模生产CQD的高效工艺技术。由于纳米级胶体颗粒，CQD很容易团聚，所以其表面通常由配体保护。另一方面，尺寸分类对于CQD来说很重要，因为光学性质与颗粒大小密切相关。最近，人们尝试了各种使用多孔膜的分离和分类方法。然而，关于在有机溶剂（如CQD）中纳米级颗粒的膜过滤的报道很少。因此，有机溶剂中配体对膜过滤的影响尚未得到充分研究。基础知识的缺乏一直是膜过滤工艺在基于有机溶剂的分散体中广泛应用的障碍。在本文中，详细研究了由有机和无机配体封端的CQD在各种溶剂中的分散体。此外，还研究了配体和溶剂对膜过滤的影响。结果表明，CQD在通常被认为是良溶剂的溶剂中可以以聚集体形式存在。而且，聚集体的大小会根据配体和溶剂之间的亲和力而变化。通过基于汉森溶解度参数的概念整理这些结果，我们成功解释了分散体中的团聚或膜上的吸附现象。此外，基于对各种溶剂的分散测试估算了碘化物配体CQD的汉森溶解度参数，并首次发现了一种用于碘化物封端CQD的新型混合溶剂。实验结果表明了单个纳米级CQD进行膜过滤的可能性。基于这项研究，我们提出了CQD分散体的最佳过滤条件。
