In applications of surface-modified nanoparticles (NPs), simple and complete washing technology without using an organic solvent and drying technique to realize good re-dispersity have been desired. In this study, we report washing and drying strategy using supercritical CO₂ (scCO₂) and applied it to the nanosuspension including decanoic acid modified Fe₃O₄ NPs and decanoic acid to be removed. Notably, scCO₂ gave the removal efficiency of decanoic acid over 99 %, almost complete washing, which can be explained by its high diffusibility. Additionally, compared to traditional heat evaporation, the re-dispersity of NPs in hexane was significantly improved for scCO₂ drying that allows the disappearance of gas-liquid interface. These results conclusively show that washing and drying technology using scCO₂, with the characteristics of high diffusibility and no interface, can be an appealing approach to realize simple and complete purification of surface modified NPs with good re-dispersity.

在表面改性纳米粒子 (NPs) 的应用中，需要不使用有机溶剂的简单而完整的洗涤技术和干燥技术来实现良好的再分散性。在这项研究中，我们报告了使用超临界 CO ₂ (scCO ₂ ) 的洗涤和干燥策略，并将其应用于纳米悬浮液，包括癸酸改性的 Fe ₃ O ₄ NPs 和要去除的癸酸。值得注意的是，scCO ₂对癸酸的去除效率超过 99%，洗涤几乎完全，这可以用其高扩散性来解释。_{此外，与传统的热蒸发相比，scCO 2}纳米粒子在己烷中的再分散性得到显着改善使气液界面消失的干燥。这些结果最终表明，使用 scCO ₂的洗涤和干燥技术具有高扩散性和无界面的特点，可以成为实现具有良好再分散性的表面改性 NP 的简单和完全纯化的一种有吸引力的方法。