Efficient purification of surface modified nanoparticles from its nanosuspension by using supercritical CO2 technology

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 redispersity.

Automated summary

In this study, a washing and drying strategy using supercritical CO2 (scCO2) was applied to surface-modified nanoparticles. The results showed that scCO2 achieved almost complete washing with a removal efficiency of over 99% for the surface modifier. Additionally, scCO2 drying improved the redispersity of the nanoparticles, leading to the disappearance of the gas-liquid interface.