Extraction of gold nanoparticles based on temperature-dependent phase separation using zwitterionic 3-(nonyldimethylammonio)-propyl sulfate

Nakagawa, Taichi  ; Suzuki, Reika*; Matsueda, Makoto   ; Terashima, Motoki  ; Hinze, W. L.*; Takagai, Yoshitaka*

The zwitterionic surfactant 3-(nonyldimethylammonio)-propyl sulfate (C-APSO) exhibits unique reversible temperature-dependent phase separation properties, which can be used for the extraction of water-miscible negatively charged gold nanoparticles (AuNPs) without any aggregation at high concentrations using only temperature change. This study investigated the extraction behaviors and properties of AuNPs transferred from the water phase to a small volume of the surfactant-rich phase. The AuNPs retained both their original shapes and sizes after temperature-dependent phase separation step. In addition, the concentration of AuNPs was enriched by a factor of 150 in the surfactant-rich phase without any changes in the sizes and shapes of AuNPs.