A rapid phase transfer method for nanoparticles using alkylamine stabilizers

Phase transfer of noble metal nanoparticles (NPs) (>20 nm) from aqueous to organic media is a challenge in colloidal science. We have developed a rapid and simple phase transfer method with alkylamine as the surfactant, through which gold (106 nm in diameter) and silver NPs (118 nm in edge length) can be transferred from aqueous to organic phases. Three alkylamines with different chain-lengths (NH(2)-(CH(2))(n-1)-CH(3), n=12, 16 and 18) were compared, and octadecylamine (ODA) was the most efficient. The ODA-NP complex rapidly formed as a result of shaking the mixture of ODA (in ethanol) and NPs (in water). After 20s, the complex separated from the liquid phase because of their hydrophobicity. The undissolved ODA-NP complex could be redispersed into organic solvents, such as chloroform. Ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM) results show that the metal NPs are still monodisperse having been transferred into organic solvents. The whole process of the phase transfer of NPs from aqueous to organic media can be made to happen in less than 1 min.