Effect of alkyl chain length on phase transfer of surfactant capped Au nanoparticles across the water/toluene interface

Gold nanoparticles synthesized in aqueous phase were modified by thioglycolic acid (TGA) and then capped with cetyltrimethyl ammonium bromide (C16TAB), myristyltrimethyl ammonium bromide (C14TAB), and dodecyltrimethyl ammonium bromide (C12TAB), respectively. The surfactant capped nanoparticles could be transferred into toluene without aggregation across the water/toluene interface under vigorous stirring. The transfer process was certified by the rapid change of color of the aqueous and organic phase, zeta potential of nanoparticles, and UV-vis absorbance spectroscopy. Experimentally, it is found that only decyltrimethyl ammonium bromide (C10TAB) capped nanoparticles were unable to ensure the phase transfer in the organic phase. Both transmission electron microscopy (TEM) images and static light scattering measurement demonstrated the narrow size distribution of the capped nanoparticles in toluene.