Room Temperature Ionic Liquids (RTILs),owing to their attributes,e.g.,negligible vapor pressure,have been expected to be the green solvents which could substitute the widely used volatile organic solvents in various cases [1-3].(T)ransfer of gold nanoparticles (GNPs) from water into RTILs is a relatively new scientific field of interest.Here,with the assistance of cetyl trimethyl ammonium bromide (CTAB),biosynthesized GNPs were transferred from water into a hydrophobic ionic liquid (IL),[Bmim]PF6.Zeta potential analysis of the GNPs illustrated that the electrostatic interaction between CTAB and the GNPs varied depending on the concentration of CTAB.And also for the first time this research revealed that the IL interacted with the adsorbed CTAB on the surface of the GNPs through an anion-exchange process.Thus in situ-produced water insoluble CTAPF6 led to the hydrophobization of the GNPs,such that these particles were transferred into the IL successfully.