AbstractThis paper reports a phase transfer based wet chemistry method for the preparation of Au/VP-1 nanofluids. The method involves the transfer of AuCl4− ions from water to the base liquid Therminol VP-1, followed by the reduction of AuCl4− ions using NaBH4. The prepared nanofluids are characterized for their thermophysical properties and stability. The results show that the mass concentration of Au particles has a significant effect on the stability of Au/VP-1 nanofluids. An increase in the Au concentration results in a higher extent of agglomeration among the particles, leading to a decrease in the nanofluid stability. The results also show that the introduction of 0.005–0.05% Au nanoparticles enhances the thermal conductivity of the fluids by up to 6.5%, whereas the viscosity increase is minimal.