In this article, equilibrium molecular dynamics are performed to investigate the thickness and thermal conductivity of interfacial layer around the nanoparticle in dilute nanofluids. A nanofluids system of a 1-nm-diameter copper spherical nanoparticle immersing into argon base liquids and then a flat interface formed by liquid argon on the solid copper surface are studied. Green-Kubo formula is developed to calculate thermal conductivity of interfacial layer. Besides, the effect of solid-liquid interaction is studied. The nano-scale thin interfacial layer with more ordered structure and higher thermal conductivity than that of the base fluids is observed. Then the simulation results are incorporated into the modified Maxwell equation to calculate the effective thermal conductivity of nanofluids. The results indicate that the contribution of interfacial layer to thermal conductivity enhancement of nanofluids can be neglected. (C) 2018 Elsevier Ltd. All rights reserved.