▎ 摘　　要

Heat transfer of nanofluids is a complex phenomenon, where many factors like viscosity, surface charge, composition, and fluid stability of the dispersed nanoplatelets will affect the final thermal performance. Various layered nanoplatelets have been applied to fabricate composite nanofluids for applications on thermal management systems. Up to date, heat transfer fluids with high thermal and electrical properties have not yet been synthesized. In this study, functionalized graphene nanoplatelets (FGNs) with 1-5 atomic-thick were synthesized via a green steam exfoliated technique. Such the FGNs can generate the highly stable aqueous suspensions with high shelf life. The FGNs-water nanofluid exhibits an unprecedented thermal conductivity of 2.52 W mK(-1) at 20 vol% loading of nanoplatelets, suggesting it has superb potential application on various thermal fields.