Solvent-free ionic nanofluids (NFs) of graphene oxide-silica hybrid nanocores (GO@SiO2) were synthesized for the first time via functionalizing in succession the nanocores with a covalently charged corona and an ionically tethered oligomeric canopy. Being intrinsically one-component materials, GO@SiO2 NFs display a liquid-like behavior in the absence of any solvent and show excellent dispersion stability in polyethylene glycol (PEG) base oil. Adding even small amount of GO@SiO2 NFs improved dramatically the lubrication performance of PEG base
oil. It was revealed that GO@SiO2 NFs played an important role in physicochemical actions on the friction interface. This work provided direct evidence that a protective tribofilm grew on the sliding surfaces when
molecular species of GO@SiO2 NFs were fed continuously onto the contact zone. In particular, graphitized GO and SiO2 nanoparticles digested in the tribofilm enhanced its lubricity and robustness. It is expected that solventfree ionic GO@SiO2 NFs open up new opportunities for developing advanced lubricating nanomaterials.