Friction-induced transfer of carbon quantum dots on the interface: Microscopic and spectroscopic studies on the role of inorganic-organic hybrid nanoparticles as multifunctional additive for enhanced lubrication

Inorganic-organic hybrid carbon quantum dots (CQDs) attached the structure of diphenylamine (DPA) on the surfaces (CQDs-N) have been successfully prepared by one-step pyrolysis method at lower temperature. The obtained N-doped carbon dots (CQDs-N) were spherical particles with a narrow size distribution exhibiting photoluminescent property, which are also proved to be an multifunctional additive exhibiting not only antioxidant but also antiwear and friction-reducing performances. Even tested under higher load, CQDs-N still exhibited superior friction-reducing performance till now in polyethylene glycol (PEG) for steel/steel pairs. The function of CQDs-N with polar nature, acting as bearing balls and depositing on the interface to form non-uniform protective film, might account for the excellent antiwear and friction-reducing performances under boundary lubrication.