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.