Synthesis of oil-soluble carbon dots modified by ionic liquid groups as the high-performance lubricant additives

Oil-soluble carbon dots modified by ionic liquid groups (O-CDs-IL) were successfully synthesized and used as the lubricant additives of polyalphaolefin. The O-CDs-IL as additives exhibited not only the excellent dispersion stability but also the prominent tribological performance. Adding 3.0 wt% of O-CDs-IL made the coefficient of friction (COF) and wear volume (WV) of base oil reduce by 37.3% and 61.1%, respectively. When the test duration prolonged from 10 to 110 min, the above COF and WV reductions further enlarged to 47.8% and 69.2%. The worn surface analysis results demonstrated that a complex boundary lubrication film has formed on the worn surface lubricated by the lubricant containing O-CDs-IL. In fact, the film was a tribofilm composed of carbon cores of O-CDs-IL and chemical reaction products such as iron oxides, N-containing compounds, metal nitrides and FePO4, well accounting for the eminent friction-reducing and anti-wear functions of O-CDs-IL.