Surface and core dual-designed carbon dots toward high-efficiency nano-lubricant additives for polyethylene glycol

Recently, energy and environmental crises have aggravated sharply, which results in the eco-friendly and high-efficiency polyethylene glycol (PEG) lubricating oils getting increasingly attention in lubrication. Advancing in PEG-based lubricating oils, especially their high-performance nano-additives is vitally important for energy conservation and reducing pollution. Therefore, a kind of surface and core dual-designed carbon dots (Zn,Cu,Fe-CDs_-N) modified by ionic liquid groups ([AMIm][N(CF₃SO₂)₂]) and doped by polymetallic atoms (Zn, Cu, and Fe) were first synthesized and creatively used as the nano-additives for the PEG200 base oil. Adding 1.0 wt% of Zn,Cu,Fe-CDs_-N can endow the PEG200 base oil with optimal friction-reduction, anti-wear, and load-supporting performances, the maximal increase amplitudes of approximately 46.6 %, 66.3 %, and 125.0 %, respectively. Additionally, the tribological properties of Zn,Cu,Fe-CDs_-N are without any weakening even under high load and long-time operating conditions, exhibiting good practicability and application prospects. Theoretical and experimental studies have illustrated the excellent tribological behaviors of Zn,Cu,Fe-CDs_-N assigned to the synergy of film-forming and nano-lubrication effects.