Fabrication of ionic liquid-functionalized carbon dots as lubricant additive for friction and wear reduction

Herein, a long-chain ionic liquid with the catecholic group was successfully synthesized and then grafted to the carbon dots surface (CDs-ILs-Br) via the self-assembly capability of catecholic compound. The resulting CDs-ILs-Br exhibit excellent dispersion stability in PEG200, maintaining a uniform dispersion for over one month. With the addition of 3.0 wt% CDs-ILs-Br, the average COF of base oil decreased to 0.113, resulting in 60 % reduction in wear volume. Furthermore, the introduction of anti-wear agent BF₄^- further reduced average COF to 0.093. XPS and EDS analysis confirm complex tribochemical reactions between CDs-ILs-Br and the friction pair, and the grafting polar molecules of ILs on the carbon dots surface enhanced adhesion effect under high shear condition, forming a robust tribochemical protective film.