One-step “green” synthesis of dispersable carbon quantum dots/poly (methyl methacrylate) nanocomposites for tribological applications

Herein, the production of a poly (methyl methacrylate)/carbon quantum dots (PMMA/CQDs)-based composite has been proposed for the first time through a one-step, mild temperature, easily scalable oleic acid- and citric acid-based green synthesis. The composite consists of an oil-compatible polymer matrix which locally releases anti-friction and anti-wear CQDs under lubrication conditions. After extensive characterization, tribological tests were performed in commercial VG 220 at different temperatures, loads and additive concentrations, showing remarkable performance. At 25 °C and under a 19 N normal pressure, with 0.3 wt% PMMA/CQDs, 20.2% and 41.6% reductions were observed for friction and wear, respectively. Furthermore, viscosities measurements at both 40 °C and 100 °C showed that the nanocomposite presence did not substantially interfere with the oil rheological parameters.