Scalable and Sustainable Synthesis of Carbon Dots from Biomass as Efficient Friction Modifiers for Polyethylene Glycol Synthetic Oil

Abstract

Carbon dots (CDs) have lately inspired extensive interest in tribology, especially in the field of friction modifiers. However, it remains an enormous challenge to obtain satisfactory compatibility between CDs and base oils without laborious and tedious chemical modifications. In this work, for the first time, we reported a scalable and sustainable synthesis of CDs from easily and cheaply available biomass via a one-pot solvothermal route, which used ethanol as the renewable reaction medium and H 2 O 2 as the clean oxidant. Typically, ginkgo leaves acting as the precursors were converted into CDs with an ultrahigh yield of 85.3%. As expected, the ginkgo leaf-derived CDs, abbreviated as GCDs, displayed excellent dispersibility, durable stability, and attractive fluorescence-emission behavior in PEG200. The as-prepared GCDs as additives for PEG200 exhibited remarkable lubricity, favorable loadcarrying ability, and long operating life under boundary lubrication. Particularly, the antiwear and friction-reducing performances of PEG200 were promoted by 70.5% and 34.7%, respectively, when only 0.20 wt % of GCDs was blended. Confirmed by the tribological investigations and surface detection of wear tracks, the essential lubrication mechanism of GCDs was chiefly associated with the generation of GCD-inserted tribochemical films with a thickness of about 80 nm and their nanolubrication functions, that is, the synergistic effects of surface organic moieties and carbonaceous cores. This study establishes a technically simple, feasible, versatile, cost-effective, and green methodology to produce CD-based friction modifiers toward PEG synthetic base oils for tribological applications.

Layered Magnesium Phosphate as an Environmentally Friendly Solid Lubrication Additive: Morphology Control and Tribological Properties

“…The pressing energy crisis and rising environ- mental standards have necessitated the development of "green tribology." 11 Lubricants based on eco-friendly raw materials and their derivatives are attracting increasing attraction in various applications. Herein, calcium grease was chosen as the base grease for investigating the tribological properties of MgP.…”

A mucus-inspired solvent-free carbon dot-based nanofluid triggers significant tribological synergy for sulfonated h-BN reinforced epoxy composites

“…31–35 Carbon dots are promising lubricant additives due to their extremely small dimensions, well-defined spherical structure and soft feature, which perform the “ball effect” and “self-healing” between counter bodies at the nanoscale, thereby reducing friction and wear up to high load. 36–38…”

“…[31][32][33][34][35] Carbon dots are promising lubricant additives due to their extremely small dimensions, well-dened spherical structure and so feature, which perform the "ball effect" and "self-healing" between counter bodies at the nanoscale, thereby reducing friction and wear up to high load. [36][37][38] Here, bio-inspired by the snail mucus, for the rst time we design an advanced lubricating system that combines the advantages of 2D materials, cf. h-BN, and a 0D carbon dot-based nanouid to form a stable, homogeneous and continuous boundary lm to effectively reduce friction and wear at polymer composite surfaces.…”

Synthesis of Eco-Friendly Carbon Dots as Self-Repairing Additives of Polyalphaolefin by Means of a Green Solvation Effect

“…Among the diverse inorganic nanoadditives, the CDs are lately becoming the most attractive additives owing to their regular morphology, small but uniform particle size, high chemical stability, and strong film-building ability. − As most CDs have been synthesized by the bottom-up method, abundant target groups could be facilely grafted on the surfaces of CDs during the synthesis processes. Based on this merit, the long-term dispersion stability of CDs in polar and partially polar base oils has been perfectly resolved. − However, the research studies on CDs as additives of nonpolar base oil of PAO were far from enough since the synthesis and extraction of CDs modified by totally nonpolar groups were especially difficult . To avoid the abovementioned tedious and even polluting chemical modification process, the amphiphilic CDs were conveniently dispersed into PAO as additives by using Span-80 as dispersant .…”