Superior lubrication effect enabled by soluble carboxylated graphene quantum dots in polyether-modified silicone oil

Achieving robust and reliable ultra to superlow friction combined with extremely low wear applicable to industrial applications has always been the pursuit of researchers. In this work, carboxylated graphene quantum dots (CGQDs) have been synthesized to be dissolved into polyether-modified silicone oil (PESO). The results indicate that CGQDs demonstrate exceptional solubility in PESO oil, which can be attributed to the favorable charge-transfer interaction occurred between CGQDs and PESO oil molecules. Tribological tests indicate that the addition of CGQDs to PESO could result in a robust and reliable superior lubrication effect for steel tribopairs under a wide range of testing conditions, with the lowest friction coefficient being approximately 0.02. The investigation of wear scars indicates that CGQDs can effectively embed into friction contacts due to the ultra-small size, allowing them to interact effectively with the steel surface through their carboxy groups and therefore forming an in-situ robust CGQDs-based lubricant film. The generated CGQDs-based lubricant film could not only effectively passivate the direct asperity contacts of tribopairs but also provide a shearable path due to its desirable lamellar characteristics. It is expected that the finding in this work would provide a novel reliable strategy to achieve ultra to super-lubrication for industrial applications.