Smooth and dense graphene quantum dots-based lubricating coatings prepared by electrophoretic deposition

Graphene quantum dots (GQDs) are very intriguing in various application fields of micro/nano-electrical-mechanical systems including biomedicine, photovoltaics, light-emitting diodes, and nanosensors devices due to their outstanding physical and chemical properties from quantum confinement and edge effects. Herein, GQDs were firstly synthesized, which can be well dispersed in water and the obtained dispersion shows high stability. Then, graphene quantum dots coatings (GQDCs) were deposited on silicon (Si) substrate via a simple electrophoretic deposition route by using GQDs aqueous dispersion as raw materials. As a result, the as-deposited GQDCs present very uniform, smooth and dense characters. The tribological measurements indicate that the optimum GQDCs sample shows effective reductions in friction coefficient (similar to 85%) and wear volume (similar to 97%) relative to those of the bare Si substrate. Based on these superior tribological performances, the deposited GQDCs are expected to be the outstanding solid lubricant coatings in Si-based devices with highly efficient lubrication and anti-wear properties.