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

•A simple route for fabricate graphene quantum dots based coatings with tunable thickness has been proposed.•The as-obtained quantum dots based coatings are very uniform, smooth and dense.•The microstructures of quantum dots based coatings were controlled by tuning the deposition voltages.•The relationships between their surface roughness and tribological performance has been established.