Dry-state-stained transmission electron microscopy (TEM) imaging was performed on Tecnai Spirit transmission electron microscope (TEM, FEI/ThermoFisher, Hillsboro, Oregon, United States) operating at 120 kV using a 2k Veleta camera (Olympus, Shinjuku, Tokyo, Japan). All dry-state samples were diluted with deionized water to appropriate analysis concentration and then deposited onto GO-coated copper grids. After roughly 1 min, excess sample was blotted from the grid and the grid was stained with methylamine vanadate (Nanovan) negative stain solution for 1 min prior to blotting, drying and microscopic analysis.