TEM was performed using a BioTwin electron microscope (Philips/FEI, Netherlands), Technai 12 instrument operated at an accelerating voltage of 100kV, a spot size of 1 and an aperture size of 3. The beam exposure time was 0.1 s whereas the camera exposure time was set to 1 s. Both 1900x and 4800x magnifications were used to image l-GO and s-GO, whereas us-GO samples were analysed using the 6800x magnification. Ten µL of sample were deposited on a carbon coated grid and filter paper was used to remove any excess of material after 1 min of deposition time. Carbon grids with the deposited l-GO samples underwent a prior glow discharge treatment. Lateral size distribution was carried out by manual counting on ImageJ software on several TEM images.