The morphology of the GO flakes was studied using optical microscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) in a complementary fashion, and is presented in Figure . In addition, a boxplot presentation of the measured lateral dimensions together with the respective number of analysed particles and statistical analysis is reported in Figure . Finally, the size distribution values (mean, minimum and maximum values) are summarised for each material in Table (Supporting Information) to support the comparison among the three GO types.