Samples were prepared after depositing 20 µL of GO dispersion (50 µg/mL) on a freshly cleaved mica surface (Agar Scientific, UK) coated with 20 µL of 0.01% poly-L-lysine (Sigma-Aldrich, UK) and allowed to adsorb for 2 min. Excess of materials was then removed by rinsing with Milli-Q ultrapure water (Merck Millipore, UK). Samples were left to dry overnight at 37ºC in a drying cabinet. AFM images were acquired in air using a Multimode 8 atomic force microscope (Bruker, UK) in tapping mode using OTESPA tips (Bruker, UK) of 10 nm curvature radius, mounted on a tapping mode silicon cantilever with a typical resonant frequency of 300 kHz and a spring constant of 42 N/m. Images were processed on Nanoscope Analysis software (version 1.4, Bruker, UK) and exported for further background removal and particle analysis on ImageJ, using a segmentation algorithm. Values obtained for lateral dimensions and thickness were used for the boxplots and statistical analysis.