The resulting graphite oxide dispersion underwent multiple centrifugation rounds, followed by the removal of a liquid supernatant containing chemical impurities or contaminants such as residual potassium permanganate, fulvic acids and other metallic species. The graphitic pellet was redispersed in sterile, endotoxin-free water before each centrifugation step, until the supernatant's pH was neutralised (pH ~ 7). As a result, the supernatant became also less turbid, progressively changing from an originally translucent dark yellow to a more transparent state. The graphitic pellet was then redispersed and vigorously exfoliated by vortexing at maximum speed for 5 minutes. After another centrifugation round, a dark orange/brown, gel-like layer containing the desired thin GO sheets was deposited on top of black by-products, mainly composed of thick graphitic and oxidised graphite materials (Figure ). This layer could be carefully extracted with warm water, avoiding the contamination of the product with unwanted graphitic impurities from the pellet. After repeating this process with a new centrifugation round, a final centrifugation step was performed on the extracted GO 24 hours post-reaction in order to confirm the purification of large GO flakes (l-GO) as the end product, by removing any graphitic impurities that might have been extracted as well in the previous step (Figure , blue arrows). The final yield of the reaction was relatively low, corresponding in mass to ~9% (w/w) of the starting graphite.