As mentioned previously, we estimated that the bath sonication step employed in the production of s-GO and us-GO (5 minutes and 4 hours, respectively) may have induced changes in the surface chemistry, potentially reducing the final GO materials. We attempted to minimise these potential changes by carefully monitoring the temperature of the sonication bath and renewing it with ice-cold water frequently. Whilst the three GO materials produced here yielded flakes with lateral dimensions inversely proportional to sonication time, the remaining physicochemical properties did not change considerably. However, it must be noted that no further change in lateral dimensions was observed beyond 4 hours of sonication, i.e. no further size reduction (data not shown). These findings are in agreement with other studies on the impact of bath sonication on the flake size of GO .