▎ 摘　　要

NOVELTY - Method for preparing graphene oxide involves (i) mixing purified microcrystalline graphite and mixed acid, adding oxidizing agent for reaction and quenching to obtain a reaction system, where the mixed acid comprises trifluoromethanesulfonic acid, and (ii) heating the reaction system at a constant temperature, cooling and adding with reducing agent for reduction to obtain the product. USE - The method is useful for preparing graphene oxide for small-sized graphene (claimed). ADVANTAGE - The method is carried out under the open system of low temperature and normal pressure, has fast reaction time, low preparation cost to obtain nano-scale small-sized graphene oxide, mild conditions, simple and high efficiency, and high safety factor, reduces the time and equipment cost, and is suitable for industrialization promotion and application. The single-layer small-sized graphene oxide has higher specific surface area, more active edge sites, and is not prone to agglomeration. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a small-sized graphene comprising graphene oxide obtained after reduction, where the reduction involves thermal reduction and/or chemical reduction.