▎ 摘　　要

NOVELTY - Preparing graphite oxide comprises adding graphite in a mixture of the phosphoric acid and sulfuric acid. USE - The method is useful for preparing graphite oxide that is used to prepare a graphene nano-sheet (claimed), and to manufacture secondary battery, energy storage unit, filtration membrane, detector, transparent electrode, fuel cell and super capacitor. ADVANTAGE - The graphite oxide is prepared with high quality. The generation of heat during the graphite synthesis can be easily controlled. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a method for manufacturing a graphene nano-sheet; and (2) a method for manufacturing graphite oxide powder comprising freezing and drying the graphite oxide.