▎ 摘　　要

NOVELTY - Graphite powder, concentrated sulfuric acid and sodium nitrate are added, and mixed uniformly. Potassium permanganate is added to the resulting mixture, stirred, deionized water is added, and reacted, to obtain brown-colored mixture. Hydrogen peroxide is added to obtained mixture, washed with hydrochloric acid, and filtered. The resulting precipitate is washed with deionized water and vacuum-dried, to obtain graphene oxide. The graphene oxide is added into sodium hydroxide solution, stirred, washed with ethyl alcohol, and vacuum-dried, to obtain water-soluble graphene. USE - Preparation of water-soluble graphene used for biomedical application, and electrical energy application. ADVANTAGE - The method economically and environmentally-friendly provides water-soluble graphene having solubility of 1.5-2 mg/ml, and excellent dispersion stability with respect to water, with high productivity. DETAILED DESCRIPTION - Graphite powder, concentrated sulfuric acid and sodium nitrate are added into dry beaker placed in ice bath, stirred, and mixed uniformly. Potassium permanganate is added to the resulting mixture, reacted at less than 10 degrees C and magnetically-stirred for 2-3 hours. The beaker is placed in water bath at 30-50 degrees C, magnetically-stirred, portion (1/6-1/2 of total volume) of deionized water is added, and reacted at 30-50 degrees C for 30-60 minutes in water bath. The remaining portion of deionized water is added, reacted at 98 degrees C or less for 30-120 minutes, to obtain brown-colored mixture. Hydrogen peroxide is added into beaker till the color of mixture changes from brown to bright yellow. The bright yellow mixture is washed with hydrochloric acid aqueous solution, supernatant is poured, and filtered. The resulting precipitate is washed with deionized water at 20-30 degrees C, and vacuum-dried in oven at 40-60 degrees C, to obtain graphene oxide. The graphene oxide is added into sodium hydroxide solution having pH of 9-12, and ultrasonic-treatment is carried out for 30-90 minutes under vacuum conditions. The resulting mixture is magnetically-stirred for 24-60 hours with a rotating speed of 150-250 rpm, washed 3-5 times with absolute ethyl alcohol, and the obtained precipitate is vacuum-dried at 40-60 degrees C for 24-48 hours in oven, to obtain water-soluble graphene. The ratio of graphite and concentrated sulfuric acid is 1g:(20-80ml). The ratio of graphite powder and sodium nitrate is 1g:(0.5-2g). The ratio of graphite powder and potassium permanganate is 1g:(3-10g). The ratio of graphite powder and deionized water is 1g:(100-200ml). The content of concentrated sulfuric acid is 98 %mass. The ratio of graphene oxide and sodium hydroxide solution is 100mg:(100-250ml).