▎ 摘　　要

NOVELTY - Extracting graphene quantum dots comprises (i) co-processing a derived nitrogen-containing and sulfur-containing coal-based material with a mixture of concentrated sulfuric acid and concentrated nitric acid using coal-based material with the above mixture; (ii) heating the liquid-solid mixture of the step (i) while stirring and performing ultrasonic treatment; (iii) cooling the reaction mixture to room temperature, carrying out neutralization reaction and washing multiple times to obtain preliminary graphene, and neutralizing the reaction using sodium hydroxide or aqueous ammonia to pH of 7; and (iv) filtering the first graphene with an organic film having a pore size of 0.1-1.0 mu m, then filtering using the secondary dialysis bag, subjecting to first dialysis bag filtration using a dialysis bag with a Darcy index of 500-1000, using a dialysis bag with a Darcy index of 100-500 for the second time and the material in the second dialysis bag is a coal-based graphene quantum dot. USE - The method is useful for extracting graphene quantum dots. ADVANTAGE - The sulfur and nitrogen contents in the raw materials are used to enrich the functional groups on the surface of the prepared carbon quantum dots, and each of the quantum dots is connected with a rich oxygen, sulfur, and nitrogen functional group to facilitate further linking with other molecules and ability to diversify. DETAILED DESCRIPTION - Extracting graphene quantum dots comprises (i) co-processing a derived nitrogen-containing and sulfur-containing coal-based material with a mixture of concentrated sulfuric acid and concentrated nitric acid using 1 g of coal-based material with the above mixture of 1-100 ml; (ii) heating the liquid-solid mixture of the step (i) to 50-150 degrees C for 1-24 hours while stirring and performing ultrasonic treatment; (iii) naturally cooling the reaction mixture to room temperature, carrying out neutralization reaction and washing multiple times to obtain preliminary graphene, and neutralizing the reaction using 1-5 moles/l of sodium hydroxide or aqueous ammonia to pH of 7; and (iv) filtering the first graphene with an organic film having a pore size of 0.1-1.0 mu m, then filtering using the secondary dialysis bag, subjecting to first dialysis bag filtration using a dialysis bag with a Darcy index of 500-1000, using a dialysis bag with a Darcy index of 100-500 for the second time and the material in the second dialysis bag is a coal-based graphene quantum dot. An INDEPENDENT CLAIM is also included for lubrication oil modified additive, is prepared by graphene quantum dots, where the graphene quantum dots are mixed with a dispersing agent at a mixing ratio of 1:100-1:1000, and the above mixture is mixed with a base oil of a lubrication oil in a mixing ratio of 1:100-1:5000 and the graphene quantum dots are obtained by the method as mentioned above.