Method for preparing graphene oxide quantum dots in a large scale with cryptocrystalline graphite

A method for preparing a graphene oxide quantum dot in a large scale with cryptocrystalline graphite, comprising the following steps:

• 1) weighing cryptocrystalline graphite powder and sodium nitrate with a mass ratio of cryptocrystalline graphite powder to sodium nitrate from 5:1 to 1:5, and weighing sulfuric acid solution having a concentration of 10˜98%, wherein the volume-to-mass ratio of the sulfuric acid solution to the graphite powder is 30˜10 ml:
• 1 g;
• 2) ultrasonically the mixture of cryptocrystalline graphite, sodium nitrate and sulfuric acid for 20 minutes to 3 hours, the resulted mixture being transferred into ice-water bath for stirring for 0.5 to 3 hours;
• 3) adding potassium permanganate while stirring and keeping temperature rising, the mass ratio of said potassium permanganate to cryptocrystalline graphite powder being from 5:1 to 1:3;
• 4) adding deionized water by drops and then raising the temperature, the mass ratio of the deionized water to cryptocrystalline graphite powder being 20˜60:1;
• 5) the resulted mixture is diluted with water to 2 to 5 times of the original volume and is added with hydrogen peroxide, followed by mixing and stirring, then is left for standing and staying overnight, the mass ratio of hydrogen peroxide to cryptocrystalline graphite powder being 1 to 4:1;
• 6) removing the supernatant, adding hydrochloric solution till evenly mixed, and implementing centrifugal clean till the pH value being 7, the volume-to-mass ratio of the added hydrochloric acid solution to cryptocrystalline graphite powder being 3˜5 ml:
• 1 g;
• 7) the solution obtained in step 6) is subjected to ultrasonic treatment at low temperature, and centrifugation treatment, so as to obtain the graphene oxide quantum dots.