Hydrochloric Acid (HCL), Graphene Oxide (GO), Deionized Water, Centrifuge Tubes and Centrifuge Machine.

Add 100ml Hydrochloric Acid in 900ml deionized water and wash Graphene Oxide with it several times for 15-20 minutes each at 5000rpm.

Wash again with deionized water 5-6 times for 30 minutes each at 6000rpm.

Concentration of HCL: Hydrochloric Acid (HCL) is used in the washing process of Graphene Oxide (GO) because HCL can remove/dissolve any metal impurity during the synthesis of GO from Hummers method. By using concentrated HCL partial reduction of GO may be possible.
Centrifuge Time and Speed: Centrifuge time and speed (rpm) decide the amount of GO settle down in the centrifuge tube. At higher speed and more time washing, even smaller size GO can settle down in the centrifuge tube.
Number of Washing: How many times you wash is very important in this washing process. More times you wash the GO, leads to good quality GO with less impurities.

Graphene Oxide (GO), Hydrazine Hydrate (10%), Deionized Water, RB Flask, Magnetic Stirrer

Add 300mg Graphene Oxide in 100 water and setup reflux at 80°C.

Graphene oxide concentration: 3mg/ml

Add 100µL Hydrazine Hydrate.

Hydrazine Hydrate concentration: 1µL per 3mg of GO

After 12 hours remove the reflux setup and filter out the reduced Graphene Oxide (rGO).

Concentration of Graphene Oxide: The main ingredient for the synthesis of reduced Graphene Oxide is Graphene Oxide. As much concentration we take initially, that much amount rGO we get at the end of the process. But much higher amount of Graphene Oxide can leads to incomplete reduction and thus bad quality final product.
Concentration of Hydrazine Hydrate: Hydrazine Hydrate acts as the reducing agent in synthesis method. For the optimum reduction of the GO, optimum quantity of Hydrazine Hydrate is needed.
Effect of Temperature: Temperature plays an important role in speeding up any reaction. High temperature synthesis give us fine product quality by consuming less time.
Why Reflux: Reflux is a very good technique, when we want to give temperature to the solvents just below their boiling point. In this synthesis method, if we do not use reflux and direct heat the solution for 24 hours. Then all the water will be evaporated within few hours and only solid non-reduced GO will be left in the RB flask.

Graphite, Sulphuric Acid, Potassium Permanganate (KMnO₄), Hydrogen Peroxide (H₂O₂), Deionized Water, RB Flask, Magnetic Stirrer

Add 1g Graphite into 25ml Sulphuric acid and setup ice-bath.

Add 3g Potassium Permanganate very slowly by keeping the temperature less than 20ºC and stir for more 3 hours.

NOTE: You may remove the ice bath after 20 minutes and again setup for step-3

Add 50ml water drop-wise by keeping the temperature less than 50ºC.

This is very dangerous step take proper precautions

After some time the color of colloidal changes to dark brown indicates the formation of Graphene Oxide

Now, add 100ml water instantly for complete oxidation.

Add 5ml Hydrogen Peroxide for the completion of the reaction.

Washing Process: Add 100ml Hydrochloric Acid in 900ml deionized water and wash Graphene Oxide (produced after step-6) with it several times for 15-20 minutes each at 5000rpm.

Wash again with deionized water 5-6 times for 30 minutes each at 6000rpm.

Concentration of Graphite: The amount of Graphite used for the synthesis of Graphene Oxide (GO) is very important factor; because oxidation penetration on Graphite depends on the concentration of the Graphite in the Sulphuric Acid. Higher the concentration of Graphite, lesser the penetration of oxidation.
Concentration of Sulphuric Acid: Concentration of Sulphuric Acid is most important in Hummers method. Higher the concentration of Sulphuric Acid, higher the chances of complete exfoliation of Graphite into Graphene Oxide; But also very high chances of unwanted accident.
Rate of Adding Water: Rate at which water is added for the oxidation matters a lot. InstaNANO suggest you to add water drop wise very slowly to avoid unwanted accidents and to get good quality Graphene Oxide.
Effect of KMnO4: In this method, KMnO4 acts as Oxidizer, Sulphuric Acid functionalize the Graphite surface to add functional groups in the presence of reagent like KMnO4. KMnO4 should be added slowly because it increases the temperature of the reaction and may lead to incomplete oxidation at the end, if poured instantly and not stirred properly.
Role of Hydrogen Peroxide: Main role of Hydrogen Peroxide is to remove the excessive KMnO4 or in other words to stop the reaction.
Concentration of HCL: Hydrochloric Acid (HCL) is used in the washing process of Graphene Oxide (GO) because HCL can remove/dissolve any metal impurity during the synthesis of GO from Hummers method. By using concentrated HCL partial reduction of GO may be possible.
Centrifuge Time and Speed: Centrifuge time and speed (rpm) decide the amount of GO settle down in the centrifuge tube. At higher speed and more time washing, even smaller size GO can settle down in the centrifuge tube.
Number of Washing: How many times you wash is very important in this washing process. More times you wash the GO, leads to good quality GO with less impurities.

Citric Acid, Sodium Hydroxide, Deionized Water, RB Flask, Magnetic stirrer

Take 5g Citric Acid in RB Flask and set temperature at 200ºC.

Color of Citric acid will change to light Yellow (after 5 min), to Orange (after 30 min), to dark Brown (after 60 min). Dark Brown color solution was used for the next step.

Add 3.5g Sodium Hydroxide in 100ml of deionized water.

Add the Dark Brown liquid (prepared in step-2) in Sodium Hydroxide Solution (prepared in step-3) drop wise.

After adding the solution will become light brown indicates the formation of Graphene Oxide.

Time Taken in Step-2: Time is very crucial factor in the synthesis of Graphene Oxide from Citric acid in the Step 4. As the time increases the size of the Graphene sheets also increases, it means if you take 60 minutes in the Step 4 then size of the Graphene sheets will be small as compared to 90 minutes in Step 2.
Effect of NaOH Solution: NaOH is used in the last step of synthesis as the synthesis of Graphene Oxide occurs in the basic medium only. If you increase the concentration of NaOH in the solution then the defects in the final product may increase and you will see D-Band intensity increase in Raman Spectroscopy.

Fresh leaves of Neem Leaves, Deionized Water, RB Flask, Dropper, Magnetic Stirrer and Furnace

Take fresh Neam leaves, wash properly and dry at 60-80°C for some time until all the water content in the leaves evaporates. Crush the dried Neem leaves to form the fine powder.

Take Neem leaves fine powder, and Pyrolysis it at 1000°C for 5 hours under inert gas to from Black colored Carbon powder.

Take Black colored Carbon powder in RB flask. Add Sulfuric Acid (H2SO4) and Nitric Acid (HNO3) in 3:1 ratio respectively, and setup reflux at 80°C for 5 hours.

Add more water to dilute the synthesized GQDs. Filter the Brown colored solution containing GQDs to separate out unreacted content.