Process for the synthesis of air stable metal sulphide quantum dots

1. A process for the preparation of metal sulphide QDs comprising the steps of:

a) reacting a metal salt with a ligand in a solvent followed by heating at a temperature ranging from 90 to 95° C. under a vacuum for a period ranging from 1 to 2 h to afford a metal oleate or a metal amine solution;

b) preparing a dithiocarbamic acid solution by mixing octyl dithiocarbamic acid with a ligand and a solvent to form a mixture followed by injecting said mixture to the metal oleate or metal amine solution of step (a) to obtain a dithiocarbamic solution;

c) injecting acetone to the dithiocarbamic solution of step (b) as an anti-solvent to obtain a precipitate, followed by collecting particles of precipitate by centrifugation to obtain metal sulfide QDs; and

d) dispersing said metal sulfide QDs in a non-polar solvent to obtain colloidal quantum dots.

2. The process as claimed in claim 1 , wherein said metal is selected from the group consisting of Lead (Pb), Cadmium (Cd), Manganese (Mn), Zinc (Zn), Copper (Cu) and Tin (Sn).

3. The process as claimed in claim 1 , wherein said salt of the metal is selected from the group consisting of an oxide salt, an acetate salt and a halide salt.

4. The process as claimed in claim 1 , wherein said ligand is selected from the group consisting of oleic acid and oleyl amine.

5. The process as claimed in claim 1 , wherein said solvent of step (a) and (b) is 1-octadecene.

6. The process as claimed in claim 1 , wherein said non-polar solvent of step (d) is selected from the group consisting of toluene, chloroform, hexane or octane.

7. The process as claimed in claim 1 , wherein said metal sulfide QDs have a particle size in the range of 2 nm to 10 nm.

8. The process as claimed in claim 1 , wherein said metal sulfides QDs are stable and mono dispersed.

9. The process as claimed in claim 1 , wherein said metal sulfides QDs absorb and emit in visible to NIR region.