One-pot synthesis of hydrophilic CuInS2 and CuInS2–ZnS colloidal quantum dots

Abstract

A green method for the one-pot direct synthesis of hydrophilic CuInS₂ and CuInS₂–ZnS colloidal quantum dots was developed employing N,N-dimethylformamide (DMF) as a solvent. Highly reactive H₂S gas, in situ generated from the reaction between FeS and H₂SO₄, was utilized as the sulphur source for the synthesis of hydrophilic CuInS₂ quantum dots. Short chain thiols were applied as ligands, reactivity controllers and sulphur sources for the growth of the ZnS shell. The growth of CuInS₂ quantum dots experiences a typical Ostwald ripening process, and it should be controlled in 45 min due to the pyrolysis of the ligands. The reaction temperature should not exceed 130 °C. The ZnS shell was grown on CuInS₂ quantum dots in a very simple and one-pot approach. Both the luminescence and optical stability were improved substantially after the formation of the ZnS shell. The versatility of this synthetic strategy was demonstrated by extending it to the synthesis of other metal sulphide quantum dots, for instance, CdS and ZnS quantum dots.