Method of exchanging ligands, quantum dot composition, and electroluminescent element
A method of exchanging ligands includes a step of mixing a QD composition in which intermediate ligands and QDs are dissolved in a water solvent with a target-ligand-substituting solvent in which target ligands are dissolved, to replace the intermediate ligands with the target ligands. The target ligands do not dissolve in the water solvent and are soluble in different solvents depending on whether or not the target ligands are coordinated to the QDs, and the target-ligand-substituting solvent dissolves the target ligands not coordinated to the QDs and does not dissolve the target ligands coordinated to the QDs.
1 . A method of exchanging ligands, the method comprising:
mixing a quantum dot composition, in which first ligands and quantum dots are dissolved in a water solvent, with a first organic solvent, in which second ligands are dissolved, to replace the first ligands with the second ligands, wherein:
the second ligands do not dissolve in the water solvent and are soluble in different solvents depending on whether the second ligands are coordinated to the quantum dots, and
the first organic solvent dissolves the second ligands that are not coordinated to the quantum dots, and does not dissolve the second ligands that are coordinated to the quantum dots.
2 . The method of exchanging ligands according to claim 1 , further comprising:
after mixing the quantum dot composition with the first organic solvent, phase-separating the quantum dots to which the second ligands are coordinated.
3 . The method of exchanging ligands according to claim 2 , wherein phase-separating the quantum dots comprises phase-separating:
the water solvent in which the first ligands are dissolved,
the first organic solvent in which one or more second ligands, among the second ligands, that are in excess and that are not coordinated to the quantum dots are dissolved, and
the quantum dots to which the second ligands are coordinated.
4 . The method of exchanging ligands according to claim 2 , wherein phase-separating the quantum dots is performed by precipitation or centrifugation.
5 . The method of exchanging ligands according to claim 2 , further comprising, after the phase-separating:
removing the first ligands and one or more second ligands, among the second ligands, that are in excess and that are not coordinated to the quantum dots together with the water solvent and the first organic solvent, to isolate the quantum dots to which the second ligands are coordinated.
6 . The method of exchanging ligands according to claim 1 , further comprising:
before mixing the quantum dot composition with the first organic solvent:
mixing another quantum dot composition, in which third ligands and the quantum dots are dissolved in a third organic solvent, with the water solvent, in which the first ligands are dissolved, to replace the third ligands with the first ligand; and
isolating the quantum dots, to which the first ligands are coordinated, and dissolving the isolated quantum dots in another water solvent to manufacture the quantum dot composition.
7 . The method of exchanging ligands according to claim 1 , wherein the first ligands are a compound that contains a functional group coordinated to the quantum dots, that is separable into quaternary ammonium ions and chloride ions, and that contains 6 or fewer carbon atoms per molecule.
8 . The method of exchanging ligands according to claim 1 , wherein the first ligands are at least one compound selected from the group consisting of 2-aminoethanethiol hydrochloride, 2-methane aminoethanethiol hydrochloride, 2-ethane aminoethanethiol hydrochloride, 2-dimethylaminoethanethiol hydrochloride, 2-methylethylaminoethanethiol hydrochloride, and 2-diethylaminoethanethiol hydrochloride.
9 . The method of exchanging ligands according to claim 1 , wherein the second ligands are at least one compound selected from the group consisting of alkyl-based linear fatty acid, alkyl-based linear thiol, and alkyl-based linear amine.
10 . The method of exchanging ligands according to claim 1 , wherein the second ligands are at least one compound selected from the group consisting of oleic acid, nonanoic acid, mystiric acid, pentanoic acid, dodecane thiol, hexadecane thiol, and octyl amine.
11 . The method of exchanging ligands according to claim 1 , wherein the first organic solvent is at least one compound selected from the group consisting of dimethyl sulfoxide, acetonitrile, N,N-dimethyl formamide, methanol, ethanol, propylene glycol monomethyl ether acetate, acetone, and isopropyl alcohol.
12 . The method of exchanging ligands according to claim 1 , wherein the first organic solvent is either one or both of propylene glycol monomethyl ether acetate and isopropyl alcohol.