Method to modify the surface of quantum dots and a method to prepare a dispersion of surface modified quantum dots

A method to modify the surface of quantum dots, said method comprising the steps of:

• providing III-V quantum dots, said quantum dots having X type ligands and L type ligands at their outer surface, with X type ligands comprising ligands able to donate one electron to a quantum dot to which the X type ligand is bound and with L type ligands comprising ligands able to donate two electrons to a quantum dot to which the L type ligand is bound;
• dispersing said quantum dots in a solvent further comprising an additional compound to form modified quantum dots, said additional compound comprising an organic acid of formula RYH or an organic salt of formula RYH+Z−, said additional compound comprising at least one acidic proton H+ having a pKa in water equal or lower than 16 and said additional compound comprising a R-group comprising at least one carbon atom, with said organic acid of formula RYH being selected from the group consisting of carboxylic acids, sulfonic acids, thiols and phenols, with said organic salt of formula RYH+Z− comprising an organic ammonium ion RYH+ and a negatively charged counterion Z−;
• whereby during said dispersing said acidic proton H+ of said additional compound protonates at least part of said L type ligands to form protonated L type ligands and at least part of said X type ligands are replaced by deprotonated acid RY− of said organic acid of formula RYH or by counterion Z− of said organic salt of formula RYH+Z− and/or by deprotonated conjugated base RY of ion RYH+ of said organic salt of formula RYH+Z−.