Architecture of stable and water-soluble CdSe/ZnS core-shell dendron nanocrystals via ligand exchange.

We describe a process for transferring octadecylamine-stabilized CdSe/ZnS core-shell semiconductor nanocrystals (ODA-QDs) from chloroform into water through a ligand exchange process with a dendron ligand which has two primary amine anchoring groups at its focal point and hydroxyl groups as its terminal groups. In this dendron ligand, two primary amine anchoring groups serve as bidentate ligands for the QD, while we expected the protruding hydroxyl groups to enhance the water-solubility of the dendron nanocrystals. The resulting dendron nanocrystals dissolved in water exhibit the same fluorescence and absorption spectra as the ODA-CdSe/ZnS core-shell nanocrystals dissolved in organic solvents such as chloroform. Furthermore, the stability of dendron nanocrystals were quantitatively examined against sintering, acid etching, oxidation with H(2)O(2) and photo-oxidation using the methods reported previously. These stable and bright dendron nanocrystals were soluble in various aqueous media, including all common biological buffer solutions tested. In addition to their superior performance, the synthetic chemistry of dendron ligands and the corresponding dendron nanocrystals is relatively simple and with high yield.