Preparation of DNA-Functionalised CdSe/ZnS Quantum Dots

Abstract

We functionalised core-shell CdSe/ZnS quantum dots (QDots) with short-chain 3-mercaptopropionic acid (3MPA) to render these nanocrystalline semiconductor water-soluble. The ligand-exchange reaction was significantly improved with the use of an organic base to first remove the thiolic hydrogen. Non-bound 3MPA could be removed from the colloid by dialysis, but it was found that the choice of membrane is important. Cellulose membrane obliterated the photoluminescence of the QDots, while cellulose-acetate membrane worked well. Amine-modified DNA was then attached to the QDots through amide bond linkage, using EDC and NHS as reaction promoters. The pH of the reaction medium has an important impact on the successful attachment of functional DNA on the QDots.