Robust DNA-functionalized core/shell quantum dots with fluorescent emission spanning from UV-vis to near-IR and compatible with DNA-directed self-assembly

The assembly and isolation of DNA oligonucleotide-functionalized gold nanoparticles (AuNPs) has become a well-developed technology that is based on the strong bonding interactions between gold and thiolated DNA. However, achieving DNA-functionalized semiconductor quantum dots (QDs) that are robust enough to withstand precipitation at high temperature and ionic strength through simple attachment of modified DNA to the QD surface remains a challenge. We report the synthesis of stable core/shell (1-20 monolayers) QD-DNA conjugates in which the end of the phosphorothiolated oligonucleotide (5-10 nucleotides) is "embedded" within the shell of the QD. These reliable QD-DNA conjugates exhibit excellent chemical and photonic stability, colloidal stability over a wide pH range (4-12) and at high salt concentrations (>100 mM Na⁺ or Mg²⁺), bright fluorescence emission with quantum yields of up to 70%, and broad spectral tunability with emission ranging from the UV to the NIR (360-800 nm).