Phase transferring luminescent gold nanoclusters via single-stranded DNA

Atomically precise gold nanoclusters (Au NCs) are an emerging class of quantum-sized nanomaterials with discrete electronic energy levels, which has led to a range of attractive electronic and optical applications. Nevertheless, the lack of general methods to transfer Au NCs protected with hydrophobic ligands to an aqueous solution hampers their use in physiological settings. Here, we developed a single-stranded DNA-based approach that could transfer similar to 90% hydrophobic Au NCs into an aqueous solution. We experimentally and theoretically established that multivalent electrostatic and hydrophobic interactions between DNA strands and the hydrophobic ligand layer on Au NCs resulted in monodispersed DNA-coated Au NCs with high physical integrity in an aqueous solution. The fluorescence quantum yield of Au NCs was increased by similar to 13 fold, and surface-constrained DNA retained the specific recognition ability for biosensing. We further demonstrated the versatility of this phase-transfer approach, which thus holds great potential to advance biological and medical applications of Au NCs.