Engineering Highly Luminescent and Chiral Metal Nanoclusters with Single-Stranded DNA.

The photoluminescent properties of atomically precise metal nanoclusters (MCs) have attracted intense interest in bioimaging and optical device applications, which are restricted by the limited brightness of MCs. In this study, we developed a single stranded (ss-) DNA-based ligand engineering approach to engineer highly luminescent and chiral MCs by transferring weakly luminescent clusters from the organic phase to the aqueous phase. Significantly, the luminescence quantum yield of the MCs was increased by up to 2 orders of magnitude (∼89-fold, reaching ∼56.18%), and the photoluminescence intensity was enhanced by up to 3 orders of magnitude (∼2127-fold) as compared to those in the organic phase. Using a set of theoretical and experimental studies including molecular dynamics simulations and ultrafast transient absorption spectroscopy, we established that the hydrophobic confinement of ssDNA on the cluster surface suppressed nonradiative transitions of excited-state clusters and reduced ligand motion at the cluster interface, which led to a fluorescence-to-phosphorescence transition that greatly contributed to the luminescence enhancement. We further observed that the chiral nature of ssDNA endowed chirality selection with a highly selective fluorescence enhancement for chiral MCs. This ssDNA-based ligand engineering approach provides a universal and powerful means for the development of water-dispersed, high-brightness photoluminescent materials for advanced optical applications.