Few-Atom Fluorescent Silver Clusters Assemble at Programmed Sites on DNA Nanotubes

We show that DNA hairpins template the site-specific assembly of fluorescent few-atom Ag clusters on DNA nanotubes. Fluorescent clusters form only at hairpin sites and not on the double stranded DNA scaffold, allowing for spatially programmed self assembly. Ag clusters synthesized on hairpins protruding from DNA nanotubes can have nearly identical fluorescence Spectra to those synthesized on free hairpins of identical sequence. Analysis of the stepwise photobleaching of individual clusters suggests a chemical yield of similar to 45%. Given the well-established sequence-specific optical properties of DNA stabilized Ag clusters, these results point the way toward high yield assembly of metal cluster fluorophores with control over spectra as well as spatial arrangement.