DNA-Protected Silver Clusters for Nanophotonics

Abstract

DNA-protected silver clusters (AgN-DNA) possess unique fluorescence properties that depend on the specific DNA template that stabilizes the cluster. They exhibit peak emission wavelengths that range across the visible and near-IR spectrum. This wide color palette, combined with low toxicity, high fluorescence quantum yields of some clusters, low synthesis costs, small cluster sizes and compatibility with DNA are enabling many applications that employ AgN-DNA. Here we review what is known about the underlying composition and structure of AgN-DNA, and how these relate to the optical properties of these fascinating, hybrid biomolecule-metal cluster nanomaterials. We place AgN-DNA in the general context of ligand-stabilized metal clusters and compare their properties to those of other noble metal clusters stabilized by small molecule ligands. The methods used to isolate pure AgN-DNA for analysis of composition and for studies of solution and single-emitter optical properties are discussed. We give a brief overview of structurally sensitive chiroptical studies, both theoretical and experimental, and review experiments on bringing silver clusters of distinct size and color into nanoscale DNA assemblies. Progress towards using DNA scaffolds to assemble multi-cluster arrays is also reviewed.

Research Update: Density functional theory investigation of the interactions of silver nanoclusters with guanine

“…[1][2][3] Small sized metal nanoclusters (with diameters up to around 2 nm) are considered to be brighter and more photostable fluorophores [4][5][6][7][8][9][10][11] compared to existing organic dyes as well as smaller and less toxic compared to quantum dots. 12 In particular, silver nanoclusters (AgNCs) are of interest, and these systems involve stabilizing ligands to prevent them from oxidation and aggregation.…”

“…30 Gwinn's group and Dickson's group have done studies especially on short singlestranded DNA. 8,9,[33][34][35][36] Yeh, Martinez, Werner, and co-workers have carried out investigations on DNA detection probes with a greater focus on guanine bases. 12,23,[37][38][39] In addition to the experimental work, theoretical investigations have also been performed on DNA-AgNCs by several groups.…”

DNA-Directed Fluorescence Switching of Silver Clusters

“…DNA strands thus locally concentrate Ag + and provide a scaffold that assembles chemically reduced silver adducts. 20–26 Oligonucleotides with 10–30 nucleobases stabilize a diverse suite of chromophores with spectra that span the 400–900 nm range, extinction coefficients of 10 4 –10 5 M −1 cm −1 , fluorescence quantum yields of 0.1–70%, and fluorescence lifetimes of 1–5 ns. 27–31 …”

Optically Activated Delayed Fluorescence

“…The readily accessible dark states, coupled with strong emission make Ag nanoclusters the ideal emitters to understand the photophysical interactions that lead to improved optical modulation, 21, 23, 33–36 paving the way for applications with more traditional emitters. Excitation of the few Ag atom chromophore produces both strong visible fluorescence and high populations of transient, photoinduced dark states that are optically depopulated with near infrared co-illumination.…”