title: Heterogeneous Solvatochromism of Fluorescent DNA-Stabilized Silver Clusters Precludes Use of Simple Onsager-Based Stokes Shift Models.
abstract: The diverse optical and chemical properties of DNA-stabilized silver clusters (AgN-DNAs) have challenged the development of a common model for these sequence-tunable fluorophores. Although correlations between cluster geometry and fluorescence color have begun to shed light on how the optical properties of AgN-DNAs are selected, the exact mechanisms responsible for fluorescence remain unknown. To explore these mechanisms, we study four distinct purified AgN-DNAs in ethanol-water and methanol-water mixtures and find that the solvatochromic behavior of AgN-DNAs varies widely among different cluster species and differs markedly from prior results on impure material. Placing AgN-DNAs within the context of standard Lippert-Mataga solvatochromism models based on the Onsager reaction field, we show that such nonspecific solvent models are not universally applicable to AgN-DNAs. Instead, alcohol-induced solvatochromism of AgN-DNAs may be governed by changes in hydration of the DNA template, with spectral shifts resulting from cluster shape changes and/or dielectric changes in the local vicinity of the cluster.
authors.affiliation: Department of Physics and ‡Department of Chemistry, University of California-Santa Barbara , Santa Barbara, California 93106-9530, United States.
authors.forename: Stacy M
authors.initials: SM
authors.lastname: Copp
authors.affiliation: Department of Physics and ‡Department of Chemistry, University of California-Santa Barbara , Santa Barbara, California 93106-9530, United States.
authors.forename: Alexis
authors.initials: A
authors.lastname: Faris
authors.affiliation: Department of Physics and ‡Department of Chemistry, University of California-Santa Barbara , Santa Barbara, California 93106-9530, United States.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Swasey
authors.affiliation: Department of Physics and ‡Department of Chemistry, University of California-Santa Barbara , Santa Barbara, California 93106-9530, United States.
authors.forename: Elisabeth G
authors.initials: EG
authors.lastname: Gwinn
mesh_terms: D004247:DNA / Q000737:chemistry*; D005453:Fluorescence; D008956:Models, Chemical; D012834:Silver / Q000737:chemistry*
chemical_list: D012834:Silver; D004247:DNA