Heterogeneous Solvatochromism of Fluorescent DNA-Stabilized Silver Clusters Precludes Use of Simple Onsager-Based Stokes Shift Models

J Phys Chem Lett. 2016 Feb 18;7(4):698-703. doi: 10.1021/acs.jpclett.5b02777. Epub 2016 Feb 3.

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • DNA / chemistry*
  • Fluorescence
  • Models, Chemical*
  • Silver / chemistry*

Substances

  • Silver
  • DNA