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2017 MRS Spring Meeting

V02 - Plasmonics at the Cluster Limit - Dielectric Sensing with DNA-Stabilized Silver Clusters

Apr 18, 2017 12:30pm ‐ Apr 18, 2017 1:15pm


Description

Few-atom silver clusters with rod-like geometries and high fluorescence quantum yields can be stabilized by DNA [1]. Now emerging in a number of sensing and photonic applications, much is still unknown about the mechanisms underlying the optical properties of these “AgN–DNA.” To better understand these mechanisms and to intelligently design applications, we investigate the effects of dielectric environment and cluster shape on electronic excitations of AgN–DNA. We first establish that the longitudinal plasmon wavelengths predicted by classical Mie-Gans (MG) theory agree with previous quantum calculations for excitation wavelengths of linear silver atom chains, even for clusters of just a few atoms. Application of MG theory to AgN–DNA with 400–850 nm cluster excitation wavelengths indicates that these clusters are characterized by a collective excitation process and suggests effective cluster thicknesses of ∼2 silver atoms and aspect ratios of 1.5 to 5. To investigate the sensitivity of these collective excitations to the surrounding medium, we measure the wavelength shifts produced by addition of glycerol. These are smaller than reported for much larger gold nanoparticles but easily detectable due to narrower line widths, suggesting that AgN–DNA may have potential for dielectric sensing in biomolecules at length scales of ∼1 nm

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