CeNS Colloquium

Bjoern Reinhard
Department of Chemistry, Boston University

Discrete assemblies of noble metal nanoparticles enable new imaging and improved sensing applications. The distance dependent interactions between individual noble metal nanoparticles can be used to engineer discrete plasmonic nanostructures for applications in microscopy, sensing and imaging. For instance, RNA tethered noble metal nanoparticles are active nanostructures which can indicate nanoscale distance changes through shifts in their resonance wavelength.[1] Plasmon coupling microscopy utilizes the distance dependent plasmon coupling to resolve close contacts between individual nanoparticle labeled membrane components during optical colocalization.[2] Direct near-field interactions between the particles red-shifts their resonance when the particles have approached within approximately one particle diameter. This shift can be conveniently detected using a ratiometric detection scheme in a wide field microscope. The near-field interactions between closely coupled nanoparticles culminate in strong E-field localizations in the junction between the particles making these materials also interesting building blocks for photonic devices. In two dimensional nanoparticle cluster arrays (NCAs) near- and far-field interactions enable a multiscale field enhancement that can be tuned in a rational fashion by controlling size and separation of the clusters.[3] NCAs represent photonic plasmonic crystals with cascade E-field enhancement that have demonstrated the ability to identify different bacteria species using surface enhanced Raman spectroscopy (SERS).

References:
[1] L.R. Skewis and B.M. Reinhard, Nano Letters 2008, 8, 214-220.
[2] G.X. Rong et al., Nano Letters, 2008, 8, 3386-3393.
[3] B. Yan et al., ACS Nano, 2009, 3, 1190 - 1202.