Virus templated plasmonic nanoclusters with icosahedral symmetry via directed assembly

Controlling the spatial and orientational order of plasmonic nanoparticles may lead to structures with novel electromagnetic properties and applications such as sub-wavelength imaging and ultra-sensitive chemical sensors. Here we report the directed assembly of three-dimensional, icosahedral plasmonic nanoclusters with resonances at visible wavelengths [1]. We show using transmission electron microcopy and \textit{in situ} dynamic light scattering the nanoclusters consist of twelve gold nanospheres attached to thiol groups at predefined locations on the surface of a genetically engineered cowpea mosaic virus with icosahedral symmetry. We measured the bulk absorbance from aqueous suspensions of nanoclusters and reproduced the major features of the spectrum using finite-element simulations. Furthermore, because the viruses are easily produced in gram quantities the directed assembly approach is capable of high-throughput, providing a strategy to realize large quantities for applications. \\[4pt] [1] J. Fontana, W. J. Dressick, J. Phelps, J. E. Johnson, R. W. Rendell, T. Sampson, B. R. Ratna and C. M. Soto, Small \textbf{10}, 3058 (2014)