The use of virus nanoparticles, specifically Chilo and Wiseana Invertebrate Iridovirus, as building blocks for iridescent nanoparticle assemblies and core substrates in the fabrication of metallodielectric nanostructures is discussed. Virus particles are assembled in vitro, yielding films and monoliths with optical iridescence arising from multiple Bragg scattering from close packed crystalline structures of the iridovirus. Bulk viral assemblies are prepared by centrifugation followed by the addition of glutaraldehyde, a cross-linking agent. Long range assemblies were prepared by employing a cell design that forced virus assembly within a confined geometry followed by cross-linking. In addition to these assemblies core-shell particles were created from the same virus. A gold shell is assembled around the viral core by attaching small gold nanoparticles to the virus surface by means of the inherent chemical functionality found within the protein cage structure of the viral capsid. These gold nanoparticles act as nucleation sites for electroless deposition of gold ions from solution. UV/Vis spectroscopy and electron microscopy, were used to verify the creation of the virus assemblages. The optical extinction spectra of the metallo-viral complex were compared to Mie scattering theory and found to be in quantitative agreement. These investigations demonstrate that direct harvesting of biological structures, rather than biochemical modification of protein sequences, is a viable route to create unique, optically active materials.
The use of virus nanoparticles, specifically Chilo and Wiseana Iridovirus, as core substrates in the fabrication of metallodielectric, plasmonic nanostructures is discussed. A gold shell is assembled around the viral core by attaching small, 2 - 5 nm, gold nanoparticles to the virus surface by means of inherent chemical functionality found within the protein cage structure of the viral capsid. These gold nanoparticles act as nucleation sites for electroless deposition of gold ions from solution. The density of the gold nucleation sites on the virus was maximized by reducing the repulsive forces between the gold particles, which was accompolished by controlling the ionic strength of the nanoparticle solution. UV/Vis spectroscopy and transmission electron microscopy were used to verify creation of the virus-Au particles. The optical extinction spectra of the metallo-viral complex were compared to Mie scattering theory and found to be in quantitative agreement.
We have demonstrated a method of fabricating long-range arrays of 2D metallic microstructures on glass surfaces and measured the optical resonances of those structures. Gold and silver stripes are fabricated using microcontact printing with PDMS gratings and electroless plating techniques without the use of resist masks or etching. Changing the blaze angle and periodicity of the gratings used to make the PDMS stamps varies the line widths. The optical response of these fabricated transmission gratings was evaluated by measuring the transmission spectra while varying the angle of the incident light.
We report a surprising chemical reactivity of gold nanoshells with carbon tetrachloride. Gold nanoshells are nanoparticles constructed from a silica core encapsulated in a gold shell. An aminoalkoxysilane linker molecule is used to derivatize the silica surface, which facilitates the attachment of the gold shell. Evidence is shown for the decomposition of the gold shell due to a reaction with carbon tetrachloride. The reaction is believed to proceed through the formation of a charge transfer complex between carbon tetrachloride and the gold-amine complex. The reaction is facilitated by the presence of defects in the shell layer.