Plasmonic nanoantennas provide an opportunity to manipulate light within nanoscale volumes. One approach to creating plasmonic antennas is to organize metal colloids to produce assemblies where coupled localize surface plasmons lead to enhanced optical near fields. Although synthesis of metal colloids is straight forward due to the extensive number of methodologies that have been developed, controlled organization of the particles remains a challenge. Based on a need for more general methodologies to control nanoparticle assembly, we developed a surface functionalization process based on spatial localization of ligands on the surface of metal nanoparticles. This surface templating process produces a nanoparticle with an asymmetrically functionalized surface, similar to a Janus particle. One type of molecule covers most of the nanoparticle surface, while a second molecule is spatially localized in a small area on the particle surface. We have expanded our asymmetric functionalization approach to incorporate a wide range of surface ligands, including organic linkers, polymers, and DNA. As the surface chemistry of the nanoparticle is manipulated, the stability of the colloids can be compromised. We will discuss the combination of polymers for stabilization and spatially localized ligands for controlled assembly of plasmonic nanoparticles. Particularly, DNA-based assembly using a simple asymmetric functionalization approach will be described. We investigated three parameters of the assembly process to control the size of the nanoparticle assemblies and the optimal conditions for high assembly yield combined with long term stability. Directing molecules of interest to regions of enhanced near fields in the assemblies will be demonstrated. The asymmetric functionalization method will have broad impact on improved colloid stability and the ability to control assembly of metal nanoparticles for plasmonic antenna applications.

Asymmetric surface functionalization for assembly of plasmonic antennas and direction of molecules into regions of enhanced fields

246th National Meeting (2013)

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