Patterned 2D and 3D Assemblies of Nanoparticles on Molecular Printboards

Abstract

Functionalized nanoparticles have powerful applications as intermediates between solution and surface chemistry and as tools for nanofabrication. Two main examples of these have been shown. The functionalization of 3 nm gold and 55 nm silica nanoparticles with cyclodextrin (CD) host sites has been achieved, which allows: (i) the controlled aggregation with guestfunctionalized dendrimers in solution, (ii) the specific adsorption onto dendrimer-patterned substrates, and (iii) the fabrication of larger architectures using the layer-by-layer methodology. Aggregation in solution was shown to proceed through specific host-guest recognition. The adsorption onto surfaces employed so-called “molecular printboards”, which are self-assembled monolayers with the same cyclodextrin host recognition sites which allow the stable assembly of molecules and nanoparticles through multivalent host-guest interactions. CD silica nanoparticles were shown to adsorb specifically onto areas of such molecular printboards which were patterned with adamantyl-functionalized dendrimers. The layer-by-layer (LBL) assembly of such dendrimers and CD gold nanoparticles led to a controllable multilayer architecture with a thickness increase of about 2 nm per bilayer. The combination of the (bottom-up) particle LBL assembly and top-down surface structuring, in particular nanoimprint lithography, was shown to result in the formation of 3D objects down to sub-100 nm in all three dimensions.