Colloidal nanocrystals (NCs) can serve as promising building blocks for the development of metamaterials. NCs show novel optical, magnetic, and catalytic properties that are not found in nature, not only by modifying surface-to-volume ratio, particle-to-particle distance, and chemical composition, but also by changing assembly structures, which stresses the importance of developing strategies that can precisely control NC assembly structures. Herein, we present preparation of polystyrene coated gold NCs (Au@PS) and manipulation of their assembly structures through PS grafting density control. As-prepared Au@PS particles with different grafting densities were self-assembled through liquid-air interface self-assembly technique which allowed formation of large area NC superlattices. The 3-dimensional structures of Au@PS with different PS grafting density were investigated using transmission electron microscope (TEM) and grazing incidence small angle x-ray scattering (GISAXS) measurements. Interestingly, we observed the structural transition from non-close packed structure (i.e., body cenetered cubic structure) to close packed structure structure (i.e., face centered cubic or hexagonal close packed structure) when increasing grafting density, which can be attributed to the transition of the polymer shell from soft shell to hard shell upon grafting density increase. We believe this work paves a new way to manipulate NC assembly structure for building new metamaterials.

Self assembly of polymer coated Au nanocrystals with controlled polymer grafting density

256th National Meeting (2018)

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