We report on the assembly of polymer-grafted nanostructures at the vapor/aqueous interface and in bulk solutions using synchrotron X-ray diffraction methods. Triangular-and octahedral-shaped gold nanostructures are synthesized and grafted with poly(ethylene glycol) (referred to as PEG-AuNTs and PEG-AuNOh, respectively), and their suspensions are manipulated with salts, (poly)electrolytes that induce interpolymer complexation and HCl to achieve organized assemblies. The assemblies at the vapor/liquid interface are explored by X-ray reflectivity and grazing-incidence small-angle X-ray scattering. Results show that PEG-AuNTs and PEG-AuNOh populate the interface, with some degree of orientation with respect to the liquid surface. The resulting assemblies can be tuned by the regulating electrolyte and pH levels of the suspensions. Similar suspension manipulations also induce three-dimensional assemblies that are revealed with solution small-angle X-ray scattering. In addition to controlling the three-dimensional (3D) aggregates by regulating the (poly)electrolytes and pH levels, we show that raising the temperature of the suspensions from 20 to above 50 degrees C induces and even improves the ordering of the assemblies. Our findings provide tools that can be used to assemble and orient anisotropic nanostructures for potential applications in photonics and plasmonics.

DNA origami can be used to create a variety of complex and geometrically unique nanostructures that can be further modified to produce building blocks for applications such as in optical metamaterials. We describe a method for creating metal-coated nanostructures using DNA origami templates and a photochemical metallization technique. Triangular DNA origami forms were fabricated and coated with a thin metal layer by photochemical silver reduction while in solution or supported on a surface. The DNA origami template serves as a localized photosensitizer to facilitate reduction of silver ions directly from solution onto the DNA surface. The metallizing process is shown to result in a conformal metal coating, which grows in height to a self-limiting value with increasing photoreduction steps. Although this coating process results in a slight decrease in the triangle dimensions, the overall template shape is retained. Notably, this coating method exhibits characteristics of self-limiting and defect-filling growth, which results in a metal nanostructure that maps the shape of the original DNA template with a continuous and uniform metal layer and stops growing once all available DNA sites are exhausted.