Assembling and Orienting Anisotropic Nanostructures

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Progress in the synthesis of diverse nanoparticles has led to the fabrication of functional nanoscale building blocks for ordered assemblies with novel collective properties that are applicable in photonics, plasmonics, electronics, catalysis, and sensing. Particularly,

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Self-assembly of anisotropic gold nanostructures grafted with poly(ethylene glycol) (PEG) induced by  electrolytes  and interpolymer complexation processes. PEG-grafted gold nanotriangles and nanooctahedra (PEG-AuNTs and PEG-AuNOh) are assembled at the liquid/vapor interface with a preferred orientation.  Combined with thermal controls, 3D assemblies of PEG-AuNOh are created in aqueous solution.

anisotropic nanostructures can provide distinct and advanced properties depending on their shape and/or size, compared with isotropic nanoparticles. Here, we report on the self-assembly of polyethylene glycol (PEG) grafted nano-triangles and nano-octahedra in the presence of an electrolyte at the vapor/liquid interfaces and in the bulk solution. The anisotropic nanostructures 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. Raising the temperature induces 3D assemblies and even improves the ordering of the assemblies. Synchrotron based X-ray reflectivity, grazing incidence small angle X-ray scattering, and small angle X-ray scattering techniques at Argonne National Laboratory’s Advanced Photon Source are used to characterize the created 2D and 3D nanostructures. This work extends the boundaries of self-assembly of nanostructures beyond that of isotropic nanoparticles, with potential applications in photonics and plasmonics.

H.J. Kim, M.M Hossen, A.C. Hillier, D. Vaknin, S.K. Mallapragada, and W. Wang. Interfacial and Bulk Assembly of Anisotropic Gold Nanostructures: Implications for Photonics and Plasmonics. ACS Applied Nano Materials. 3(8), 8216-8223.