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Emerging properties of disordered plasmonic metamaterials

Zahra Fakhraai
Associate Professor, Department of Chemistry University of Pennsylvania
Zoom Meeting
Departmental Colloquium

Ordered plasmonic structures have been utilized for a wider range of applications. However, their properties suffer from defects, when large-scale applications are desired. There is growing evidence that the exceptional properties can be produced and tuned in disordered packings with built-in heterogeneities. For example, self-assembled, tightly packed spherical clusters of nanobeads (plasmonic metamolecules) have been shown to produce strong magnetic dipole resonances, with strong local hotspots that can be used for applications such as surface enhanced Raman scattering. I discuss how one can dynamic ally control these properties by using temperature-responsive hydrogel cores, and producing clusters with mixed particle sizes and materials. The robust synthesis of these structures affords large variations in their structure and properties. I will detail how variations in these parameters can affect the magnetic response of these dynamic metamolecules (DMMs). In large enough clusters, with large nanobeads, high-order magnetic multipole modes, i.e. magnetic quadrupole, octupole, and hexadecapole resonances, are observed in simulations as well as far-field extinction experiments [1]. In another example, anisotropic plasmonic nanoparticles and two-dimensional inorganic materials can be embedded in polymer matrices to produce disordered metamaterials. The properties of these materials can be studied using linear optical methods and readily modeled using metamaterial optical modeling. This combination of experiments and modeling provides a facile in-situ technique to study self-assembly, orientation ordering, and other phase changes such as degradation in polymer nanocomposites.

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