19 February 2014 Metallic nanoparticles arranged in a Helical geometry: route towards strong and broadband chiro-optical response
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Abstract
Recent advances in nanotechnology have paved ways to various techniques for designing and fabricating novel nanostructures incorporating noble metal nanoparticles, for a wide range of applications. The interaction of light with metal nanoparticles (NPs) can generate strongly localized electromagnetic fields (Localized Surface Plasmon Resonance, LSPR) at certain wavelengths of the incident beam. In assemblies or structures where the nanoparticles are placed in close proximity, the plasmons of individual metallic NPs can be strongly coupled to each other via Coulomb interactions. By arranging the metallic NPs in a chiral (e.g. helical) geometry, it is possible to induce collective excitations, which lead to differential optical response of the structures to right- and left circularly polarized light (e.g. Circular Dichroism - CD). Earlier reports in this field include novel techniques of synthesizing metallic nanoparticles on biological helical templates made from DNA, proteins etc. In the present work, we have developed new ways of fabricating chiral complexes made of metallic NPs, which demonstrate a very strong chiro-optical response in the visible region of the electromagnetic spectrum. Using DDA (Discrete Dipole Approximation) simulations, we theoretically studied the conditions responsible for large and broadband chiro-optical response. This system may be used for various applications, for example those related to polarization control of visible light, sensing of proteins and other chiral bio-molecules, and many more.
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Greshma Nair, Johnson Haobijam Singh, Murugesan Venkatapathi, Ambarish Ghosh, "Metallic nanoparticles arranged in a Helical geometry: route towards strong and broadband chiro-optical response", Proc. SPIE 8994, Photonic and Phononic Properties of Engineered Nanostructures IV, 89941X (19 February 2014); doi: 10.1117/12.2039320; https://doi.org/10.1117/12.2039320
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