Browsing by Author "Kulkarni, Vikram"

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    A first principles approach to describing novel plasmonic phenomena
    (2015-04-09) Kulkarni, Vikram; Nordlander, Peter J.; Hafner, Jason; Halas, Naomi
    Plasmonic phenomena are described using first principles approaches such as time-dependent density functional theory (TDDFT) and molecular dynamics. These techniques are used to study hot electron generation via plasmon decay, charge transfer plasmons, plasmons in doped semiconductor nanocrystals, and heat dissipation around nanostructures. The theory presented is fully developed for spherical nanoparticles yet the physics is qualitatively the same for nanostructures of arbitrary complexity. The quantum nature of the electron gas is present in all investigations. Effects of size quantization, electronic lifetimes, resonant tunneling, exchange and correlation, Friedel oscillations and Kapitza resistance are all incorporated. Non-radiative plasmon decay into electron-hole pairs is shown to be dependent on the size of the nanoparticle and the lifetime of the electronic levels. Small nanoparticles and systems with long lifetimes are more efficient at generating high energy carriers. Charge transfer plasmons are demonstrated in dimer systems with quantized conducting junctions. An energy level of the junction must be resonant with the Fermi energy of the nanoparticles to facilitate the charge transfer. Thus the optical properties of the dimer are dictated by the electronic structure of the junction. The plasmon energies of semiconductor nanocrystals are tuned via doping. Plasmons consisting of a few hundred charge carriers are observed in the mid and far infrared regions of the electromagnetic spectrum. Many body effects are shown to correct the calculated plasmon energies when compared to classical theory. Heated nanoparticles are shown to distort the density of the surrounding solvent when illuminated at high intensities on resonance. The distortion of water around a nanoparticle leads to a significant interfacial resistance and a nonlinearity of the steady state temperature of the nanoparticle. However the nanoparticle does not produce a well-defined bubble in its immediate surroundings. This work is important for applications such as plasmon-enhanced catalysis, photocurrent generation, molecular electronics, steam generation and nanoscale heating.
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    Impurity-Induced Plasmon Damping in Individual Cobalt-Doped Hollow Au Nanoshells
    (American Chemical Society, 2014) Thibodeaux, Christyn A.; Kulkarni, Vikram; Chang, Wei-Shun; Neumann, Oara; Cao, Yang; Brinson, Bruce; Ayala-Orozco, Ciceron; Chen, Chih-Wei; Morosan, Emilia; Link, Stephan; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics; Rice Quantum Institute
    The optical properties of plasmonic nanoparticles in the size range corresponding to the electrostatic, or dipole, limit have the potential to reveal effects otherwise masked by phase retardation. Here we examine the optical properties of individual, sub-50 nm hollow Au nanoshells (Co-HGNS), where Co is the initial sacrificial core nanoparticle, using single particle total internal reflection scattering (TIRS) spectroscopy. The residual Co present in the metallic shell induces a substantial broadening of the homogeneous plasmon resonance line width of the Co-HGNS, where the full width at half-maximum (fwhm) broadens proportionately with increasing Co content. This doping-induced line broadening provides a strategy for controlling plasmon line width independent of nanoparticle size, and has the potential to substantially modify the relative decay channels for localized nanoparticle surface plasmons.