Browsing by Author "Large, Nicolas"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Reversible Shape and Plasmon Tuning in Hollow AgAu Nanorods
    (American Chemical Society, 2016) Yazdi, Sadegh; Daniel, Josée R.; Large, Nicolas; Schatz, George C.; Boudreau, Denis; Ringe, Emilie
    The internal structure of hollow AgAu nanorods created by partial galvanic replacement was manipulated reversibly, and its effect on optical properties was mapped with nanometer resolution. Using the electron beam in a scanning transmission electron microscope to create solvated electrons and reactive radicals in an encapsulated solution-filled cavity in the nanorods, Ag ions were reduced nearby the electron beam, reshaping the core of the nanoparticles without affecting the external shape. The changes in plasmon-induced near-field properties were then mapped with electron energy-loss spectroscopy without disturbing the internal structure, and the results are supported by finite-difference time-domain calculations. This reversible shape and near-field control in a hollow nanoparticle actuated by an external stimulus introduces possibilities for applications in reprogrammable sensors, responsive materials, and optical memory units. Moreover, the liquid-filled nanorod cavity offers new opportunities for in situ microscopy of chemical reactions.
  • Thumbnail Image
    Item
    Surface enhanced resonant Raman scattering in hybrid MoSe2@Au nanostructures
    (Optical Society of America, 2018) Abid, Inès; Chen, Weibing; Yuan, Jiangtan; Najmaei, Sina; Peñafiel, Emil C.; Péchou, Renaud; Large, Nicolas; Lou, Jun; Mlayah, Adnen
    We report on the surface enhanced resonant Raman scattering (SERRS) in hybrid MoSe2@Au plasmonic-excitonic nanostructures, focusing on the situation where the localized surface plasmon resonance of Au nanodisks is finely tuned to the exciton absorption of monolayer MoSe2. Using a resonant excitation, we investigate the SERRS in MoSe2@Au and the resonant Raman scattering (RRS) in a MoSe2@SiO2 reference. Both optical responses are compared to the non-resonant Raman scattering signal, thus providing an estimate of the relative contributions from the localized surface plasmons and the confined excitons to the Raman scattering enhancement. We determine a SERRS/RRS enhancement factor exceeding one order of magnitude. Furthermore, using numerical simulations, we explore the optical near-field properties of the hybrid MoSe2@Au nanostructure and investigate the SERRS efficiency dependence on the nanodisk surface morphology and on the excitation wavelength. We demonstrate that a photothermal effect, due to the resonant plasmonic pumping of electron-hole pairs into the MoSe2 layer, and the surface roughness of the metallic nanostructures are the main limiting factors of the SERRS efficiency.