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We propose a composite layered structure for tunable, low-loss plasmon resonances, which consists of a noble-metal thin film coated in graphene and supported on a hexagonal boron nitride (hBN) substrate. We calculate electron energy loss spectra (EELS) for these structures, and numerically demonstrate that bulk plasmon losses in noble-metal films can be significantly reduced, and surface coupling enhanced, through the addition of a graphene coating and the wide-bandgap hBN substrate. Silver films with a trilayer graphene coating and hBN substrate demonstrated surface plasmon-dominant spectral profiles for metallic layers as thick as 34 nm. A continued-fraction expression for the effective dielectric function, based on a specular reflection model which includes boundary interactions, is used to systematically demonstrate plasmon peak tunability for a variety of configurations. Variations include substrate, plasmonic metal, and individual layer thickness for each material. Mesoscale calculation of EELS is performed with individual layer dielectric functions as input to the effective dielectric function calculation, from which the loss spectra are directly determined.

Electrical bistability and negative differential resistance in diodes based on silver nanoparticle-poly(Nvinylcarbazole) composites J. Appl. Phys. 108, 094320 (2010); 10.1063/1.3506708Large broadband visible to infrared plasmonic absorption from Ag nanoparticles with a fractal structure embedded in a Teflon AF® matrix

Gold nanoparticles with shapes which varied from spheres to multipods and polygons were prepared with a seedless approach in water/methanol mixtures in the presence of polyvinyl alcohol using sodium ascorbate as the reducing agent. The shape of Au nanoparticles is critically affected by the water/methanol ratio, as well as by the ratio of hydrogen tetrachloroaurate (HAuCl4) to sodium ascorbate and the concentration of HAuCl4 in the reaction mixture. A decreased ratio of water to methanol below 30/70 leads to the formation of multi-branched nanoparticles with the size in the range of 30-70 nm at relatively low HAuCl4 concentration, whereas polygons are formed when HAuCl4 concentration increases. The polyvinyl alcohol stabilized multi-branched Au nanoparticle colloids were stable at room temperature for a period of at least six-month.

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