Metal-Core/Dielectric-Shell/Metal-Cap Composite Nanoparticle\nfor Upconversion Enhancement

Abstract

We\nhave developed an upconversion composite nanoparticle composed\nof a metal core, an upconversion shell, and a metal cap. Numerical\nsimulation of the nanocomposite revealed that hybridization of the\nlocalized surface plasmon modes of the core and the cap results in\nthe emergence of novel bonding and antibonding modes. The latter mode\nhas wide tunability in the resonance wavelength and strong field confinement\nat the position of the upconversion shell. For the fabrication of\nthe composite nanoparticle, we developed a process that combines liquid-phase\nsynthesis and vapor deposition processes. The scattering spectra of\nsingle composite nanoparticles agreed well with those in the numerical\nsimulation. The comparison of the upconversion intensity between the\nmetal-core/dielectric-shell structure and the metal-core/dielectric-shell/metal-cap\nstructure revealed that the cap formation increases the intensity\nseveral folds.