Core–Shell Nanocuboid Dimers with Nanometric Gaps

Abstract

Nanometric gaps in plasmonic structures can lead to huge optical near fields and, related, to strongly enhanced interaction of molecules and light. Nanocavities formed by sphere-on-film or cube-on-film systems were recently established as promising systems, eventually reaching the strong coupling regime. However, such structures are limited with respect to being bound to a surface and by having no means of adjusting the resonance wavelength to the requirements of arbitrary analytes, independent of the gap width. We suggest and investigate in this paper silver−gold compound nanocuboid dimers in colloidal solution as potential structures to mitigate both limitations. We analyze the dimers' plasmonic properties by a combination of optical spectroscopy, electron energy loss spectroscopy, and numerical simulations, focusing on the longitudinal dimer geometry and the dominant light-coupled plasmon mode. We then calculate optical field enhancements under light and electron excitation to assess the cuboid dimer's potential in sensing and spectroscopy applications.

Single-Particle Investigation of Plexcitons in Bimetallic Nanorods

“…Bimetallic nanostructure-based plasmonic systems have a significant advantage over their monometallic counterparts due to the spectral tunability of the localized plasmon resonances arising from the compositional difference. − Herein, we investigate the strong plasmon-exciton coupling interactions of bimetallic gold-silver core-shell NRs with the J -aggregate of the cationic cyanine dye, 1,1′-diethyl-2,2′-cyanine iodide (Cy). The nanostructure with Au NRs as the core and silver as the shell (hereafter referred as Au@Ag NRs) is employed as an effective plasmonic material where the Ag shell thickness is used as the parameter for fine-tuning the plasmon resonance to establish a perfect resonance with the excitonic counterparts. , The ensemble-level plasmon-exciton coupling is monitored using UV–vis absorption spectroscopy, whereas DFM is adopted to monitor these interactions at the single-particle level.…”

Mass-determining role in the electrophoretic separation of colloidal plasmonic nanoparticle oligomers

“…[7][8][9][10][11][12][13][14][15] For example, gold nanoparticle dimers, as the simplest structure of plasmonic oligomers, can produce a new extinction band relating to a gapdependent near-field coupling resonance and have been applied for ultrasensitive sensing. [16][17][18][19][20][21][22][23][24][25] Besides, further assembling different kinds of plasmonic nanoparticles into heterostructured oligomers enables the smooth tuning of their polarization resonance modes from symmetric to asymmetric, resulting in more variable and intricate optical properties. However, the accurate and controllable assembly of desirable plasmonic oligomers with both high purity and high yield remains a great challenge due to the lack of well-established strategies, particularly for hetero-structured oligomers, severely hampering their in-depth optical research.…”