Abstract
We explore the excitation of plasmons in 3D plasmon crystal metamaterials and report the observation of a delocalized plasmon mode, which provides extremely high spectral sensitivity (>2600 nm per refractive index unit (RIU) change), outperforming all plasmonic counterparts excited in 2D nanoscale geometries, as well as a prominent phase-sensitive response (>3*104 deg. of phase per RIU). Combined with a large surface for bioimmobilization provided by the 3D matrix, the proposed sensor architecture promises a new important landmark in the advancement of plasmonic biosensing technology.
Highlights
Figure 1. 3D plasmonic metamaterial based on Ag-coated woodpile crystal. (a) Schematic illustration of biosensing using the metamaterial
Unit cell is highlighted by orange; (c) Scanning electron microscopy of woodpile metamaterial structures produced by multiphoton laser polymerization, followed by Ag-based metallization
We explore 3D geometries of plasmon excitation by employing designed plasmon crystal metamaterials. We show that such a transition to 3D nanoarchitectures leads to the excitation of a novel plasmon mode, resulting in very high sensitivities in both spectral (>2600 nm/RIU) and phase (>3*104 deg. of phase per RIU) interrogations
Summary
Our tests showed that this approximation could provide a fairly precise description of the optical properties of silver-coated woodpile metamaterial structures In this case, the effective dielectric constant of the hybrid medium (silver-coated piles with air filled gaps) is approximated by the following Bruggeman equation:. The illumination of such structures by light causes the excitation of delocalized plasmon oscillations (electric currents) over electrically connected elements of the medium (metallized woodpile structures), which leads to a drastic loss of effective reflectivity at an appropriate combination of angle of light incidence and the pumping wavelength Such plasmon mode provides a much improved response to refractive index variations, as the sensed dielectric environment becomes a part of the artificially formed effective metal-dielectric medium. A strong field enhancement at some points of the metamaterial matrix makes possible the involvement of an additional Surface Enhanced Raman Scattering (SERS) channel, which can be used in parallel with the main optical transduction channel
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