High figure of merit (FOM) of Bragg modes in Au-coated nanodisk arrays for plasmonic sensing

Couture, Maxime and Brule, Thibault and Laing, Stacey and Cui, Wenli and Sarkar, Mitradeep and Charron, Benjamin and Faulds, Karen and Peng, Wei and Canva, Michael and Masson, Jean-Francois (2017) High figure of merit (FOM) of Bragg modes in Au-coated nanodisk arrays for plasmonic sensing. Small, 13 (38). 1700908. ISSN 1613-6810

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    Abstract

    We report that gold-coated nanodisk arrays of nearly micron periodicity have high figure of merit (FOM) and sensitivity necessary for plasmonic refractometric sensing, with the added benefit of suitability for surface-enhanced Raman scattering (SERS), large scale microfabrication using standard photolithographic techniques and a simple instrumental setup. Gold nanodisk arrays were covered with a gold layer to excite the Bragg modes (BM) which are the propagative surface plasmons localized by the diffraction from the disk array. This generated surface-guided modes, localized as standing waves, leading to highly confined fields confirmed by a mapping of the SERS intensity and numerical simulations with 3D finite element method (3D FEM). The optimal gold-coated nanodisk arrays were applied for refractometric sensing in transmission spectroscopy with better performance than nanohole arrays and they were integrated to a 96-well plate reader for detection of IgY proteins in the nM range in PBS. The potential for sensing in biofluids was assessed with IgG detection in 1:1 diluted urine. The structure exhibits a high FOM of up to 46, exceeding the FOM of structures supporting surface plasmon polaritons (SPPs) and comparable to more complex nanostructures, demonstrating that sub-wavelength features are not necessary for high performance plasmonic sensing.