Ultra-Sensitive Surface Plasmon Resonance Detection by Colocalized 3D Plasmonic Nanogap Arrays

Ultra-sensitive detection based on surface plasmon resonance (SPR) was investigated using 3D nanogap arrays for colocalization of target molecular distribution and localized plasmon wave in the near-field. Colocalization was performed by oblique deposition of a dielectric mask layer to create nanogap at the side of circular and triangular nanoaperture, where fields localized by surface plasmon localization coincide with the spatial distribution of target molecular interactions. The feasibility of ultra-sensitivity was experimentally verified by measuring DNA hybridization. Triangular nanopattern provided an optimum to achieve highly amplified angular shifts and led to enhanced detection sensitivity on the order of 1 fg/mm² in terms of molecular binding capacity. We confirmed improvement of SPR sensitivity by three orders of magnitude, compared with conventional SPR sensors, using 3D plasmonic nanogap arrays.