Self-aligned colocalization of 3D plasmonic nanogap arrays for ultra-sensitive surface plasmon resonance detection.

We report extremely sensitive plasmonic detection that was performed label-free based on the colocalization of target DNA molecules and electromagnetic hot spots excited at 3D nanogap arrays. The colocalization was self-aligned by oblique evaporation of a dielectric mask over the 3D nanopatterns, which creates nanogaps for spatially selective target binding. The feasibility was experimentally confirmed by measuring hybridization of 24-mer single-stranded DNA oligonucleotides on triangular and circular 3D nanogap arrays. We were able to achieve significantly amplified optical signatures that lead to sensitivity enhancement in terms of detectable binding capacity in reference to conventional thin film-based surface plasmon resonance detection on the order of 1 fg/mm(2).