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

•We describe 3D nanoplasmonic detection of surface bioaffinity interactions.•The detection is based on self-aligned colocalization of fields and molecules.•The experimental evaluation was performed by measuring DNA hybridization.•The results show enhanced sensitivity by 1000 times over traditional detection.•The approach introduces a way to attaining molecular sensitivity for SPR 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/mm2.