Sensing properties of infrared nanostructured plasmonic crystals fabricated by electron beam lithography and argon ion milling

Abstract

In this paper, the authors report on the fabrication, theory simulation, and optical characterization of X-shaped nanoscale plasmonic crystals (PCs) and their application in biosensors. X-shaped PCs with 30 nm feature line-widths and different intersection angles were fabricated by a combination of electron beam lithography and argon ion beam milling techniques. Both experimental measurement and finite-difference time-domain simulations were employed to study the transmission properties of PCs under two different incident light polarizations. With the reduction of the symmetry of the X-shaped PCs, the transmission spectra of PCs show a new peak at ∼900 nm in the near-infrared region, and the optical experimental results were consistent with the simulated results. Plasmonic crystal-based biosensors were then prepared by self-assembly of octadecanethiol to the PCs followed by biotinylation and immobilization of streptavidin to the biosensor. The sensing properties of the PC-based biosensors with a 30° intersection angle, which is enhanced by a localized surface plasmon resonance with the asymmetry of the PC, are superior to those with a larger intersection angle in biosensor application. The robust fabrication technique and the strategy for enhancing the sensitivity of the biosensor endow X-shaped PCs with a great competitive advantage over other candidates.