Patterned Arrays of Au rings for localized surface plasmon resonance

In this paper, we examined the characteristic behavior of localized surface plasmon resonances (LSPR) of Au dot and ring arrays in response to the selective binding of biomolecules. To do this, patterned arrays of Au rings and dots with various feature scales were fabricated over large areas by an imprint lithography technique. Our results showed that the LSPR spectra of the Au nanorings exhibited a blue shift with increase in the ring widths and asymptotically converged to those for Au nanodots. This clearly implies that the LSPR spectra can be tuned over an extended wavelength range by varying the ring width. For an illustrative purpose, the patterned Au structures were used to detect the binding of streptavidin to biotin. In doing this, the Au patterns were chemically modified with G4 dendrimers of amine terminated poly(amidoamine), which facilitated the tethering of biotin onto the Au pattern. Exposure of the biotinylated Au nanorings to aqueous streptavidin solution induced both red-shifts of the LSPR spectra and changes in the peak intensities. The sensitivity of the LSPR spectra to the binding of the biomolecules was enhanced as the ring width of Au rings was decreased.