Core–Shell-Structured Gold Nanocone Array for Label-Free DNA Sensing

Abstract

The refractive index sensitivity of a localized surface plasmon resonance (LSPR) sensor is correlated to an enhanced local electromagnetic (EM) field originating from noble metal nanostructures. Here, we demonstrated that extensive EM field enhancement by a gold (Au) nanocone array (AuNCA) allowed highly sensitive and label-free detection of biomolecules in the visible wavelength spectrum. The AuNCA consisted of a polymer core and an Au shell, which was fabricated by using simple and inexpensive nanoimprint lithography. Under LSPR excitation, AuNCA absorbs visible light of a specific wavelength and extensively enhances the EM field near its surface. It was shown that AuNCA had high refractive index sensitivity (417.5 nm/RIU) because of the large distribution of the enhanced EM field, covering a large surface of the NCA. Moreover, in DNA hybridization detection, a very low limit of detection of 161 fM was achieved, and 1-base mismatch DNA was successfully discriminated by using AuNCA.