Using the nanoimprint-in-metal method to prepare corrugated metal structures for plasmonic biosensors through both surface plasmon resonance and index-matching effects

In this study, we prepared metallic corrugated structures for use as ultra-sensitive plasmonic sensors. Relying on the direct nanoimprint-in-metal method, fabrication of this metallic corrugated structure was readily achieved in a single step. The metallic corrugated structures were capable of sensing both surface plasmon resonance (SPR) wavelengths and index-matching effects. The corrugated Au films exhibited ultrahigh sensitivity (ca. 800 nm/RIU), comparable with or even higher than those of other reported SPR-based sensors. Moreover, here we first demonstrate the experimental realization of quantified refractometric sensing by index-matching effect. Because of the unique index-matching effect, refractometric sensing could also be performed by measuring the transmission intensity of the Au/substrate SPR mode-conveniently, without a spectrometer. In the last, we demonstrated the corrugated Au film was capable of sensing trace amount of cysteine, revealing the ability of the structure to be a highly sensitive biosensor.