All-Metal Plasmonic Metamaterials for Structure Color and as Colorimetric Biosensors

Abstract

Colorimetric and label-free plasmonic biosensors, relying on localized surface plasmon resonance (LSPR) on metallic subwavelength structures, have significant potential for many application areas such as clinical diagnosis and environmental monitoring detection by simple instrumentation or even naked eye. In this paper, we present a high-performance colorimetric and label-free plasmonic biosensors, consisting of an array of three-dimensional all-metal nano-cavities. The nanostructures, composed of a top array of gold disk, aluminum pillar and bottom gold reflection film, are similar to metal-insulator-metal and the insulating layer is air cavities that are easy to be filled with other gaseous or liquid dielectric. Therefore, the analytes could permeate into the nano-scale cavities and enable strong light-matter interactions there. The sensor shows significant color difference with small refraction index changes and the sensitivity reaches 683.5 nm/RIU. Moreover, when a monomolecular layer of Dithiobis(succinimidyl propionate) (DSP) was bonded to the surface of the nanostructure, the color of the metamaterials change from blue to green back. The metamaterials will offer great potential for detection and studies of binding events between the target analyte and its corresponding receptor.