Enhancing Detection Sensitivity of ZnO-Based Infrared Plasmonic Sensors Using Capped Dielectric GaO Layers for Real-Time Monitoring of Biological Interactions.

Surface plasmon resonances on Ga-doped ZnO (ZnO/Ga) layer surfaces (ZnO-SPRs) have attracted substantial attention as alternative plasmonic materials in the infrared range. We present further enhancement of the detection limits of ZnO-SPRs to monitor biological interactions by introducing thin dielectric layers into ZnO-SPRs, which remarkably modify the electric fields and the corresponding decay lengths on the sensing surfaces. The presence of a high-permittivity dielectric layer of GaO provides high wavelength sensitivities of the ZnO-SPRs due to the strongly confined electric fields. The superior sensing capabilities of the proposed samples were verified by real-time monitoring of the biological interactions between biotin and streptavidin molecules. Introduction of the high-permittivity dielectric layer into ZnO-SPRs effectively enhances the detection sensitivity and therefore allowed for the observation of biological interactions. This paper provides useful information for the development of optical detection techniques for use in biological fields based on ZnO from the viewpoints of plasmonic applications.