Localized Surface Plasmon Resonant Metal Nanostructures as Refractive Index Sensors

Abstract

The sensitivities of localized surface plasmon resonant sensors can be improved by changing the shape, size, and arrangement of nanosized metal dots on a substrate. In this study, we fabricated nanosized gold structure arrays on a silica substrate by electron beam lithography combined with a liftoff process, and studied their performance as refractive index sensors. We found that the sensitivity of single gold square dot arrays increases with the pitch while the absorbance decreases. On the other hand, both the sensitivity and absorbance of twin gold square dot arrays increase as the gap distance decreases for a particular incident polarization. We discuss the sensitivity of these structures for practical sensor applications.

Overview of the Characteristics of Micro- and Nano-Structured Surface Plasmon Resonance Sensors

“…This process leads to a local increase in the refractive index at the metal surface. The refractive index variation gives rise to an increase in the propagation constant of SPP ( β spp ), and this variation can then be accurately measured with the sensor [ 73 ]. However, there are some limitations because the surface plasmon wave is bound to the surface.…”

Development of a mass-producible on-chip plasmonic nanohole array biosensor

“…They enable us to employ a simple optical setting such as localized surface plasmon resonance (LSPR) or a grating based plasmonic sensor by deploying gold or silver nano-structures. 11,12 Various plasmonic substrates with nanoparticle, 13 nanorod, 14 nanorice, 15 nanopyramid, 16 and nanoshell structures 17 have been investigated to obtain a strong electromagnetic field, because optical absorption or scattering derived from LSPR is strongly influenced by nanoparticle size, shape and packing density. Various LSPR sensor structures have exhibited sensitivity values ranging from roughly several tens to several hundreds of nm RIU À1 .…”

Gold Sunflower Microelectrode Arrays with Dendritic Nanostructures on the Lateral Surfaces for Antireflection and Surface-Enhanced Raman Scattering

“…SERS is currently the most powerful application of plasmonics relying on the extraordinary enhancement (up to 10 8 or higher) in inelastic scattering (Raman scattering) of incident photons by molecules present in the vicinity of metallic nanostructures and surfaces with unique designs. − For reliable detection of analytes at low concentrations using SERS, surfaces that demonstrate a low detection limit, high Raman intensity, and a uniform SERS response across the substrate are desired. When light is incident on metallic nanostructures, localized surface plasmons (LSPs) are generated at resonant wavelengths and their properties are governed by the shape, size (i.e., morphology), and refractive index of the metallic nanostructures and dielectric material around it . The performance of a SERS substrate is dependent upon the magnitude of the localized electromagnetic field (EMF) enhancement at the hot spots (regions on the surface, where EMF is high) in the electromagnetic enhancement mechanism and interactions of the analyte molecules with the substrate in the chemical enhancement mechanism. , Generally, a reduction of the gap between hot spots on the metal nanostructures and creation of uniform population of hot spots across the surface can be used to reduce the detection limit .…”

“…Microelectrode arrays are generally fabricated using various lithography techniques such as electron beam lithography (EBL), colloidal lithography (CL), photolithography, on-wire lithography (OWL), , nanoimprint lithography (NIL), and so on. Self-assembly-based lithography methods such as CL allow large area and high throughput patterning of surfaces at low cost.…”