A Short Review on the Role of the Metal-Graphene Hybrid Nanostructure in Promoting the Localized Surface Plasmon Resonance Sensor Performance

Abstract

Localized Surface Plasmon Resonance (LSPR) sensors have potential applications in essential and important areas such as bio-sensor technology, especially in medical applications and gas sensors in environmental monitoring applications. Figure of Merit (FOM) and Sensitivity (S) measurements are two ways to assess the performance of an LSPR sensor. However, LSPR sensors suffer low FOM compared to the conventional Surface Plasmon Resonance (SPR) sensor due to high losses resulting from radiative damping of LSPs waves. Different methodologies have been utilized to enhance the performance of LSPR sensors, including various geometrical and material parameters, plasmonic wave coupling from different structures, and integration of noble metals with graphene, which is the focus of this report. Recent studies of metal-graphene hybrid plasmonic systems have shown its capability of promoting the performance of the LSPR sensor to a level that enhances its chance for commercialization. In this review, fundamental physics, the operation principle, and performance assessment of the LSPR sensor are presented followed by a discussion of plasmonic materials and a summary of methods used to optimize the sensor's performance. A focused review on metal-graphene hybrid nanostructure and a discussion of its role in promoting the performance of the LSPR sensor follow.

Keywords: figure of merit; graphene; hybrid; localized plasmons; metal; sensitivity; sensor.

Figure 1

Metal NP external electric field interaction [17].

Figure 2

Scanning electron microscopy (SEM) images of a bare Ag nanoantenna (a) and a graphene-passivated Ag nanoantenna (b) after 30 days (scale bars are 200 nm), showing how graphene protects Ag NPs from degradation [60]. Bare Ag nanoantenna’s (c) and graphene-passivated Ag NPs’ (d) normalized (Norm.) reflection spectra over 30 days, which shows how the passivation of Ag with graphene enhances the stability of Ag NPs [60]. Optical absorption spectra for the Cu NPs coated with a few graphene layers [61].

Figure 3

Absorption spectra of gold NPs coated (a) and encapsulated (b) by graphene layers. (c) Gold NP LSPR wavelengths for Setups 1 and 2. (d,e) The structures of the setups used in (b,a) [67].

Figure 4

(a) Extinction spectrum for three different nanostructures; Au NP square array, nanohole array perforated in 20 nm-thick graphene film, and Au NPs/G hybrid structure showing three main resonance modes; Mode I (λ = 1532 nm), Mode II (λ = 1632 nm), and Mode III (λ = 1793 nm). (b,c) are the electric field profiles at the resonance wavelength of Mode II for the graphene nanohole structure and the Au-graphene hybrid structure, respectively [24].