Sensitivity comparison of graphene-based nearly guided-wave surface plasmon resonance biosensors with Au, Ag, Cu, and Al

Abstract

A comparative study of sensitivity of guided-wave surface plasmon resonance (NGWSPR) biosensors with Au, Ag, Cu, and Al is presented. The thicknesses of metal films in NGWSPR biosensors were optimized first to realize minimal reflectivity at resonance angle. Then, the sensitivities of NGWSPR biosensors were optimized by optimizing the thickness of dielectric film, and the peak sensitivities for different metals are determined. By comparing peak sensitivities of different metals, we find that the Ag-based NGWSPR biosensor always exhibits largest peak sensitivity for different dielectrics, followed by Cu-, Au-, and Al-based ones. When using PbS as the dielectric in the NGWSPR biosensor, the largest peak sensitivity of Ag-based NGWSPR biosensor is up to 232.48 deg / RIU at 632.8 nm wavelength, which is 45.72%, 31.58%, or 271.49% higher than the sensitivity of Au-, Cu-, or Al-based ones. In addition, the reflectance curves and electric field intensity distributions of optimized NGWSPR biosensors with different metals are studied to analyze the origin of high sensitivity achieved by Ag. Furthermore, the effect of the number of graphene layers on the peak sensitivity of an NGWSPR biosensor is also investigated. It is believed that the sensitivity comparison of graphene-based NGWSPR biosensors with Au, Ag, Cu, and Al could be helpful for highly sensitive biosensors development.