Absorption and Sensitivity Measurements of Noble Metals (Au, Ag, Cu) Thin Film Biosensor Based on SPR Simulation Characterizations

Abstract

Abstract In this paper, we investigate the influence of varying the thickness of noble metals, namely gold (Au), silver (Ag), and copper (Cu), and the incident light wavelength on the surface plasmon resonance (SPR) properties for biosensor applications. Our analysis employs the Fresnel equations to examine the absorption characteristics of these metals. We explore metal layer thicknesses ranging from d = 30 to 70 nm and incident light wavelengths of λ = 500 and 600 nm, with incident angles (θ) ranging from 0° to 90°. Utilizing simulation analysis in MATLAB, we simulate the SPR responses of these metals when deposited on N_LASF9 and BK-7 glass prisms, with air as the surrounding medium. Our calculations reveal the absorption properties of Au, Ag, and Cu, as indicated by the angle of incidence (θSPR). Our findings demonstrate that the highest absorption occurs with copper (Cu) at A = 0.999 (a.u.) for λ = 500 nm and d = 30 nm. When λ is adjusted to 600 nm, gold (Au) exhibits the highest absorption at A = 0.997 (a.u.) with a thickness of d = 40 nm. Additionally, we calculate sensitivity values for all three metals, with copper (Cu) yielding the highest sensitivity of 101.6 Reflected Index Units (RIU− 1) for both λ = 500 and 600 nm. Furthermore, we compute the figure of merit (FOM), with silver (Ag) achieving the highest FOM of 443 at λ = 500 nm and 451 at λ = 600 nm. These findings provide valuable insights into the SPR properties of noble metals for biosensing applications and offer guidance for optimizing biosensor designs.