We present a surface plasmon resonance-based sensor with good sensitivity and a very high Figure of merit (FOM) using a multi-layered structure (plasmonic metal-nitrite material-2D nanomaterial) in the near-infrared region. The proposed sensor consists of a glass prism, Aluminum as a plasmonic metal, Gallium Nitride as a dielectric material, and a layer of antimonene as a 2D nanomaterial for binding with bio-analyte. The transfer Matrix method is used to engineer the proposed plasmonic structure and to calculate the sensor’s performance parameters. The proposed sensor can achieve the FOM of 821.43RIU−1 at the wavelength of 1550 nm, much better than the results reported in the literature on SPR sensors. Finally, the refractive index of different urine concentrations is considered an application to show its glucose-sensing capability.