Highly sensitive mid-infrared SPR biosensor for a wide range of biomolecules and biological cells based on graphene-gold grating

Due to the increase in blood diseases such as diabetes, detecting the concentration of some biomolecules relating to these diseases, such as glucose, is very important; therefore, designing high quality, cheap, and easy-to-build biosensors is one of the most important targets of researchers. For this reason, a graphene-gold ellipse grating SPR biosensor has been proposed based on FEM modeling. While analyzing the extinction curve, an SPR mode was observed in the mid-infrared region. The sensitivity and quality factor of this mode were calculated with small changes in the sensing mediums' refractive index. After studying the SPR mode, the geometry structure and the properties of the incoming light beam were optimized, to increase the sensitivity and quality factor of the sensor, and the highest values of 1782 nm/RIU and 21214 were obtained, respectively. The proposed biosensor was based on the surface plasmons resonance and placed in the free label category also can measure with a high sensitivity and excellent performance many biomolecules and biological cells such as blood, glucose, water and MDCK by detecting the refractive their index variation. Furthermore, materials with a refractive index in the range of 1.100-2.100, up to a precision of 0.00005, are also detectable.