Theoretical and experimental study of a highly sensitive SPR biosensor based on Au grating and Au film coupling structure

A high-sensitivity surface plasmon resonance (SPR) sensor based on the coupling of Au grating and Au film is investigated through simulations and experiments. The SPR sensor is designed by using a hybrid method composed of genetic algorithm (GA) and rigorous coupled wave analysis (RCWA). The numerical results indicate the sensor has an angular sensitivity of 397.3 degrees/RIU (refractive index unit), which is approximately 2.81 times higher than the conventional Au-based sensor and it is verified by experiments. Theoretical analysis, by finite-difference time-domain (FDTD) method, demonstrates the co-coupling between surface plasmon polaritons (SPPs) propagating on the surface of Au film and localized surface plasmon (LSPs) in the Au grating nanostructure, improving the sensitivity of the SPR sensor. According to the optimized structural parameters, the proposed sensor is fabricated using e-beam lithography and magnetron sputtering. In addition, the proposed sensor is very sensitive to the detection of small molecules. The limit of detection (LOD) for okadaic acid (OA) is 0.72 ng/mL based on an indirect competitive inhibition method, which is approximately 38 times lower than the conventional Au sensor. Such a high-sensitivity SPR biosensor has potential in the applications of immunoassays and clinical diagnosis. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

A high-sensitivity surface plasmon resonance (SPR) sensor based on the coupling of Au grating and Au film is investigated through simulations and experiments. The sensor, designed using a hybrid method of genetic algorithm (GA) and rigorous coupled wave analysis (RCWA), exhibits significantly higher angular sensitivity compared to conventional Au-based sensors. Theoretical analysis reveals enhanced sensitivity through the co-coupling of surface plasmon polaritons (SPPs) propagating on the Au film surface and localized surface plasmons (LSPs) in the Au grating nanostructure. The proposed sensor, fabricated using e-beam lithography and magnetron sputtering, demonstrates high sensitivity for the detection of small molecules, with a lower limit of detection (LOD) compared to conventional Au sensors. This high-sensitivity SPR biosensor shows potential in immunoassays and clinical diagnosis applications.