Ultra-high sensitivity optical fiber SARS-CoV-2 biosensor based on triangular gold nanosheets/gold film coupling enhancement

To tackle the demand for highly accurate and real-time diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a highly sensitive optical fiber SARS-CoV-2 antigen sensor based on triangular gold nanosheets/gold film coupling is proposed. The coupling effect between the local surface plasmon resonance effect of the triangular gold nanosheets and the surface plasmon resonance effect of the gold film increases the local electric field, resulting in higher sensitivity and lower detection limit of the sensor, and the refractive index sensitivity of the sensor is increased to 3894.3 nm/RIU. The antigen reacts specifically with the viral antibody adsorbed on the surface of the optical fiber, which leads to a small change in refractive index, which ultimately leads to a shift in the resonance peak of the optical fiber, thus enabling antigen detection. The biosensor showed good response in the range of SARS-CoV-2 antigen concentration from 0.035 to 100 ng/mL, and the limit of detection (LOD) was 0.017 ng/mL (S/N=3). The biosensor has good selectivity and stability, possesses a short response time (10 min), which provides a new idea for the detection of SARS-CoV-2 in the biomedical field.