Ultralow limit human IgG detection with 2H-MoS2/L-cysteine based plasmonic fiber-optic spectral combs

The detection of human immunoglobulin G (human IgG) provides crucial evidence in diagnosis of infectious diseases and monitoring of therapeutic effects. Here, we propose a plasmonic fiber-optical surface plasmon resonance (SPR) based sensor to realize the ultralow limit human IgG detection. The proposed sensor is fabricated by attaching a mixture of 2H-MoS2 nanosheets with L-cysteine on a gold-coated tilted fiber Bragg grating. The 2H-MoS2 possesses a large specific surface area, where the L-cysteine can enhance the stability of antibody modification. The composite membrane of 2H-MoS2 and L-cysteine can adsorb more probe rabbit anti-human IgG, which can improve sensitivity of the proposed sensor. The experimental results show that the proposed sensor exhibits a response time of approximately 220 s and a sensitivity of 0.11 dB/(ng/ml). The limit of detection of 0.87 ng/ml of the proposed sensor is one order of magnitude lower than those of other fiber-optic SPR human IgG sensors.