High sensitivity rabbit IgG biosensor co-enhanced by tapered noncore fiber and coupling effect between SPR and LSPR

An optical fiber biosensor based on tapered noncore fiber (NCF) and coupling effect between surface plasmon resonance (SPR) and localized surface plasmon resonance is proposed in this paper. The sensor consists of two multimode fibers and a tapered NCF spliced in the middle. The tapered fiber with a waist diameter of 40 μm is fabricated by flame-heated drawing technology, and then a layer of Au film of 50 nm thickness is deposited on the surface of the taper waist. Au nanoparticles (AuNPs) are immobilized on the surface of the Au film by using the rich functional groups of polydopamine (PDA). The sensitivity is improved by reducing the diameter of the NCF and the electric field coupling between the Au film and AuNPs. The refractive index sensitivity of the sensor is increased to 3558 nm/RIU in the detection range of 1.335–1.365, which is about 1.8 times higher than that of Au-NCF sensor without tapering and AuNPs. Goat anti-rabbit IgG was fixed on the sensor surface through the adhesion effect of PDA and used for the specificity detection of rabbit IgG. The sensitivity and limit of detection (LOD) of the proposed biosensor are 1.16 nm/(μg/ml) and 0.017 μg/ml, respectively. The proposed biosensor has low manufacturing cost and high biological sensitivity, which has potential applications in low concentration biomolecular detection and human health monitoring.