A dual channel self-compensation optical fiber biosensor based on coupling of surface plasmon polariton

We propose a dual-channel fiber-optic biosensor based on electronic field coupling between surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR). One sensing channel is coated with a bilayer of graphene oxide/Au, whose surface is modified with goat anti-human immunoglobulin G (IgG) to detect human IgG labeled with Au nanoparticles (Au NPs). The graphene oxide film in the region of the coupled electric fields increases the loading of biomolecules on the sensor surface and the immunological response. This sandwich structure can make full use of the coupled electric field excited by Au film and Au NPs, compared to the traditional LSPR sensor. The other sensing channel is coated only with Ag film as a reference channel to eliminate measurement error caused by non-specific binding and temperature cross-sensitivity. We numerically investigate the electric field coupling strength of SPR/LSPR and conducted corresponding experiments. The sensor had a high refractive index sensitivity with 13,592 nm/RIU and limit of detection of human IgG can be reduced to 15 ng/mL, which is 15.3 times lower than that of conventional SPR sensors. The proposed biosensor has sensing superiorities of high sensitivity, accuracy and temperature insensitive.