Sensitivity Enhanced SPR Biosensor Based on Au Nanoparticles and Polydopamine Co-modified D-shaped Photonic Crystal Fiber
摘要
In this paper, a fiber-optic biosensor with the structure of both Au film and Au nanoparticles (AuNps) co-modified on D-shaped photonic crystal fiber (PCF) by adhesion with polydopamine (PDA) is proposed and experimentally fabricated, where the electric field near the sensing surface is increased and thus the sensitivity is improved by coupling the surface plasmon resonance (SPR) in Au film with the localized surface plasmon resonance (LSPR) in Au nanoparticles (AuNps), D-shaped PCF as well as high refractive index of PDA. In addition, due to excellent adhesion and biocompatibility properties of PDA, an extra layer of PDA is modified on the surface of AuNps to anchor a layer of goat anti-rabbit IgG on it, which is a bioassay for rabbit IgG. The experimental results show that the sensor obtains a high sensitivity of 4301.49 nm/RIU in the refractive index (RI) range of 1.335 ~ 1.365, which is 2.4 times the RI sensitivity of the PCF-Au sensor. The bio-sensitivity of the sensor for rabbit IgG reaches 1.017 nm/(µg/ml), and the limit of detection (LOD) is 0.019 µg/ml. This sensitized fiber-optic biosensor based on the SPR-LSPR coupling effect has a potential application in clinical disease diagnosis and immunoassay.