Polyelectrolyte-Enhanced Localized Surface Plasmon Resonance Optical Fiber Sensors: Properties Interrogation and Bioapplication
Ming Lin, Mengdi Lu, Yuzhang Liang, Li Yu, Wei Peng
Abstract
Localized surface plasmon resonance (LSPR) and lossy mode resonance (LMR) are excited simultaneously by the gold nanoparticle (AuNP) arrays and the top-coated polyelectrolyte layer on optical fibers. The well-dispersed and dense AuNP arrays ordered by the diblock copolymer-template have LSPR sensing characteristics, whereas the layer-by-layer coated polyelectrolyte film carries LMR-based sensitivity enhancement. Both the experimental and simulation results illustrated that the thickness of the polyelectrolyte layer is the key factor affecting the optical properties of the proposed polyelectrolyte-enhanced LSPR sensor, and the sensor with a thicker polyelectrolyte layer presents a higher refractive index (RI) sensitivity because the lossy mode of the polyelectrolyte layer enhances the plasmonic resonance of AuNP arrays. The optimal sensor, which self-assembles with 50 nm AuNPs and 20 PAH/PSS bilayers, shows higher sensitivity and stability, with an RI sensitivity of 1312 nm/RIU and a detection limit for human IgG of 32.1 μg/mL. In addition, we observed an abnormally enhanced peak with an invariable wavelength, which has great potential to eliminate interference as a self-reference signal.