Hetero-core fiber optic pH sensor coated with Au nanoparticles immobilized in pH-sensitive polymer multilayers

In this paper, we have conducted a comparative study between hetero-core optical fiber localized surface plasmon resonance-based pH sensors that have been coated with a combination of different pH-sensitive polymers using the self-assembling layer-by-layer technique in the acidic pH range of 4.0-6.0. We have found that the pH response of the sensors in the given pH range increased with an increase in the number of self-assembled bilayers, and have concluded that the Poly-L-Lysine, Poly Acrylic Acid pair containing 30 layers had the highest optical loss change of 0.315 dB in response to pH change in the range of 4.0-5.5 at 650 nm wavelength out of all the other combinations.