Real-time cationic sensing using plasmonic fiber optic sensor based phosphoryl-carrageenan

• Main Authors: Abu Bakar, Mohd Hafiz, Azeman, Nur Hidayah, Mobarak, Nadhratun Naiim, Ahmad Nazri, Nur Afifah, Mohd Daniyal, Wan Mohd Ebtisyam Mustaqim, Dzulkefly Zan, Mohd Saiful, Mahdi, Mohd Adzir, Md Zain, Ahmad Rifqi, Gupta, Ruchi, Abdullah, Fairuz, A. Bakar, Ahmad Ashrif
• Format: Article
• Published: Elsevier B.V. 2024
• Online Access: http://psasir.upm.edu.my/id/eprint/113645/; https://linkinghub.elsevier.com/retrieve/pii/S0924424724007192
• Institution: Universiti Putra Malaysia

We report Fiber Optic-Localized Surface Plasmon Resonance (FO-LSPR) spectroscopy sensors comprising a coating of spherical silver nanoparticles (AgNPs) embedded in phosphoryl-carrageenan. This is a novel report on modified carrageenan namely phosphoryl-carrageenan as sensing materials for cations specifically ammonium ions (NH4+). The morphology of carrageenan and phosphoryl-carrageenan coatings on the fiber optic probe was uneven and wavelike topography, indicating the successful coating on the fiber optic probe surface. The FO-LSPR showed a distinct dip in reflectivity in the region of 370–400 nm due to the resonance frequency of spherical AgNPs. The response and recovery times of FO-LSPR sensors for 1 ppm NH4+ and deionized water were <20 s and ∼1.2 minutes, respectively, with five times stable repeatability. The sensitivity of the FO-LSPR phosphoryl-carrageenan was 3.441 nm/ppm. Equally, the limits of detection and quantitation of fiber optic FO-LSPR were 0.336 and 1.018 ppm, respectively. Meanwhile, the dynamic range of the FO-LSPR was 0.3 – 2.0 ppm. The proposed sensor demonstrated strong selectivity towards NH4+ over common cationic interferents. Furthermore, the reported FO-LPSR sensor offered a comparable measurement performance to current methods, while being low cost and portable, and allowing in-situ real-time monitoring of cation ammonium. Thus, reported FO-LPSR sensors are highly promising for water monitoring applications.