The investigation of optical sensors for the identification of particular ions is currently a highly active field of study. In this regard, gold nanoparticles (Au NPs) and rare-earth-doped materials, such as europium oxide (Eu2O3), are frequently employed due to their distinctive optical properties, which make them suitable for sensing applications. A cladding-modified optical fiber sensor coated with Eu2O3 modified reduced graphene oxide/tri-sodium citrate functionalized Au NPs is presented for phosphate ion sensing. The phosphate ion sensing of the optical fiber was studied for different tri-sodium citrate concentrations and different europium concentrations against a fixed concentration of phosphate ion. Upon the introduction of phosphate ions to the optical fiber sensor, a voltage shift is detected in all tested samples. The performance of the optical fiber sensor was evaluated throughout a wide range of phosphate ion concentrations, from 100 nM to 500 nM. The sensor's reaction to rising phosphate ion concentrations follows a polynomial pattern. Furthermore, selectivity experiments demonstrate that the optical fiber sensor displays a more pronounced response to phosphate ions when compared to various other ions, including potassium, ammonium, calcium, copper, manganese, magnesium, nitrate, sulfate, bromine, carbonate, chlorine, and others. The sensor characteristics like repeatability, response time variation, and stability were also studied.
Read full abstract