2-Mercaptobenzimidazole/Polyvinylpyrrolidone functionalized gold nanoparticles clad optical fiber for copper ion detection: A novel evanescent wave-based sensing approach

Gold nanoparticle-based optical fiber sensors are extensively utilized for the development of chemical sensors. The optical sensing capabilities of the chemical sensor are improved by the localized surface plasmon resonance that is linked with the gold nanoparticles. This study introduces a modified optical fiber sensor with cladding, which is coated with functionalized gold nanoparticles (Au NPs) containing 2′-mercaptobenzimidazole (MBI)/polyvinylpyrrolidone (PVP) to detect copper (Cu⁺²) ions. The study investigated the Cu²⁺ ions sensing capabilities of optical fiber under varying concentrations of PVP while maintaining a constant concentration of Cu⁺²ions. The optical fiber sensor's output voltage increased upon the addition of Cu²⁺ ions, as observed in all samples. The sensor's response was analyzed for Cu²⁺ ions concentrations ranging from 100 to 1000 ppm. The sensor displays a polynomial relationship with increasing Cu²⁺ ions concentration. The optical fiber sensor exhibits higher selectivity towards Cu²⁺ ions compared to sodium, potassium, ammonium, calcium, zinc, phosphate, nitrate, and chlorine ions.