An inline intermodal no core fiber (NCF) sensor based on direct ligand immobilization for detection of nickel ions (Ni<sup>2+</sup>) is proposed. Covalently immobilized nickel specific ligand, Meso-Tetra(4-carboxyphenyl)porphine, on the NCF surface serves as adsorption site for Ni<sup>2+</sup> and can induce ambient refractive index (RI) change around the NCF on occurrence of binding events. The change in RI results in spectrum wavelength shifts, which was measured for continuous monitoring of Ni<sup>2+</sup> concentration. The proposed sensor was observed to exhibit a sensitivity of 121.03 nm/mM towards Ni<sup>2+</sup> ions.
A no-core fiber (NCF) based intermodal sensor for nickel ion (Ni<sup>2+</sup>) detection is proposed. Bilayers of chitosan and Poly Acrylic acid (PAA) functionalized on the sensor surface serve as adsorption sites for nickel ions thereby causing change in refractive index (RI) along the cladding bilayer boundary. Nickel adsorption at different concentrations was monitored continuously through measurement of wavelength shifts. As observed, the proposed sensor exhibits Ni<sup>2+</sup> detection sensitivity of 0.0237 nm/μM.