AUTHOR=Botewad S. N. , Pahurkar V. G. , Muley G. G. , Gaikwad D. K. , Bodkhe Gajanan A. , Shirsat Mahendra D. , Pawar P. P. TITLE=PANI-ZnO Cladding-Modified Optical Fiber Biosensor for Urea Sensing Based on Evanescent Wave Absorption JOURNAL=Frontiers in Materials VOLUME=7 YEAR=2020 URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00184 DOI=10.3389/fmats.2020.00184 ISSN=2296-8016 ABSTRACT=

In the present investigation, we demonstrated a simple, rapid, and highly sensitive cladding-modified optical fiber urea sensor based on the evanescent wave absorption (EWA) technique. Cladding modification was performed over a 2-cm unclad portion of optical fiber using a polyaniline-zinc oxide (PANI-ZnO) matrix with enzyme-Urease (Urs) cross-linked to it using glutarldehyde as a cross-linking agent. The PANI-ZnO matrix was characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible, and Fourier transform-infrared spectroscopy to explore its various properties. The developed sensor shows a linear response to urea concentration in the range 10 nM−1 M in the form of the absorption spectrum at a wavelength of ~250 nm with specific selectivity. Under the proper conditions (storage at temperature 4°C after each measurement), it shows 40-day stability without any decrement in the intensity of the absorption spectrum. Thus, the developed sensor is highly sensitive, stable, and specific, with a lower detection limit of a urea concentration of 10 nM.