Tailoring the Field Distribution of ZnO by Polyaniline for SPR-Based Fiber Optic Detection of Hardness of the Drinking Water

Abstract

Due to the industrial development, drinking water is getting polluted by disposing several waste products of the industries. Hardness is one of the prominent impurities in drinking water which is mainly due to the presence of carbonate and bicarbonate ions (CO 3 2− and HCO 3 − ) in it. Here, we present the synthesis of the zinc oxide (ZnO) and polyaniline (PANI) nanocomposite for the detection and estimation of hardness of the drinking water. The chemical formula of such a nanocomposite is defined in terms of the fraction of polyaniline nanoparticles reinforced in ZnO matrix and is derived as ZnO (1−x) PANI x (0≤x≤0.9); x is the composition ratio. Silver and ZnO (1−x) PANI x layers are coated over the unclad core of the optical fiber so as to create the four layer system as that of Kretschmann configuration SPR structure. The working principle involves the change in dielectric constant of (ZnO (1−x) PANI x ) by CO 3 2− or HCO 3 − ions in aqueous atmosphere. Due to the strong interaction of the sensing surface to the CO 3 2− and HCO 3 − ions, a red shift in the SPR spectrum is observed in the concentration range 0-200 μg/l. The sensitivity of the sensor depends on the composition ratio of the nanocomposite and has been found to be maximum for the composition ratio lying in the range 0.45-0.60. This has been further confirmed in terms of the enhancement of the electric field density and found to be in agreement with the experimental value. The sensitivity of the sensor with optimum value of the composition ratio is 0.094 and 0.065 nm/(μg/l) for CO 3 2− and HCO 3 − , respectively. The sensor is highly selective to CO 3 2− and HCO 3 − . The sensor has advantages of online monitoring and remote sensing of water quality because the probe is fabricated over an optical fiber.

Performance Analysis of Bimetallic Layer With Zinc Oxide for SPR-Based Fiber Optic Sensor

“…1(a) shows the five layers SPR sensor consisting of fiber core, Ag layer, Au layer, ZnO layer and the sensing medium as in ref. [18]. The proposed fiber optic SPR sensor is analyzed using 2-D multilayer model and geometrical optics as shown in Fig.…”