z Materials Science inc. Nanomaterials & Polymers Selective Fabrication of an Electrochemical Sensor for Pb 2 + Based on Poly(pyrrole-co-o–toluidine)/CoFe 2 O 4 Nanocomposites Dina F. Katowah, [a] Mahmoud A. Hussein,* [a, b] M. M. Alam, [c] M. A. Gabal, [a, d] T. R. Sobahi, [a] Abdullah M. Asiri, [a, e] Jamal Uddin, [f] and Mohammed M. Rahman* [a, e] We report the synthesis of a novel nanocomposites based Poly (pyrrole-co-o-toluidine) copolymer and cobalt ferrite (CoFe 2 O 4 ) as an electrochemical sensor for selective Pb 2 + detection. The general abbreviation of these new materials are given as P(Py- co-OT)/CF nanocomposites (P(Py-co-OT)/CF NCs). The synthesis was performed via in situ-chemical oxidative polymerization method at different CoFe 2 O 4 weight ratio (5%, 10%, 30%, 50% and 70%), whereas CoFe 2 O 4 nanoparticle (NPs) was synthesized by an egg white method prior the nanocomposite formation. The structural, morphological, thermal, magnetic, electrical and electrochemical properties of pure P(Py-co-OT), CoFe 2 O 4 and P (Py-co-OT)/CF NCs were characterized by XRD, FTIR, TGA-DTG, SEM-EDX, TEM, VSM and electrical conductivity. The results of XRD and FTIR confirmed the formation of P(Py-co-OT)/CF NCs with the component CoFe 2 O 4 showing spinel structure. The analysis of TGA-DTG presented that CoFe 2 O 4 NPs improved the thermal stability of NCs indicated the presence of some interactions between the interface of P(Py-co-OT) and CoFe 2 O 4 NPs, which affects the chemical and physical properties of the NCs. The ac conductivity was also examined as a function of temperature. The measures showed a decrease in the con- ductivity of NCs when increasing the insulating CoFe 2 O 4 NPs contents. A cost-effective and reliable electrochemical sensor selective to Pb 2 + ion was fabricated using P(Py-co-OT)/CF NCs on glassy carbon (GCE). It was found that the P(Py-co-OT)/CF 10 NCs exhibit excellent detection of Pb 2 + ion. The proposed Pb 2 + ion sensor was performed linearly over the large concentration range of 0.1 nM ∼ 0.01 mM labelled as linear dynamic range (LDR). The sensitivity as well as detection limit were estimated to be 22.39 μAμM 1 cm 2 and 42.39 � 2.12 pM, respectively. The desired ionic sensor-based on P(Py-co-OT)/CF 10 NCs/binder/GCE was found as efficient to detect Pb 2 + ion in environmental and biological samples significantly. The analytical sensor perform- ances such as reproducibility, sensitivity, stability, validation, and response time were reliable and significant. 1. Introduction Conducting polymers (CPs) have received much attention in recent years due to their potential uses in a wide range of applications in the numerous fields of energy devices, electronics, optics, actuators and medicine. CPs have further been used for sensor applications. However, CPs bears some limitations such as processability, low sensitivity and poor selectivity. Addition of other components during composite formations overcome these problems and improve much specific functionality for the tunable applications as various selective sensors. [1] Conducting polymer nanocomposites (CPNCs)-based sensors have an enhancement in selectivity, sensitivity and reversibility because of the synergistic effect of high electrical conductivity of CPs and size reduction for nanofiller in nanocomposites NCs. [2] Because of its executive electrical and physical properties and biocompatibility, poly- pyrrole PPy is mostly used CPs as supporting matrix in electrochemical systems and for the formation of bioanalytical sensors. [3] In addition, PPy can provision good dispersion of metal NPs because of the essential existence of functional groups as well as long chains of carbon. [4,5] O-toluidine POT as a derivative of polyaniline PANI is one of the hopeful CPs because of its potential applications in batteries, electronic devices, and sensors. [6] POT has higher solubility and process- [a] D. F. Katowah, Dr. M. A. Hussein, Prof. M. A. Gabal, Prof. T. R. Sobahi, Prof. A. M. Asiri, Prof. M. M. Rahman Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia E-mail: maabdo@kau.edu.sa mahmali@aun.edu.eg [b] Dr. M. A. Hussein Polymer chemistry Lab., Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt [c] M. M. Alam Department of Chemical Engineering and Polymer Science, Shahjalal University of Science and Technology, Sylhet 3100, Bangladesh [d] Prof. M. A. Gabal Chemistry Department, Faculty of Science, Benha University, Benha, Egypt [e] Prof. A. M. Asiri, Prof. M. M. Rahman Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, Jeddah 21589, Saudi Arabia E-mail: mahussein74@yahoo.com mmrahman@kau.edu.sa [f] Prof. J. Uddin Center for Nanotechnology, Department of Natural Sciences, Coppin State University, 2500 W. N. Ave, Baltimore, MD, USA Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201902714 Full Papers DOI: 10.1002/slct.201902714 10609 ChemistrySelect 2019, 4, 10609–10619 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim