Composite Material–Based Conducting Polymers for Electrochemical Sensor Applications: a Mini Review Sara A. Alqarni 1,2 & Mahmoud A. Hussein 1,3 & Aisha A. Ganash 1 & Anish Khan 1,4 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Conducting polymers (CPs) represent a sizeable range of useful organic substances. Their unique electrical, chemical, and physical properties; reasonable price; simple preparation; small dimensions; and large surface area have enabled researchers to discover a wide variety of uses, including sensors, supercapacitors, solar cells, batteries, biochemical applications, and electrochromic devices. To promote the success of CPs, unique composite materials have been prepared with metals or steel oxides. The goal of this overview is to characterize the electrochemical sensor utility of CPs and their composites and to categorize future components of electrochemical sensing materials. CPs have been comprehensively applied over a wide range of variable industrial fields; such CPs have used many new materials with diverse compositions that are utilized as electrochem- ical sensors and biosensors. These materials have been fabricated inside numerous analytical instruments that are applied in healthcare settings and clinical, environmental, food, and pharmaceutical laboratories. Electrochemical sensors are essentially based on CPs and/or their corresponding composite materials. Therefore, the present work provides a brief illustration of electrochemical sensor and biosensor applications for the most important conducting polymer composite materials. Polyaniline (PANI), poly(o-toluidine) (PoT), and poly(o-anisidine) (PoAN) were considered in this study. Moreover, the most important electrochemical properties of these conducting polymer composite materials are discussed. Keywords Polyaniline . Poly(o-anisidine) . Poly(o-toluidine) . Conducting polymer . Composites . Electrochemical technique . Sensor application 1 Introduction Polymers are molecules composed of many repeated subunits referred to as monomers [1]. Polymers have received considerable interest since the first electro- chemical synthesis of polyaniline in acidic media by Letheby in 1862 [2]. CPs are polymers that exhibit electrical behavior [3]. CPs such as insulating polymers are organic substances. Such CPs can display high elec- trical conductivity but do not display mechanical prop- erties equal to those of other commercially available polymers [3]. The electrical properties may be optimized via superior dispersion techniques and natural synthesis strategies [4]. The conductivity of CPs was first ob- served in polyacetylene [5]. Polyacetylene instability in air has led to the discovery of diverse forms of CPs, including polyaniline (PANI), poly(o-toluidine) (PoT), poly(o-anisidine) (PoAN), polypyrrole (PPy), polythiophene (PTh), and polyfluorene (PF). CPs pre- pared in the form of nanomaterials are of interest be- cause their properties drastically differ from the proper- ties in their bulk counterpart [4]. Natural CPs have low conductivity and are semiconductive. Therefore, it is essential to increase their conductivity, mainly for use in electrochemical sensor programs. To address this problem in CPs, composites and nanocomposites of * Mahmoud A. Hussein maabdo@kau.edu.sa; mahmali@aun.edu.eg; mahussein74@yahoo.com 1 Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia 2 Chemistry Department, Faculty of Science, University of Jeddah, P.O. Box 34, Jeddah 21959, Saudi Arabia 3 Polymer Chemistry Lab., Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt 4 Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Kingdom of Saudi Arabia BioNanoScience https://doi.org/10.1007/s12668-019-00708-x