**1. Introduction**

The information carried by an electrochemical redox reaction (the reaction between electrode and analyte) is converted into an applicable quantitative or qualitative signal by electrochemical sensors. The sensors can generate electronic outputs in the form of digital signals that can be analysed further [1]. Depending on the mechanism involved in recognition, the sensors can be chemical or biological (biosensor). Electrochemistry is found to play a crucial role in medical technology, forensics, food, environmental sciences, defence settings, agriculture, among others [2, 3].

Electrochemical sensors and detectors are very appealing for applications, viz. on-site monitoring of environmental contaminants, addressing varied environmental needs, health monitoring, testing of adulterants in food samples, forensic drug analysis, and many more. Many of the specifications for on-site environmental scanning are met by sensing devices. They are intrinsically sensitive and selective to electroactive species and are fast, reliable, portable, compact and economical [4]. A transducer and a chemical recognition system are the two primary components of an electrochemical sensor, and collectively these two components constitute a sensing electrode. Other electrodes may also be used in electrical measurements like reference and counter electrodes (CEs) [5]. In electrochemical sensors, a potential difference is applied in between working and counter electrodes, and on the basis of redox reactions caused by the analyte at the electrode's interface, the resulting current response is measured. Voltammetry, conductometry, potentiometry, or amperometry can be used to study the transduction of biological or chemical signal to electrical signal. Since their invention, the electrochemical sensors are being studied extensively for their applications in efficient biosensors, immunosensors, special electrode design automated systems, and microelectrodes, etc. [6]. With the recent advancements in the designing and synthesis of nanomaterials along with the evaluation of intrinsic properties of nanoparticles (NPs) based on carbon [7] and many other types of base materials, the engine of nano-electrochemistry has begun to gain speed in the field of electrosensing.
