Organic conjugated polymers (conducting polymers) have emerged as potentialcandidates for electrochemical sensors. Due to their straightforward preparation methods,unique properties, and stability in air, conducting polymers have been applied to energystorage, electrochemical devices, memory devices, chemical sensors, and electrocatalysts.Conducting polymers are also known to be compatible with biological molecules in aneutral aqueous solution. Thus, these are extensively used in the fabrication of accurate,fast, and inexpensive devices, such as biosensors and chemical sensors in the medicaldiagnostic laboratories. Conducting polymer-based electrochemical sensors and biosensorsplay an important role in the improvement of public health and environment because rapiddetection, high sensitivity, small size, and specificity are achievable for environmentalmonitoring and clinical diagnostics. In this review, we summarized the recent advances inconducting polymer-based electrochemical sensors, which covers chemical sensors(potentiometric, voltammetric, amperometric) and biosensors (enzyme based biosensors,immunosensors, DNA sensors).

The earlier stage of the polymerization reaction of polyaniline has been studied employing in situ spectroelectrochemical techniques. The results indicate that the nitrene cation appears to be a key intermediate species, which leads to all three possible dimers including a head‐to‐tail dimer (N‐phenyl‐p‐phenylenediamine), a tail‐to‐tail dimer (benzidine), and a head‐to‐head dimer (hydrazobenzene). The oxidized forms of these dimers were all shown to be capable of growing polyaniline in the presence of aniline, even though aniline was not oxidized. The cyclic voltammetric peaks observed during the PA synthesis in the middle potential regions were shown to arise from the redox reactions of these dimers, oligomers, and degradation products of polyaniline including quinoneimines and p‐benzoquinone.