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Sensor properties of polyaniline (PANI) depend on its interesting chemical structure. It is well-known that this polymer exists in non-conducting and conducting forms. Non-conducting ones are polybases with different degrees of oxidation and differing in colors. Specifically these are completely reduced form – almost colorless leucoemeraldine, the most stable half-oxidized form – blue emeraldine base, and completely oxidized form – pernigraniline also blue colored. These forms can be easily transformed from one to another in the course of reversible chemical or electrochemical redox reactions.


  In fact, these reactions plus ability to participate in acid-base and donor-acceptor interactions with corresponding changes of optical and electrical properties are a good prerequisite for its application as a sensing element in devices based on different registration principles (e.g. measurements of PANI electrochemical responses, conductivity, weight, optical parameters etc. In most cases the fast and reversible reactions of PANI with bases (when it is in doped state - emeraldine salt, ES) and acids (when it is in undoped state - emeraldine base, EB) are the chemical basis of these registration principles. Corresponding chemical, color and conductivity changes in PANI during such reactions are shown in this scheme:



One of the disadvantages PANI which hinder its industrial application is its poor mechanics and machinability. In our department, this problem was solved by creating a composite polyaniline-polyethylene terephthalate (PET-PANI composite), which combines the sensory properties of polyaniline and mechanical characteristics of polyethylene terephthalate.
  Such a composite, without any additional processing, in doped state showed marked sensory responses to ammonia. But they were insufficient forces for easy registration.
  Because the original composite was subjected to two types of modifications, which resulted in the surface were molded two types of structures  

 
 
Fibrillar structure
Finely porous structure

  These two types of composites were tested for sensitivity to ammonia and it was found that the composite with fine structure on the surface has a significantly higher sensitivity (red curve).



Thus obtained material can be used not only as a sensor for ammonia, but also a number of substances capable which capable to chemical protonation PANI (a pair of organic acids, halogenated, etc.). Also contained in the composite PANI can participate in the electronic interactions with analyte on donor-acceptor mechanism, which makes it sensitive to many organic substances.

1. Polyaniline/poly (ethylene terephthalate) film as a new optical sensing material, Ie. P. Duboriz, A. A. Pud, Sensors and Actuators B: Chemical, 2014, 190, 398-407 DOI:10.1016/j.snb.2013.09.005

2. P2.3.9 Polyaniline/poly(ethylene terephthalate) films as a sensing material in optical sensors for basic and acidic substances. A. Pud, I. Duboriz, 14th International Meeting on Chemical Sensors - IMCS 2012
DOI:10.5162/IMCS2012/P2.3.9  



intrinsically conducting polymers, ICP, electrochromic devices, nanocomposites, ECD, gas sensor, photovoltaic, electrochemical simulation and regulation of redox-processes, poly(3-methylthiophene), P3MT, poly(3-alkylthiophene), P3HT, PEDOT:PSS, PEDOT, нанокомпозиты, газовые сенсоры, фотовольтаика, электрохромные устройства, электрохимическая симуляция и регуляция редокс-процессовна нокомпозиты, газовые сенсоры, фотовольтаика, электрохромные устройства, электрохимическая симуляция и регуляция редокс-процессов, П3МТ, поли(3-метилтиофен), поли(3-гексилтиофен), поли(3-алкилтиофен), ПЕДОТ:ПСС