OPTICAL рН SENSOR BASED ON POLYANILINE FILMS
Journal Title: Праці Наукового товариства ім. Шевченка - Year 2018, Vol 53, Issue
Abstract
The films of polyaniline were deposited by in situ chemical oxidation of 0.05 М aniline monomer by 0.08 М ammonium persulfate in 0.5 M citric acid aqueous solution in the presence of polyethylene terephthalate films. The doping-dedoping-redoping processes of polyaniline films accompanies by change of color of its films from green to violet and to green, respectively, that confirms the formation of the different forms of polyaniline visually. In particular, the synthesized films of polyaniline were green, indicating the formation of polyaniline in the conductive form – of protoned emeraldine salt. The dedoped films of polyaniline (after exposure to alkaline solutions) were blue, which indicates the formation of polyaniline in the non-conducting form of – of emeraldine base. The optical properties of polyaniline on the polyethylene terephthalate substrate have been investigated using ultraviolet-visible and Fourier transform infrared spectroscopy. It is shown the possibility of using the obtained polyaniline films as materials for pH sensors in the wide range 2–12. In particular, the curve of the dependence of the polyaniline film the maximum wavelength (λmax) on the pH of buffer solutions has a sigmoidal character, conditioned both by the dopant, and the nature of the processes occurring in the polyaniline film, caused by doping or de doping of the polyaniline at a given pH value of the medium. The influence of the time of exposure the polyaniline films in buffer solutions on its optical properties was investigated. It was established that the transformation of the emeraldine salt of polyaniline into the emeraldine base of polyaniline depends on the pH of the solution and the time of exposure the samples in buffer solutions. At pH 12.43, the transformation of a polyaniline film from emeraldine salt into emeraldine base occurs very rapidly, whereas in a solution with pH of 1.68 the reverse process is somewhat slower, due to the nature of the ions that take part in them.
Authors and Affiliations
Yuliia STETSIV, Мykhaylo YATSYSHYN, Оleksandr RESHETNYAK
Keywords
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