Electrodeposition of thin films of polypyrrole-polyelectrolyte complexes and their ammonia-sensing properties
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ORIGINAL PAPER
Electrodeposition of thin films of polypyrrole-polyelectrolyte complexes and their ammonia-sensing properties O. L. Gribkova 1
&
V. A. Kabanova 1 & A. A. Nekrasov 1
Received: 28 April 2020 / Revised: 25 June 2020 / Accepted: 13 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Polypyrrole (PPy) films were electrodeposited in a galvanostatic mode in the presence of salt and acid forms of sulfonated polyelectrolytes distinguished by different rigidity of the polymer backbone. The process of PPy electrosynthesis was studied by in situ spectroscopy in the UV-visible-NIR spectral regions with simultaneous monitoring of the electrochemical parameters of the synthesis. The PPy films were characterized by Raman spectroscopy. The morphology of the PPy-polyelectrolyte films was investigated by atomic force microscopy. PPy-polyelectrolyte films were successfully tested as sensitive layers in optical ammonia sensors. The behavior of the polymer-based gas sensors, including response time and response amplitude, to various ammonia gas concentrations ranging from 25 to 529 ppm was investigated. The experimental results showed that these parameters are dependent on the polyelectrolytes structure and form (acid or salt). The optical sensors based on the films of PPy complexes with the salt forms of all polyelectrolytes and the acid form of the rigid-chain polyelectrolytes can reliably detect 25ppm ammonia, the complexes of the rigid-chain polyacids responding significantly faster. Keywords Polypyrrole . Electropolymerization . Polyelectrolyte . UV-Vis-NIR spectroelectrochemistry . Conducting polymers . Ammonia-sensor
Introduction Conducting polymers, such as polyaniline, polypyrrole (PPy), polythiophene, and their derivatives, are actively used as sensing materials in gas sensors [1, 2]. Compared with the most commercially available sensors, which are usually based on metal oxides and operate at high temperatures, the sensors based on conducting polymers have good mechanical properties, stability in air, and high sensitivity at room temperature [1, 2]. Moreover, they are easily synthesized and have high sensitivity and short response time. PPy is one of the most promising materials for gas sensing applications [1–11]. Basically, rapid response to various chemical species is caused by changes in the oxidation level of the PPy, which is readily affected by chemical or electrochemical doping/ dedoping (oxidation/reduction). The sensing mechanism of PPy varies for different analytes depending on their functional groups.
* O. L. Gribkova [email protected] 1
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Leninskii prospect 31, Moscow, Russia 119071
Most of the sensors based on PPy films operate via a chemiresistive transducing mechanism [1–9]. For example, electron-donating gas NH3 reduces and therefore dedopes PPy, which leads to an increase in the resistance. The application of PPy films for ammonia-sensing has been widely investigated [1–11]. The interact
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