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It included complicated separation of target compound from by-products 25 — We propose a simple, one-step protocol for the PTZANI preparation by oxidation of the mixture of phenothiazine and aniline with an excess of ammonium persulfate Fig. The p -toluenesulfonic acid and ammonium persulfate were added to convert arylamines into corresponding salts and their oxidation, respectively. The formation of the target product, PTZANI, in the above reaction was confirmed by GC—MS using the reaction mixture washed with aqueous ammonia and water to remove excess of p- toluenesulfonic acid and inorganic impurities Supporting Information.

The formation of the polyaniline nanostructures is commonly achieved by the variation of the reaction conditions application of templates, surfactants, sonication of the mixture at the stage of oxidative polymerization 28 , It is known that some aromatic compounds, e. We supposed that interaction between the dispersion of emeraldine salt and PTZANI could result in formation of the charge-transfer complex via interaction of aniline fragments with electron-rich aryl groups of PTZANI and that such an interaction would affect morphology of the product.

To prove this hypothesis, the molar ratio of emeraldine tetraaniline fragment and PTZANI in reaction medium was chosen to be An intense absorption in the near IR region was reported for imino derivatives of phenothiazine. This made them very promising for application in the photothermal therapy Thus, continuous ultrasonication led to self-organization associates with smaller size in submicron range and lower PdI.

Three dispersions in water were considered, i. Continuous ultrasonication of the dispersion of PTZANI and polyaniline resulted in color change from dark-green to black. SEM results are in agreement with the DLS data previously described and confirmed aggregation process. Measurements on bare a , b and carbon black covered c , d electrodes. In the literature, disaggregation of emeraldine was mostly followed by size exclusion chromatography. Its dispersion in N -methylpyrrolidone led to lower size of the particles. The process was accelerated by lithium salts or ionic liquids addition In aqueous solutions, stabilization of emeraldine particles with poly N -vinylpyrrolidone was reported In this work, similar effect of PTZANI explained by intermolecular interactions has been for the first time described.

Significant morphological changes observed were stimulated by two factors, i. Both PTZANI as phenothiazine derivative and emeraldine should exert reversible redox conversion at appropriate potentials. Being pH-sensitive, redox equilibria result in possibility to measure species that either change the charge of the layers or redox potential of the environment.

Structural similarity of emeraldine trimer and PTZANI and their ability to form composite nanofibers can significantly alter their redox activity. For this reason, it was interesting to compare the performance of solid-contact potentiometric sensors obtained from PTZANI or emeraldine separately deposited on the screen-printed electrode. Three redox active substrates different in charge and redox properties, i. Deposition of sensing layer was performed by drop-casting of the suspensions containing carbon black as support providing mechanical durability of the layer and better reproducibility of the sensor characteristics.

Prior to potentiometric measurements, redox reversibility of the modified electrode was estimated using ferricyanide ion as redox probe with direct current voltammetry Fig. A reversible peak pair was observed on cyclic voltammograms in accordance with the transfer of one electron. Ratio of the cathodic and anodic peak currents tends to 1. Together with symmetrical shape of the peaks and small peak potential difference this confirms high rate of the electron exchange and suitability of the modified electrode for the application in the assembly of potentiometric sensor. The parameters of the electron transfer, i.

Scan rate Measurements on bare a,b and carbon black covered c,d electrodes. As could be seen, all the modification protocols provide a high rate of the electron transfer indicating their applicability as transducers of potentiometric sensors measuring redox potential of the environment.

Meanwhile the transfer coefficient remains below theoretic value of 0. This might be due to negative charge of the electrode support caused by carboxylic groups placed on the surface of carbon paste of the electrode layer and carbon black particles. The following experiments were performed in open circuit mode with no ferricyanide ions in the solution. The appropriate dependence is linear in the pH range from 3. The pH changes of the potential are fully reversible and did not depend on the direction of the pH shift from acidic media to basic solution or vice versa.

In case of carbon black deposition, the pH response becomes slightly lower in neutral and acidic media due to own buffering properties of the support caused by carboxylic groups of carbon particles. Besides, the addition of carbon black in the surface layer improved the repeatability of the potential 3. The ability of potentiometric sensors to monitor redox properties of the samples tested was confirmed by determination of Fe III ions and two antioxidants ascorbic acid and hydroquinone different in charge and oxidation mechanism. Ascorbic acid is irreversibly oxidized to dehydroascorbic acid whereas hydroquinone undergoes reversible two electron oxidation to benzoquinone.

Higher amount of the PTZANI added in the surface layer increases sensitivity of signal whereas carbon black improves reproducibility of the results. The dependence of the sensor potential on the Fe III ion concentration. It has a super-Nernstian slope in a narrow range of concentrations with two sloping items in the area of small and high Fe II concentrations This is explained with direct oxidation of emeraldine with Fe III ions. No other ions affect the signal of potentiometric sensor in a similar manner except Ag I and copper II.

However, their influence was found insignificant because of the lower ionic potential and lack of spatial complementarity to potential binding sites of the polymer.

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Taking into account simple preparation of the sensing layer and cost-effective protocol of screen-printing, such a behavior can be considered as important advantage of the potentiometric sensor with PTZANI layer over the analogs described in the literature. Similar experiments have been performed with hydroquinone and ascorbic acid Fig. Calibration curve of ascorbic acid is influenced by the presence of carbon black and lesser depends on the PTZANI quantities. This might be due similar charge of the analyte and carboxylate groups of the carrier and hence to higher contribution of electrostatic interaction to the sensor potential.

Thus, in both cases substitution of polyaniline with PTZANI improved the analytical characteristics of antioxidant determination. Sensor-to-sensor repeatability was found to be 4. The dependence of the sensor potential on the hydroquinone A and ascorbic acid B concentration. Measurements on bare a,b and carbon black covered c,d electrodes. The determination was performed by addition method after dissolution of the grinded tablets. With no pre-treatment, iron content was underestimated against standard samples of Fe NO 3 3 and nominal content of iron in the medication. To improve the recovery, the samples were heated with nitric acid to destroy the complexes with dextran followed by neutralization of the solution.

Modern Aspects of Electrochemistry №31

As could be seen, the potentiometric sensor proposed showed satisfactory results of the determination of iron. Similar protocol can be used for estimation of biochemically available content of iron in foodstuffs and beverages.

We have studied the interaction of the synthesized PTZANI with emeraldine form of polyaniline and found aggregation of the mixture resulted in formation of the micron-sized particles. During the continuous ultrasonication, emeraldine particles are rearranged due to interaction between emeraldine and PTZANI with formation of stable self-organization associates.

To the best of our knowledge, this is the first report on reorganization of emeraldine into nanofibrillar structures. The introduction of the PTZANI in the surface layer of the solid-contact potentiometric sensor on the platform of screen-printed carbon electrode was also performed. The potentiometric sensor exerted high reversibility of the redox reactions and ion-to-electron conductivity typical for emeraldine.

In all these cases, significant enhancement of the linear range of concentrations was achieved against polyaniline sensor. Addition of carbon black to the surface layer improved reversibility of the redox reactions as was shown by kinetic parameters of electron transfer obtained by constant current voltammetry with ferricyanide redox probe. Besides, potentiometric sensors with carbon black layer exerted higher reproducibility of the signal toward hydroquinone and Fe III ions and in the case of ascorbic acid improved sensitivity of the response and decreased in the detection limit by two orders of concentration magnitude.

Similar measurement protocols can be proposed for the assessment of biologically accessible amounts of iron and antioxidant capacity determination in food quality control. All authors have read the manuscript and agree with it. Supplementary information accompanies this paper at National Center for Biotechnology Information , U.

Sci Rep. Published online Jan Alena I. Khadieva , 1 Vladimir V. Gorbachuk , 1 Gennady A. Evtugyn , 1 Svetlana V. Belyakova , 1 Ruslan R. Latypov , 2 Sergey V. Drobyshev , 3 and Ivan I. Stoikov 1. Khadieva 1 A. Vladimir V. Gorbachuk 1 A. Gennady A. Evtugyn 1 A. Svetlana V.

Belyakova 1 A. Ruslan R. Sergey V. Ivan I.

Modern Aspects of Electrochemistry Series by John O'M. Bockris

Stoikov 1 A. Author information Article notes Copyright and License information Disclaimer. Stoikov, Email: ur.

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Corresponding author. Received Jun 18; Accepted Nov This article has been cited by other articles in PMC. Associated Data Supplementary Materials Supplementary information. Abstract Synthesis and application of nanostructured materials applicable in the assembly of electrochemical sensors is one of the important trends in material sciences and analytical chemistry. Introduction Growing technological applications of electroactive polymers keep the development and improvement of appropriate materials as one of the most important challenges.

Experimental Materials Ammonium persulfate, p -toluenesulfonic acid, ascorbic acid, hydroquinone and phenothiazine were purchased from Sigma-Aldrich and used as received without additional purification. Oxidative polymerization of aniline Aniline 0. Open in a separate window. Figure 1.

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Synthesis of nanofibers: self-organization of PTZANI and polyaniline The formation of the polyaniline nanostructures is commonly achieved by the variation of the reaction conditions application of templates, surfactants, sonication of the mixture at the stage of oxidative polymerization 28 , Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Conclusion We have studied the interaction of the synthesized PTZANI with emeraldine form of polyaniline and found aggregation of the mixture resulted in formation of the micron-sized particles.

Supplementary information Supplementary information K, pdf. Author Contributions A. Notes Competing Interests The authors declare no competing interests. Electronic supplementary material Supplementary information accompanies this paper at References 1. Kluwer Acad, Plenum Publ. Metodi ismerenii v elektrohimii [Measurement Methods in Electrochemistry]. Theory of Chemisorption.

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Berlin, Springer, , p. L, Quijada C. Langmuir , , vol. Elektrokhimiya [Russian Journal of Electrochemistry], , vol. Marangoni D. Chinese Universitie, , vol. Safonova T. Kuleshova N. Electrokchimiya [Russian Journal of Electrochemistry], , vol.

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Bobrinskaya E. Korrosia: materialy i zashita [Corrosion: Materials, Protection], , no. Bragin O. Russian Chemical Reviews , , vol. Catalysis , , vol. In: Mechanisms of Hydrocarbon Reactions. Anderson R. Chemisorption and Reactions on Metallic Films. London, New-York. Press, , p. Kinetica i katalys [ Kinetics and Catalysis ], , vol. Maire G.