Synthesis and characterization of polypyrrole thin films in a resistive plasma reactor by high frequency
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.49
Synthesis and characterization of polypyrrole thin films in a resistive plasma reactor by high frequency E. De la Cruz-Reyes1, C. Hernández-Tenorio1, M. Villanueva-Castañeda1, H. Moreno-Saavedra1, R. Alejo-Eleuterio1 1 Tecnologico Nacional de México/Instituto Tecnológico de Toluca, Av. Tecnológico s/n. Agrícola Bella Vista C.P.52149 Metepec, Edo. De México, México.
ABSTRACT
Polypyrrole (PPy) thin films were synthetized by plasma and simultaneously doped with Iodine to enhance electromagnetic absorption and charge transfer capability in a resistive coupling cylindrical reactor. Pyrrole monomer and Iodine were the principal reagents used and the chemical reactions were created by high frequency plasma. Micrographs show an irregular surface formed by semi-spherical protrusions with tiny particles in the PPy/I samples and a rather smooth surface with wrinkles and less participation of tiny particles to PPy ones. Infrared spectroscopy analysis reveals important absorption peaks at 3253, 2932, 1668 and 635 cm-1 corresponding to the chemical bonds N-H and C-H, C-H aliphatic, C=C and C-I, respectively, belonging to the chemical structure of Pyrrole. Electrical conductivity of PPy increased from 10-10 to 10-8 S/cm due to Iodine doping. Electromagnetic absorption showed a higher response between 340 and 800 nm in the visible region. Activation energy was calculated in the range from -0.09 to 0.49 eV.
INTRODUCTION Nowadays, polymers as Polypyrrole (PPy) have arisen interest in materials engineering for their capacity to control the thermal stability, optical properties, electrical conductivity, and catalytic activity by adding small amounts of other elements (dopants) to modify the polymer structure. The doping of PPy with iodine (I) creates polar sites that favors the diffusion of charges; in this way, the energy gap between the valence and conduction bands decreases. Therefore, increases the mobility of electric charges in the polymer, improving electrical and optical properties of the material [1-5]. PPy can be obtained by electrochemical, chemical and plasma-polymerization synthesis; however, PPy films synthetized by plasma offers a great number of advantages because plasma-polymerization occurs in gas phase without another chemical solvents, which sometimes are harmful to the
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environment [6]. In the present work, we synthetized PPy and PPy/I films by high frequency plasma. We studied the influence of the dopant in the electrical conductive and optical properties of the thin films. Both PPy films, undoped and doped are studied by Infrared Spectroscopy (FTIR), UV-Vis Absorption Spectroscopy, Scanning Electronic Microscopy (SEM) and electrical conductivity, as a function of the doping. EXPERIMENTAL SETUP Experime
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