Electropolymerization of polyaniline thin films

Abstract

Polyaniline (PANI) thin films have been electrochemically synthesized onto conducting glass substrates. The current study demonstrates that the properties of PANI films depend on the concentration of dopant acid. Well-adherent PANI coatings were obtained under potentiodynamic conditions during sequential scanning of the potential region between −0.35 V and +1.7 V with respect to silver/silver chloride. The structural, optical, and morphological properties of PANI films were studied with the aid of X-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and field-emission scanning electron microscopy (FESEM). Current–voltage ( I- V) measurements were performed to study the electrical properties of PANI films. The XRD peaks observed at 2 θ = 15.4°, 24.2°, and 25.1° confirm the synthesis of emeraldine form of PANI. The strong absorption peaks observed in the UV-Vis absorption spectra at 317 nm (π–π* interband transition), 371–427 nm (polaron band transition), and 750 nm (bipolaron band transition) confirm the formation of emeraldine oxidation state of PANI. A broad peak attributed in the PL spectra around 395 nm is related to the transition from polaronic band to the π band. All the intense bands attributed in the Raman spectra are associated with the emeraldine oxidation state of PANI. FESEM images reveal the formation of fibers and belts of PANI. Highly conducting thin films of PANI deposited at higher concentrations of dopant acid were confirmed by I- V measurements.

Characterization of Electrochromic Properties of Polyaniline Thin Films Electropolymerized in H<sub>2</sub>SO<sub>4</sub> Solution

“…The conductivity of PANI films mainly depends on the oxidation state, pH of the electrolyte and the type of dopant used for protonation [11]. PANI exhibits reverse electrochromic performance; it is able to switch from a transparent yellow state to a green one, according to reduction and oxidation processes [12].…”

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“…Beyond this ratio, the film becomes brittle and poorly conductive. The photoluminescent (PL) emission spectra of PANi/PVA recorded in the 340–600 nm show (Figure b, curve a) a maxima at 396 nm due to the π‐π transition in PANi (Rohom, Londhe, Mahapatra, Kulkarni, & Chaure, ) and no evidence for the PL property of the PVA is noticed, confirming the fact that PVA does not influence the conducting property of the PANi (Figure b, curve a). The FTIR spectra of freestanding PANi–PVA film exhibit characteristic peaks for the chemical interactions of PVA and PANi.…”

Hybrid TiO2–Polyaniline Photocatalysts and their Application in Building Gypsum Plasters

“…Therefore, the visible luminescence band for TiO2 originates from the oxygen vacancies associated with Ti 3+ in the TiO2 structure. The polyaniline PL spectrum is corresponding to the PL spectra presented in the literature [47,48]. Emission from the UV region, with the maximum at 395 nm, could be attributed to the π*-π transition of the benzoic units in the The UV-Vis absorption spectrum of pure TiO 2 , PANI, and the PANI-TiO 2 nanocomposite is presented in Figure 3a.…”

“…The peak at 487 nm is related to d-excitation from the polaron band. Rohom et al [47] also detected a similar emission peak at 613 nm; however, its origin is not clarified. In the visible light region, the intensity of the PL signal was lower for PANI and PANI/TiO 2 materials compared to TiO 2 P25.…”