Tight-Binding Effective Hamiltonians for the Electronic States of Polyaniline Chains

Abstract

By means of strictly one-dimensional effective Hamiltonians, in the tight-binding scheme, we obtain band structures and densities of states of the main forms of polyanilines, which compare favourably with existing theoretical and experimental studies. We first consider the band structures of the three polymeric base forms: leucoemeraldine, emeraldine and pernigraniline; then we study the pernigraniline salt and the emeraldine salt in the polaronic and bipolaronic configurations. The 1D p-electron effective Hamiltonians are obtained exploiting a modified version of the recursion method and successively the application of the renormalization method. The procedure here outlined can be adopted for any polymeric chain; it is so flexible to embody known relevant structural and optical properties of the polymer, moreover it provides a useful tool for successive iterative calculations in the study of the electronic transport properties of the polymer also in the presence of disorder.

Crucial role of decoherence for electronic transport in molecular wires: Polyaniline as a case study

“…We first calculated the coherent transmission probability as a function of energy for a set of chain configurations drawn from the representative ensemble. Results are in full agreement with the those of Farchioni et al [14,15,48] and evidence the mobility edges induced by correlated disorder in this 1-D system [9]. While there is an appreciable density of states at the Fermi energy, it corresponds to localized states.…”

“…where E o and E p are bare site energies for electrons in the p z -orbitals of ortho-C and para-C respectively; V oo is the hopping between ortho-C and V po is the hopping between a para-C and ortho-C. In this work we use the tight binding parametrization of Vignolo et al [15] for the bipolaron lattice model of base-emeraldine doped with HCl.…”

“…This opened the possibility that Fermi energy might lie in a delocalized region. However, Farchioni et al [14], by using an ab initio parametrization, made a detailed tightbinding based study of PAni-HCl comparing the BL and PL models [15]. They showed that even when the BL model exhibits extended states, its Fermi energy is far from the high transmission regions.…”

Theory of electron transport through single molecules of polyaniline

“…Leucoemeraldine base (LEB), containing only phenyl rings connected by an amine nitrogen, is known to be an insulator with a bandgap of ∼3.6 eV [29,30]. There has been much research concerning its electronic band-structure [11,16,20,31,32], and the chainlength dependence [14] of its electronic and optical properties. Additionally, the torsion angle dependence of its electronic properties [12,33] has been studied.…”

Tuning the Fluorescent Response of a Novel Electroactive Polymer with Multiple Stimuli

“…A tiny drift of fluorescence intensity was also observed during the doping/dedoping process, again due to the dilution effect by adding H 2 SO 4 and/or NaOH solution. The pH‐dependent fluorescence switching could be explained by means of oligoaniline's electronic structure, which changes during the doping/dedoping process and thus influences its photophysical properties. Consequently, the fluorescence switching of EPOP was achieved by pH stimuli.…”