Theory of electron transport through single molecules of polyaniline

Abstract

We present theoretical results for the electron transport properties of the organic molecule polyaniline, especially leucoemeraldine (LEB), the fully reduced form. The electron tunnelling characteristics of these chain-like molecules are described by their complex band-structure. We explore how the bandgap and tunnelling decay parameter β depend on the oxidation state of the molecule and on the torsion angle between rings. It is found that the metal Fermi level lies near the HOMO for gold contacts with a single leucoemeraldine molecule, which results in non-linear I -V characteristics. The conductance of a hepta-aniline (LEB) oligomer is obtained from a first-principles I -V curve and compared with the recent experimental results. We examine the effect of stretching of the molecule on its conductance to explain the discrepancy between the theoretical simulations and single-molecule conductance measurement experiment.

Vacuum‐Processed Polyaniline–C60 Organic Field Effect Transistors

“…In order to measure the DC conductivity of the evaporated polyaniline film, the same sample used for the dielectric investigation was measured with a Keithley 617 electrometer. The measured D.C. conductivity of the polyaniline film was found to be below 5 Â 10 À10 S cm À1 , very close to similar values reported elsewhere for hepta-aniline (LB) oligomer of polyaniline [16] or thin evaporated polyaniline films. [28] Therefore, both the A.C. and Transmittance /a.u.…”

Effect of TiO2 Nanoparticles on Polyaniline Films Electropolymerized at Different pH

“…19 The fineness of the real- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 The employed DFT based methodology predicts band gaps of 2.7, 2.3 and 0.8 eV for TiO 2 , leucoemeraldine and emeraldine, respectively, which are in agreement with previous calculations. 20,21 In addition, such a methodology has successfully predicted a broken gap heterojunction (analogous to the one predicted in this work) formed by 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 8 a semiconductor carbon nanotube deposited on diamond. 22,…”

Nucleobases tagged to gold nanoclusters cause a mechanistic crossover in the oxidation of CO

“…5,9,11 Essential structural and energetic features along with mechanistic pathways of many important chemical reactions can be studied using small gold clusters as catalytic models. [30][31][32][33][34][35][36] A unique feature of complexes between DNA bases and small gold clusters is the existence of nonconventional N-HÁ Á ÁAu hydrogen bonds. [27][28][29] The interaction of DNA with small gold clusters received special attention owing to its diverse applications in the field of electronics, sensors, drug delivery, chips, imaging, and more recently in heterogeneous catalysis.…”