used ab initio Hartree–Fock (HF/6-31G) and density functional theory (DFT/6-31G) methods to exhibit relative stability of the aromatic and quinoid forms of neutral PEDOT in the ground state. In theoretical studies, structural and electronic properties of PEDOT and PEDOT:PSS have been investigated by many research groups, i.e., Dkhissi et al. cm −1) with solubility in water which allows the conductive polymer to be easily-processed as an electronic ink for practical applications in field of printed electronics.Combination of PEDOT and PSS (PEDOT:PSS) provides the enhanced electrical conductivity (1–10 S To improve the solubility and conductivity of PEDOT, poly(styrenesulfonate) (PSS) as a dispersant and a charge-balancing dopant is usually doped into PEDOT during the polymerization. Because of its unique properties such as low redox potential, low band gap (1.5–1.6 eV), and good stability (below 150 ☌), PEDOT can be used in several applications such as transparent electrodes, printing circuit boards, OLED displays, solar cell, and textile fibers. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising π-conjugated polymers. The most favorable adsorption site for PEDOT:PSS-NH 3 interaction was found to be at the nitrogen atom of NH 3 and hydrogen atoms of SS with an average optimal binding distance of 2.00 Å. The NH 3 molecules preferred to bind with PEDOT:PSS via physisorption. The SCC-DFTB calculation suggested domination of direct charge transfer process in changing of PEDOT:PSS conductivity upon NH 3 exposure at room temperature. Printed PEDOT:PSS gas sensor exhibited relatively high response and selectivity to NH 3. Electrical conductivity of EDOT increased with increasing oligomers and doping SS due to enhancement of π conjugation. The results showed an important role of H-bonds in EDOT:SS oligomers complex conformation. An application of PEDOT:PSS for ammonia (NH 3) detection was highlighted and investigated both experimentally and theoretically. Geometric and electronic properties of 3,4-ethylenedioxythiophene (EDOT), styrene sulfonate (SS), and EDOT: SS oligomers up to 10 repeating units were studied by the self-consistent charge density functional tight-binding (SCC-DFTB) method.

Homo and lumo of ammonia