Self-Consistent Charge Density Functional Tight-Binding Study of Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) Ammonia Gas Sensor

Ampaiwan Marutaphan; Yotsarayuth Seekaew; Chatchawal Wongchoosuk

doi:10.1186/s11671-017-1878-2

Self-Consistent Charge Density Functional Tight-Binding Study of Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) Ammonia Gas Sensor

Nanoscale Res Lett. 2017 Dec;12(1):90. doi: 10.1186/s11671-017-1878-2. Epub 2017 Feb 6.

Authors

Ampaiwan Marutaphan^{1

2}, Yotsarayuth Seekaew¹, Chatchawal Wongchoosuk³

Affiliations

¹ Department of Physics, Faculty of Science, Kasetsart University, 10900, Chatuchak, Bangkok, Thailand.
² Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, 11000, Nonthaburi, Thailand.
³ Department of Physics, Faculty of Science, Kasetsart University, 10900, Chatuchak, Bangkok, Thailand. Chatchawal.w@ku.ac.th.

Abstract

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. An application of PEDOT:PSS for ammonia (NH₃) detection was highlighted and investigated both experimentally and theoretically. The results showed an important role of H-bonds in EDOT:SS oligomers complex conformation. Electrical conductivity of EDOT increased with increasing oligomers and doping SS due to enhancement of π conjugation. Printed PEDOT:PSS gas sensor exhibited relatively high response and selectivity to NH₃. The SCC-DFTB calculation suggested domination of direct charge transfer process in changing of PEDOT:PSS conductivity upon NH₃ exposure at room temperature. The NH₃ molecules preferred to bind with PEDOT:PSS via physisorption. The most favorable adsorption site for PEDOT:PSS-NH₃ interaction was found to be at the nitrogen atom of NH₃ and hydrogen atoms of SS with an average optimal binding distance of 2.00 Å.

Keywords: Ammonia gas sensor; Conducting polymers; PEDOT:PSS; QM/MD simulation; SCC-DFTB.