Fabrication of plasma polymerized polythiophene and polypyrrole thin films as chloroform vapor sensors

Abstract

Polythiophene (PTH) and polypyrrole (PPY) thin films were fabricated via a plasma polymerization technique, using a plasma based electron beam generator Glass and quartz crystal substrates were used for the deposition of thin layers, at a pressure of 1 mbar The electron beam generator had a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow discharge and high-current pulsed one. As conjugated polymers, PTH and PPY have been used as the active layers of gas sensors, due to their high sensitivities and short response times, A novel plasma polymerization method was employed to synthesize the PTH and PPY films. The characterisation of these films by UV-visible spectroscopy, and the sensing properties against chloroform vapor using different concentration ratios, were studied by the Quartz Crystal Microbalance (QCM) method. Our results show that these plasma polymerized thin films were found to be highly sensitive to chloroform, with a fast, large and reversible response that depends on the concentration.