DC electrical conductivity retention and acetone/acetaldehyde sensing on polythiophene/molybdenum disulphide composites

In this study, polythiophene (PTh) and a series of polythiophene/molybdenum disulphide (PTh/MoS ₂ ) composites were prepared by in-situ chemical oxidative polymerization method using anhydrous ferric chloride (FeCl ₃ ) as an oxidant and chloroform (CHCl ₃ ) as a solvent. The successful formation of PTh and PTh/MoS ₂ composites were confirmed by various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance electron microscopy (TEM). DC electrical conductivity and acetone/acetaldehyde sensing studies were carried out by a four-in-line probe device. PTh/MoS ₂ composites exhibited significantly improved DC electrical conductivity and acetone/acetaldehyde sensing properties as compared to PTh. The electrical properties were investigated in terms of initial conductivity (i.e. conductivity at room temperature) as well as retention of conductivity, i.e. stability under isothermal and cyclic ageing conditions. The maximum initial conductivity, along with the highest conductivity retention, was observed for PTh/MoS ₂ -2 (PTh/MoS ₂ composite comprising 10% MoS ₂ with respect to the weight of thiophene monomer). The initial DC electrical conductivity of PTh, PTh/MoS ₂ -1, PTh/MoS ₂ -2 and PTh/MoS ₂ -3 was found to be 5.72 × 10 ⁻⁵ Scm ⁻¹ , 4.03 × 10 ⁻⁴ Scm ⁻¹ , 1.09 × 10 ⁻³ Scm ⁻¹ and 8.96 × 10 ⁻⁴ Scm ⁻¹ , respectively. The sensing performance at room temperature has been studied in terms of % sensing response, response/recovery time. All the PTh/MoS ₂ composites based sensors performed much better than PTh. The % sensing response of PTh, PTh/MoS ₂ -1, PTh/MoS ₂ -2 and PTh/MoS ₂ -3 based pellet-shaped sensors towards acetone/acetaldehyde were affirmed as 30.6/22.9, 69.9/47.3, 93.7/70.3, 78.1/65.1, respectively. The purposed sensing mechanism involved the adsorption of acetone/acetaldehyde vapours on the surface of the sensors where electronic interaction between lone pair of electrons on oxygen atoms of the carbonyl group and charge carriers of PTh was responsible for the change in conductivity.