Conjugated polymer /multi wall carbon nanotubes composite characterisation for application in volatile organic compounds sensors

Abstract

Composites of conjugated polymers (CP) are becoming increasingly used in nanoelectronics devices, due to their electronic and optical properties. Recent efforts have demonstrated that the incorporation of materials like carbon nanotubes (CNTs) that have excellent physical and chemical properties, within the matrix of CP could improve the sensing proficiency. The monitoring of pollutants for human health, as they can cause several diseases, is an important aspect of research, and the detection of toxic species is an issue of growing interest. A lot of research work on the application of CP/CNTs composite in gas sensing has been conducted but more research is needed to explore their potentials as sensing elements. The aim of our work is to use a simple chemical and low-cost method to coat CNTs with polyimidazole polymer (Plm) and test their ability to sense pollutants. Polyimidazole multi-walled carbon nanotubes (Plm/MWCNTs) nanocomposite film was synthesised by chemical oxidation of imidazole monomer and the addition of MWCNTs to the conductive polymer (CP) solution in 1:1 ratio. Chemical characterisation using FTIR where there is an increase in intensity of peaks in the control sample from 2823 and 2937 cm-1 to 2833 and 2947 cm-1 in Plm/MWCNTs composite respectively and Raman spectroscopy in which Plm/MWCNTs shows the so-called D-band (attributed to disordered sp2 and non-sp2 carbon defects in graphitic sheets) and G-band (attributed to the C–C vibration with the sp2 hybridised orbital in graphene structures) peaks at 1355 cm-1 and 1593 cm-1, but chemical analysis confirmed the mixing of the polymer and the MWCNTs. Electrical measurements using current voltammetry (CV) show a reversible wave that is the typical behaviour of conductive surfaces in the presence of the redox couple and Impedance measurements in which the largest semicircle was obtained with Plm/CNTs film that corresponds to a film resistance on the real axis of 350 MΩ which is an indication of a higher electron transfer rate in the redox probe and good electrical behaviour. The overall results have shown that the composite has significant electrical conductivity and can be applied in sensing volatile organic compounds in the environment.