A Simple Route to Prepare Polypyrrole-Coated Filter Papers via Vapor Phase Polymerization and Their Gas Sensing Application

Vapor phase polymerization has been used for the synthesis of polypyrrole-coated filter paper (PPy-FP) using a simple experimental setup. In addition, we have doped the polymer-coated filter papers with hydrochloric acid (HCl), camphorsulfonic acid (CSA), and p-toluenesulfonic acid (PTSA) to prepare HCl-PPy-FP, CSA-PPy-FP, and PTSA–PPy-FP, respectively. These samples were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), energy dispersive X-ray (EDX) analysis, and powder X-ray diffraction (PXRD) techniques. The prepared PPy-coated filter papers have been used for ammonia vapor sensing studies at room temperature. The sensing device of the hybrid filter papers was developed by pasting Cu strips as electrodes. It has been observed that doping enhances the conductivity from 1.78 × 10–5 to 3.34 × 10–5 S/cm. The sensing performance also improved on doping, and among the developed sensors, HCl-PPy-FP shows the best result. The limit of detection (LOD) value for PPy-FP is found to be 13 ppm, which has been improved up to 5.2 ppm for HCl-PPy-FP. Doping increases the delocalization along the PPy chain to generate more active sites. The fabricated devices are flexible, easy to handle, and cost-effective.