• crystallinity;
  • poly(N-propylaniline);
  • sensor;
  • solubility;
  • tartaric acid


We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for hydrogen sulfide detection and quantification using poly(N-propylaniline) (PNPA). This sensor shows an excellent wide range of detection with very good selectivity and reproducibility. Organic acid and HCl doped poly(N-propylaniline) PNPA were synthesized by chemical oxidative polymerization. It was found that the polymer synthesized using DL-(±)-Tartaric acid is formed in conducting emeraldine oxidation state and displayed higher doping level and crystallinity than HCl doped poly-(N-propylaniline). The polymers were characterized by techniques such as UV-Visible and FTIR spectroscopy, XRD, SEM and conductivity measurement. The synthesized materials were tested as sensors for acids, bases and organic vapors etc. and categorized. Comparison of the responses of these two polymers reveals that the tartaric acid doped polymer exhibits higher sensitivity and reversibility. The result is discussed with reference to HCl doped and DL-(±)-Tartaric acid doped poly(N-propylaniline). The poly(N-propyl)aniline pellets were used as sensor by measuring change in resistance before and after exposure to analyte gas. On exposure to H2S gas (10 to 1000 ppm in air) at room temperature, it was found that the PNPA film resistance increases, while that of the PNPA pellet decreases from the respective unexposed value. These changes on removal of H2S gas are reversible in nature, and the polymer PNPA showed good sensitivity with relatively faster response/recovery time. The XRD of PNPA is found to exhibit partial crystallinity as observed from the presence of several peaks at 2θ values of 18 to 41°. The SEM figure indicates that the PNPA/TA consist of coral-like granular particulates with diameter in the range of 50 to 100 nm.