Preparation, characterization and gas sensitivity of polypyrrole/γ-Fe_2O_3 hybrid materials

摘要

Polypyrrole (PPy)/γ-Fe_2O_3 hybrid materials were prepared by sol-gel polymerization in situ and characterized by Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA) and high-resolution transmission electron microscope (HRTEM). The gas sensitivities in CO, H_2, NH_3, ethanol or acetone atmospheres were determined at 30℃, 60℃ and 90℃. FT-IR and XRD patterns suggest that ferric oxide in the hybrids was γ-Fe_2O_3, with a diameter of approximately 5 nm. TG-DTA and HRTEM analyses showed that different reactant molar ratios of pyrrole monomer: Fe(NO_3)_3·9H_2O resulted in different microstructures of γ-Fe_2O_3 and molecular weights of PPy. An increased amount of Fe(NO_3)_3·9H_2O increased the degree of uniformity of the molecular weight of PPy and resulted in a change of γ-Fe_2O_3 microstructure from granular to stick particles. The results of gas sensitivities showed that the PPy/γ-Fe_2O_3 hybrids exhibited high sensitivity to NH_3 at mild operating temperature (<100℃). Furthermore, the sensing mechanism was also discussed.