Synthesis, characterization, and comparative gas-sensing properties of Fe2O3 prepared from Fe3O4 and Fe3O4-chitosan

In this paper, Fe3O4 and chitosan (CS)-coated Fe3O4 nanoparticles were synthesized via co-precipitation method and subsequent covalent binding of CS onto the surface for functionalization, respectively. Characterization of the crystal structures and morphologies of as-synthesized nanoparticles by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy demonstrated that Fe3O4 had a cubic spinal structure with irregular shapes and average diameters of 10–20 nm. The surface states and magnetic properties of Fe3O4-CS nanoparticles were characterized by Fourier transform infrared spectra and vibrating sample magnetometry. Results showed that Fe3O4-CS nanoparticles possessed super-paramagnetic properties, with saturated magnetization up to 60 emu/g. In addition, Fe3O4 and CS-coated Fe3O4 nanoparticles were used in the fabrication of α-Fe2O3 based gas sensors. Gas sensing measurements revealed that the α-Fe2O3 gas sensor prepared from Fe3O4-CS had a better response to H2, CO, C2H5OH, and NH3 compared with the device prepared from pristine Fe3O4. Furthermore, the α-Fe2O3 sensor prepared from Fe3O4-CS nanoparticles exhibited the highest response to CO among the test gases, suggesting that it has great potential for practical applications in environmental monitoring.

► We have demonstrated a facile method to prepare Fe3O4 nanoparticles and chitosan-coated Fe3O4 nanoparticles.
► α-Fe2O3 sensors prepared from those Fe3O4 materials have been investigated and compared.
► The results show potential application of α-Fe2O3 for CO sensors in environmental monitoring.