A novel structure for enhancing the sensitivity of gas sensors - α-Fe2O3 nanoropes containing a large amount of grain boundaries and their excellent ethanol sensing performance

Novel one-dimensional (1D) alpha-Fe2O3 nanostructures containing a large amount of grain boundaries have been synthesized through the combination of electrospinning and precursor-calcination techniques. The as-prepared alpha-Fe2O3 nanostructures were composed of orderly arranged building blocks (alpha-Fe2O3 nanoparticles) which are connected to each other. The investigation of the morphology evolution revealed that the template fiber geometry has an influential impact on the grain growth behavior during preparation and thus the nanostructures of the final products. Different alpha-Fe2O3 nanostructures (nanostrings and nanoropes) were synthesized using different PAN nanofibers as templates. These two samples are similar in microstructures but very different in grain boundary content. FT-IR spectra, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, UV-vis diffuse reflection spectra and nitrogen adsorption-desorption analysis were used to characterize the structures of the synthesized products. Comparative ethanol sensing measurements between the alpha-Fe2O3 nanostrings and nanoropes were conducted. The nanoropes which contain more grain boundaries showed a 3 to 4-time enhancement in ethanol response compared to the nanostrings. The results prove that creating a large amount of well-ordered grain boundaries is an effective way to enhance the sensing performance.