A comparison of the ethanol sensing properties of -iron oxide nanostructures prepared via the sol-gel and electrospinning techniques

Haematite (alpha-Fe2O3) nanostructures were synthesized via a Pechini sol-gel method (PSG) and an electrospinning (ES) technique. Their texture and morphology were investigated by scanning and transmission electron microscopy. alpha-Fe2O3 nanoparticles were obtained by the PSG method, whereas fibrous structures consisting of interconnected particles were synthesized through the ES technique. The crystallinity of the alpha-Fe2O3 nanostructures was also studied by means of x-ray diffraction and Raman spectroscopy. Gas-sensing devices were fabricated by printing the synthesized samples on ceramic substrates provided with interdigitated Pt electrodes. The sensors were tested towards low concentrations of ethanol in air in the temperature range (200-400 degrees C). The results show that the alpha-Fe2O3 nanostructures exhibit somewhat different gas-sensing properties and, interestingly, their sensing behaviour is strongly temperature-dependent. The availability of active sites for oxygen chemisorption and the diffusion of the analyte gas within the sensing layer structure are hypothesized to be the key factors responsible for the different sensing behaviour observed.