Sol-gel route to pseudocubic shaped α-Fe2O3 alcohol sensor: preparation and characterization

α-Fe2O3 hydrosol was synthesized by sol-gel method with FeCl3·6H2O as the raw material and its thin films were prepared by dip-coating technique. The structure, morphology and spectroscopy of the thin films were characterized by XRD, AFM, UV-vis and FT-IR analysis methods. The results showed that uniform α-Fe2O3 monolayer and multilayers could be obtained at certain dip-coating speed. The particles were pseudocubic shaped, with the mean particle size of about 58 nm. The formation mechanism of α-Fe2O3 particles was explored by IR spectra and the change of the system acidity and conductivity. The results indicated that α-Fe2O3 particles formed from the intermediate complex β-FeOOH. The gas-sensing properties of the multilayers to alcohols with different chain length were measured at room temperature. The thin films exhibited high sensitivity and rapid response-recovery characteristics to these gases. The film can detect C3H7OH vapor concentration as low as 2 ppm. The response and recovery time of the film to CH3OH and C2H5OH vapor is within 20 and 50 s, respectively.