Controllable synthesis of α-Fe 2 O 3 micro-flowers with enhanced gas sensitivity to acetone

The structure and surface properties of the sensing materials have been considered as the main factors for the fabrication of metal–oxide semiconductor gas sensors. In this paper, a one-step hydrothermal method for the preparation and control of the morphology of α-Fe2O3 is reported. The results show that the amount of glycol has a great influence on the morphology of the products. With the variation in ethylene glycol concentration (from 30 to 110 ml), we can obviously see the product was assembled into three-dimensional porous α-Fe2O3 micro-flower structure from two-dimensional nanochips from scanning electron microscope (SEM) pictures. When the ethylene glycol was 70 ml, the micro-flower structure was the most uniform and perfect. It additionally showed the largest specific surface area (63.69 m2/g) and the biggest oxygen vacancy in nitrogen adsorption–desorption and XPS analysis. Further gas sensitivity test showed that gas sensitivity was also the best. Under the low operating temperature (210 °C), the porous α-Fe2O3 micro-flower (70 ml glycol) showed the highest response (49.4) to 100 ppm acetone, the sensitivity of other materials was 8.2/30 ml, 14.7/40 ml, 38.4/50 ml, 36.7/90 ml, 10.3/100 ml, 4.8/110 ml, respectively. In addition, the porous α-Fe2O3 micro-flower (70 ml glycol) has excellent selectivity, short response/recovery time (1 s/31 s), low detection offline (2.2 to 0.2 ppm acetone), and good stability. The reason for the improvement of gas-sensing performance is mainly due to the change of morphology, decrease of crystallite size, the increase of oxygen vacancy, and specific surface area.