Open-system nanocasting synthesis of nanoscale α-Fe_2O_3 porous structure with enhanced acetone-sensing properties

摘要

Nanoscale α-Fe_2O_3 with porous structure was synthesized via an open-system nanocasting method. Characterization of the crystal structures, morphologies, surface areas, and pore size distributions of the as-synthesized α-Fe_2O_3 by wide-angle and small-angle X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen physisorption analysis demonstrated that the nanoscale α-Fe_2O_3 synthesized in open system had a less crystallinity with average diameter of ~6.0 nm, higher BET specific surface area of 205.4 m~2 g~(-1) and wider pore size distribution from ~2.2 nm to 15.7 nm compared with that of the mesoporous α-Fe_2O_3 synthesized in closed system. The gas-sensing measurement results revealed that the nanoscale α-Fe_2O_3 based gas sensor had a much better response to acetone than that of the device prepared from the mesoporous α-Fe_2O_3. A possible gas-sensing mechanism based on the α-Fe_2O_3 samples synthesized with different nanocasting systems was discussed in detail. Wide porous distribution of the nanoscale α-Fe_2O_3, as well as small particle size and high surface area are effective for gas molecules diffusion and formation of sufficient electron depletion area and result the enhanced sensor response, which suggests that it has great potential for practical applications in diabetes diagnosis.