Preparation of mesoporous In₂O₃ nanofibers by electrospinning and their application as a CO gas sensor

Mesoporous In₂O₃ nanofibers with a high surface area were synthesized by calcining electrospun polyvinyl alcohol (PVA)/indium acetate composite fibers. A PVA solution and indium acetate were mixed and electrospun. After calcining the PVA/indium acetate composite nanofiber precursor, mesoporous In₂O₃ nanofibers were successfully formed. These nanofibers had diameters in the range of 150-200 nm and consisted of cubic indium oxide nanocrystals with a primary particle size of 10-20 nm. The Brunauer-Emmett-Teller (BET) surface area of the In₂O₃ nanofibers was strongly affected by the calcining temperature. The BET surface area of the fibers calcined at 400 °C was significantly higher than the surface area of the nanofibers calcined at 500 °C or 600 °C and of the commercial In₂O₃ powder. The response of mesoporous In₂O₃ nanofibers to CO in air is strongly affected by the surface area. The highly elevated response of In₂O₃ nanofibers calcined at 400 °C could be attributed to the high surface area, which provides a large amount of surface sites for adsorption and reaction of CO. The results demonstrate that the electrospinning approach is an easy and useful method to synthesize metal oxides with mesopores and high surface area, which may enhance their gas sensing properties.