| In recent years, the concern on the environmental protection and the gradually increasing demands about the timely monitor hazardous gases in industry and home has attracted extensive investigations in developing gas sensors with the characteristics of high sensitivity, fast response and good reversibility. Hematite (α-Fe2O3), as the most stable iron oxide, is one of the most important multifunctional materials having different applications on gas sensors, catalysts, ion-exchangers, magnetic materials, and lithium-ion batteries. In this paper, we reported the fabrication ofα-Fe2O3 nanobelts by a facile electro-spinning method, and further promoted the gas-sensing performances by doping with other elements.In order to preparation ofα-Fe2O3, the process is summarized as follows. Firstly, an certain proportion of Fe(NO3)3 and PVP are used as the initial material to dissolve in the dimethyformamide (DMF) solution. After stirring for some times, the suspensions for the electro-spinning process is formed. The effects of experimental conditions, including angles, humidity, and reaction temperature, on the size and morphology of nanobelts have been studied. The subsequent doping process is reported by the addition of salt nitrates in the reaction solution. The phase structure and morphology of products were characterized by XRD and FESEM, and the results indicate that the products are belt-shape nanostructures with almost uniform width and slick surface. After the anneal disposal at 600℃for 3 h in air, the nitrogen element and few polymers in the products are wiped off, and the pureα-Fe2O3, LaFeO3, and La0.7Sr0.3FeO3 with uniform shapes are gained.The second part of this paper, the ethanol sensing properties were investigated by our designed gas sensitive testing system, which is established on the base of LabVIEW. Firstly, nanobelts, includingα-Fe2O3, LaFeO3, and La0.7Sr0.3FeO3, are used to fabricate the traditional side-heating thick film gas sensors and the corresponding ethanol sensing properties, respectively. The results display thatα-Fe2O3-based sensor is sensitive to ethanol, and the response is about 4 for 500 ppm with the response time of 20 s and recovery time of 40 s. After the doping, the sensors based on LaFeO3, and La0.7Sr0.3FeO3 nanobelts are also fabricated. The ethanol sensing properties are promoted by the efficient dopants and the transformation of electric type from n-type ofα-Fe2O3 to p-type of LaFeO3, and La0.7Sr0.3FeO3. After the doping process, the decrease in the resistance of these nanobelts is expected. These doped nanobelt sensors show an enhanced response as high as 25 for 500 ppm ethanol, which have an obviously reduced response and recovery times of 0.5 and 1 s, respectively.In the experiments, the n-typeα-Fe2O3 and p-type LaFeO3 or La0.7Sr0.3FeO3 nanobelts have been synthesized. The simple electro-spinning route and subsequent doping process are efficient ways to synthesize these sensing materials and promote their sensing properties. The enhanced ethanol properties may be ascribed to the high surface-to-volume of the belt-shaped nanostructures, which are composed of compact grains with reduced potential energy between adjacent grains.
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