High sensing properties of Ce-doped α-Fe2O3 nanotubes to acetone
Introduction
Semiconductors oxides have attracted considerable attention around the world, because of their multitudinous applications in photosensitization [1], photocatalysis [2], magnetism [3], batteries [4] and gas sensors [5]. Nowadays, due to an urgent necessary in air-quality detection and environmental monitoring, the application field of semiconductors oxides in gas sensors has been more and more important. Owing to the low cost and easy availability, various semiconductors oxides, just like ZnO, SnO2, Fe2O3, WO3, In2O3, TiO2, have been used to act as the gas sensitive materials to detect ethanol, acetone, toluene, H2, CO, H2S, formaldehyde [6], [7], [8], [9], [10], [11], [12], [13]. However, as the high requirements of detection precision of pollution gases, the shortcomings of these semiconductors oxides come out gradually, such as high operating temperature, low sensitivity, poor selectivity and bad stability. Cerium, a kind of lanthanide elements, has been proved to be an effective dopant element to enhance the gas sensing properties of semiconductors oxides. For instance, Song et al. have proved that Ce doped SnO2 exhibited a higher sensitive toward acetone than pure SnO2 [14]. Mohammadi et al. have demonstrated that Ce doped TiO2 gas sensors have a good capability for the detection of low concentration of CO [15]. Luo et al. have reported that the sensitivity of WO3 to xylene is enhanced significantly after doping with Ce [16]. However, the gas sensing properties of Ce doped α-Fe2O3 have rarely been reported.
α-Fe2O3 is a common and potential n-type semiconductor, which has been widely applied in pigment [17], catalysts [18], batteries [19], gas sensors [6] and drug delivery [20]. Especially, α-Fe2O3 nanotubes have been more and more important in the field of gas sensors in recent years, due to its hollow structure and large specific surface area. In this paper, we synthesize Ce doped α-Fe2O3 nanotubes and investigate their gas sensing properties. The results show that the as-prepared Ce doped α-Fe2O3 nanotubes possess an excellent sensitivity to acetone.
Section snippets
Experimental procedure
All the chemical reagents used were analytical grade and used without further purification. Fe(NO3)3·6H2O, Ce(NO3)3·6H2O, N,N-dimethylformamide (DMF) and ethanol were obtained from Aladdin (China). Poly(vinyl pyrrolidone) (PVP, Mw=1,300,000) was purchased from Sigma-Aldrich (USA).
The procedure of electrospinning was according to the reported paper [5]. Typically, 0.7 g Fe(NO3)3·6H2O was dissolved with the 1:1 weight ratio of DMF and ethanol under vigorous magnetic stirring for 30 min. After that,
Results and discussion
The structures and morphologies of all samples are characterized by SEM, and the results are shown in Fig. 1. We can see from Fig. 1 that, these nanofibers are distributed disorderly and unsystematic. The structure of nanotubes can be clearly indicated from the four insets. Compared with the pure α-Fe2O3, the surfaces of nanotubes of Ce-doped (3, 4, 5 at%) α-Fe2O3 are more coarser, which can be benefit the gas absorption.
Fig. 2 shows the XRD patterns of pristine and Ce-doped (3, 4, and 5 at%) α-Fe
Conclusion
In summary, pristine and Ce-doped (3, 4, 5 at% Ce) α-Fe2O3 nanotubes are synthesized by electrospinning method and their gas sensing properties are investigated. The sensitivity, recovery time and response time of this sample (4 at% Ce) towards 50 ppm at 240 °C were 21.5, 3 s and 8 s, respectively. The lowest detecting limit of the sensor can reach 1 ppm. The sensitivity of the pure α-Fe2O3 nanotubes gas sensor has been improved by more than 8 times after doping with 4 at% Ce. Moreover, the sensor (4
Acknowledgments
The work has been supported by the Jilin Environment Office (2009-22), Jilin Provincial Science and Technology Department (20100344), and the National Innovation Experiment Program for University Students (2010C65188).
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