Elsevier

Sensors and Actuators B: Chemical

Volume 184, 31 July 2013, Pages 243-247
Sensors and Actuators B: Chemical

Highly sensitive acetone sensors based on La-doped α-Fe2O3 nanotubes

https://doi.org/10.1016/j.snb.2013.04.088Get rights and content

Abstract

Pure and La-doped (5 wt%, 7 wt% and 10 wt%) α-Fe2O3 nanotubes are synthesized by an electrospinning method and followed by calcination. The as-synthesized nanotubes are characterized by scanning electron microscope (SEM) and X-ray powder diffraction (XRD). Compared with pure α-Fe2O3 nanotubes, La-doped α-Fe2O3 nanotubes exhibit improved acetone sensing properties at 240 °C. The response of 7 wt% La-doped α-Fe2O3 nanotubes to 50 ppm acetone is about 26, which is 10 times larger than that of pure α-Fe2O3 nanotubes. The response and recovery times of 7 wt% La-doped α-Fe2O3 nanotubes to 50 ppm acetone are about 3 and 10 s, respectively. Moreover, 7 wt% La-doped α-Fe2O3 nanotubes show a good selectivity to acetone.

Introduction

Metal-oxide-semiconductors (MOS) have been widely used in photocatalytic degradation, lithium storage, electrode materials, catalyst and gas sensors [1], [2], [3], [4], [5]. Especially in the field of gas sensors, MOS have been proved to be the highly sensitive materials to detect various gases, including ethanol, acetone, H2, O2, H2S, NO2, NO, NH3 and other species [6], [7], [8], [9], [10], [11], [12], [13]. However, they usually suffer from several shortcomings, such as limited maximum sensitivity, high working temperatures, lack of long-term stability and poor selectivity. Up to now, significant efforts have been made to overcome these limitations and improve the performance by doping lanthanide, such as La, Nd and Yb [14], [15], [16]. For example, La-doped SnO2 sensors have been reported to exhibit high response to ethanol when work at low temperature [14]. Nb-doped ZnO sensors are demonstrated to presented much higher sensitivity, better selectivity and shorter response–recovery time to 100 ppm ethanol than the pure ZnO [15]. In contrast to pure In2O3, the room temperature response sensitivity of the Yb-doped In2O3 sensors to 20 ppm H2S increased about 7 times, and the response time of the Yb-doped In2O3 sensors was shortened 4 times [16]. Nevertheless, to the best of our knowledge, there has been no study on the gas sensing properties of La-doped α-Fe2O3 sensors.

α-Fe2O3, an n-type semiconductor, which is the most stable iron under ambient conditions, has been widely fabricated as gas sensor because of its good stability, lower cost, and easy availability. Electrospinning technique is a simple and an easy way to fabricate nanofibers [17], [18]. In a typical electrospinning process, a sample solution is pumped through a nozzle to which a high voltage is applied relative to grounded aluminum foil, which acts as a collector, to form an electrically charged jet of solution. The solution jet solidifies with evaporation of solvent and forms a mat on the collector.

In this paper, we report the fabrication of La-doped α-Fe2O3 nanotubes by combining electrospinning and calcination method. The acetone sensing properties of the gas sensors based on La-doped α-Fe2O3 nanotubes were investigated, and the results showed that the gas sensing properties of α-Fe2O3 nanotubes could be significantly enhanced by doping La.

Section snippets

Experimental

Poly(vinyl pyrrolidone) (PVP, Mw = 1,300,000) was purchased from Sigma–Aldrich (USA). Fe(NO3)3·9H2O (99.99%), La(NO3)3·6H2O (99.99%), N,N-dimethylformamide (DMF, ≥99.5%) and ethanol (≥99.7%) were obtained from Aladdin (China). The above chemical reagents used were analytical grade and used without further purification.

Pure and La-doped α-Fe2O3 nanotubes were synthesized via a simple electrospinning method. Typically, an appropriate amount of Fe(NO3)3·9H2O was mixed with the 1:1 weight ratio of

Structural and morphological characteristics

Fig. 1 shows the XRD patterns of the La-doped α-Fe2O3 nanotubes. The main peaks can be indexed as cubic single crystal Fe2O3, with lattice constants of a = c = 8.351 Å. These parameters agree well with the reported values from the JCPDS card (39-1346). According to the Debye–Scherrer formula,D=Kλβcos(θ)where λ is the wavelength of the X-ray radiation (Cu Kα = 0.15418 nm), K is 0.89 as a constant, β is the line width at half-maximum height and θ is the diffracting angle. The average crystallite sizes

Conclusion

In summary, pure and La-doped α-Fe2O3 nanotubes are synthesized by an electrospinning and followed by calcination. Gas sensing investigation reveals that La-doping can enhance the acetone sensing properties of α-Fe2O3 nanotubes efficiently. The response of 7 wt% La-doped α-Fe2O3 nanotubes to 50 ppm acetone is 26 at 240 °C, which is 10 times larger than the pure α-Fe2O3 nanotubes, and the response and recovery times are 3 and 10 s, respectively. Moreover, 7 wt% La-doped α-Fe2O3 nanotubes shows a good

Acknowledgements

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).

Hao Shan received his BAG degree from Jilin University in 2011. He is currently pursuing his master degree from the College of Physics, Jilin University. Now, he is interested in the field of nanomaterials and gas sensors and humidity sensors.

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Hao Shan received his BAG degree from Jilin University in 2011. He is currently pursuing his master degree from the College of Physics, Jilin University. Now, he is interested in the field of nanomaterials and gas sensors and humidity sensors.

Changbai Liu is currently pursuing his bachelor degree form the College of Electronic Science & Engineering, Jilin University.

Li Liu received her PhD degree in the field of microelectronics and solid state electronics from the College of Electronic Science & Engineering, Jilin University in 2008. She was appointed a full professor in College of Physics, Jilin University in 2010. Now, she is interested in the field of sensing functional materials and chemical sensors.

Shouchun Li received his MS degree from the College of Physics, Jilin University, China in 2005. He was appointed a full professor in College of Physics, Jilin University in 2007. Now, he is interested in the field of gas sensors and humidity sensors.

Lianyuan Wang received his MS degree from the College of Electronic Science & Engineering, Jilin University in 2006. Now, he is interested in the field of gas sensors and humidity sensors.

Xiaobo Zhang received her BS degree from Changchun University of Science and Technology in 2011. She is currently pursuing her master degree from the College of Physics, Jilin University. Now, she is interested in the field of the design and research of Microstructure gas sensor.

Xiaoqing Bo received her BS degree from Daqing Normal University in 2012. She is currently pursuing her master degree from the College of Physics, Jilin University. Now, she is interested in the field of sensing functional materials and gas sensors and humidity sensors.

Xiao Chi received his Physical bachelor's degree from Shandong University at Weihai in 2012. He is currently pursuing his master degree from the College of Physics, Jilin University. Now, he is engaged in researches the field of sensing functional materials and gas sensors.

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