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Ethanol sensor based on indium oxide nanowires prepared by carbothermal reduction reaction
Chemical Physics Letters 399 (2004) 461–464 www.elsevier.com/locate/cplett
Ethanol sensor based on indium oxide nanowires prepared by carbothermal reduction reaction Chu Xiangfeng *, Wang Caihong, Jiang Dongli, Zheng Chenmou School of Chemistry and Chemical Engineering, Sun Yat-sen University, XinÕgang West Road, Guangzhou, 510275 Guangdong, PR China Received 31 August 2004; in final form 12 October 2004 Available online 2 November 2004
Abstract In2O3 nanowires were prepared by carbothermal reduction reaction between indium oxide and active carbon at 1000 °C in flowing nitrogen atmosphere. In2O3 sensors were fabricated from In2O3 nanowires and their gas sensing properties were investigated. It was found that the sensors based on In2O3 nanowires exhibited the best performance, characterized by high response, good selectivity and very short response time to dilute C2H5OH, making them to be promising candidates for practical detectors for dilute C2H5OH. Ó 2004 Published by Elsevier B.V.
1. Introduction Metal oxide semiconductor sensors are the most promising devices among the solid state chemical sensors, because they have many advantages such as small dimensions, low cost, low power consumption, on-line operation, and high compatibility with microelectronic processing. They could be used in environmental monitoring, automotive applications, industry production control, and sensor network. Hence, the metal oxide gas-sensing materials have been widely investigated for a long time [1–3]. The sensing mechanism of metal oxide gas-sensing materials is based on the reaction between the adsorbed oxygen on the surface of materials and the gas molecules to be detected. The state and the amount of oxygen on the surface of materials were strongly dependent on the microstructure of materials, namely, specific area, particle size, as well as the film thickness of the sensing film. In order to obtain the gas sensors with good performance, the most recent research work [3–5] were devoted to nanomaterials *
Corresponding author. Fax: +86 20 84112245. E-mail address: [email protected] (C. Xiangfeng).
0009-2614/$ - see front matter Ó 2004 Published by Elsevier B.V. doi:10.1016/j.cplett.2004.10.053
because nanomaterials have high specific area and contain more grain boundaries. Since the discovery of carbon nanotubes [6], interest in one-dimensional (1D) nanostructures has been greatly stimulated due to their theory importance and potential application in many areas such as materials science, chemistry, physics and engineering [7]. So far, main investigations were focused on the preparation of 1D nanomaterials, many kinds of metal oxides, such as SnO2 [8,9], ZnO [7,10], In2O3 [11,12], Ga2O3 [13,14] 1D nanostructure materials have been prepared by different methods. Recently, Some authors reported the gas-sensing properties of single carbon nanotube [15], SnO2 nanowire [16] and In2O3 nanowire [17,18]. These sensors have higher performance, but they are difficult to fabricate in large quantities. Film gas sensors based on ZnO nanowires have been reported to have good gas-sensing properties by Wan et al. [19]. It is convenient to fabricate the film sensors based on nanowire materials in large quantities. Many researchers reported that In2O3 is a promising material for detection of low concentrations of oxidizing gases like O3 [20,21], NOx [22,23] and reducing gases like CO, H2 [24,25]. But the preparation process of In2O3
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C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
materials was complicated and the response of pure In2O3 sensor to C2H5OH was lower. In this Letter, we prepared In2O3 nanowires by carbothermal reduction reaction and investigated the gas-sensing properties of sensors based on In2O3 nanowire film. The results revealed that the sensors exhibited good response to ethanol.
2. Experimental In2O3 nanowires were prepared according to the literature [11]: the mixture of In2O3 and active carbon were ground for 30 min and put into alumina boat. The boat was covered with a ceramic plate, placed at the center of a quartz tube that was inserted in a horizontal tube furnace. Prior to heating, the system was flushed with nitrogen gas for 30 min to eliminate O2. Then, under constant flow of N2 (15 sccm), the furnace was heated to 1000 °C (60 min), and held at this temperature for 180 min. After the furnace cooled to room temperature, a light yellow product was found on the surface of cover and the wall of the boat. The phase composition and the morphology of the materials were characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The paste formed from a mixture of In2O3 nanowires with PVA solution was coated onto the Al2O3 tube on which two gold leads had been installed at each end. The Al2O3 tube was about 8 mm in length and 2 mm in external diameter and 1.6 mm in internal diameter. A heater using Ni–Cr wire was inserted into the Al2O3 tube to supply the operating temperature that could be controlled in the range of 100–500 °C. The structure of sensor device was shown in Fig. 1. The electrical resistance of sensor was measured in air and in sample gases. The response was defined as the ratio of the electrical resistance in air (Ra) to that in sample gases (Rg).
Fig. 1. The structure of sensor device.
3. Results and discussion The XRD pattern and TEM photo were shown in Fig. 2. Our results were similar to the [11]. All peaks in Fig. 2 could be indexed to In2O3 (ASTM card No. 6-416). The nanowires had a diameter ranging from 60 to 160 nm and a length ranging from 0.5 to a few micrometers. The responses to volatile gases of In2O3 sensor based on nanowires were shown in Fig. 3 as a function of operating temperature. The sensor almost showed no response to 1000 ppm CH4 and CH3OH gas when operating at 150–350 °C. The sensor exhibited lower response to 1000 ppm (C2H5)3N and CH3COCH3 when operating at 150–400 °C. But for the response to 1000 ppm C2H5OH gas, maximum appeared at 370 °C, the response was 25.3. This suggests that the sensor based on In2O3 nanowires is selective to C2H5OH gas at 370 °C. If keeping the evaporation temperature at 1100 °C, the product morphology was also wire with large length (about 4 mm) and big diameter. The sensor based on In2O3 wires prepared at 1100 °C exhibited
Fig. 2. The XRD pattern and TEM photo of the product.
C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
Fig. 3. The responses to volatile gases of In2O3 sensor based on nanowires.
no response to CH4, (C2H5)3N, CH3COCH3, CH3OH and C2H5OH. Besides the response, two other important parameters for chemical sensors are the minimum detectable concentrations for gas and the response time. Fig. 4 depicted the correlation between C2H5OH gas concentration and responses of In2O3 sensor. The response decreased with decreasing C2H5OH gas concentration. The curve of response vs C2H5OH gas concentration exhibited better linearity. The response to 100 ppm C2H5OH gas was higher than 2 at 370 °C. The response transients of sensors to 100 and 1000 ppm
463
Fig. 5. The response transients of sensors to 100 and 1000 ppm C2H5OH gas.
C2H5OH gas are shown in Fig. 5. The response times and the recovery times were very short, the response times were about 10 s and the recovery times were shorter than 20 s.
4. Conclusion The sensor based on In2O3 nanowires prepared by carbothermal reduction reaction showed higher response and good selectivity to C2H5OH at 370 °C. The response to 100 ppm C2H5OH attained two, the response time was about 10 s and recovery time was shorter than 20 s. This sensor will be a promising practical device for detecting dilute C2H5OH.
Acknowledgements This work was supported by the project sponsored by scientific research foundation for return from overseas Chinese scholars of State Education Ministry. References
Fig. 4. The correlation between C2H5OH gas concentration and responses of In2O3 sensor.
[1] M. Ando, S. Suto, T. Suzuki, T. Tsuchida, C. Nakayama, N. Miura, N. Yamazoe, Chem. Lett. 335 (1994). [2] M. Bendahan, R. Boulmani, J.L. Seguin, K. Aguir, Sensor. Actuator. B 100 (2004) 320. [3] Ulrich Hoefer, Joachim Frank, Maximilian Fleischer, Sensor. Actuator. B 78 (2001) 6. [4] L.G. Teoh, Y.M. Hon, J. Shieh, W.H. Lai, M.H. Hon, Sensor. Actuator. B 96 (2003) 219. [5] Yong-Gyu Choi, Go Sakai, Kengo Shimanoe, Yasutake Teraoka, Norio Miura, Noboru Yamazoe, Sensor. Actuator. B 93 (2003) 486.
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C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
[6] S. Iijima, Nature (London) 354 (1991) 56. [7] Seung Eon Ahn, Jong Soo Lee, Hyunsuk Kim, Sangsig Kim, Byung Hyun Kang, Kang Hyun Kim, Gyu Tae Kim, Appl. Phys. Lett. 84 (2004) 5022. [8] Dong-Feng Zhang, Ling-Dong Sun, Jia-Lu Yin, Chun-Hua Yan, Adv. Mater. 15 (2003) 1022. [9] Z.R. Dai, J.L. Gole, J.D. Stout, Z.L. Wang, J. Phys. Chem. B 106 (2002) 1274. [10] Q. Wan, C.L. Lin, X.B. Yu, T.H. Wang, Appl. Phys. Lett. 84 (2004) 124. [11] X.C. Wu, J.M. Hong, Z.J. Han, Y.R. Tao, Chem. Phys. Lett. 373 (2003) 28. [12] Yingjiu Zhang, Hiroki Ago, Jun Liu, Motoo Yumura, Kunio Uchida, Satoshi Ohshima, Sumio Iijiama, Jing Zhu, Xiaozhong Zhang, J. Cryst. Growth 264 (2004) 363. [13] Ko-wei Chang, Jih-Jen Wu, J. Phys. Chem. B 108 (2004) 1838. [14] Y.C. Choi, W.S. Kim, Y.S. Park, S.M. Lee, D.J. Bae, Y.H. Lee, G.S. Park, W.B. Choi, N.S. Lee, J.M. Kim, Adv. Mater. 12 (2000) 746. [15] Jing Kong, Nathan R. Franklin, Chongwu Zhou, Michael G. Chapline, Shu Peng, Kyeongjae Cho, Hongjie Dai, Science 287 (2000) 622.
[16] Andrei Kolmakov, Youxiang Zhang, Guosheng Cheng, Matin Moskovits, Adv. Mater. 15 (2003) 997. [17] Chao Li, Daihua Zhang, Xiaolei Liu, Song Han, Tao Tang, Jie Han, Chongwu Zhou, Appl. Phys. Lett. 82 (2003) 1613. [18] Daihua Zhang, Chao Li, Xiaolei Liu, Song Han, Tao Tang, Chongwu Zhou, Appl. Phys. Lett. 83 (2003) 1845. [19] O. Wan, Q.H. Li, Y.J. Chen, T.H. Wang, X.L. He, J.P. Li, C.L. Lin, Appl. Phys. Lett. 84 (2004) 3654. [20] M.Z. Atashbar, B. Gongb, H.T. Sun, W. Wlodarski, R. Lamb, Thin Solid Films 354 (1999) 222. [21] Tadashi Takada, Hiromasa Tanjou, Tatsuo Saito, Kenji Harada, Sensor. Actuator. B 25 (1995) 548. [22] A. Gurlo, M. Ivanovskaya, N. Barsan, M. Schweizer-Berberich, U. Weimar, W. Gopel, A. Dieguez, Sensor. Actuator. B 44 (1997) 327. [23] A. Gurlo, M. Ivanovskaya, A. Pfau, U. Weimar, W. Gopel, Thin Solid Films 307 (1997) 288. [24] G. Korotcenkov, V. Brinzari, A. Cerneavschi, M. Ivanov, V. Golovanov, A. Cornet, J. Morante, A. Cabot, J. Arbiol, Thin Solid Films 460 (2004) 315. [25] Hiroyuki Yamaura, Koji Moriya, Norio Miura, Noboru Yamazoe, Sensor. Actuator. B 65 (2000) 39.
Ethanol sensor based on indium oxide nanowires prepared by carbothermal reduction reaction Chu Xiangfeng *, Wang Caihong, Jiang Dongli, Zheng Chenmou School of Chemistry and Chemical Engineering, Sun Yat-sen University, XinÕgang West Road, Guangzhou, 510275 Guangdong, PR China Received 31 August 2004; in final form 12 October 2004 Available online 2 November 2004
Abstract In2O3 nanowires were prepared by carbothermal reduction reaction between indium oxide and active carbon at 1000 °C in flowing nitrogen atmosphere. In2O3 sensors were fabricated from In2O3 nanowires and their gas sensing properties were investigated. It was found that the sensors based on In2O3 nanowires exhibited the best performance, characterized by high response, good selectivity and very short response time to dilute C2H5OH, making them to be promising candidates for practical detectors for dilute C2H5OH. Ó 2004 Published by Elsevier B.V.
1. Introduction Metal oxide semiconductor sensors are the most promising devices among the solid state chemical sensors, because they have many advantages such as small dimensions, low cost, low power consumption, on-line operation, and high compatibility with microelectronic processing. They could be used in environmental monitoring, automotive applications, industry production control, and sensor network. Hence, the metal oxide gas-sensing materials have been widely investigated for a long time [1–3]. The sensing mechanism of metal oxide gas-sensing materials is based on the reaction between the adsorbed oxygen on the surface of materials and the gas molecules to be detected. The state and the amount of oxygen on the surface of materials were strongly dependent on the microstructure of materials, namely, specific area, particle size, as well as the film thickness of the sensing film. In order to obtain the gas sensors with good performance, the most recent research work [3–5] were devoted to nanomaterials *
Corresponding author. Fax: +86 20 84112245. E-mail address: [email protected] (C. Xiangfeng).
0009-2614/$ - see front matter Ó 2004 Published by Elsevier B.V. doi:10.1016/j.cplett.2004.10.053
because nanomaterials have high specific area and contain more grain boundaries. Since the discovery of carbon nanotubes [6], interest in one-dimensional (1D) nanostructures has been greatly stimulated due to their theory importance and potential application in many areas such as materials science, chemistry, physics and engineering [7]. So far, main investigations were focused on the preparation of 1D nanomaterials, many kinds of metal oxides, such as SnO2 [8,9], ZnO [7,10], In2O3 [11,12], Ga2O3 [13,14] 1D nanostructure materials have been prepared by different methods. Recently, Some authors reported the gas-sensing properties of single carbon nanotube [15], SnO2 nanowire [16] and In2O3 nanowire [17,18]. These sensors have higher performance, but they are difficult to fabricate in large quantities. Film gas sensors based on ZnO nanowires have been reported to have good gas-sensing properties by Wan et al. [19]. It is convenient to fabricate the film sensors based on nanowire materials in large quantities. Many researchers reported that In2O3 is a promising material for detection of low concentrations of oxidizing gases like O3 [20,21], NOx [22,23] and reducing gases like CO, H2 [24,25]. But the preparation process of In2O3
462
C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
materials was complicated and the response of pure In2O3 sensor to C2H5OH was lower. In this Letter, we prepared In2O3 nanowires by carbothermal reduction reaction and investigated the gas-sensing properties of sensors based on In2O3 nanowire film. The results revealed that the sensors exhibited good response to ethanol.
2. Experimental In2O3 nanowires were prepared according to the literature [11]: the mixture of In2O3 and active carbon were ground for 30 min and put into alumina boat. The boat was covered with a ceramic plate, placed at the center of a quartz tube that was inserted in a horizontal tube furnace. Prior to heating, the system was flushed with nitrogen gas for 30 min to eliminate O2. Then, under constant flow of N2 (15 sccm), the furnace was heated to 1000 °C (60 min), and held at this temperature for 180 min. After the furnace cooled to room temperature, a light yellow product was found on the surface of cover and the wall of the boat. The phase composition and the morphology of the materials were characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The paste formed from a mixture of In2O3 nanowires with PVA solution was coated onto the Al2O3 tube on which two gold leads had been installed at each end. The Al2O3 tube was about 8 mm in length and 2 mm in external diameter and 1.6 mm in internal diameter. A heater using Ni–Cr wire was inserted into the Al2O3 tube to supply the operating temperature that could be controlled in the range of 100–500 °C. The structure of sensor device was shown in Fig. 1. The electrical resistance of sensor was measured in air and in sample gases. The response was defined as the ratio of the electrical resistance in air (Ra) to that in sample gases (Rg).
Fig. 1. The structure of sensor device.
3. Results and discussion The XRD pattern and TEM photo were shown in Fig. 2. Our results were similar to the [11]. All peaks in Fig. 2 could be indexed to In2O3 (ASTM card No. 6-416). The nanowires had a diameter ranging from 60 to 160 nm and a length ranging from 0.5 to a few micrometers. The responses to volatile gases of In2O3 sensor based on nanowires were shown in Fig. 3 as a function of operating temperature. The sensor almost showed no response to 1000 ppm CH4 and CH3OH gas when operating at 150–350 °C. The sensor exhibited lower response to 1000 ppm (C2H5)3N and CH3COCH3 when operating at 150–400 °C. But for the response to 1000 ppm C2H5OH gas, maximum appeared at 370 °C, the response was 25.3. This suggests that the sensor based on In2O3 nanowires is selective to C2H5OH gas at 370 °C. If keeping the evaporation temperature at 1100 °C, the product morphology was also wire with large length (about 4 mm) and big diameter. The sensor based on In2O3 wires prepared at 1100 °C exhibited
Fig. 2. The XRD pattern and TEM photo of the product.
C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
Fig. 3. The responses to volatile gases of In2O3 sensor based on nanowires.
no response to CH4, (C2H5)3N, CH3COCH3, CH3OH and C2H5OH. Besides the response, two other important parameters for chemical sensors are the minimum detectable concentrations for gas and the response time. Fig. 4 depicted the correlation between C2H5OH gas concentration and responses of In2O3 sensor. The response decreased with decreasing C2H5OH gas concentration. The curve of response vs C2H5OH gas concentration exhibited better linearity. The response to 100 ppm C2H5OH gas was higher than 2 at 370 °C. The response transients of sensors to 100 and 1000 ppm
463
Fig. 5. The response transients of sensors to 100 and 1000 ppm C2H5OH gas.
C2H5OH gas are shown in Fig. 5. The response times and the recovery times were very short, the response times were about 10 s and the recovery times were shorter than 20 s.
4. Conclusion The sensor based on In2O3 nanowires prepared by carbothermal reduction reaction showed higher response and good selectivity to C2H5OH at 370 °C. The response to 100 ppm C2H5OH attained two, the response time was about 10 s and recovery time was shorter than 20 s. This sensor will be a promising practical device for detecting dilute C2H5OH.
Acknowledgements This work was supported by the project sponsored by scientific research foundation for return from overseas Chinese scholars of State Education Ministry. References
Fig. 4. The correlation between C2H5OH gas concentration and responses of In2O3 sensor.
[1] M. Ando, S. Suto, T. Suzuki, T. Tsuchida, C. Nakayama, N. Miura, N. Yamazoe, Chem. Lett. 335 (1994). [2] M. Bendahan, R. Boulmani, J.L. Seguin, K. Aguir, Sensor. Actuator. B 100 (2004) 320. [3] Ulrich Hoefer, Joachim Frank, Maximilian Fleischer, Sensor. Actuator. B 78 (2001) 6. [4] L.G. Teoh, Y.M. Hon, J. Shieh, W.H. Lai, M.H. Hon, Sensor. Actuator. B 96 (2003) 219. [5] Yong-Gyu Choi, Go Sakai, Kengo Shimanoe, Yasutake Teraoka, Norio Miura, Noboru Yamazoe, Sensor. Actuator. B 93 (2003) 486.
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C. Xiangfeng et al. / Chemical Physics Letters 399 (2004) 461–464
[6] S. Iijima, Nature (London) 354 (1991) 56. [7] Seung Eon Ahn, Jong Soo Lee, Hyunsuk Kim, Sangsig Kim, Byung Hyun Kang, Kang Hyun Kim, Gyu Tae Kim, Appl. Phys. Lett. 84 (2004) 5022. [8] Dong-Feng Zhang, Ling-Dong Sun, Jia-Lu Yin, Chun-Hua Yan, Adv. Mater. 15 (2003) 1022. [9] Z.R. Dai, J.L. Gole, J.D. Stout, Z.L. Wang, J. Phys. Chem. B 106 (2002) 1274. [10] Q. Wan, C.L. Lin, X.B. Yu, T.H. Wang, Appl. Phys. Lett. 84 (2004) 124. [11] X.C. Wu, J.M. Hong, Z.J. Han, Y.R. Tao, Chem. Phys. Lett. 373 (2003) 28. [12] Yingjiu Zhang, Hiroki Ago, Jun Liu, Motoo Yumura, Kunio Uchida, Satoshi Ohshima, Sumio Iijiama, Jing Zhu, Xiaozhong Zhang, J. Cryst. Growth 264 (2004) 363. [13] Ko-wei Chang, Jih-Jen Wu, J. Phys. Chem. B 108 (2004) 1838. [14] Y.C. Choi, W.S. Kim, Y.S. Park, S.M. Lee, D.J. Bae, Y.H. Lee, G.S. Park, W.B. Choi, N.S. Lee, J.M. Kim, Adv. Mater. 12 (2000) 746. [15] Jing Kong, Nathan R. Franklin, Chongwu Zhou, Michael G. Chapline, Shu Peng, Kyeongjae Cho, Hongjie Dai, Science 287 (2000) 622.
[16] Andrei Kolmakov, Youxiang Zhang, Guosheng Cheng, Matin Moskovits, Adv. Mater. 15 (2003) 997. [17] Chao Li, Daihua Zhang, Xiaolei Liu, Song Han, Tao Tang, Jie Han, Chongwu Zhou, Appl. Phys. Lett. 82 (2003) 1613. [18] Daihua Zhang, Chao Li, Xiaolei Liu, Song Han, Tao Tang, Chongwu Zhou, Appl. Phys. Lett. 83 (2003) 1845. [19] O. Wan, Q.H. Li, Y.J. Chen, T.H. Wang, X.L. He, J.P. Li, C.L. Lin, Appl. Phys. Lett. 84 (2004) 3654. [20] M.Z. Atashbar, B. Gongb, H.T. Sun, W. Wlodarski, R. Lamb, Thin Solid Films 354 (1999) 222. [21] Tadashi Takada, Hiromasa Tanjou, Tatsuo Saito, Kenji Harada, Sensor. Actuator. B 25 (1995) 548. [22] A. Gurlo, M. Ivanovskaya, N. Barsan, M. Schweizer-Berberich, U. Weimar, W. Gopel, A. Dieguez, Sensor. Actuator. B 44 (1997) 327. [23] A. Gurlo, M. Ivanovskaya, A. Pfau, U. Weimar, W. Gopel, Thin Solid Films 307 (1997) 288. [24] G. Korotcenkov, V. Brinzari, A. Cerneavschi, M. Ivanov, V. Golovanov, A. Cornet, J. Morante, A. Cabot, J. Arbiol, Thin Solid Films 460 (2004) 315. [25] Hiroyuki Yamaura, Koji Moriya, Norio Miura, Noboru Yamazoe, Sensor. Actuator. B 65 (2000) 39.