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Facile fabrication and enhanced formaldehyde gas sensing properties of nanoparticles-assembled chain-like NiO architectures
Materials Letters 185 (2016) 40–42
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Facile fabrication and enhanced formaldehyde gas sensing properties of nanoparticles-assembled chain-like NiO architectures Jing Cao n, Haiming Zhang n, Xuequn Yan School of Science, Tianjin Polytechnic University, Tianjin 300387, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 15 July 2016 Received in revised form 19 August 2016 Accepted 20 August 2016 Available online 21 August 2016
The chain-like NiO architectures are successfully fabricated by a facile electrospinning route followed by a subsequent annealing treatment and are exploited for formaldehyde (HCHO) gas detection. The asprepared NiO nanochains are regularly assembled by nanoparticles along the same direction and present unique necklace-like structures. Gas sensing performances of chain-like NiO architectures are also investigated. The result indicates that the gas sensor based on chain-like NiO exhibits good selectivity, superior sensitivity, fast response/recovery rate and low concentration detection limit towards formaldehyde gas at a relatively low operating temperature. The facile synthesis route and promising formaldehyde sensing properties enable chain-like NiO architecture to be a competitive candidate for formaldehyde gas detection in practice. & Published by Elsevier B.V.
Keywords: Semiconductors Nickel oxide Chain-like architectures Sensors
1. Introduction NiO, as an important p-type oxide semiconductor, has attracted considerable attention due to excellent application prospects in supercapacitors, catalysts, water treatment and gas sensors [1–5]. In particular, gas sensors based on NiO nanomaterials exhibit morphology and structure-dependent gas sensing properties, which impels researchers to explore facile routes to prepare NiO nanomaterials with novel morphologies and unique structures. Up to now, multifarious strategies have been employed to synthesize diverse NiO nanomaterials [6,7]. Among synthesis methods of nanomaterials, electrospinning is an excellent method to obtain the controllable fabrication of different oxide semiconductors with more uniform characteristics, higher reproducibly and lower cost [8]. Meanwhile, for gas sensing applications, the as-prepared long and continuous one dimensional architectures own high specific surface areas and form massive gaps among each other after nanomaterials are coated on a ceramic tube to form a sensing layer, just like incompact knitting wool, which can greatly increase utilization rate of nanomaterials and then enhance gas sensing performances [9]. In this paper, NiO nanochains architectures have been successfully fabricated via a facile electrospinning technique and the subsequent annealing treatment. The as-synthesized NiO nanochains are regularly assembled by nanoparticles of similar size along the same direction. The gas sensor based on chain-like NiO n
Corresponding authors. E-mail addresses: [email protected] (J. Cao), [email protected] (H. Zhang).
http://dx.doi.org/10.1016/j.matlet.2016.08.099 0167-577X/& Published by Elsevier B.V.
architectures exhibits an excellent gas sensing performance towards formaldehyde.
2. Experiments All reagents were analytical-grade purity and used as purchased without further purification. The chain-like NiO were fabricated by a electrospinning route. In a typical procedure, 0.5 g Ni (NO3)2 6H2O and 1.8 g PVP were dissolved in 10 mL DMF under vigorous stirring to form a pale green solution. The as-prepared precursor solution was loaded into the syringe for subsequent electrospinning. The electrospinning installation was composed of a high voltage DC power supply, a nozzle and a collecting board. A metal board covered with aluminum foil was used as the collecting board. During the process of electrospinning, a voltage of 18 kV was applied to provide a high voltage electric field. In addition, a collection distance of 20 cm was reserved between the pinpoint of syringe and the collecting board to prepare NiO precursors. Finally, the as-electrospun PVP/Ni(NO3)2 6H2O composites were calcined in a tube-type furnace. To obtain the desired chain-like NiO architectures, the calcination temperature was kept at 600 °C for 1 h in air and the heating rate was controlled at 1 °C/min. During the whole electrospinning procedure, ambient temperature of 24– 27 °C and humidity of 30–40% were kept. The morphology of as-prepared chain-like NiO was examined using a JEOL JSM-6700F field emission scanning electron microscope (FESEM). X-ray diffraction (XRD) pattern of the products was conducted on a Rigaku D/max 2550 X-ray diffractometer. The fabrication method of the sensor was similar to that in our
J. Cao et al. / Materials Letters 185 (2016) 40–42
previous report [10]. The paste formed by mixing 0.01 g NiO nanomaterials with 0.1 mL deionized water was painted on a ceramic tube to construct a sensing materials layer. To transfer electrical signal, a pair of gold electrodes had been previously printed on the ceramic tube, and a Ni-Cr heating wire was inserted into the tube as a heater to control the working temperature by tuning the heating current. The as-prepared sensor was dried at 100 °C for 2 h and then welded onto a socket for testing. The electrical performances of the sensor were measured by a CGS-8 intelligent gas sensing analysis system. The sensor sensitivity was defined as S ¼ (Rg- Ra)/ Ra%. Here, Ra and Rg was the resistance of the sensor in the air and target gas, respectively. The time taken by the sensor to change from Ra to Ra 90% (Ra Rg) was defined as the response time when the NiO sensor was placed into the target gas. The time taken by the NiO sensor to change from Rg to Rg þ90% (Ra Rg) was defined as the recovery time when the NiO sensor was taken out of the target gas.
3. Results and discussion Fig. 1a and Fig. 1b presents a low-magnification and high-magnification FESEM image of as-prepared chain-like NiO architectures, respectively. It can be easily seen that the NiO products are composed of a large number of chain-like structures, are randomly oriented and show uniform and continuous surfaces. Further observation from Fig. 1b indicates that NiO samples are regularly assembled by many nanoparticles of similar size along the same direction and present unique necklace-like structures. The nanochain diameter is equal to the nanoparticle size. The average diameter of chain-like NiO architectures is about 60 nm. The crystal phase of chain-like NiO architectures is characterized by XRD. As shown in Fig. 1c, all of the diffraction peaks can be indexed to the standard NiO (JCPDS no. 731519). No diffraction peaks from any other impurities are observed, indicating high purity of NiO products.
41
Fig. 2a shows responses of chain-like NiO architectures based sensors to 50 ppm HCHO as a function of operating temperature. Obviously, responses of the sensor present “increase-maximum-decrease” parabola-like tendency with the increasement of operating temperature. The decrease in the sensitivity at high temperature may result from the decrease in the number of active sites for the adsorption of formaldehyde. The other possibility is that at such high temperature, the rate of desorption is higher than that of adsorption [11]. The sensitivity reaches a maximum value at 210 °C. Thus, the optimum operating temperature of 210 °C is chosen for formaldehyde to further examine the characteristics of the sensor. The selectivity is a crucial parameter of gas sensor for the practical application. To evaluate the selectivity of the sensor, the responses of the NiO sensor to 50 ppm different gases are measured at 210 °C. As shown in Fig. 2b, the NiO sensor exhibits an obvious response for formaldehyde but a lesser effect for ethanol, methanol, ammonia, benzene and toluene, which is mainly attributed to the enhanced reaction between the formaldehyde and the adsorbed oxygen at the optimum operating temperature [12]. Fig. 3a shows dynamic response transients of chain-like NiO architectures to 1, 5, 10, 30, 50 and 100 ppm formaldehyde at 210 °C. It is apparent that the resistance of the sensor changes rapidly on being exposed to formaldehyde and to air and presents a ladder-like increasement as the sensor is orderly exposed to different concentrations of formaldehyde, indicating an excellent reproducibility and stability. Fig. 3b exhibits responses of chain-like NiO architectures to different concentrations of formaldehyde. In the concentration range from 1 to 100 ppm, the sensitivity of the sensor almost linearly increases with the increasement of the formaldehyde concentration, indicating the sensor is more suitable for low concentration formaldehyde gas detection. Moreover, the NiO sensor shows a low concentration detection limit (1 ppm). The response time and recovery time of the gas sensor is very important parameter and is calculated to be 1 s and 10 s, respectively. Compared
Fig. 1. (a) The low magnification FESEM image and (b) high magnification FESEM image of chain-like NiO architectures; (c) XRD pattern of chain-like NiO architectures.
42
J. Cao et al. / Materials Letters 185 (2016) 40–42
Fig. 2. (a) Responses of chain-like NiO architectures based sensors to 50 ppm HCHO as a function of operating temperature; (b) responses of chain-like NiO architectures based sensors to 50 ppm various testing gases at 210 °C: (A) formaldehyde; (B) ethanol; (C) methanol; (D) ammonia; (E) benzene and (F) toluene.
the nanochain diameter is equal to the nanoparticle size. The sensors based on chain-like NiO architectures exhibit excellent HCHO gas sensing performances in terms of fast response/recovery time, good selectivity, low concentration detection limit and well reproducibility. The current work clearly demonstrates that as-prepared chain-like NiO architectures can be developed to be high response/recovery rate formaldehyde gas sensor.
Acknowledgments This work was funded by the National Natural Science Foundation of China, No. 61274064 and the Open Project of State Key Laboratory of Separation Membranes and Membrane Processes, No. Z2–201554.
References
Fig. 3. (a) Dynamic response transients of chain-like NiO architectures to 1, 5, 10, 30, 50 and 100 ppm HCHO at 210 °C; (b) responses of chain-like NiO architectures to different concentrations of HCHO. The inset is the response transient of chainlike NiO architectures to 50 ppm HCHO at 210 °C.
with many other formaldehyde gas sensors [13–16], the gas sensor based on chain-like NiO architectures presents a quite competitive gas sensing performance, which is predominantly attributed to the distinctive one dimensional nanoparticles-assembled chain-like structure of NiO nanomaterials.
4. Conclusions Chain-like NiO architectures have been successfully prepared by a facile electrospinning technique. The as-prepared chain-like NiO is regularly assembled by nanoparticles along the same direction and
[1] S.S. Zhu, Y.M. Dai, W. Huang, C.X. Zhang, Y.Q. Zhao, L.H. Tan, et al., Mater. Lett. 161 (2015) 731–734. [2] S.F. Tong, M.B. Zheng, Y. Lu, Z.X. Lin, J. Li, X.P. Zhang, et al., J. Mater. Chem A 3 (2015) 16177–16182. [3] J.F. Zhao, Y. Tan, K. Su, J.J. Zhao, C. Yang, L.L. Sang, et al., Appl Surf. Sci. 337 (2015) 111–117. [4] K. Tian, X.X. Wang, H.Y. Li, R. Nadimicherla, X. Guo, Sens. Actuators B 227 (2016) 554–560. [5] R.Y. Miao, X. Yu, W. Zeng, Mater. Lett. 173 (2016) 107–110. [6] H.S. Jadhav, G.M. Thorat, J. Mun, J.G. Seo, J. Power Sources 302 (2016) 13–31. [7] X.J. Ma, N.N. Wang, Y.T. Qian, Z.C. Bai, Mater. Lett. 168 (2016) 5–8. [8] X. Luo, Z.J. Zhang, Q.J. Wan, K.B. Wu, N.J. Yang, Electrochem. Commun. 61 (2015) 89–92. [9] J. Cao, Z.Y. Wang, R. Wang, S. Liu, T. Fei, L.J. Wang, et al., J. Mater. Chem. A 3 (2015) 5635–5641. [10] J. Cao, H.M. Dou, H. Zhang, H.X. Mei, S. Liu, T. Fei, et al., Sens. Actuators B 198 (2014) 180–187. [11] X.M. Xu, X. Li, W.B. Wang, B. Wang, P. Sun, Y.F. Sun, et al., RSC Adv. 4 (2014) 4831–4835. [12] S.M. Wang, P. Wang, C.H. Xiao, B.B. Yao, R. Zhao, M.Z. Zhang, CrystEngComm 15 (2013) 9170–9175. [13] L. Xu, R.Q. Xing, J. Song, W. Xu, H.W. Song, J. Mater. Chem. C 1 (2013) 2174–2182. [14] L.X. Zhang, J.H. Zhao, H.Q. Lu, L.M. Gong, L. Li, J.F. Zheng, et al., Sens. Actuators B 160 (2011) 364–370. [15] W. Yang, P. Wan, X.D. Zhou, J.M. Hu, Y.F. Guan, L. Feng, Sens. Actuators B 201 (2014) 228–233. [16] S. Hussain, T.M. Liu, M. Kashif, S.X. Cao, W. Zeng, S.B. Xu, et al., Mater. Lett. 128 (2014) 35–38.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Facile fabrication and enhanced formaldehyde gas sensing properties of nanoparticles-assembled chain-like NiO architectures Jing Cao n, Haiming Zhang n, Xuequn Yan School of Science, Tianjin Polytechnic University, Tianjin 300387, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 15 July 2016 Received in revised form 19 August 2016 Accepted 20 August 2016 Available online 21 August 2016
The chain-like NiO architectures are successfully fabricated by a facile electrospinning route followed by a subsequent annealing treatment and are exploited for formaldehyde (HCHO) gas detection. The asprepared NiO nanochains are regularly assembled by nanoparticles along the same direction and present unique necklace-like structures. Gas sensing performances of chain-like NiO architectures are also investigated. The result indicates that the gas sensor based on chain-like NiO exhibits good selectivity, superior sensitivity, fast response/recovery rate and low concentration detection limit towards formaldehyde gas at a relatively low operating temperature. The facile synthesis route and promising formaldehyde sensing properties enable chain-like NiO architecture to be a competitive candidate for formaldehyde gas detection in practice. & Published by Elsevier B.V.
Keywords: Semiconductors Nickel oxide Chain-like architectures Sensors
1. Introduction NiO, as an important p-type oxide semiconductor, has attracted considerable attention due to excellent application prospects in supercapacitors, catalysts, water treatment and gas sensors [1–5]. In particular, gas sensors based on NiO nanomaterials exhibit morphology and structure-dependent gas sensing properties, which impels researchers to explore facile routes to prepare NiO nanomaterials with novel morphologies and unique structures. Up to now, multifarious strategies have been employed to synthesize diverse NiO nanomaterials [6,7]. Among synthesis methods of nanomaterials, electrospinning is an excellent method to obtain the controllable fabrication of different oxide semiconductors with more uniform characteristics, higher reproducibly and lower cost [8]. Meanwhile, for gas sensing applications, the as-prepared long and continuous one dimensional architectures own high specific surface areas and form massive gaps among each other after nanomaterials are coated on a ceramic tube to form a sensing layer, just like incompact knitting wool, which can greatly increase utilization rate of nanomaterials and then enhance gas sensing performances [9]. In this paper, NiO nanochains architectures have been successfully fabricated via a facile electrospinning technique and the subsequent annealing treatment. The as-synthesized NiO nanochains are regularly assembled by nanoparticles of similar size along the same direction. The gas sensor based on chain-like NiO n
Corresponding authors. E-mail addresses: [email protected] (J. Cao), [email protected] (H. Zhang).
http://dx.doi.org/10.1016/j.matlet.2016.08.099 0167-577X/& Published by Elsevier B.V.
architectures exhibits an excellent gas sensing performance towards formaldehyde.
2. Experiments All reagents were analytical-grade purity and used as purchased without further purification. The chain-like NiO were fabricated by a electrospinning route. In a typical procedure, 0.5 g Ni (NO3)2 6H2O and 1.8 g PVP were dissolved in 10 mL DMF under vigorous stirring to form a pale green solution. The as-prepared precursor solution was loaded into the syringe for subsequent electrospinning. The electrospinning installation was composed of a high voltage DC power supply, a nozzle and a collecting board. A metal board covered with aluminum foil was used as the collecting board. During the process of electrospinning, a voltage of 18 kV was applied to provide a high voltage electric field. In addition, a collection distance of 20 cm was reserved between the pinpoint of syringe and the collecting board to prepare NiO precursors. Finally, the as-electrospun PVP/Ni(NO3)2 6H2O composites were calcined in a tube-type furnace. To obtain the desired chain-like NiO architectures, the calcination temperature was kept at 600 °C for 1 h in air and the heating rate was controlled at 1 °C/min. During the whole electrospinning procedure, ambient temperature of 24– 27 °C and humidity of 30–40% were kept. The morphology of as-prepared chain-like NiO was examined using a JEOL JSM-6700F field emission scanning electron microscope (FESEM). X-ray diffraction (XRD) pattern of the products was conducted on a Rigaku D/max 2550 X-ray diffractometer. The fabrication method of the sensor was similar to that in our
J. Cao et al. / Materials Letters 185 (2016) 40–42
previous report [10]. The paste formed by mixing 0.01 g NiO nanomaterials with 0.1 mL deionized water was painted on a ceramic tube to construct a sensing materials layer. To transfer electrical signal, a pair of gold electrodes had been previously printed on the ceramic tube, and a Ni-Cr heating wire was inserted into the tube as a heater to control the working temperature by tuning the heating current. The as-prepared sensor was dried at 100 °C for 2 h and then welded onto a socket for testing. The electrical performances of the sensor were measured by a CGS-8 intelligent gas sensing analysis system. The sensor sensitivity was defined as S ¼ (Rg- Ra)/ Ra%. Here, Ra and Rg was the resistance of the sensor in the air and target gas, respectively. The time taken by the sensor to change from Ra to Ra 90% (Ra Rg) was defined as the response time when the NiO sensor was placed into the target gas. The time taken by the NiO sensor to change from Rg to Rg þ90% (Ra Rg) was defined as the recovery time when the NiO sensor was taken out of the target gas.
3. Results and discussion Fig. 1a and Fig. 1b presents a low-magnification and high-magnification FESEM image of as-prepared chain-like NiO architectures, respectively. It can be easily seen that the NiO products are composed of a large number of chain-like structures, are randomly oriented and show uniform and continuous surfaces. Further observation from Fig. 1b indicates that NiO samples are regularly assembled by many nanoparticles of similar size along the same direction and present unique necklace-like structures. The nanochain diameter is equal to the nanoparticle size. The average diameter of chain-like NiO architectures is about 60 nm. The crystal phase of chain-like NiO architectures is characterized by XRD. As shown in Fig. 1c, all of the diffraction peaks can be indexed to the standard NiO (JCPDS no. 731519). No diffraction peaks from any other impurities are observed, indicating high purity of NiO products.
41
Fig. 2a shows responses of chain-like NiO architectures based sensors to 50 ppm HCHO as a function of operating temperature. Obviously, responses of the sensor present “increase-maximum-decrease” parabola-like tendency with the increasement of operating temperature. The decrease in the sensitivity at high temperature may result from the decrease in the number of active sites for the adsorption of formaldehyde. The other possibility is that at such high temperature, the rate of desorption is higher than that of adsorption [11]. The sensitivity reaches a maximum value at 210 °C. Thus, the optimum operating temperature of 210 °C is chosen for formaldehyde to further examine the characteristics of the sensor. The selectivity is a crucial parameter of gas sensor for the practical application. To evaluate the selectivity of the sensor, the responses of the NiO sensor to 50 ppm different gases are measured at 210 °C. As shown in Fig. 2b, the NiO sensor exhibits an obvious response for formaldehyde but a lesser effect for ethanol, methanol, ammonia, benzene and toluene, which is mainly attributed to the enhanced reaction between the formaldehyde and the adsorbed oxygen at the optimum operating temperature [12]. Fig. 3a shows dynamic response transients of chain-like NiO architectures to 1, 5, 10, 30, 50 and 100 ppm formaldehyde at 210 °C. It is apparent that the resistance of the sensor changes rapidly on being exposed to formaldehyde and to air and presents a ladder-like increasement as the sensor is orderly exposed to different concentrations of formaldehyde, indicating an excellent reproducibility and stability. Fig. 3b exhibits responses of chain-like NiO architectures to different concentrations of formaldehyde. In the concentration range from 1 to 100 ppm, the sensitivity of the sensor almost linearly increases with the increasement of the formaldehyde concentration, indicating the sensor is more suitable for low concentration formaldehyde gas detection. Moreover, the NiO sensor shows a low concentration detection limit (1 ppm). The response time and recovery time of the gas sensor is very important parameter and is calculated to be 1 s and 10 s, respectively. Compared
Fig. 1. (a) The low magnification FESEM image and (b) high magnification FESEM image of chain-like NiO architectures; (c) XRD pattern of chain-like NiO architectures.
42
J. Cao et al. / Materials Letters 185 (2016) 40–42
Fig. 2. (a) Responses of chain-like NiO architectures based sensors to 50 ppm HCHO as a function of operating temperature; (b) responses of chain-like NiO architectures based sensors to 50 ppm various testing gases at 210 °C: (A) formaldehyde; (B) ethanol; (C) methanol; (D) ammonia; (E) benzene and (F) toluene.
the nanochain diameter is equal to the nanoparticle size. The sensors based on chain-like NiO architectures exhibit excellent HCHO gas sensing performances in terms of fast response/recovery time, good selectivity, low concentration detection limit and well reproducibility. The current work clearly demonstrates that as-prepared chain-like NiO architectures can be developed to be high response/recovery rate formaldehyde gas sensor.
Acknowledgments This work was funded by the National Natural Science Foundation of China, No. 61274064 and the Open Project of State Key Laboratory of Separation Membranes and Membrane Processes, No. Z2–201554.
References
Fig. 3. (a) Dynamic response transients of chain-like NiO architectures to 1, 5, 10, 30, 50 and 100 ppm HCHO at 210 °C; (b) responses of chain-like NiO architectures to different concentrations of HCHO. The inset is the response transient of chainlike NiO architectures to 50 ppm HCHO at 210 °C.
with many other formaldehyde gas sensors [13–16], the gas sensor based on chain-like NiO architectures presents a quite competitive gas sensing performance, which is predominantly attributed to the distinctive one dimensional nanoparticles-assembled chain-like structure of NiO nanomaterials.
4. Conclusions Chain-like NiO architectures have been successfully prepared by a facile electrospinning technique. The as-prepared chain-like NiO is regularly assembled by nanoparticles along the same direction and
[1] S.S. Zhu, Y.M. Dai, W. Huang, C.X. Zhang, Y.Q. Zhao, L.H. Tan, et al., Mater. Lett. 161 (2015) 731–734. [2] S.F. Tong, M.B. Zheng, Y. Lu, Z.X. Lin, J. Li, X.P. Zhang, et al., J. Mater. Chem A 3 (2015) 16177–16182. [3] J.F. Zhao, Y. Tan, K. Su, J.J. Zhao, C. Yang, L.L. Sang, et al., Appl Surf. Sci. 337 (2015) 111–117. [4] K. Tian, X.X. Wang, H.Y. Li, R. Nadimicherla, X. Guo, Sens. Actuators B 227 (2016) 554–560. [5] R.Y. Miao, X. Yu, W. Zeng, Mater. Lett. 173 (2016) 107–110. [6] H.S. Jadhav, G.M. Thorat, J. Mun, J.G. Seo, J. Power Sources 302 (2016) 13–31. [7] X.J. Ma, N.N. Wang, Y.T. Qian, Z.C. Bai, Mater. Lett. 168 (2016) 5–8. [8] X. Luo, Z.J. Zhang, Q.J. Wan, K.B. Wu, N.J. Yang, Electrochem. Commun. 61 (2015) 89–92. [9] J. Cao, Z.Y. Wang, R. Wang, S. Liu, T. Fei, L.J. Wang, et al., J. Mater. Chem. A 3 (2015) 5635–5641. [10] J. Cao, H.M. Dou, H. Zhang, H.X. Mei, S. Liu, T. Fei, et al., Sens. Actuators B 198 (2014) 180–187. [11] X.M. Xu, X. Li, W.B. Wang, B. Wang, P. Sun, Y.F. Sun, et al., RSC Adv. 4 (2014) 4831–4835. [12] S.M. Wang, P. Wang, C.H. Xiao, B.B. Yao, R. Zhao, M.Z. Zhang, CrystEngComm 15 (2013) 9170–9175. [13] L. Xu, R.Q. Xing, J. Song, W. Xu, H.W. Song, J. Mater. Chem. C 1 (2013) 2174–2182. [14] L.X. Zhang, J.H. Zhao, H.Q. Lu, L.M. Gong, L. Li, J.F. Zheng, et al., Sens. Actuators B 160 (2011) 364–370. [15] W. Yang, P. Wan, X.D. Zhou, J.M. Hu, Y.F. Guan, L. Feng, Sens. Actuators B 201 (2014) 228–233. [16] S. Hussain, T.M. Liu, M. Kashif, S.X. Cao, W. Zeng, S.B. Xu, et al., Mater. Lett. 128 (2014) 35–38.