- Email: [email protected]
SnO2 nanocomposite
Materials Today: Proceedings xxx (xxxx) xxx
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Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite Sukhwinder Singh, Suresh Kumar, Sandeep Sharma ⇑ Department of Physics, Guru Nanak Dev University, Amritsar 143005, India
a r t i c l e
i n f o
Article history: Received 2 December 2019 Received in revised form 4 January 2020 Accepted 8 January 2020 Available online xxxx Keywords: Nanostructures Room temperature ammonia sensor Sensing response Transition metal dichalcogenides SnO2/MoS2 composite
a b s t r a c t A MoS2/SnO2 composite based ammonia gas sensor working at room temperature has been demonstrated in present work. Structural and vibrational analysis confirmed the formation of MoS2/SnO2 composite. Compared with SnO2 based sensor, the device made from composite showed exceptional selectivity and sensitivity towards ammonia at room temperature. The sensor showed a room temperature relative response of nearly 10% with 50 ppm of ammonia. The corresponding response and recovery times are 35 s and 15 s, respectively, much smaller than value found for SnO2/multi-walled carbon nanotubes based composite sensor at room temperature. The obtained relative response value is larger than the value obtained while using pure SnO2 as ammonia sensing device. The latter, though responds only at high temperature and has poor selectivity towards various gases. These, initial results provides a new direction to improve both room temperature sensitivity as well as selectivity behaviour of sensors based on composite materials derived from transition metal dichalcogenides and SnO2. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.
1. Introduction In the past metal oxide based sensors have been widely investigated as they can detect a wide range of gases with larger sensitivity, stability but generally at elevated temperature [1]. Among the metal oxides, SnO2 has been widely employed in gas sensing applications due to high sensitivity to various environmental conditions [2], but its use is limited due to its inferior selectivity behavior. To overcome this issue, various researchers have shown that gas sensitivity behavior of SnO2 can be modulated by using various dopants, for instance Pt, Pd and Rh etc [3]. While platinum offers an expensive route for doping, palladium based compounds on the other sides are highly toxic and carcinogenic in nature. Therefore, an alternate route is sought where the issues pertaining to high temperature operation and selectivity can be encountered. The composites of different materials have been found to address all these challenges. For instance, SiO2 and SnO2 composites with carbon nano tubes (CNT) have been reported [4]. But their gas sensing performance has not improved significantly when compared with individual SnO2 and CNT based sensors [5]. In another ⇑ Corresponding author. E-mail address: [email protected] (S. Sharma).
report by Hieu et al, reported highly sensitive room temperature NH3 gas sensor using SnO2/multi-walled carbon nanotubes composite. But corresponding response and recovery time were close to five minutes [6]. In a few cases ternary composites using SnO2 have also been tested for room temperature gas sensing operation. Though, sensitivity has been improved significantly but response and recovery times were reported to be quite large [7]. Further, Wang et.al has also shown that SnO2 when doped with Pt or SiO2, shows a small change in response when compared with parent material [5]. In this case sensing results were obtained at elevated temperature of 160 °C. In present work we focus on NH3 gas sensing as it is widely used in chemical industries and can have very harmful effects on human body. Therefore, effective monitoring of ammonia is required. In principle, SnO2 has been used earlier for ammonia gas sensing. Such sensors have shown better response recovery characteristics but only at high temperature [5]. Hence, devices which can operate at room temperature and with fast response recovery characteristics are required. In order to address these issues, we have focused on SnO2 composite with MoS2 nanostructures. Latter have 2-dimensional structures and offer a very large surface-to-volume ratio, prerequisite for sensing. Specifically, we will demonstrate the facile synthesis of this composite and also show that when used as a sensing device they have better
https://doi.org/10.1016/j.matpr.2020.01.208 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
2
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
sensing response at room temperature as compared to SnO2 based ammonia sensors that operated at elevated temperature. Hence, these initial results serve as a guide to explore the gas sensing kinetics of SnO2/MoS2 based composites. 2. Materials and method MoS2/SnO2 composite was prepared by following hydrothermal route. Ammonium tetrathiomolybdate and SnCl45H2O with NaOH were used as precursors of MoS2 and SnO2. Initially, 0.5 g (NH4)2 MoS4 was dissolved in 50 ml of de-ionized water. To this solution, we added 10 ml Hydrazine Hydrate, which acts as a reducing agent. This mixture was bath sonicated for an hour and then transferred to 100 ml autoclave. The autoclave was kept in a furnace at 180 °C for 10 h and allowed to cool naturally. After completion of this process, obtained black colored precipitates were washed several times with ethanol, acetone and DI-water. At the end, obtained sample was dried at 60 °C for 6 h in a vacuum oven. Further, we took 0.5 g of prepared black powder and mixed them in 50 ml of DI-water. To this solution we added 0.2 g SnCl45H2O and continued bath sonication for another two hours. Finally 0.15 g NaOH was added into previous solution to adjust pH value close to seven. The resulting solution was again transferred into an autoclave which was kept at 180 °C for 16 h. The resulting black colored precipitates were washed with ethanol, acetone and distilled water and then finally dried at 65 °C for 10 h in a vacuum oven. The black powder obtained in final step was used for structural as well as for gas sensing measurements. Two terminal devices were made on a glass substrate with pre-deposited electrode separated by 5 mm. All measurements were carried out at room temperature. 3. Results and discussion 3.1. Structure and morphology The morphology and structural analysis of the as-prepared MoS2/SnO2 nanohybrids were carried out using scanning electron microscopy (SUPRA-55) and high resolution transmission electron microscopy (HR-TEM, JEOL JEM-2100). Fig. 1(a) shows the SEM images of the hybrid. One can clearly see small particles on thick layered flakes of MoS2. In 1(b) the low resolution TEM image is shown. Figure displays thick as well ultra thin nanostructures. Fig. 1(c) shows HR-TEM image of the sample transferred on carbon coated copper grid. The enhanced view of highlighted area (upper left side) display fringes with interplanar spacing of 2.12 Å corresponding to (2 1 0) planes of SnO2. On the right side, another inset clearly display hexagonal arrangement of Mo and S atoms. Fringes with spacing 0.35 Å and 0.25 Å corresponds to (300) and (211) planes of MoS2. Therefore, HR-TEM images clearly establish the formation of MoS2/SnO2 composite.
Fig. 1. (a) Scanning electron microscopy image of MoS2/SnO2 hybrid. (b) Corresponding TEM image of same sample (c) HR-TEM image of sample clearly showing fringes corresponding to SnO2 and MoS2.
3.2. Raman spectra from MoS2/SnO2 composite The Raman spectrum of obtained SnO2 powder in the range 380–800 cm 1 is shown in Fig. 2(a). After deconvolution, various vibrational modes can be seen in Figure. The peaks at 485.71, 627.96 and 771.64 cm 1 have been identified as E2g, A1g and B2g, respectively [8,9]. The modes A1g and B2g arise due to relative expansion and contraction of Sn-O bonds. On the other hand in B2g mode, all Sn-O bonds surrounding Sn ion, contract simultaneously and result in larger repulsive force of O-O bonds as compared to A1g mode. For this reason B2g mode appears at higher energy that A1g mode. The E2g mode originates from vibration of oxygen atom. These modes indicate that synthesized SnO2 has tetragonal rutile structure. It is to be noted that in addition to these three modes we have observed two more at 561 and 578.98 cm 1. Various researchers have attributed these new modes to vacant lattice sites and local disorder in the lattice [9]. Further, in Fig. 2(b), a similar Raman spectrum is shown for MoS2/SnO2 composite. We clearly observe A1g mode at 404 cm 1. For bulk crystalline MoS2, this mode usually occurs at 409 cm 1. A shift in peak position might arise either due to dimensional scaling or defects in the host lattice. This mode arises due to out-of-plane vibrations of sulfur atoms and transition metal atom fixed. A signature of peaks at 578 and 627 cm 1 corresponding to SnO2 confirms the formation of MoS2/SnO2 hybrid. 3.3. Ammonia sensing with MoS2/SnO2 composite based sensor Further, two terminal gas sensing measurements were performed on device made from composite. Fig. 3 (a) displays a typical response curve to NH3 gas at room temperature. As we see, the resistance of the device varies with time upon exposure to NH3. When exposed to ammonia, the resistance reduces and attains a minimum value, depending upon the level of ammonia and again recovers its value when ammonia gas is removed from the measurement chamber. Since NH3 molecule is an electron donating species, the decrease in sensor resistance indicates that composite behave like n-type semiconductor. The gas sensing mechanism in semiconducting metal oxide is a well understood phenomena involving gas adsorption, charge transfer (between adsorbed gas molecule and underlying semiconducting channel) and desorption of gas molecules [10]. It is known that at room temperature SnO2
Fig. 2. Raman spectra from (a) SnO2 (b) MoS2/SnO2 composite acquired with excitation wavelength of 488 nm at room temperature.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
Fig. 3. (a) Sensor response to ammonia vapors at 27 °C, this figure also defines various parameters describing the properties of a sensor. (b) Relative response (DR/Rb in %) of sensor at various concentrations of ammonia. (c) Relative response in percent with ammonia concentration.
does not respond to NH3, implying the observed decrease in resistance is due to the formation of composite. A complete understanding of charge transfer process, and hence decrease in resistance requires more surface sensitive measurements which are underway and will be reported in future. Relative response is defined as DR/Rb, where DR is the absolute change in resistance and Rb is the base resistance of the device in air. Fig. 3(b) also displays the room temperature sensor response to various ammonia concentrations. It is more clear from 3 (c), showing variation of relative response with ammonia concentration. The relative response of the sensor increases linearly from 50 to 500 ppm. As we notice from the data, the relative response of sensor for 50 and 200 ppm NH3 level are 10% and 35%, respectively. These values are much larger than SnO2 based composite or Pt and SiO2 doped SnO2 composites. In the latter case, the relative response measured at 160 °C is below 3% and 25%, respectively at 50 and 200 ppm levels of ammonia. Thus, these results suggest that, by making composite of TMDCs based nanostructures and SnO2 sensing capability can be improved at room temperature.
lished various planes corresponding to SnO2 and MoS2. Raman spectroscopy confirmed the presence of various modes corresponding to MoS2 and SnO2 establishing the formation of composite. Room temperature ammonia (50 ppm) sensing using this composite yielded a relative response of nearly 10%. This is larger than the response when SnO2 is used as a sensing material. Note that latter can sense ammonia only at 160 °C and has poor selectivity behavior. Initial measurements have also revealed that composite based sensor is highly selective towards ammonia and has faster response recovery times of 35 and 15 s, respectively, much smaller than values earlier observed for SnO2 based composites used as NH3 sensors. Results also reveal a decrease in sensor resistance upon exposure to ammonia gas, implying n-type conductivity of the composite. Therefore, these results suggest that composite of SnO2 with TMDCs can significantly alter the response as well as selectivity towards various gases and may pave the way for developing highly sensitive and selective gas sensor which can operate at room temperature. CRediT authorship contribution statement
4. Conclusion MoS2/SnO2 nanocomposite was obtained successfully via hydrothermal method. Structural analysis using HR-TEM estab-
Sukhwinder Singh: Conceptulization, Data curation, Investigation. Suresh Kumar: Data curation, Acquisition. Sandeep Sharma: Conceptulization, Supervision, Draft writing.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
4
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was financially supported by department of science and technology, DST-New Delhi through grant EMR/2016/007483.
References [1] [2] [3] [4] [5] [6] [7] [8]
S. Das, V. Jayaraman, Prog. Mater. Sci. 66 (2014) 112–255. N. Yamazoe, Sens. Actuators B 5 (1991) 7–19. D.D. Lee, W.T. Chung, Sens. Actuators 20 (3) (1989) 301–305. Y.L. Liu, H.F. Yang, et al., Thin Solid Films 497 (2006) 355–360. Y.D. Wang, X.H. Wu, et al., Solid State Electron. 45 (2001) 347–350. N.V. Hieu, L.T.B. Thuy, N.D. Chien, Sens. Actuators B 129 (2008) 888–895. P.G. Su, L.Y. Yang, Sens. Actuators B 223 (2016) 202–208. A. Dieguez, A.R. Rodriguez, A. Vila, J.R. Morante, J. Appl. Phys. 90 (3) (2001) 1550–1557. [9] X. Caoshui, X. Yonghong, et al., Sci. China 40 (11) (1997) 1222–1227. [10] Md. Shahabuddin, A. Sharma, J. Kumar, M. Tomar, A. Umar, V. Gupta, Sens. Actuators B 194 (2014) 410–418.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite Sukhwinder Singh, Suresh Kumar, Sandeep Sharma ⇑ Department of Physics, Guru Nanak Dev University, Amritsar 143005, India
a r t i c l e
i n f o
Article history: Received 2 December 2019 Received in revised form 4 January 2020 Accepted 8 January 2020 Available online xxxx Keywords: Nanostructures Room temperature ammonia sensor Sensing response Transition metal dichalcogenides SnO2/MoS2 composite
a b s t r a c t A MoS2/SnO2 composite based ammonia gas sensor working at room temperature has been demonstrated in present work. Structural and vibrational analysis confirmed the formation of MoS2/SnO2 composite. Compared with SnO2 based sensor, the device made from composite showed exceptional selectivity and sensitivity towards ammonia at room temperature. The sensor showed a room temperature relative response of nearly 10% with 50 ppm of ammonia. The corresponding response and recovery times are 35 s and 15 s, respectively, much smaller than value found for SnO2/multi-walled carbon nanotubes based composite sensor at room temperature. The obtained relative response value is larger than the value obtained while using pure SnO2 as ammonia sensing device. The latter, though responds only at high temperature and has poor selectivity towards various gases. These, initial results provides a new direction to improve both room temperature sensitivity as well as selectivity behaviour of sensors based on composite materials derived from transition metal dichalcogenides and SnO2. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.
1. Introduction In the past metal oxide based sensors have been widely investigated as they can detect a wide range of gases with larger sensitivity, stability but generally at elevated temperature [1]. Among the metal oxides, SnO2 has been widely employed in gas sensing applications due to high sensitivity to various environmental conditions [2], but its use is limited due to its inferior selectivity behavior. To overcome this issue, various researchers have shown that gas sensitivity behavior of SnO2 can be modulated by using various dopants, for instance Pt, Pd and Rh etc [3]. While platinum offers an expensive route for doping, palladium based compounds on the other sides are highly toxic and carcinogenic in nature. Therefore, an alternate route is sought where the issues pertaining to high temperature operation and selectivity can be encountered. The composites of different materials have been found to address all these challenges. For instance, SiO2 and SnO2 composites with carbon nano tubes (CNT) have been reported [4]. But their gas sensing performance has not improved significantly when compared with individual SnO2 and CNT based sensors [5]. In another ⇑ Corresponding author. E-mail address: [email protected] (S. Sharma).
report by Hieu et al, reported highly sensitive room temperature NH3 gas sensor using SnO2/multi-walled carbon nanotubes composite. But corresponding response and recovery time were close to five minutes [6]. In a few cases ternary composites using SnO2 have also been tested for room temperature gas sensing operation. Though, sensitivity has been improved significantly but response and recovery times were reported to be quite large [7]. Further, Wang et.al has also shown that SnO2 when doped with Pt or SiO2, shows a small change in response when compared with parent material [5]. In this case sensing results were obtained at elevated temperature of 160 °C. In present work we focus on NH3 gas sensing as it is widely used in chemical industries and can have very harmful effects on human body. Therefore, effective monitoring of ammonia is required. In principle, SnO2 has been used earlier for ammonia gas sensing. Such sensors have shown better response recovery characteristics but only at high temperature [5]. Hence, devices which can operate at room temperature and with fast response recovery characteristics are required. In order to address these issues, we have focused on SnO2 composite with MoS2 nanostructures. Latter have 2-dimensional structures and offer a very large surface-to-volume ratio, prerequisite for sensing. Specifically, we will demonstrate the facile synthesis of this composite and also show that when used as a sensing device they have better
https://doi.org/10.1016/j.matpr.2020.01.208 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
2
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
sensing response at room temperature as compared to SnO2 based ammonia sensors that operated at elevated temperature. Hence, these initial results serve as a guide to explore the gas sensing kinetics of SnO2/MoS2 based composites. 2. Materials and method MoS2/SnO2 composite was prepared by following hydrothermal route. Ammonium tetrathiomolybdate and SnCl45H2O with NaOH were used as precursors of MoS2 and SnO2. Initially, 0.5 g (NH4)2 MoS4 was dissolved in 50 ml of de-ionized water. To this solution, we added 10 ml Hydrazine Hydrate, which acts as a reducing agent. This mixture was bath sonicated for an hour and then transferred to 100 ml autoclave. The autoclave was kept in a furnace at 180 °C for 10 h and allowed to cool naturally. After completion of this process, obtained black colored precipitates were washed several times with ethanol, acetone and DI-water. At the end, obtained sample was dried at 60 °C for 6 h in a vacuum oven. Further, we took 0.5 g of prepared black powder and mixed them in 50 ml of DI-water. To this solution we added 0.2 g SnCl45H2O and continued bath sonication for another two hours. Finally 0.15 g NaOH was added into previous solution to adjust pH value close to seven. The resulting solution was again transferred into an autoclave which was kept at 180 °C for 16 h. The resulting black colored precipitates were washed with ethanol, acetone and distilled water and then finally dried at 65 °C for 10 h in a vacuum oven. The black powder obtained in final step was used for structural as well as for gas sensing measurements. Two terminal devices were made on a glass substrate with pre-deposited electrode separated by 5 mm. All measurements were carried out at room temperature. 3. Results and discussion 3.1. Structure and morphology The morphology and structural analysis of the as-prepared MoS2/SnO2 nanohybrids were carried out using scanning electron microscopy (SUPRA-55) and high resolution transmission electron microscopy (HR-TEM, JEOL JEM-2100). Fig. 1(a) shows the SEM images of the hybrid. One can clearly see small particles on thick layered flakes of MoS2. In 1(b) the low resolution TEM image is shown. Figure displays thick as well ultra thin nanostructures. Fig. 1(c) shows HR-TEM image of the sample transferred on carbon coated copper grid. The enhanced view of highlighted area (upper left side) display fringes with interplanar spacing of 2.12 Å corresponding to (2 1 0) planes of SnO2. On the right side, another inset clearly display hexagonal arrangement of Mo and S atoms. Fringes with spacing 0.35 Å and 0.25 Å corresponds to (300) and (211) planes of MoS2. Therefore, HR-TEM images clearly establish the formation of MoS2/SnO2 composite.
Fig. 1. (a) Scanning electron microscopy image of MoS2/SnO2 hybrid. (b) Corresponding TEM image of same sample (c) HR-TEM image of sample clearly showing fringes corresponding to SnO2 and MoS2.
3.2. Raman spectra from MoS2/SnO2 composite The Raman spectrum of obtained SnO2 powder in the range 380–800 cm 1 is shown in Fig. 2(a). After deconvolution, various vibrational modes can be seen in Figure. The peaks at 485.71, 627.96 and 771.64 cm 1 have been identified as E2g, A1g and B2g, respectively [8,9]. The modes A1g and B2g arise due to relative expansion and contraction of Sn-O bonds. On the other hand in B2g mode, all Sn-O bonds surrounding Sn ion, contract simultaneously and result in larger repulsive force of O-O bonds as compared to A1g mode. For this reason B2g mode appears at higher energy that A1g mode. The E2g mode originates from vibration of oxygen atom. These modes indicate that synthesized SnO2 has tetragonal rutile structure. It is to be noted that in addition to these three modes we have observed two more at 561 and 578.98 cm 1. Various researchers have attributed these new modes to vacant lattice sites and local disorder in the lattice [9]. Further, in Fig. 2(b), a similar Raman spectrum is shown for MoS2/SnO2 composite. We clearly observe A1g mode at 404 cm 1. For bulk crystalline MoS2, this mode usually occurs at 409 cm 1. A shift in peak position might arise either due to dimensional scaling or defects in the host lattice. This mode arises due to out-of-plane vibrations of sulfur atoms and transition metal atom fixed. A signature of peaks at 578 and 627 cm 1 corresponding to SnO2 confirms the formation of MoS2/SnO2 hybrid. 3.3. Ammonia sensing with MoS2/SnO2 composite based sensor Further, two terminal gas sensing measurements were performed on device made from composite. Fig. 3 (a) displays a typical response curve to NH3 gas at room temperature. As we see, the resistance of the device varies with time upon exposure to NH3. When exposed to ammonia, the resistance reduces and attains a minimum value, depending upon the level of ammonia and again recovers its value when ammonia gas is removed from the measurement chamber. Since NH3 molecule is an electron donating species, the decrease in sensor resistance indicates that composite behave like n-type semiconductor. The gas sensing mechanism in semiconducting metal oxide is a well understood phenomena involving gas adsorption, charge transfer (between adsorbed gas molecule and underlying semiconducting channel) and desorption of gas molecules [10]. It is known that at room temperature SnO2
Fig. 2. Raman spectra from (a) SnO2 (b) MoS2/SnO2 composite acquired with excitation wavelength of 488 nm at room temperature.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
Fig. 3. (a) Sensor response to ammonia vapors at 27 °C, this figure also defines various parameters describing the properties of a sensor. (b) Relative response (DR/Rb in %) of sensor at various concentrations of ammonia. (c) Relative response in percent with ammonia concentration.
does not respond to NH3, implying the observed decrease in resistance is due to the formation of composite. A complete understanding of charge transfer process, and hence decrease in resistance requires more surface sensitive measurements which are underway and will be reported in future. Relative response is defined as DR/Rb, where DR is the absolute change in resistance and Rb is the base resistance of the device in air. Fig. 3(b) also displays the room temperature sensor response to various ammonia concentrations. It is more clear from 3 (c), showing variation of relative response with ammonia concentration. The relative response of the sensor increases linearly from 50 to 500 ppm. As we notice from the data, the relative response of sensor for 50 and 200 ppm NH3 level are 10% and 35%, respectively. These values are much larger than SnO2 based composite or Pt and SiO2 doped SnO2 composites. In the latter case, the relative response measured at 160 °C is below 3% and 25%, respectively at 50 and 200 ppm levels of ammonia. Thus, these results suggest that, by making composite of TMDCs based nanostructures and SnO2 sensing capability can be improved at room temperature.
lished various planes corresponding to SnO2 and MoS2. Raman spectroscopy confirmed the presence of various modes corresponding to MoS2 and SnO2 establishing the formation of composite. Room temperature ammonia (50 ppm) sensing using this composite yielded a relative response of nearly 10%. This is larger than the response when SnO2 is used as a sensing material. Note that latter can sense ammonia only at 160 °C and has poor selectivity behavior. Initial measurements have also revealed that composite based sensor is highly selective towards ammonia and has faster response recovery times of 35 and 15 s, respectively, much smaller than values earlier observed for SnO2 based composites used as NH3 sensors. Results also reveal a decrease in sensor resistance upon exposure to ammonia gas, implying n-type conductivity of the composite. Therefore, these results suggest that composite of SnO2 with TMDCs can significantly alter the response as well as selectivity towards various gases and may pave the way for developing highly sensitive and selective gas sensor which can operate at room temperature. CRediT authorship contribution statement
4. Conclusion MoS2/SnO2 nanocomposite was obtained successfully via hydrothermal method. Structural analysis using HR-TEM estab-
Sukhwinder Singh: Conceptulization, Data curation, Investigation. Suresh Kumar: Data curation, Acquisition. Sandeep Sharma: Conceptulization, Supervision, Draft writing.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208
4
S. Singh et al. / Materials Today: Proceedings xxx (xxxx) xxx
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was financially supported by department of science and technology, DST-New Delhi through grant EMR/2016/007483.
References [1] [2] [3] [4] [5] [6] [7] [8]
S. Das, V. Jayaraman, Prog. Mater. Sci. 66 (2014) 112–255. N. Yamazoe, Sens. Actuators B 5 (1991) 7–19. D.D. Lee, W.T. Chung, Sens. Actuators 20 (3) (1989) 301–305. Y.L. Liu, H.F. Yang, et al., Thin Solid Films 497 (2006) 355–360. Y.D. Wang, X.H. Wu, et al., Solid State Electron. 45 (2001) 347–350. N.V. Hieu, L.T.B. Thuy, N.D. Chien, Sens. Actuators B 129 (2008) 888–895. P.G. Su, L.Y. Yang, Sens. Actuators B 223 (2016) 202–208. A. Dieguez, A.R. Rodriguez, A. Vila, J.R. Morante, J. Appl. Phys. 90 (3) (2001) 1550–1557. [9] X. Caoshui, X. Yonghong, et al., Sci. China 40 (11) (1997) 1222–1227. [10] Md. Shahabuddin, A. Sharma, J. Kumar, M. Tomar, A. Umar, V. Gupta, Sens. Actuators B 194 (2014) 410–418.
Please cite this article as: S. Singh, S. Kumar and S. Sharma, Room temperature high performance ammonia sensor using MoS2/SnO2 nanocomposite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.208