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Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material
Materials Today: Proceedings xxx (xxxx) xxx
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Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material Jiss Paul a,b,⇑, Jacob Philip a,c a
Department of Instrumentation, Cochin University of Science & Technology, Cochin 682 022, India Department of Electronics and Communication, Mar Athanasius College of Engineering, Kothamangalam 686666, India c Amal Jyothi College of Engineering, Kanjirappally, Kottayam 686518, India b
a r t i c l e
i n f o
Article history: Received 28 November 2019 Received in revised form 22 December 2019 Accepted 24 December 2019 Available online xxxx Keywords: Inter-digital capacitive sensor Polyvinyl alcohol (PVA) CoFe2O4 nanocomposite Ethanol Sensor Gas response
a b s t r a c t Sensor design for environmental pollution monitoring is a great challenge, as the selectivity and sensitivity of the sensor for a desired pollutant gas should be high enough to be detected at low concentrations. This work presents an ethanol gas sensor using inter-digital capacitive (IDC) structure coated with Cobalt ferrite (CoFe2O4) nanocomposite as gas sensing material. CoFe2O4 nanocomposite are prepared by sol gel auto-combustion method. Gas sensing properties of the IDC structure are investigated under various gas concentrations. The sensor exhibits high sensitivity of the order of 100 nF/ppm with a response of 1.4% for ethanol gas at room temperature with a very low gas concentration of 7 ppm, compared to 0.4% and 0.2% respectively for methanol and acetone vapors. The response and recovery times of the sensor are about 180 s. The superior activity of the sensor indicates possible industrial and commercial applications. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on the Science and Technology of Advanced Materials.
1. Introduction Need for chemical gas sensors is increasing as environmental pollution monitoring and control are becoming stringent worldwide. Nano-structured metal oxides are widely used as gas sensors to detect many pollutant gases [1–3]. All these sensors are resistive type sensors in which the conductivity of the sensing material changes as it adsorb gas vapors. Inter-digital transducers are now increasingly used in a variety of applications such as proximity sensors, bio-sensors, gas sensors, chemical sensors etc. The structural geometry of the IDC sensor and the sensitive layer over the IDC structure determines the sensitivity and selectivity for a particular gas [4]. CoFe2O4 nano-crystallites prepared by hydrothermal method, coated over Al2O3 tubes, has been reported to sense ethanol and triethylamine at 150 °C and 190 °C respectively. This is a resistive sensor which detect a gas concentration of the order of 10 ppm [5]. Nano-crystalline CuO–CuFe2O4 composite thin films developed from CuFeO2 ceramic target is used as resistive gas sensors for sensing ethanol and hydrogen gas in dry air. The operating temperature ranges from 250 °C to 500 °C and gas concentration
from 10 ppm to 500 ppm [6]. A new blended material, consists of multiwall carbon nanotubes, NaClO4 and polypyrrole (Ppy), was developed as a gas sensor to detect ethanol concentrations of 18,000–40,000 ppm at room temperature [7]. Wet chemically prepared magnesium zinc ferrite (MZFO) nano-particle based sensor is more sensitive to acetone than ethanol and can detect even 10 ppm of acetone and ethanol vapors at 350 °C [8]. The surfacemodified ZnFe2O4 nanoparticles exhibit the highest sensitivity (0.51 ppm 1), good selectivity with 168.2% (2.7 times) higher response toward ethanol compared to major interferents, fast response (sres = 50 s) and recovery (srec = 116 s) times [11]. Most of the ethanol sensors are sensitive at higher operating temperature and concentrations. The main objective of this work is to implement a capacitive gas sensor by combining the sensing properties of IDC structure and the ethanol gas sensing properties of CoFe2O4 nanocomposite at room temperature.
2. Experimental method 2.1. IDC sensor fabrication
⇑ Corresponding author at: Department of Instrumentation, Cochin University of Science & Technology, Cochin 682 022, India. E-mail address: [email protected] (J. Paul).
IDC sensor is fabricated on a FR4 glass epoxy board with digit width as well as separation between digits at 0.254 mm using
https://doi.org/10.1016/j.matpr.2019.12.247 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on the Science and Technology of Advanced Materials.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247
2
J. Paul, J. Philip / Materials Today: Proceedings xxx (xxxx) xxx
conventional printed circuit board (PCB) fabrication technology. CoFe2O4 nanocomposite were prepared by sol gel autocombustion method [10]. For the coating of gas sensing layer, PVA and deionized water in the mass ratio 1:10 was heated at 100 °C for 10 min and 0.1 ml of the resulting homogenous solution is mixed with 0.05 g of CoFe2O4 nanocomposite was coated over the IDC sensor followed by air drying overnight for strong bonding with IDC. The geometry of the structure is shown in Fig. 1. For capacitance measurement, two conducting leads are connected to the copper electrodes. The sensing area of the ethanol sensor is 645.16 mm2. 2.2. Gas sensing measurements For gas sensing measurements the IDC sensor was first inserted in to an indigenously made gas chamber of known volume and excited with an ac excitation of 1 V, with frequency of 1 MHz and capacitance of the sensor was measured in ambient air using an Impedance analyzer (Hioki make, IM 3570). Further measurements on the IDC sensor were carried out by inserting various gas vapors of known volumes, keeping the temperature at ambient condition (31 °C). For gas selectivity studies, different gases at the same concentration were admitted separately and the corresponding capacitance of the IDC sensor was measured using an Impedance analyzer (Hioki make, IM 3570). Further gas responses were done using the gas vapor with highest selectivity. Gas responses measurements were carried out with increasing ethanol concentrations. The response time as well as adsorption and desorption isotherms were conceded out in the same gas chamber at the same temperature. The reversibility of sensing activity was studied at different gas concentrations by moving the sensor from ambient air to gas chamber with gas and then back to ambient air. 3. Results and discussions It is of very substantial advantage to measure the concentration of a particular gas in a mixture of gases in ambient air. The selectivity of the present sensor for ethanol gas is 1.4%, whereas for methanol and acetone it is only 0.4% and 0.2% respectively, as shown in Fig. 2. The measurements have been carried out for a gas concentration of 7 ppm at a room temperature of 31 °C. The gas response of the sensor against different concentrations of ethanol at 31 °C and relative humidity (RH) 74% is depicted in Fig. 3. It indicates that the sensor is highly sensitive to ethanol gas at concentration as low as 7 ppm. Variation of sensor response increases with increase in gas concentration over a wide range. It can be noted that there is almost 1000% increase in the response of sensor for a change in gas concentration from 7 ppm to 100 ppm. Comparing IDC sensor gas responses with the resistive type of CoFe2O4 ethanol sensor, operating temperature, selectivity and minimum detectable gas concentration are superior [5]. The resulting sensitivity of the IDC sensor is remarkable as shown in Table 1. Resistive type of various ethanol gas sensors gives lower sensitivity especially at lower concentrations com-
Fig. 1. Geometry of the ethanol sensor. (a) Top view; (b) Side view.
Fig. 2. Selectivity of the sensor for various gas vapors at 7 ppm, 31 °C and RH 74%.
Fig. 3. Response of the sensor for different ethanol vapor concentrations at temperature 31 °C and RH 74%.
Table 1 Sensitivity of the sensor with various gas concentrations. Gas concentration (ppm)
Sensitivity (nF/ppm)
7 ppm 14 ppm 21 ppm 30 ppm 100 ppm
100 103.5714 138.0952 123.3333 48.8
pared to this capacitive type of sensor [6]. The gas response variation is about 1000% against 100% variation in the resistive type sensor [5,6,9]. The gas-sensing mechanism is based on changes in conductance of CoFe2O4. The oxygen adsorbed on the surface of the material influences the conductance of the CoFe2O4 sensing layer and hence the capacitance of the IDC sensor. The amount of oxygen on the surface of the material depends on the particle size, specific area, and operating temperature of the sensor [5]. The adsorption and desorption isotherms of the sensor at 31 °C, as shown in Fig. 4,
Fig. 4. Variations in sensor capacitance for the adsorption and desorption isotherms of ethanol gas at 7 ppm.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247
J. Paul, J. Philip / Materials Today: Proceedings xxx (xxxx) xxx
3
requirement of any sample heating element for the recovery of the gas sensor. Technical performance of this system, along with the low cost of production, points to potential commercialization of this sensor for ethanol gas. CRediT authorship contribution statement Jiss Paul: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing - original draft, Visualization. Jacob Philip: Supervision, Writing - review & editing. References
Fig. 5. Sensor capacitance transients for ethanol gas and air at 31 °C.
gives 0.3% error in the recovered capacitance of the sensor for an ethanol concentration of 7 ppm. Sensor capacitance transients for various concentrations of ethanol gas and ambient air are shown in Fig. 5. It gives a response and recovery times of about 180 sec. for different concentrations at room temperature. The percentage error in the recovered values are in the order of 1% for all concentrations. 4. Conclusions Nanocomposite of CoFe2O4 prepared by sol gel autocombustion method is coated on an IDC structure. Gas sensing properties are measured using impedimetric technique. The combination of IDC structure and CoFe2O4 sensitive layer provides a very good alternative gas sensor with high sensitivity, dynamic range and selectivity for ethanol gas even at very low gas concentration of 7 ppm. The response time of the sensor for adsorption and desorption is typically 180 sec., and hysteresis within 1%. All these results lead to the possible use of IDC structure with CoFe2O4 nanocomposite sensing layer as a capacitive sensor for very low ethanol concentrations at room temperature and also without the
[1] A.B. Gadkari, T.J. Shinde, P.N. Vasambekar, Ferrite gas sensors, IEEE Sens. J. 11 (4) (2010) 849–861. [2] E. Rossinyol, J. Arbiol, F. Peiró, A. Cornet, J.R. Morante, B. Tian, T. Bo, D. Zhao, Nanostructured metal oxides synthesized by hard template method for gas sensing applications, Sens. Actuators, B 109 (1) (2005) 57–63. [3] G. Eranna, Metal Oxide Nanostructures as Gas Sensing Devices, CRC Press, 2012. [4] A.V. Mamishev, K. Sundara-Rajan, F. Yang, Y. Du, M. Zahn, Interdigital sensors and transducers, Proc. IEEE 92 (5) (2004) 808–845. [5] C. Xiangfeng, J. Dongli, G. Yu, Z. Chenmou, Ethanol gas sensor based on CoFe2O4 nano-crystallites prepared by hydrothermal method, Sens. Actuators, B 120 (1) (2006) 177–181. [6] S. De, N. Venkataramani, S. Prasad, R.O. Dusane, L. Presmanes, Y. Thimont, P. Tailhades, V. Baco-Carles, C. Bonningue, S.T. Pisharam, A. Barnabe, Ethanol and hydrogen gas-sensing properties of CuO–CuFe2O4 nanostructured thin films, IEEE Sens. J. 18 (17) (2018) 6937–6945. [7] R.J. Wu, Y.C. Huang, M.R. Yu, T.H. Lin, S.L. Hung, Application of m-CNTs/NaClO4/ Ppy to a fast response, room working temperature ethanol sensor, Sens. Actuators, B 134 (1) (2008) 213–218. [8] M. Karmakar, P. Das, M. Pal, B. Mondal, S.B. Majumder, K. Mukherjee, Acetone and ethanol sensing characteristics of magnesium zinc ferrite nano-particulate chemi-resistive sensor, J. Mater. Sci. 49 (16) (2014) 5766–5771. [9] I. Singh, R.K. Bedi, Ethanol, acetone and ammonia gas room temperature operated sensor, in: AIP Conference Proceedings, AIP, 2013 June, Vol. 1536, No. 1, pp. 1175–1176. [10] M. Kurian, S. Thankachan, D.S. Nair, E.K. Aswathy, A. Babu, A. Thomas, K.T. Prabhath Kumar, Structural, magnetic, and acidic properties of cobalt ferrite nanocomposite synthesized by wet chemical methods, J. Adv. Ceram. 4 (3) (2015) 199–205. [11] R. Khurshid, F. Ali, A. Afzal, Z. Ali, M.T. Qureshi, Polyol-mediated coprecipitation and aminosilane grafting of superparamagnetic, spinel ZnFe2O4 nanoparticles for room-temperature ethanol sensors, J. Electrochem. Soc. 166 (4) (2019) B258–B265.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material Jiss Paul a,b,⇑, Jacob Philip a,c a
Department of Instrumentation, Cochin University of Science & Technology, Cochin 682 022, India Department of Electronics and Communication, Mar Athanasius College of Engineering, Kothamangalam 686666, India c Amal Jyothi College of Engineering, Kanjirappally, Kottayam 686518, India b
a r t i c l e
i n f o
Article history: Received 28 November 2019 Received in revised form 22 December 2019 Accepted 24 December 2019 Available online xxxx Keywords: Inter-digital capacitive sensor Polyvinyl alcohol (PVA) CoFe2O4 nanocomposite Ethanol Sensor Gas response
a b s t r a c t Sensor design for environmental pollution monitoring is a great challenge, as the selectivity and sensitivity of the sensor for a desired pollutant gas should be high enough to be detected at low concentrations. This work presents an ethanol gas sensor using inter-digital capacitive (IDC) structure coated with Cobalt ferrite (CoFe2O4) nanocomposite as gas sensing material. CoFe2O4 nanocomposite are prepared by sol gel auto-combustion method. Gas sensing properties of the IDC structure are investigated under various gas concentrations. The sensor exhibits high sensitivity of the order of 100 nF/ppm with a response of 1.4% for ethanol gas at room temperature with a very low gas concentration of 7 ppm, compared to 0.4% and 0.2% respectively for methanol and acetone vapors. The response and recovery times of the sensor are about 180 s. The superior activity of the sensor indicates possible industrial and commercial applications. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on the Science and Technology of Advanced Materials.
1. Introduction Need for chemical gas sensors is increasing as environmental pollution monitoring and control are becoming stringent worldwide. Nano-structured metal oxides are widely used as gas sensors to detect many pollutant gases [1–3]. All these sensors are resistive type sensors in which the conductivity of the sensing material changes as it adsorb gas vapors. Inter-digital transducers are now increasingly used in a variety of applications such as proximity sensors, bio-sensors, gas sensors, chemical sensors etc. The structural geometry of the IDC sensor and the sensitive layer over the IDC structure determines the sensitivity and selectivity for a particular gas [4]. CoFe2O4 nano-crystallites prepared by hydrothermal method, coated over Al2O3 tubes, has been reported to sense ethanol and triethylamine at 150 °C and 190 °C respectively. This is a resistive sensor which detect a gas concentration of the order of 10 ppm [5]. Nano-crystalline CuO–CuFe2O4 composite thin films developed from CuFeO2 ceramic target is used as resistive gas sensors for sensing ethanol and hydrogen gas in dry air. The operating temperature ranges from 250 °C to 500 °C and gas concentration
from 10 ppm to 500 ppm [6]. A new blended material, consists of multiwall carbon nanotubes, NaClO4 and polypyrrole (Ppy), was developed as a gas sensor to detect ethanol concentrations of 18,000–40,000 ppm at room temperature [7]. Wet chemically prepared magnesium zinc ferrite (MZFO) nano-particle based sensor is more sensitive to acetone than ethanol and can detect even 10 ppm of acetone and ethanol vapors at 350 °C [8]. The surfacemodified ZnFe2O4 nanoparticles exhibit the highest sensitivity (0.51 ppm 1), good selectivity with 168.2% (2.7 times) higher response toward ethanol compared to major interferents, fast response (sres = 50 s) and recovery (srec = 116 s) times [11]. Most of the ethanol sensors are sensitive at higher operating temperature and concentrations. The main objective of this work is to implement a capacitive gas sensor by combining the sensing properties of IDC structure and the ethanol gas sensing properties of CoFe2O4 nanocomposite at room temperature.
2. Experimental method 2.1. IDC sensor fabrication
⇑ Corresponding author at: Department of Instrumentation, Cochin University of Science & Technology, Cochin 682 022, India. E-mail address: [email protected] (J. Paul).
IDC sensor is fabricated on a FR4 glass epoxy board with digit width as well as separation between digits at 0.254 mm using
https://doi.org/10.1016/j.matpr.2019.12.247 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on the Science and Technology of Advanced Materials.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247
2
J. Paul, J. Philip / Materials Today: Proceedings xxx (xxxx) xxx
conventional printed circuit board (PCB) fabrication technology. CoFe2O4 nanocomposite were prepared by sol gel autocombustion method [10]. For the coating of gas sensing layer, PVA and deionized water in the mass ratio 1:10 was heated at 100 °C for 10 min and 0.1 ml of the resulting homogenous solution is mixed with 0.05 g of CoFe2O4 nanocomposite was coated over the IDC sensor followed by air drying overnight for strong bonding with IDC. The geometry of the structure is shown in Fig. 1. For capacitance measurement, two conducting leads are connected to the copper electrodes. The sensing area of the ethanol sensor is 645.16 mm2. 2.2. Gas sensing measurements For gas sensing measurements the IDC sensor was first inserted in to an indigenously made gas chamber of known volume and excited with an ac excitation of 1 V, with frequency of 1 MHz and capacitance of the sensor was measured in ambient air using an Impedance analyzer (Hioki make, IM 3570). Further measurements on the IDC sensor were carried out by inserting various gas vapors of known volumes, keeping the temperature at ambient condition (31 °C). For gas selectivity studies, different gases at the same concentration were admitted separately and the corresponding capacitance of the IDC sensor was measured using an Impedance analyzer (Hioki make, IM 3570). Further gas responses were done using the gas vapor with highest selectivity. Gas responses measurements were carried out with increasing ethanol concentrations. The response time as well as adsorption and desorption isotherms were conceded out in the same gas chamber at the same temperature. The reversibility of sensing activity was studied at different gas concentrations by moving the sensor from ambient air to gas chamber with gas and then back to ambient air. 3. Results and discussions It is of very substantial advantage to measure the concentration of a particular gas in a mixture of gases in ambient air. The selectivity of the present sensor for ethanol gas is 1.4%, whereas for methanol and acetone it is only 0.4% and 0.2% respectively, as shown in Fig. 2. The measurements have been carried out for a gas concentration of 7 ppm at a room temperature of 31 °C. The gas response of the sensor against different concentrations of ethanol at 31 °C and relative humidity (RH) 74% is depicted in Fig. 3. It indicates that the sensor is highly sensitive to ethanol gas at concentration as low as 7 ppm. Variation of sensor response increases with increase in gas concentration over a wide range. It can be noted that there is almost 1000% increase in the response of sensor for a change in gas concentration from 7 ppm to 100 ppm. Comparing IDC sensor gas responses with the resistive type of CoFe2O4 ethanol sensor, operating temperature, selectivity and minimum detectable gas concentration are superior [5]. The resulting sensitivity of the IDC sensor is remarkable as shown in Table 1. Resistive type of various ethanol gas sensors gives lower sensitivity especially at lower concentrations com-
Fig. 1. Geometry of the ethanol sensor. (a) Top view; (b) Side view.
Fig. 2. Selectivity of the sensor for various gas vapors at 7 ppm, 31 °C and RH 74%.
Fig. 3. Response of the sensor for different ethanol vapor concentrations at temperature 31 °C and RH 74%.
Table 1 Sensitivity of the sensor with various gas concentrations. Gas concentration (ppm)
Sensitivity (nF/ppm)
7 ppm 14 ppm 21 ppm 30 ppm 100 ppm
100 103.5714 138.0952 123.3333 48.8
pared to this capacitive type of sensor [6]. The gas response variation is about 1000% against 100% variation in the resistive type sensor [5,6,9]. The gas-sensing mechanism is based on changes in conductance of CoFe2O4. The oxygen adsorbed on the surface of the material influences the conductance of the CoFe2O4 sensing layer and hence the capacitance of the IDC sensor. The amount of oxygen on the surface of the material depends on the particle size, specific area, and operating temperature of the sensor [5]. The adsorption and desorption isotherms of the sensor at 31 °C, as shown in Fig. 4,
Fig. 4. Variations in sensor capacitance for the adsorption and desorption isotherms of ethanol gas at 7 ppm.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247
J. Paul, J. Philip / Materials Today: Proceedings xxx (xxxx) xxx
3
requirement of any sample heating element for the recovery of the gas sensor. Technical performance of this system, along with the low cost of production, points to potential commercialization of this sensor for ethanol gas. CRediT authorship contribution statement Jiss Paul: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing - original draft, Visualization. Jacob Philip: Supervision, Writing - review & editing. References
Fig. 5. Sensor capacitance transients for ethanol gas and air at 31 °C.
gives 0.3% error in the recovered capacitance of the sensor for an ethanol concentration of 7 ppm. Sensor capacitance transients for various concentrations of ethanol gas and ambient air are shown in Fig. 5. It gives a response and recovery times of about 180 sec. for different concentrations at room temperature. The percentage error in the recovered values are in the order of 1% for all concentrations. 4. Conclusions Nanocomposite of CoFe2O4 prepared by sol gel autocombustion method is coated on an IDC structure. Gas sensing properties are measured using impedimetric technique. The combination of IDC structure and CoFe2O4 sensitive layer provides a very good alternative gas sensor with high sensitivity, dynamic range and selectivity for ethanol gas even at very low gas concentration of 7 ppm. The response time of the sensor for adsorption and desorption is typically 180 sec., and hysteresis within 1%. All these results lead to the possible use of IDC structure with CoFe2O4 nanocomposite sensing layer as a capacitive sensor for very low ethanol concentrations at room temperature and also without the
[1] A.B. Gadkari, T.J. Shinde, P.N. Vasambekar, Ferrite gas sensors, IEEE Sens. J. 11 (4) (2010) 849–861. [2] E. Rossinyol, J. Arbiol, F. Peiró, A. Cornet, J.R. Morante, B. Tian, T. Bo, D. Zhao, Nanostructured metal oxides synthesized by hard template method for gas sensing applications, Sens. Actuators, B 109 (1) (2005) 57–63. [3] G. Eranna, Metal Oxide Nanostructures as Gas Sensing Devices, CRC Press, 2012. [4] A.V. Mamishev, K. Sundara-Rajan, F. Yang, Y. Du, M. Zahn, Interdigital sensors and transducers, Proc. IEEE 92 (5) (2004) 808–845. [5] C. Xiangfeng, J. Dongli, G. Yu, Z. Chenmou, Ethanol gas sensor based on CoFe2O4 nano-crystallites prepared by hydrothermal method, Sens. Actuators, B 120 (1) (2006) 177–181. [6] S. De, N. Venkataramani, S. Prasad, R.O. Dusane, L. Presmanes, Y. Thimont, P. Tailhades, V. Baco-Carles, C. Bonningue, S.T. Pisharam, A. Barnabe, Ethanol and hydrogen gas-sensing properties of CuO–CuFe2O4 nanostructured thin films, IEEE Sens. J. 18 (17) (2018) 6937–6945. [7] R.J. Wu, Y.C. Huang, M.R. Yu, T.H. Lin, S.L. Hung, Application of m-CNTs/NaClO4/ Ppy to a fast response, room working temperature ethanol sensor, Sens. Actuators, B 134 (1) (2008) 213–218. [8] M. Karmakar, P. Das, M. Pal, B. Mondal, S.B. Majumder, K. Mukherjee, Acetone and ethanol sensing characteristics of magnesium zinc ferrite nano-particulate chemi-resistive sensor, J. Mater. Sci. 49 (16) (2014) 5766–5771. [9] I. Singh, R.K. Bedi, Ethanol, acetone and ammonia gas room temperature operated sensor, in: AIP Conference Proceedings, AIP, 2013 June, Vol. 1536, No. 1, pp. 1175–1176. [10] M. Kurian, S. Thankachan, D.S. Nair, E.K. Aswathy, A. Babu, A. Thomas, K.T. Prabhath Kumar, Structural, magnetic, and acidic properties of cobalt ferrite nanocomposite synthesized by wet chemical methods, J. Adv. Ceram. 4 (3) (2015) 199–205. [11] R. Khurshid, F. Ali, A. Afzal, Z. Ali, M.T. Qureshi, Polyol-mediated coprecipitation and aminosilane grafting of superparamagnetic, spinel ZnFe2O4 nanoparticles for room-temperature ethanol sensors, J. Electrochem. Soc. 166 (4) (2019) B258–B265.
Please cite this article as: J. Paul and J. Philip, Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.247