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Humidity-sensing properties of LiCl-loaded 3D cubic mesoporous silica KIT-6 composites
Materials Letters 147 (2015) 54–57
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Humidity-sensing properties of LiCl-loaded 3D cubic mesoporous silica KIT-6 composites Hongran Zhao a, Sen Liu a, Rui Wang a,n, Tong Zhang a,b a b
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, PR China State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 26 August 2014 Accepted 31 January 2015 Available online 11 February 2015
Lithium chloride (LiCl)-loaded 3D cubic mesoporous silica KIT-6 (LiCl-KIT-6) composites were prepared as resistance-type humidity-sensitive materials. The structures of the resultant composites were characterized by X-ray diffraction, N2 adsorption–desorption, and transmission electron microscopy. The humidity sensors based on LiCl-KIT-6 composites were fabricated and the sensing properties were investigated. Results indicate the uniform pore distribution of KIT-6 contributes to the rapid hydrone transport in mesoporous channels. The impedance of optimized 3 wt% LiCl-KIT-6 sensor changed by more than three orders of magnitude over the relative humidity range of 11–95%. The response and recovery times of the sensor were 15 s and 28 s, respectively. Finally, the complex impedance method was used to analyze the humidity sensing mechanism of the sensor based on LiCl-KIT-6. & 2015 Elsevier B.V. All rights reserved.
Keywords: Humidity Sensor Three-dimensional cubic mesoporous silica Electronic materials
1. Introduction Humidity is an important physical parameter that is closely related to industrial production, environmental protection, and many other fields [1,2]. Along with scientific development, the demand for monitoring and detecting humidity has become increasingly strict in recent years. Different kinds of materials have been used to prepare humidity sensors, including ceramics [3,4], metal oxides [5–7], and polymers [8,9]. Humidity sensors based on ceramics or metal oxides exhibit good chemical and thermal stabilities; however, heating equipment is needed during the dehydration process. Meanwhile, humidity sensors based on polymers exhibit humidity-sensitive characteristic, but poor stability limits their applications. Mesoporous materials have attracted considerable attention because of their high pore volume, high specific surface, and uniform pore distribution [10,11]. Different kinds of mesoporous materials have been used as humidity-sensing materials [12–14]. In our previous works, lithium chloride (LiCl) was highly dispersed in the channels of mesoporous silica to overcome the problem of LiCl's deliquescing at high relative humidity (RH). Compared with mesoporous materials with 2D hexagonal pores, such as SBA-15, 3D mesoporous silica SBA-16 exhibits better humidity-sensitive characteristics [14].
n
Corresponding author. Tel.: þ 86 431 85168385; fax: þ 86 431 85168417. E-mail address: [email protected] (R. Wang).
http://dx.doi.org/10.1016/j.matlet.2015.01.154 0167-577X/& 2015 Elsevier B.V. All rights reserved.
KIT-6 is a mesoporous silica material with a 3D cubic Ia3d pore structure. Compared with the 3D cubic cage-like pore structure of SBA-16, the uniform pore distribution of the former is expected to be conducive to transporting hydrone in mesoporous channels. In the present study, the humidity-sensing properties of LiCl-KIT-6 composites were investigated, and a possible mechanism was also provided.
2. Experimental Prepariation of mesoporous silica KIT-6: Mesoporous silica KIT-6 was prepared according to a previous report [15]. In a typical synthesis, 2 g triblock copolymer P123 (EO20PO70EO20) was dissolved in a solution with 7 g HCl (36 wt%) and 60 g deionized water under stirring at room temperature. Then, 2 g n-butanol was added to the solution and after 1 h 4 g tetraethoxysilane was added. The mixture was heated at 35 1C and stirred for 24 h. The mixture was then treated in an autoclave at 140 1C for 24 h. The product was centrifuged at 11,000 rpm for 15 min, washed with deionized water, and dried at 60 1C. Finally, the product was calcined in air at 550 1C for 2 h to remove the surfactant, and pure mesoporous silica KIT-6 was obtained. Preparation of LiCl-KIT-6 composites: LiCl-KIT-6 composites were prepared through the following procedures. Different amounts of LiCl (0.005, 0.015, 0.025, 0.05, and 0.1 g) were dissolved in 10 mL deionized water under constant stirring at room temperature for 20 min. Then, 0.5 g KIT-6 was added to the solution and the
H. Zhao et al. / Materials Letters 147 (2015) 54–57
mixture was stirred for 30 min and dried at 60 1C. The products were denoted as LiCl-KIT-6 (X), where X represents the mass ratio of LiCl to KIT-6. Characterization: Powder X-ray diffraction (XRD) patterns were obtained with a Rigaku D/Max-2550 diffractometer with Cu Kα radiation (λ ¼ 1.5406 Å). The N2 adsorption–desorption isotherm measurements were performed on a Micromeritics ASAP 2010 volumetric adsorption analyzer at 77 K. The transmission electron microscopy (TEM) image was recorded on a Hitachi H-8100 IV operating at 200 kV. Humidity-sensitive properties were measured on a ZL-5 Intelligent LCR tester at room temperature. Saturated aqueous solutions of different salts in closed glass vessels were used to achieve different humidity environments. The humidity sensors were measured in different glass vessels with given relative humidity for 10 min, and within this time, the impedance could reach a stable value.
3. Results and discussion The small-angle XRD patterns of KIT-6 and LiCl-KIT-6 samples are shown in Fig. 1a. All samples exhibit a sharp intense peak at 2θ of 0.95 and another peak at 2θ of 1.10. The result shows d1/d2 ¼81/2/61/2 planes associated with the body-centered cubic Ia3d group of 3D mesoporous silica [16]. The peaks at 2θ of 0.95 and 2θ of 1.10 are attributed to the (211) and (220) planes, respectively. After loading LiCl, the intensity of the peaks is reduced with increasing LiCl amount. This result is attributed to the channels of KIT-6 being partly blocked by LiCl. Fig. 1b and c shows the N2 adsorption–desorption isotherm of KIT-6 and LiCl-KIT-6 (0.03), respectively. Both KIT-6 and LiCl-KIT-6
55
(0.03) exhibit type-IV isotherms with an H1 hysteresis loop, which indicates channel-like mesoporous silica with narrow pore size distribution [17]. The insets of Fig. 1b and c show that the average pore sizes of KIT-6 and LiCl-KIT-6 (0.03) are 10.9 nm and 10.7 nm, with the pore volumes of 1.50 cm3 g 1 and 1.38 cm3 g 1, respectively. Both KIT-6 and LiCl-KIT-6 (0.03) have a large BET surface area, i.e., 470.1 m2 g 1 and 464.7 m2 g 1, respectively. The decrease in pore size, pore volume, and BET surface area after LiCl loading further confirms that LiCl is successful loaded in the channels of KIT-6. Fig. 1d shows the representative TEM image of the LiCl-KIT-6 (0.03) sample, which reveals a well-ordered cubic 3D mesoporous pore structure. Pore size is approximately 10 nm based on the TEM image, which is similar to the result of the N2 adsorption– desorption isotherm. Fig. 2a shows the dependence of impedance on RH for sensors based on LiCl-KIT-6 composites (1 V, 100 Hz). The impedance of pure mesoporous silica KIT-6 did not decrease until RH increased to 75%. By contrast, adding LiCl leads to a distinct increase in RH sensitivity. The materials with 3% and 5% LiCl both exhibit great linearity. But when the amount of loaded LiCl rises to 5%, the composite shows lager humidity hysteresis (10% RH) and longer recovery time (64 s). So 3% was chosen as the optimal ratio. The humidity hysteresis curve of LiCl-KIT-6 (0.03) is shown in Fig. 2b. The maximum humidity hysteresis of this humidity sensor is 7% RH. Fig. 2c shows the temperature influence on the humidity sensing properties. The impedance of sensor decreased to the lower level, when the temperature increased. The average temperature coefficient in the range of 30–60 1C was 0.18% RH/1C. The response and recovery curves of LiCl-KIT-6 (0.03) are shown in Fig. 2d. Response and recovery times are defined as the time taken by a sensor to achieve 90% of the total impedance change in case of
Fig. 1. (a) Small-angle XRD patterns of KIT-6 and LiCl-KIT-6 (X) (X ¼0.01, 0.03, 0.05, 0.10, and 0.20), N2 adsorption–desorption isothermals of (b) KIT-6 and (c) LiCl-KIT-6 (0.03) (the insets show the pore size distribution), and (d) TEM image of LiCl-KIT-6 (0.03).
56
H. Zhao et al. / Materials Letters 147 (2015) 54–57
Fig. 2. (a) Humidity sensing properties of sensors based on KIT-6 and LiCl-KIT-6 (X) (X ¼ 0.01, 0.03, 0.05, 0.10, and 0.20), (b) hysteresis of sensor based on LiCl-KIT-6 (0.03), (c) impedance of LiCl-KIT-6 (0.03) sensor vs RH at different temperatures and (d) response and recovery characteristic of sensor based on LiCl-KIT-6 (0.03).
Fig. 3. The complex impedance plots of sensor based on LiCl-KIT-6 (0.03). The insets show the complex impedance plots of sensor based on KIT-6.
H. Zhao et al. / Materials Letters 147 (2015) 54–57
adsorption and desorption [18]. The response and recovery times are 15 s and 28 s, respectively. The recovery time of the LiCl-KIT-6 composite (28 s) is considerably shorter than that of the LiCl-SBA-16 composite (approximately 60 s) [14]. To analyze the humidity-sensing mechanism of LiCl-KIT-6, the complex impedances of LiCl-KIT-6 (0.03) and pure KIT-6 were studied, and their typical plots are shown in Fig. 3 with a frequency range from 20 Hz to 100 Hz. ReZ and ImZ are the real and imaginary parts of the complex impedance, respectively. KIT-6 nearly exhibits a non-conducting behavior before RH reaches an extremely high level. Fig. 3 indicates that a semicircle is observed at low RH. The curvature radius of the semicircle reduces when RH increases from 11% to 33%. In addition, a type of polarization leads to a “non-Debye” behavior within this humidity range [19]. The complex impedance plots can be modeled by an equivalent circuit of a parallel capacitor and resistor. The sensing mechanism at low RH is based on the conductivity of proton. An increasing amount of water molecules is adsorbed when RH increases. The semicircle shrinks and a straight line appears at low frequency. In this condition, few LiCl molecules dissolve in the adsorbed water and electrolytic conduction occurs with protonic transport during the conducting process. When RH becomes exceedingly high, the semicircle nearly disappears completely and only a straight line is left. During this time, one or several serial water layers are formed by physisorption. A significant amount of LiCl dissolves in liquid water, and the dissociated ions are transported freely in the water layers. Hence, whether the good humidity sensitivity of the composite is caused by adding LiCl can be proven by comparing complex impedance plots of LiCl-KIT-6 (0.03) and pure KIT-6. 4. Conclusion
material used in this study significantly affected the humidity properties of the composites. Therefore, LiCl-loaded mesoporous silica composites should be further investigated.
Acknowledgment This research work was financially supported by Innovative Research Team in University (Grant no. IRT13018), the Open Project from State Key Laboratory of Transducer Technology (Grant no. SKT1402), the Special Financial Grant from the China Postdoctoral Science Foundation (Grant no. 2014T70289), the General Financial Grant from the China Postdoctoral Science Foundation (Grant no. 2012M510878), the Natural Science Foundation Committee NSFC, (Grant no. 51102109), the Program for Science and Technology Development (No. 20110725), and Jilin Province Department of Education Science and Technology Project. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
A novel humidity sensor with excellent humidity-sensing properties was successfully constructed using LiCl-KIT-6 composite. Resistance-type humidity sensing properties and LiCl-loading amount were studied. Compared with other works in which LiClloaded mesoporous silica was used as a humidity sensor, the 3D pore structure and the uniform pore distribution of the host
57
[15] [16] [17] [18] [19]
Nitta T. Ind Eng Chem Prod Res Dev 1981;20:669–74. Chen C. Biosyst Eng 2004;88:231–41. Wang J, Yan WP, Zhang JC, Qiu FB, Zhang T. Mater Chem Phys 2001;69:288–91. Xia Y, He Y, Wang R, Feng J, Zhang T. Mater Lett 2012;88:43–6. Xu C, Miyazaki K. Sens Actuator B: Chem 1993;14:523–4. Sundaram R, Nagaraja K. Phys Status Solidi (a) 2004;201:529–35. Cosentino I, Muccillo E, Muccillo R. Mater Chem Phys 2007;103:407–14. Li Y, Yang M. Sens Actuators B: Chem 2002;86:155–9. Su P, Wang C. Sens Actuators B: Chem 2007;124:303–8. Wang L, Teng F, Lou Z, Zhang T. Appl Mater Interfaces 2011;3:4689–94. Nandhakumar I, Elliott J, Attard G. Chem Mater 2001;13:3840–2. Qi Q, Zhang T, Zheng X, Wan L. Sens Actuators B: Chem 2008;135:255–61. Geng W, Wang R, Li X, Zou Y, Zhang T, Tu J, et al. Sens Actuators B: Chem 2007;127:323–9. Tu J, Wang R, Geng W, Lai X, Zhang T, Li N, et al. Sens Actuators B: Chem 2009;136:392–8. Qian L, Ren Y, Liu T, Pan D, Wang H, Chen G. Chem Eng J 2012;213:186–94. Kleitz F, Choi S, Ryoo R. Chem Commun 2003:2136–7. Teng Y, Wu X, Zhou Q, Chena C, Zhao H, Lan M. Sens Actuators B: Chem 2009;142:267–72. Agarwal S, Sharma GL. Sens Actuators B: Chem 2002;85:205–11. Yeh YC, Tseng TY. J Mater Sci 1989;24:2739–45.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Humidity-sensing properties of LiCl-loaded 3D cubic mesoporous silica KIT-6 composites Hongran Zhao a, Sen Liu a, Rui Wang a,n, Tong Zhang a,b a b
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, PR China State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 26 August 2014 Accepted 31 January 2015 Available online 11 February 2015
Lithium chloride (LiCl)-loaded 3D cubic mesoporous silica KIT-6 (LiCl-KIT-6) composites were prepared as resistance-type humidity-sensitive materials. The structures of the resultant composites were characterized by X-ray diffraction, N2 adsorption–desorption, and transmission electron microscopy. The humidity sensors based on LiCl-KIT-6 composites were fabricated and the sensing properties were investigated. Results indicate the uniform pore distribution of KIT-6 contributes to the rapid hydrone transport in mesoporous channels. The impedance of optimized 3 wt% LiCl-KIT-6 sensor changed by more than three orders of magnitude over the relative humidity range of 11–95%. The response and recovery times of the sensor were 15 s and 28 s, respectively. Finally, the complex impedance method was used to analyze the humidity sensing mechanism of the sensor based on LiCl-KIT-6. & 2015 Elsevier B.V. All rights reserved.
Keywords: Humidity Sensor Three-dimensional cubic mesoporous silica Electronic materials
1. Introduction Humidity is an important physical parameter that is closely related to industrial production, environmental protection, and many other fields [1,2]. Along with scientific development, the demand for monitoring and detecting humidity has become increasingly strict in recent years. Different kinds of materials have been used to prepare humidity sensors, including ceramics [3,4], metal oxides [5–7], and polymers [8,9]. Humidity sensors based on ceramics or metal oxides exhibit good chemical and thermal stabilities; however, heating equipment is needed during the dehydration process. Meanwhile, humidity sensors based on polymers exhibit humidity-sensitive characteristic, but poor stability limits their applications. Mesoporous materials have attracted considerable attention because of their high pore volume, high specific surface, and uniform pore distribution [10,11]. Different kinds of mesoporous materials have been used as humidity-sensing materials [12–14]. In our previous works, lithium chloride (LiCl) was highly dispersed in the channels of mesoporous silica to overcome the problem of LiCl's deliquescing at high relative humidity (RH). Compared with mesoporous materials with 2D hexagonal pores, such as SBA-15, 3D mesoporous silica SBA-16 exhibits better humidity-sensitive characteristics [14].
n
Corresponding author. Tel.: þ 86 431 85168385; fax: þ 86 431 85168417. E-mail address: [email protected] (R. Wang).
http://dx.doi.org/10.1016/j.matlet.2015.01.154 0167-577X/& 2015 Elsevier B.V. All rights reserved.
KIT-6 is a mesoporous silica material with a 3D cubic Ia3d pore structure. Compared with the 3D cubic cage-like pore structure of SBA-16, the uniform pore distribution of the former is expected to be conducive to transporting hydrone in mesoporous channels. In the present study, the humidity-sensing properties of LiCl-KIT-6 composites were investigated, and a possible mechanism was also provided.
2. Experimental Prepariation of mesoporous silica KIT-6: Mesoporous silica KIT-6 was prepared according to a previous report [15]. In a typical synthesis, 2 g triblock copolymer P123 (EO20PO70EO20) was dissolved in a solution with 7 g HCl (36 wt%) and 60 g deionized water under stirring at room temperature. Then, 2 g n-butanol was added to the solution and after 1 h 4 g tetraethoxysilane was added. The mixture was heated at 35 1C and stirred for 24 h. The mixture was then treated in an autoclave at 140 1C for 24 h. The product was centrifuged at 11,000 rpm for 15 min, washed with deionized water, and dried at 60 1C. Finally, the product was calcined in air at 550 1C for 2 h to remove the surfactant, and pure mesoporous silica KIT-6 was obtained. Preparation of LiCl-KIT-6 composites: LiCl-KIT-6 composites were prepared through the following procedures. Different amounts of LiCl (0.005, 0.015, 0.025, 0.05, and 0.1 g) were dissolved in 10 mL deionized water under constant stirring at room temperature for 20 min. Then, 0.5 g KIT-6 was added to the solution and the
H. Zhao et al. / Materials Letters 147 (2015) 54–57
mixture was stirred for 30 min and dried at 60 1C. The products were denoted as LiCl-KIT-6 (X), where X represents the mass ratio of LiCl to KIT-6. Characterization: Powder X-ray diffraction (XRD) patterns were obtained with a Rigaku D/Max-2550 diffractometer with Cu Kα radiation (λ ¼ 1.5406 Å). The N2 adsorption–desorption isotherm measurements were performed on a Micromeritics ASAP 2010 volumetric adsorption analyzer at 77 K. The transmission electron microscopy (TEM) image was recorded on a Hitachi H-8100 IV operating at 200 kV. Humidity-sensitive properties were measured on a ZL-5 Intelligent LCR tester at room temperature. Saturated aqueous solutions of different salts in closed glass vessels were used to achieve different humidity environments. The humidity sensors were measured in different glass vessels with given relative humidity for 10 min, and within this time, the impedance could reach a stable value.
3. Results and discussion The small-angle XRD patterns of KIT-6 and LiCl-KIT-6 samples are shown in Fig. 1a. All samples exhibit a sharp intense peak at 2θ of 0.95 and another peak at 2θ of 1.10. The result shows d1/d2 ¼81/2/61/2 planes associated with the body-centered cubic Ia3d group of 3D mesoporous silica [16]. The peaks at 2θ of 0.95 and 2θ of 1.10 are attributed to the (211) and (220) planes, respectively. After loading LiCl, the intensity of the peaks is reduced with increasing LiCl amount. This result is attributed to the channels of KIT-6 being partly blocked by LiCl. Fig. 1b and c shows the N2 adsorption–desorption isotherm of KIT-6 and LiCl-KIT-6 (0.03), respectively. Both KIT-6 and LiCl-KIT-6
55
(0.03) exhibit type-IV isotherms with an H1 hysteresis loop, which indicates channel-like mesoporous silica with narrow pore size distribution [17]. The insets of Fig. 1b and c show that the average pore sizes of KIT-6 and LiCl-KIT-6 (0.03) are 10.9 nm and 10.7 nm, with the pore volumes of 1.50 cm3 g 1 and 1.38 cm3 g 1, respectively. Both KIT-6 and LiCl-KIT-6 (0.03) have a large BET surface area, i.e., 470.1 m2 g 1 and 464.7 m2 g 1, respectively. The decrease in pore size, pore volume, and BET surface area after LiCl loading further confirms that LiCl is successful loaded in the channels of KIT-6. Fig. 1d shows the representative TEM image of the LiCl-KIT-6 (0.03) sample, which reveals a well-ordered cubic 3D mesoporous pore structure. Pore size is approximately 10 nm based on the TEM image, which is similar to the result of the N2 adsorption– desorption isotherm. Fig. 2a shows the dependence of impedance on RH for sensors based on LiCl-KIT-6 composites (1 V, 100 Hz). The impedance of pure mesoporous silica KIT-6 did not decrease until RH increased to 75%. By contrast, adding LiCl leads to a distinct increase in RH sensitivity. The materials with 3% and 5% LiCl both exhibit great linearity. But when the amount of loaded LiCl rises to 5%, the composite shows lager humidity hysteresis (10% RH) and longer recovery time (64 s). So 3% was chosen as the optimal ratio. The humidity hysteresis curve of LiCl-KIT-6 (0.03) is shown in Fig. 2b. The maximum humidity hysteresis of this humidity sensor is 7% RH. Fig. 2c shows the temperature influence on the humidity sensing properties. The impedance of sensor decreased to the lower level, when the temperature increased. The average temperature coefficient in the range of 30–60 1C was 0.18% RH/1C. The response and recovery curves of LiCl-KIT-6 (0.03) are shown in Fig. 2d. Response and recovery times are defined as the time taken by a sensor to achieve 90% of the total impedance change in case of
Fig. 1. (a) Small-angle XRD patterns of KIT-6 and LiCl-KIT-6 (X) (X ¼0.01, 0.03, 0.05, 0.10, and 0.20), N2 adsorption–desorption isothermals of (b) KIT-6 and (c) LiCl-KIT-6 (0.03) (the insets show the pore size distribution), and (d) TEM image of LiCl-KIT-6 (0.03).
56
H. Zhao et al. / Materials Letters 147 (2015) 54–57
Fig. 2. (a) Humidity sensing properties of sensors based on KIT-6 and LiCl-KIT-6 (X) (X ¼ 0.01, 0.03, 0.05, 0.10, and 0.20), (b) hysteresis of sensor based on LiCl-KIT-6 (0.03), (c) impedance of LiCl-KIT-6 (0.03) sensor vs RH at different temperatures and (d) response and recovery characteristic of sensor based on LiCl-KIT-6 (0.03).
Fig. 3. The complex impedance plots of sensor based on LiCl-KIT-6 (0.03). The insets show the complex impedance plots of sensor based on KIT-6.
H. Zhao et al. / Materials Letters 147 (2015) 54–57
adsorption and desorption [18]. The response and recovery times are 15 s and 28 s, respectively. The recovery time of the LiCl-KIT-6 composite (28 s) is considerably shorter than that of the LiCl-SBA-16 composite (approximately 60 s) [14]. To analyze the humidity-sensing mechanism of LiCl-KIT-6, the complex impedances of LiCl-KIT-6 (0.03) and pure KIT-6 were studied, and their typical plots are shown in Fig. 3 with a frequency range from 20 Hz to 100 Hz. ReZ and ImZ are the real and imaginary parts of the complex impedance, respectively. KIT-6 nearly exhibits a non-conducting behavior before RH reaches an extremely high level. Fig. 3 indicates that a semicircle is observed at low RH. The curvature radius of the semicircle reduces when RH increases from 11% to 33%. In addition, a type of polarization leads to a “non-Debye” behavior within this humidity range [19]. The complex impedance plots can be modeled by an equivalent circuit of a parallel capacitor and resistor. The sensing mechanism at low RH is based on the conductivity of proton. An increasing amount of water molecules is adsorbed when RH increases. The semicircle shrinks and a straight line appears at low frequency. In this condition, few LiCl molecules dissolve in the adsorbed water and electrolytic conduction occurs with protonic transport during the conducting process. When RH becomes exceedingly high, the semicircle nearly disappears completely and only a straight line is left. During this time, one or several serial water layers are formed by physisorption. A significant amount of LiCl dissolves in liquid water, and the dissociated ions are transported freely in the water layers. Hence, whether the good humidity sensitivity of the composite is caused by adding LiCl can be proven by comparing complex impedance plots of LiCl-KIT-6 (0.03) and pure KIT-6. 4. Conclusion
material used in this study significantly affected the humidity properties of the composites. Therefore, LiCl-loaded mesoporous silica composites should be further investigated.
Acknowledgment This research work was financially supported by Innovative Research Team in University (Grant no. IRT13018), the Open Project from State Key Laboratory of Transducer Technology (Grant no. SKT1402), the Special Financial Grant from the China Postdoctoral Science Foundation (Grant no. 2014T70289), the General Financial Grant from the China Postdoctoral Science Foundation (Grant no. 2012M510878), the Natural Science Foundation Committee NSFC, (Grant no. 51102109), the Program for Science and Technology Development (No. 20110725), and Jilin Province Department of Education Science and Technology Project. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
A novel humidity sensor with excellent humidity-sensing properties was successfully constructed using LiCl-KIT-6 composite. Resistance-type humidity sensing properties and LiCl-loading amount were studied. Compared with other works in which LiClloaded mesoporous silica was used as a humidity sensor, the 3D pore structure and the uniform pore distribution of the host
57
[15] [16] [17] [18] [19]
Nitta T. Ind Eng Chem Prod Res Dev 1981;20:669–74. Chen C. Biosyst Eng 2004;88:231–41. Wang J, Yan WP, Zhang JC, Qiu FB, Zhang T. Mater Chem Phys 2001;69:288–91. Xia Y, He Y, Wang R, Feng J, Zhang T. Mater Lett 2012;88:43–6. Xu C, Miyazaki K. Sens Actuator B: Chem 1993;14:523–4. Sundaram R, Nagaraja K. Phys Status Solidi (a) 2004;201:529–35. Cosentino I, Muccillo E, Muccillo R. Mater Chem Phys 2007;103:407–14. Li Y, Yang M. Sens Actuators B: Chem 2002;86:155–9. Su P, Wang C. Sens Actuators B: Chem 2007;124:303–8. Wang L, Teng F, Lou Z, Zhang T. Appl Mater Interfaces 2011;3:4689–94. Nandhakumar I, Elliott J, Attard G. Chem Mater 2001;13:3840–2. Qi Q, Zhang T, Zheng X, Wan L. Sens Actuators B: Chem 2008;135:255–61. Geng W, Wang R, Li X, Zou Y, Zhang T, Tu J, et al. Sens Actuators B: Chem 2007;127:323–9. Tu J, Wang R, Geng W, Lai X, Zhang T, Li N, et al. Sens Actuators B: Chem 2009;136:392–8. Qian L, Ren Y, Liu T, Pan D, Wang H, Chen G. Chem Eng J 2012;213:186–94. Kleitz F, Choi S, Ryoo R. Chem Commun 2003:2136–7. Teng Y, Wu X, Zhou Q, Chena C, Zhao H, Lan M. Sens Actuators B: Chem 2009;142:267–72. Agarwal S, Sharma GL. Sens Actuators B: Chem 2002;85:205–11. Yeh YC, Tseng TY. J Mater Sci 1989;24:2739–45.