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Janus Mesostructures for Simultaneous Multivariable Gases Sensors
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Janus Mesostructures for Simultaneous Multivariable Gases Sensors Jin-Long Wang1 and Shu-Hong Yu1,* Conventional mesoporous materials-based transducers generally possess symmetrical geometries and are unable to easily distinguish two or more components in mixtures and reject the interferences. In this issue, Zhao et al. develop Janus mesostructures to realize a simultaneous multivariable gases sensor using solvent evaporation-induced self-assembly (EISA) with subsequent surface modifications. To date, gas sensors are becoming one of the most representative techniques in monitoring of health care, chemical synthesis, environmental safety, and industrial process.1–3 The key challenges for gas sensors are their sensitivity and selectivity, which are highly dependent on the high surface-to-volume ratio of the sensors and interaction between sensors and gases. Mesoporous materials with high surface areas or uniform channels have been widely applied in realizing gas sensors with much higher performance.4,5 However, the present sensors based on the mesoporous structure are mostly limited in detecting specific single gases, which is far from being desired for the increasing requirement for sensing platforms. As a result, the design of mesoporous materials-based sensors with multiple sensitivity for various gases in one unit is critical to overcome the limitation of existing sensors. Intensive efforts have been paid in fabrication of multivariable sensors, including nonresonant and resonantimpedance sensors, electromechanical resonant sensors, field-effect transistor sensors, photonic resonant sensors, and so on.6 It was exciting that recently the group led by Dongyuan Zhao at Fudan University, China, has demon-
strated an outstanding sensor device for simultaneously detection of multiple gases based on the Janus mesoporous carbon/silica films with asymmetric mesostructures and disparate active sites (–NH2 and –COOH groups).7 These Janus mesoporous sensor devices exhibited very excellent performances in detection of H2S and NH3, including distinct ultrafast response times (2 s for H2S, 10 s for NH3), ultralow limits of detection (0.01 ppm for H2S, 0.1 ppm for NH3), superior stability, and high selectivity. A facile solvent evaporation-induced self-assembly (EISA) method and subsequent surface modifications (Figure 1A) were applied to prepare the highly ordered mesostructured and uniform films (Figure 1B). Briefly, the mesostructured silica layer was formed (step 1), and then the mesostructured carbon layer was further coated on the silica layer to form asymmetric Janus structures (step 2). After a thermal treatment in an inert atmosphere, ordered mesoporous carbon/silica Janus structures that modified with –COOH groups on the surface of the mesoporous carbon layer could be formed (step 3). PMMA was coated on the mesoporous carbon layer to protect the -COOH groups during amino modification (step 4), during which the (3-aminopropyl) triethoxysi-
1110 Matter 1, 1104–1118, November 6, 2019 ª 2019 Published by Elsevier Inc.
lane (APTES) was used to modify the silica mesopore walls with –NH2 groups (step 5). According to the nitrogen adsorption isotherms, the Brunauer-Emmett-Teller (BET) surface area and pore volume of the Janus thin film reach 497 m2$g 1 and 0.47 cm3$g 1, with mesopores centered at 24.0 (top mesoporous carbon layer) and 6.5 nm (silica layer). This mesopore distribution provides a large accessible surface area and sufficient exposed active sites for ultrafast gas diffusion and unimpeded contact with gas molecules. The results of Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS) and high-resolution N1s spectrum demonstrate that the -NH2 groups are successfully grafted on the surface of the silica mesopore walls with -COOH groups remaining on the top layer of mesoporous carbon. They used this asymmetric architecture with independent –NH2 and –COOH sites as platform to detect multiple gases by the mass-sensitive sensing mode at room temperature (Figure 1C). The results (Figure 1D) show that the response time and corresponding frequency shifts of the device are 2 s (10 s) and 171 Hz ( 49 Hz) when exposed to pure H2S (NH3). Notably, when exposed to mixed H2S and NH3, the device shows a fast frequency decrease in first 2 s and a moderate drop in next 8 s with frequency shifts of 183 Hz and 38 Hz, demonstrating that no cross-responses are involved in the Janus mesoporous sensor during simultaneous H2S and NH3 sensing process. When the sensor device was fabricated with the symmetric film that
1Department
of Chemistry, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, China *Correspondence: [email protected] https://doi.org/10.1016/j.matt.2019.10.009
Figure 1. Fabrication of Janus Mesoporous Sensor Device and Its Sensing Performance (A) Schematic illustration of the process for preparation of Janus mesoporous carbon/silica thin film device via the successive solvent evaporationinduced self-assembly approach and selective surface functionalization strategy. (B) Cross-section field emission scanning electron microscope (FESEM) image of the Janus mesoporous carbon/silica thin film. Scale bar, 100 nm. (C) Schematic illustration of the gas sensor device based on the Janus mesoporous carbon/silica thin films with independent –NH 2 and –COOH groups. (D) Response and recovery curves of the Janus mesoporous carbon/silica thin film (orange)-, mesoporous silica thin film (green)-, and mesoporous carbon thin film (blue)-based sensors to 20 ppm of NH 3 , 20 ppm of H2 S, and mixed gases of NH3 (20 ppm) and H 2 S (20 ppm).
the COOH groups are obscured after NH2 functionalization, the frequency shift of this device to H2S is about 325 Hz and no response to NH3, suggesting the necessity of Janus architecture for multiple sensing outputs simultaneously. Furthermore, theoretical calculations based on the Langmuir adsorption model, the following derived equation, and the kinetic Monte Carlos revealed that the different free energy between NH3 and H2S to the Janus mesoporous carbon/silica led to the different response times. Thus, both the experimental and theoretical results indicate that this designed unique Janus
mesoporous architecture is a promising candidate for the next generation of multivariable sensors for multiple gas sensing, which are highly demanded in chemical industries, environmental monitoring, and other related fields. 1. Mao, S., Chang, J., Pu, H., Lu, G., He, Q., Zhang, H., and Chen, J. (2017). Twodimensional nanomaterial-based field-effect transistors for chemical and biological sensing. Chem. Soc. Rev. 46, 6872–6904. 2. Tchalala, M.R., Bhatt, P.M., Chappanda, K.N., Tavares, S.R., Adil, K., Belmabkhout, Y., et al. (2019). Fluorinated MOF platform for selective removal and sensing of SO2 from flue gas and air. Nat. Comm. 10, 1328. 3. Zhu, Y., Zhao, Y., Ma, J., Cheng, X., Xie, J., Xu, P., Liu, H., Liu, H., Zhang, H., Wu, M., et al. (2017). Mesoporous Tungsten Oxides with Crystalline Framework for Highly Sensitive and
Selective Detection of Foodborne Pathogens. J. Am. Chem. Soc. 139, 10365–10373. 4. Lakhi, K.S., Park, D.H., Al-Bahily, K., Cha, W., Viswanathan, B., Choy, J.H., and Vinu, A. (2017). Mesoporous carbon nitrides: synthesis, functionalization, and applications. Chem. Soc. Rev. 46, 72–101. 5. Li, Y., Luo, W., Qin, N., Dong, J., Wei, J., Li, W., et al. (2014). Highly Ordered Mesoporous Tungsten Oxides with a Large Pore Size and Crystalline Framework for H2S Sensing. Angew. Chem. Int. Ed. 53, 9035–9040. 6. Potyrailo, R.A. (2016). Multivariable Sensors for Ubiquitous Monitoring of Gases in the Era of Internet of Things and Industrial Internet. Chem. Rev. 116, 11877–11923. 7. Wang, R., Lan, K., Chen, Z., Zhang, X., Hung, C.-T., Zhang, W., Wang, C., Wang, S., Chen, A., Li, W., et al. (2019). Janus Mesoporous Sensor Devices for Simultaneous Multivariable Gases Detection. Matter 1, this issue, 1274– 1284.
Matter 1, 1104–1118, November 6, 2019 1111
Janus Mesostructures for Simultaneous Multivariable Gases Sensors Jin-Long Wang1 and Shu-Hong Yu1,* Conventional mesoporous materials-based transducers generally possess symmetrical geometries and are unable to easily distinguish two or more components in mixtures and reject the interferences. In this issue, Zhao et al. develop Janus mesostructures to realize a simultaneous multivariable gases sensor using solvent evaporation-induced self-assembly (EISA) with subsequent surface modifications. To date, gas sensors are becoming one of the most representative techniques in monitoring of health care, chemical synthesis, environmental safety, and industrial process.1–3 The key challenges for gas sensors are their sensitivity and selectivity, which are highly dependent on the high surface-to-volume ratio of the sensors and interaction between sensors and gases. Mesoporous materials with high surface areas or uniform channels have been widely applied in realizing gas sensors with much higher performance.4,5 However, the present sensors based on the mesoporous structure are mostly limited in detecting specific single gases, which is far from being desired for the increasing requirement for sensing platforms. As a result, the design of mesoporous materials-based sensors with multiple sensitivity for various gases in one unit is critical to overcome the limitation of existing sensors. Intensive efforts have been paid in fabrication of multivariable sensors, including nonresonant and resonantimpedance sensors, electromechanical resonant sensors, field-effect transistor sensors, photonic resonant sensors, and so on.6 It was exciting that recently the group led by Dongyuan Zhao at Fudan University, China, has demon-
strated an outstanding sensor device for simultaneously detection of multiple gases based on the Janus mesoporous carbon/silica films with asymmetric mesostructures and disparate active sites (–NH2 and –COOH groups).7 These Janus mesoporous sensor devices exhibited very excellent performances in detection of H2S and NH3, including distinct ultrafast response times (2 s for H2S, 10 s for NH3), ultralow limits of detection (0.01 ppm for H2S, 0.1 ppm for NH3), superior stability, and high selectivity. A facile solvent evaporation-induced self-assembly (EISA) method and subsequent surface modifications (Figure 1A) were applied to prepare the highly ordered mesostructured and uniform films (Figure 1B). Briefly, the mesostructured silica layer was formed (step 1), and then the mesostructured carbon layer was further coated on the silica layer to form asymmetric Janus structures (step 2). After a thermal treatment in an inert atmosphere, ordered mesoporous carbon/silica Janus structures that modified with –COOH groups on the surface of the mesoporous carbon layer could be formed (step 3). PMMA was coated on the mesoporous carbon layer to protect the -COOH groups during amino modification (step 4), during which the (3-aminopropyl) triethoxysi-
1110 Matter 1, 1104–1118, November 6, 2019 ª 2019 Published by Elsevier Inc.
lane (APTES) was used to modify the silica mesopore walls with –NH2 groups (step 5). According to the nitrogen adsorption isotherms, the Brunauer-Emmett-Teller (BET) surface area and pore volume of the Janus thin film reach 497 m2$g 1 and 0.47 cm3$g 1, with mesopores centered at 24.0 (top mesoporous carbon layer) and 6.5 nm (silica layer). This mesopore distribution provides a large accessible surface area and sufficient exposed active sites for ultrafast gas diffusion and unimpeded contact with gas molecules. The results of Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS) and high-resolution N1s spectrum demonstrate that the -NH2 groups are successfully grafted on the surface of the silica mesopore walls with -COOH groups remaining on the top layer of mesoporous carbon. They used this asymmetric architecture with independent –NH2 and –COOH sites as platform to detect multiple gases by the mass-sensitive sensing mode at room temperature (Figure 1C). The results (Figure 1D) show that the response time and corresponding frequency shifts of the device are 2 s (10 s) and 171 Hz ( 49 Hz) when exposed to pure H2S (NH3). Notably, when exposed to mixed H2S and NH3, the device shows a fast frequency decrease in first 2 s and a moderate drop in next 8 s with frequency shifts of 183 Hz and 38 Hz, demonstrating that no cross-responses are involved in the Janus mesoporous sensor during simultaneous H2S and NH3 sensing process. When the sensor device was fabricated with the symmetric film that
1Department
of Chemistry, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, China *Correspondence: [email protected] https://doi.org/10.1016/j.matt.2019.10.009
Figure 1. Fabrication of Janus Mesoporous Sensor Device and Its Sensing Performance (A) Schematic illustration of the process for preparation of Janus mesoporous carbon/silica thin film device via the successive solvent evaporationinduced self-assembly approach and selective surface functionalization strategy. (B) Cross-section field emission scanning electron microscope (FESEM) image of the Janus mesoporous carbon/silica thin film. Scale bar, 100 nm. (C) Schematic illustration of the gas sensor device based on the Janus mesoporous carbon/silica thin films with independent –NH 2 and –COOH groups. (D) Response and recovery curves of the Janus mesoporous carbon/silica thin film (orange)-, mesoporous silica thin film (green)-, and mesoporous carbon thin film (blue)-based sensors to 20 ppm of NH 3 , 20 ppm of H2 S, and mixed gases of NH3 (20 ppm) and H 2 S (20 ppm).
the COOH groups are obscured after NH2 functionalization, the frequency shift of this device to H2S is about 325 Hz and no response to NH3, suggesting the necessity of Janus architecture for multiple sensing outputs simultaneously. Furthermore, theoretical calculations based on the Langmuir adsorption model, the following derived equation, and the kinetic Monte Carlos revealed that the different free energy between NH3 and H2S to the Janus mesoporous carbon/silica led to the different response times. Thus, both the experimental and theoretical results indicate that this designed unique Janus
mesoporous architecture is a promising candidate for the next generation of multivariable sensors for multiple gas sensing, which are highly demanded in chemical industries, environmental monitoring, and other related fields. 1. Mao, S., Chang, J., Pu, H., Lu, G., He, Q., Zhang, H., and Chen, J. (2017). Twodimensional nanomaterial-based field-effect transistors for chemical and biological sensing. Chem. Soc. Rev. 46, 6872–6904. 2. Tchalala, M.R., Bhatt, P.M., Chappanda, K.N., Tavares, S.R., Adil, K., Belmabkhout, Y., et al. (2019). Fluorinated MOF platform for selective removal and sensing of SO2 from flue gas and air. Nat. Comm. 10, 1328. 3. Zhu, Y., Zhao, Y., Ma, J., Cheng, X., Xie, J., Xu, P., Liu, H., Liu, H., Zhang, H., Wu, M., et al. (2017). Mesoporous Tungsten Oxides with Crystalline Framework for Highly Sensitive and
Selective Detection of Foodborne Pathogens. J. Am. Chem. Soc. 139, 10365–10373. 4. Lakhi, K.S., Park, D.H., Al-Bahily, K., Cha, W., Viswanathan, B., Choy, J.H., and Vinu, A. (2017). Mesoporous carbon nitrides: synthesis, functionalization, and applications. Chem. Soc. Rev. 46, 72–101. 5. Li, Y., Luo, W., Qin, N., Dong, J., Wei, J., Li, W., et al. (2014). Highly Ordered Mesoporous Tungsten Oxides with a Large Pore Size and Crystalline Framework for H2S Sensing. Angew. Chem. Int. Ed. 53, 9035–9040. 6. Potyrailo, R.A. (2016). Multivariable Sensors for Ubiquitous Monitoring of Gases in the Era of Internet of Things and Industrial Internet. Chem. Rev. 116, 11877–11923. 7. Wang, R., Lan, K., Chen, Z., Zhang, X., Hung, C.-T., Zhang, W., Wang, C., Wang, S., Chen, A., Li, W., et al. (2019). Janus Mesoporous Sensor Devices for Simultaneous Multivariable Gases Detection. Matter 1, this issue, 1274– 1284.
Matter 1, 1104–1118, November 6, 2019 1111