PERTANIKA JOURNAL OF SCIENCE AND TECHNOLOGY

 

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Home / Regular Issue / JST Vol. 32 (6) Oct. 2024 / JST-5032-2024

 

A Comprehensive Review of State-of-the-art Optical Methods for Methane Gas Detection

Sayma Khandaker, Nurulain Shaipuzaman, Md Mahmudul Hasan, Mohd Amir Shahlan Mohd Aspar and Hadi Manap

Pertanika Journal of Science & Technology, Volume 32, Issue 6, October 2024

DOI: https://doi.org/10.47836/pjst.32.6.19

Keywords: Methane absorption spectra, methane detection, methane sensing materials, optical fiber sensor, optical methods

Published on: 25 October 2024

Methane (CH), a potent greenhouse gas, significantly contributes to climate change and global warming. Its impact over 100 years surpasses carbon dioxide (CO) by 28 times. Addressing methane emissions, particularly from oil and gas production activities such as transmission pipelines, is imperative. One promising avenue is the development of reliable sensors to detect and mitigate methane leaks and prevent hazardous issues. Optical-based methods present notable advantages, including versatility and remote operation, making them pivotal in this endeavor. This review article provides a concise overview of optical-based methane identification technologies, encompassing sensing materials, absorption spectra, operational mechanisms, and recent advancements. Potential perspectives are explored, and inferences from this assessment are also derived. Emphasizing the significance of optical fiber-based methane detection methods, the authors advocate for further research to support ongoing efforts and foster innovation in this critical area.

  • Abb, M., Wang, Y., Papasimakis, N., De Groot, C. H., & Muskens, O. L. (2014). Surface-enhanced infrared spectroscopy using metal oxide plasmonic antenna arrays. Nano Letters, 14(1), 346–352. https://doi.org/10.1021/nl404115g

  • Agius, C., Brenon, M., Dill, W. G., Kelly, P., Klausmeyer, U., McManama, K., Pogorelsky, A., & Zalogine, A. S. (2000). The impact of the IECEx scheme on the global availability of explosion protected apparatus-update 2000 (parts IV-VII). In Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No. 00CH37129) (Vol. 4, pp. 2844-2851). IEEE Publishing. https://doi.org/10.1109/IAS.2000.883225

  • Allsop, T., & Neal, R. (2021). A review: Application and implementation of optic fibre sensors for gas detection. Sensors, 21(20), Article 6755. https://doi.org/10.3390/s21206755

  • Allsop, T., Kundrat, V., Kalli, K., Lee, G. B., Neal, R., Bond, P., Shi, B., Sullivan, J., Culverhouse, P., & Webb, D. J. (2018). Methane detection scheme based upon the changing optical constants of a zinc oxide/platinum matrix created by a redox reaction and their effect upon surface plasmons. Sensors and Actuators B: Chemical, 255, 843–853. https://doi.org/10.1016/j.snb.2017.08.058

  • Atherton, K., Yu, H., Stewart, G., & Culshaw, B. (2004). Gas detection with fibre amplifiers by intra-cavity and cavity ring-down absorption. Measurement Science and Technology, 15, 1621–1628.

  • Bachu, S. (2017). Analysis of gas leakage occurrence along wells in Alberta, Canada, from a GHG perspective – Gas migration outside well casing. International Journal of Greenhouse Gas Control, 61, 146–154. https://doi.org/10.1016/j.ijggc.2017.04.003

  • Beckwith, P. H., Brown, C. E., Danagher, D. J., Smith, D. R., & Reid, J. (1987). High sensitivity detection of transient infrared absorption using tunable diode lasers. Applied Optics, 26(13), Article 2643. https://doi.org/10.1364/AO.26.002643

  • Bito, K., Okuno, M., Kano, H., Leproux, P., Couderc, V., & Hamaguchi, H. (2013). Three-pulse multiplex coherent anti-Stokes/Stokes Raman scattering (CARS/CSRS) microspectroscopy using a white-light laser source. Chemical Physics, 419, 156–162. https://doi.org/10.1016/j.chemphys.2013.02.007

  • Butt, M. A., Voronkov, G. S., Grakhova, E. P., Kutluyarov, R. V., Kazanskiy, N. L., & Khonina, S. N. (2022). Environmental monitoring: A comprehensive review on optical waveguide and fiber-based sensors. Biosensors, 12(11), Article 1038. https://doi.org/10.3390/bios12111038

  • Caumon, M. C., Robert, P., Laverret, E., Tarantola, A., Randi, A., Pironon, J., Dubessy, J., & Girard, J. P. (2014). Determination of methane content in NaCl–H2O fluid inclusions by Raman spectroscopy. Calibration and application to the external part of the Central Alps (Switzerland). Chemical Geology, 378–379, 52–61. https://doi.org/10.1016/j.chemgeo.2014.03.016

  • Collins, W., Orbach, R., Bailey, M., Biraud, S., Coddington, I., DiCarlo, D., Peischl, J., Radhakrishnan, A., & Schimel, D. (2022). Monitoring methane emissions from oil and gas operations. Optics Express, 30(14), Article 24326. https://doi.org/10.1364/OE.464421

  • Dong, L., Yin, W., Ma, W., Zhang, L., & Jia, S. (2007). High-sensitivity, large dynamic range, auto-calibration methane optical sensor using a short confocal Fabry–Perot cavity. Sensors and Actuators B: Chemical, 127(2), 350–357. https://doi.org/10.1016/j.snb.2007.04.030

  • Fawcett, B. L., Parkes, A. M., Shallcross, D. E., & Orr-Ewing, A. J. (2002). Trace detection of methane using continuous wave cavity ring-down spectroscopy at 1.65 μm. Physical Chemistry Chemical Physics, 4(24), 5960–5965. https://doi.org/10.1039/B208486B

  • Foltynowicz, A., Schmidt, F. M., Ma, W., & Axner, O. (2008). Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy: Current status and future potential. Applied Physics B, 92(3), Article 313. https://doi.org/10.1007/s00340-008-3126-z

  • Formisano, V., Atreya, S., Encrenaz, T., Ignatiev, N., & Giuranna, M. (2004). Detection of methane in the atmosphere of Mars. Science, 306(5702), 1758–1761. https://doi.org/10.1126/science.1101732

  • Gao, Q., Zhang, Y., Yu, J., Wu, S., Zhang, Z., Zheng, F., Lou, X., & Guo, W. (2013). Tunable multi-mode diode laser absorption spectroscopy for methane detection. Sensors and Actuators A: Physical, 199, 106–110. https://doi.org/10.1016/j.sna.2013.05.012

  • Gardiner, T., Mead, M. I., Garcelon, S., Robinson, R., Swann, N., Hansford, G. M., Woods, P. T., & Jones, R. L. (2010). A lightweight near-infrared spectrometer for the detection of trace atmospheric species. Review of Scientific Instruments, 81(8), Article 083102. https://doi.org/10.1063/1.3455827

  • Gomolka, G., Stępniewski, G., Pysz, D., Buczynski, R., Klimczak, M., & Nikodem, M. (2021). Methane sensing inside anti-resonant hollow-core fiber in the near- and mid-infrared spectral regions. In P. Peterka, K. Kalli, & A. Mendez (Eds.), Micro-structured and Specialty Optical Fibres VII (p. 6). SPIE. https://doi.org/10.1117/12.2592300

  • Gurlit, W., Zimmermann, R., Giesemann, C., Fernholz, T., Ebert, V., Wolfrum, J., Platt, U., & Burrows, J. P. (2005). Lightweight diode laser spectrometer CHILD (Compact High-altitude In-situ Laser Diode) for balloonborne measurements of water vapor and methane. Applied Optics, 44(1), Article 91. https://doi.org/10.1364/AO.44.000091

  • Hamilton, D. J., & Orr-Ewing, A. J. (2011). A quantum cascade laser-based optical feedback cavity-enhanced absorption spectrometer for the simultaneous measurement of CH4 and N2O in air. Applied Physics B, 102(4), 879–890. https://doi.org/10.1007/s00340-010-4259-4

  • Hansuld, E. M., & Briens, L. (2014). A review of monitoring methods for pharmaceutical wet granulation. International Journal of Pharmaceutics, 472(1–2), 192–201. https://doi.org/10.1016/j.ijpharm.2014.06.027

  • He, Y., & Orr, B. J. (2000). Ringdown and cavity-enhanced absorption spectroscopy using a continuous-wave tunable diode laser and a rapidly swept optical cavity. Chemical Physics Letters, 319(1–2), 131–137. https://doi.org/10.1016/S0009-2614(00)00107-X

  • Hennig, O., Strzoda, R., Mágori, E., Chemisky, E., Tump, C., Fleischer, M., Meixner, H., & Eisele, I. (2003). Hand-held unit for simultaneous detection of methane and ethane based on NIR-absorption spectroscopy. Sensors and Actuators B: Chemical, 95(1–3), 151–156. https://doi.org/10.1016/S0925-4005(03)00399-X

  • Hester, K. C., Dunk, R. M., White, S. N., Brewer, P. G., Peltzer, E. T., & Sloan, E. D. (2007). Gas hydrate measurements at Hydrate Ridge using Raman spectroscopy. Geochimica et Cosmochimica Acta, 71(12), 2947–2959. https://doi.org/10.1016/j.gca.2007.03.032

  • Hippler, M., & Quack, M. (2002). High-resolution Fourier transform infrared and cw-diode laser cavity ringdown spectroscopy of the ν2+2ν3 band of methane near 7510 cm−1 in slit jet expansions and at room temperature. The Journal of Chemical Physics, 116(14), 6045–6055. https://doi.org/10.1063/1.1433505

  • Hodgkinson, J., & Pride, R. D. (2010). Methane-specific gas detectors: The effect of natural gas composition. Measurement Science and Technology, 21(10), Article 105103. https://doi.org/10.1088/0957-0233/21/10/105103

  • Hodgkinson, J., & Tatam, R. P. (2013). Optical gas sensing: A review. Measurement Science and Technology, 24(1), Article 012004. https://doi.org/10.1088/0957-0233/24/1/012004

  • Hodgkinson, J., Shan, Q., & Pride, R. D. (2006). Detection of a simulated gas leak in a wind tunnel. Measurement Science and Technology, 17(6), 1586–1593. https://doi.org/10.1088/0957-0233/17/6/041

  • Hollenbeck, D., Zulevic, D., & Chen, Y. (2021). Advanced leak detection and quantification of methane emissions using sUAS. Drones, 5(4), Article 117. https://doi.org/10.3390/drones5040117

  • Homola, J., & Piliarik, M. (2006). Surface Plasmon Resonance (SPR) sensors. Springer.

  • Hong, T., Culp, J. T., Kim, K. J., Devkota, J., Sun, C., & Ohodnicki, P. R. (2020). State-of-the-art of methane sensing materials: A review and perspectives. TrAC Trends in Analytical Chemistry, 125, Article 115820. https://doi.org/10.1016/j.trac.2020.115820

  • Ingraffea, A. R., Wawrzynek, P. A., Santoro, R., & Wells, M. (2020). Reported methane emissions from active oil and gas wells in Pennsylvania, 2014–2018. Environmental Science & Technology, 54(9), 5783–5789. https://doi.org/10.1021/acs.est.0c00863

  • Iseki, T., Tai, H., & Kimura, K. (2000). A portable remote methane sensor using a tunable diode laser. Measurement Science and Technology, 11(6), 594–602. https://doi.org/10.1088/0957-0233/11/6/302

  • Ismaeel, R., Beaton, A., Donko, A., Talataisong, W., Lee, T., Brotin, T., Beresna, M., Mowlem, M., & Brambilla, G. (2019). High sensitivity all-fibre methane sensor with gas permeable teflon/cryptophane-a membrane. In The European Conference on Lasers and Electro-Optics (p. ch_6_5). Optica Publishing Group.

  • Jaramillo, P., Griffin, W. M., & Matthews, H. S. (2008). Comparative analysis of the production costs and life-cycle GHG emissions of FT liquid fuels from coal and natural gas. Environmental Science & Technology, 42(20), 7559–7565. https://doi.org/10.1021/es8002074

  • Kamal, D. A. M., Ibrahim, S. F., Kamal, H., Kashim, M. I. A. M., & Mokhtar, M. H. (2021). Physicochemical and medicinal properties of Tualang, Gelam and Kelulut Honeys: A comprehensive review. Nutrients, 13(1), Article 197. https://doi.org/10.3390/nu13010197

  • Kannath, A., Hodgkinson, J., Gillard, R. G., Riley, R. J., & Tatam, R. P. (2011). A VCSEL based system for on-site monitoring of low level methane emission. In Vertical-Cavity Surface-Emitting Lasers XV (Vol. 7952, pp. 99-107). SPIE. https://doi.org/10.1117/12.874513

  • Kim, K. J., Chong, X., Kreider, P. B., Ma, G., Ohodnicki, P. R., Baltrus, J. P., Wang, A. X., & Chang, C. H. (2015). Plasmonics-enhanced metal–organic framework nanoporous films for highly sensitive near-infrared absorption. Journal of Materials Chemistry C, 3(12), 2763–2767. https://doi.org/10.1039/C4TC02846E

  • Kwaśny, M., & Bombalska, A. (2023). Optical methods of methane detection. Sensors, 23(5), Article 2834. https://doi.org/10.3390/s23052834

  • Lang, N., Macherius, U., Wiese, M., Zimmermann, H., Röpcke, J., & Van Helden, J. H. (2016). Sensitive CH_4 detection applying quantum cascade laser based optical feedback cavity-enhanced absorption spectroscopy. Optics Express, 24(6), Article A536. https://doi.org/10.1364/OE.24.00A536

  • Lawrence, N. (2006). Analytical detection methodologies for methane and related hydrocarbons. Talanta, 69(2), 385–392. https://doi.org/10.1016/j.talanta.2005.10.005

  • Liu, H., Wang, H., Chen, C., Zhang, W., Bai, B., Chen, C., Zhang, Y., & Shao, Q. (2020). High sensitive methane sensor based on twin-core photonic crystal fiber with compound film-coated side-holes. Optical and Quantum Electronics, 52(2), Article 81. https://doi.org/10.1007/s11082-020-2198-9

  • Liu, H., Wang, M., Wang, Q., Li, H., Ding, Y., & Zhu, C. (2018). Simultaneous measurement of hydrogen and methane based on PCF-SPR structure with compound film-coated side-holes. Optical Fiber Technology, 45, 1–7. https://doi.org/10.1016/j.yofte.2018.05.007

  • Liu, H., Zhang, Y., Chen, C., Bai, B., Shao, Q., Wang, H., Zhang, W., Chen, C., & Tang, S. (2019). Transverse-stress compensated methane sensor based on long-period grating in photonic crystal fiber. IEEE Access, 7, 175522–175530. https://doi.org/10.1109/ACCESS.2019.2951133

  • McDermitt, D., Burba, G., Xu, L., Anderson, T., Komissarov, A., Riensche, B., Schedlbauer, J., Starr, G., Zona, D., Oechel, W., Oberbauer, S., & Hastings, S. (2011). A new low-power, open-path instrument for measuring methane flux by eddy covariance. Applied Physics B, 102(2), 391–405. https://doi.org/10.1007/s00340-010-4307-0

  • McManus, J. B. (2010). Application of quantum cascade lasers to high-precision atmospheric trace gas measurements. Optical Engineering, 49(11), Article 111124. https://doi.org/10.1117/1.3498782

  • McManus, J. B., Shorter, J. H., Nelson, D. D., Zahniser, M. S., Glenn, D. E., & McGovern, R. M. (2008). Pulsed quantum cascade laser instrument with compact design for rapid, high sensitivity measurements of trace gases in air. Applied Physics B, 92(3), Article 387. https://doi.org/10.1007/s00340-008-3129-9

  • Mikołajczyk, J., Wojtas, J., Bielecki, Z., Stacewicz, T., Szabra, D., Magryta, P., Prokopiuk, A., Tkacz, A., & Panek, M. (2016). System of optoelectronic sensors for breath analysis. Metrology and Measurement Systems, 23(3), 481–489. https://doi.org/10.1515/mms-2016-0030

  • Mishra, S. K., Tripathi, S. N., Choudhary, V., & Gupta, B. D. (2015). Surface plasmon resonance-based fiber optic methane gas sensor utilizing graphene-carbon nanotubes-poly(methyl methacrylate) hybrid nanocomposite. Plasmonics, 10(5), 1147–1157. https://doi.org/10.1007/s11468-015-9914-5

  • Ohodnicki Jr., P. R., Brown, T. D., Holcomb, G. R., Tylczak, J., Schultz, A. M., & Baltrus, J. P. (2014). High temperature optical sensing of gas and temperature using AU-nanoparticle incorporated oxides. Sensors and Actuators B: Chemical, 202, 489–499. https://doi.org/10.1016/j.snb.2014.04.106

  • Olmer, N., Comer, B., Roy, B., Mao, X., & Rutherford, D. (2019, November 25). Greenhouse gas emissions from global shipping, 2013—2015 Detailed Methodology. https://www.theicct.org/publications/GHG-emissions-globalshipping-2013-2015

  • Paldus, B. A., & Kachanov, A. A. (2005). An historical overview of cavity-enhanced methods. Canadian Journal of Physics, 83(10), 975–999. https://doi.org/10.1139/p05-054

  • Park, J. H., Cho, J. H., Kim, Y. J., Kim, E. S., Han, H. S., & Shin, C. H. (2014). Hydrothermal stability of Pd/ZrO2 catalysts for high temperature methane combustion. Applied Catalysis B: Environmental, 160–161, 135–143. https://doi.org/10.1016/j.apcatb.2014.05.013

  • Pipino, A. C. R. (1999). Ultrasensitive surface spectroscopy with a miniature optical resonator. Physical Review Letters, 83(15), 3093–3096. https://doi.org/10.1103/PhysRevLett.83.3093

  • Pyun, S. H., Cho, J., Davidson, D. F., & Hanson, R. K. (2011). Interference-free mid-IR laser absorption detection of methane. Measurement Science and Technology, 22(2), Article 025303. https://doi.org/10.1088/0957-0233/22/2/025303

  • Richard, E. C., Kelly, K. K., Winkler, R. H., Wilson, R., Thompson, T. L., McLaughlin, R. J., Schmeltekopf, A. L., & Tuck, A. F. (2002). A fast-response near-infrared tunable diode laser absorption spectrometer for in situ measurements of CH 4 in the upper troposphere and lower stratosphere. Applied Physics B: Lasers and Optics, 75(2–3), 183–194. https://doi.org/10.1007/s00340-002-0935-3

  • Romanini, D., Kachanov, A. A., & Stoeckel, F. (1997). Diode laser cavity ring down spectroscopy. Chemical Physics Letters, 270(5–6), 538–545. https://doi.org/10.1016/S0009-2614(97)00406-5

  • Rothman, L. S., Gordon, I. E., Barbe, A., Benner, D. C., Bernath, P. F., Birk, M., Boudon, V., Brown, L. R., Campargue, A., Champion, J.-P., Chance, K., Coudert, L. H., Dana, V., Devi, V. M., Fally, S., Flaud, J.-M., Gamache, R. R., Goldman, A., Jacquemart, D., … & Vander Auwera, J. (2009). The HITRAN 2008 molecular spectroscopic database. Journal of Quantitative Spectroscopy and Radiative Transfer, 110(9–10), 533–572. https://doi.org/10.1016/j.jqsrt.2009.02.013

  • Schlücker, S. (2014). Surface‐enhanced Raman spectroscopy: Concepts and chemical applications. Angewandte Chemie International Edition, 53(19), 4756–4795. https://doi.org/10.1002/anie.201205748

  • Shao, L., Fang, B., Zheng, F., Qiu, X., He, Q., Wei, J., Li, C., & Zhao, W. (2019). Simultaneous detection of atmospheric CO and CH4 based on TDLAS using a single 2.3 μm DFB laser. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 222, Article 117118. https://doi.org/10.1016/j.saa.2019.05.023

  • Shemshad, J., Aminossadati, S. M., & Kizil, M. S. (2012). A review of developments in near infrared methane detection based on tunable diode laser. Sensors and Actuators B: Chemical, 171–172, 77–92. https://doi.org/10.1016/j.snb.2012.06.018

  • Stocker, T. F., Dahe, Q., Plattner, G. K., Tignor, M. B., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., & Midgley, P. (2014). Climate Change 2013: The Physical Science Basis. Cambridge University Press.

  • Tiemann, M. (2007). Porous metal oxides as gas sensors. Chemistry – A European Journal, 13(30), 8376–8388. https://doi.org/10.1002/chem.200700927

  • Tombez, L., Zhang, E. J., Orcutt, J. S., Kamlapurkar, S., & Green, W. M. J. (2017). Methane absorption spectroscopy on a silicon photonic chip. Optica, 4(11), Article 1322. https://doi.org/10.1364/OPTICA.4.001322

  • Tran, M. K., & Fowler, M. (2020). A review of lithium-ion battery fault diagnostic algorithms: Current progress and future challenges. Algorithms, 13(3), Article 62. https://doi.org/10.3390/a13030062

  • Turner, A. J., Frankenberg, C., & Kort, E. A. (2019). Interpreting contemporary trends in atmospheric methane. Proceedings of the National Academy of Sciences, 116(8), 2805–2813. https://doi.org/10.1073/pnas.1814297116

  • Vargas-Rodríguez, E., & Rutt, H. N. (2009). Design of CO, CO2 and CH4 gas sensors based on correlation spectroscopy using a Fabry–Perot interferometer. Sensors and Actuators B: Chemical, 137(2), 410–419. https://doi.org/10.1016/j.snb.2009.01.013

  • Vasiliev, A. A., Pisliakov, A. V., Sokolov, A. V., Polovko, O. V., Samotaev, N. N., Kujawski, W., Rozicka, A., Guarnieri, V., & Lorencelli, L. (2014). Gas sensor system for the determination of methane in water. Procedia Engineering, 87, 1445–1448. https://doi.org/10.1016/j.proeng.2014.11.721

  • Wang, X., & Wolfbeis, O. S. (2016). Fiber-optic chemical sensors and biosensors (2013–2015). Analytical Chemistry, 88(1), 203–227. https://doi.org/10.1021/acs.analchem.5b04298

  • Wang, Z., Gao, P., Liu, S., & Chen, X. (2021). A reflective methane concentration sensor based on biconvex cone photonic crystal fiber. Optik, 241, Article 166983. https://doi.org/10.1016/j.ijleo.2021.166983

  • Wei, T., Wu, H., Dong, L., Cui, R., & Jia, S. (2021). Palm-sized methane TDLAS sensor based on a mini-multi-pass cell and a quartz tuning fork as a thermal detector. Optics Express, 29(8), Article 12357. https://doi.org/10.1364/OE.423217

  • Wei, W., Nong, J., Zhang, G., Tang, L., Jiang, X., Chen, N., Luo, S., Lan, G., & Zhu, Y. (2016). Graphene-based long-period fiber grating surface plasmon resonance sensor for high-sensitivity gas sensing. Sensors, 17(12), Article 2. https://doi.org/10.3390/s17010002

  • Wild, K. (2000). Gas quality measurement: A gas control revolution? Gas Engineering and Management, 40, 12–14.

  • Wisen, J., Chesnaux, R., Werring, J., Wendling, G., Baudron, P., & Barbecot, F. (2020). A portrait of wellbore leakage in northeastern British Columbia, Canada. Proceedings of the National Academy of Sciences, 117(2), 913–922. https://doi.org/10.1073/pnas.1817929116

  • Xie, S., Pennetta, R., & Russell, P. St. J. (2016). Self-alignment of glass fiber nanospike by optomechanical back-action in hollow-core photonic crystal fiber. Optica, 3(3), Article 277. https://doi.org/10.1364/OPTICA.3.000277

  • Yang, J., Che, X., Shen, R., Wang, C., Li, X., & Chen, W. (2017). High-sensitivity photonic crystal fiber long-period grating methane sensor with cryptophane-A-6Me absorbed on a PAA-CNTs/PAH nanofilm. Optics Express, 25(17), Article 20258. https://doi.org/10.1364/OE.25.020258

  • Yu, X., Lv, R. H., Song, F., Zheng, C. T., & Wang, Y. D. (2014). Pocket-sized nondispersive infrared methane detection device using two-parameter temperature compensation. Spectroscopy Letters, 47(1), 30–37. https://doi.org/10.1080/00387010.2013.780082

  • Zhang, J. Y., Ding, E. J., Xu, S. C., Li, Z. H., Wang, X. X., & Song, F. (2017). Sensitization of an optical fiber methane sensor with graphene. Optical Fiber Technology, 37, 26–29. https://doi.org/10.1016/j.yofte.2017.06.011

  • Zhang, Y., Zhao, Y., & Wang, Q. (2015). Measurement of methane concentration with cryptophane E infiltrated photonic crystal microcavity. Sensors and Actuators B: Chemical, 209, 431–437. https://doi.org/10.1016/j.snb.2014.12.002