{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,11]],"date-time":"2026-07-11T00:29:49Z","timestamp":1783729789815,"version":"3.55.0"},"reference-count":44,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2021,6,4]],"date-time":"2021-06-04T00:00:00Z","timestamp":1622764800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["11674109"],"award-info":[{"award-number":["11674109"]}]},{"name":"National Natural Science Foundation of China","award":["61774062"],"award-info":[{"award-number":["61774062"]}]},{"name":"Natural Science Foundation of Guangdong Province of China","award":["2016A030313443"],"award-info":[{"award-number":["2016A030313443"]}]},{"name":"Science and Technology Planning Project of Guangdong Province of China","award":["2017A020219007"],"award-info":[{"award-number":["2017A020219007"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm\/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging\/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.<\/jats:p>","DOI":"10.3390\/s21113886","type":"journal-article","created":{"date-parts":[[2021,6,7]],"date-time":"2021-06-07T01:56:40Z","timestamp":1623031000000},"page":"3886","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":32,"title":["Ammonia Gas Sensor Based on Graphene Oxide-Coated Mach-Zehnder Interferometer with Hybrid Fiber Structure"],"prefix":"10.3390","volume":"21","author":[{"given":"Xiaofeng","family":"Fan","sequence":"first","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuying","family":"Deng","sequence":"additional","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3586-2180","authenticated-orcid":false,"given":"Zhongchao","family":"Wei","sequence":"additional","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7223-1877","authenticated-orcid":false,"given":"Faqiang","family":"Wang","sequence":"additional","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chunhua","family":"Tan","sequence":"additional","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4321-3148","authenticated-orcid":false,"given":"Hongyun","family":"Meng","sequence":"additional","affiliation":[{"name":"Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,6,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1016\/j.snb.2004.11.054","article-title":"Ammonia sensors and their applications\u2014A review","volume":"107","author":"Timmer","year":"2015","journal-title":"Sens. Actuator B Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"129444","DOI":"10.1016\/j.snb.2021.129444","article-title":"The gas sensor utilizing polyaniline\/MoS2 nanosheets\/SnO2 nanotubes for the room temperature detection of ammonia","volume":"332","author":"Liu","year":"2021","journal-title":"Sens. Actuator B Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"128217","DOI":"10.1016\/j.snb.2020.128217","article-title":"Drastically enhanced ammonia sensing of Pt\/ZnO ordered porous ultra-thin films","volume":"317","author":"Li","year":"2020","journal-title":"Sens. Actuator B Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1479","DOI":"10.1007\/s12274-020-2825-6","article-title":"Bioelectronic protein nanowire sensors for ammonia detection","volume":"13","author":"Alexander","year":"2020","journal-title":"Nano Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"128198","DOI":"10.1016\/j.snb.2020.128198","article-title":"Trace-level ammonia detection at room temperature based on porous flexible polyaniline\/polyvinylidene fluoride sensing film with carbon nanotube additives","volume":"316","author":"Wu","year":"2020","journal-title":"Sens. Actuator B Chem."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"252","DOI":"10.1016\/j.snb.2005.02.015","article-title":"Optical fiber-based evanescent ammonia sensor","volume":"110","author":"Cao","year":"2005","journal-title":"Sens. Actuator B Chem."},{"key":"ref_7","first-page":"976","article-title":"Surface plasmon resonance based fiber optic ammonia gas sensor using ITO and polyaniline","volume":"171","author":"Mishra","year":"2005","journal-title":"Sens. Actuator B Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1007\/s13320-014-0216-x","article-title":"Optimization study on graphene-coated microfiber Bragg grating structures for ammonia gas sensing","volume":"5","author":"Zhang","year":"2015","journal-title":"Photonic. Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/j.optcom.2018.06.059","article-title":"Ultra sensitive NH3 gas detection using microfiber Bragg grating","volume":"427","author":"Fu","year":"2018","journal-title":"Opt. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2022","DOI":"10.1364\/AO.28.002022","article-title":"Porous plastic optical fiber sensor for ammonia measurement","volume":"28","author":"Zhou","year":"1989","journal-title":"Appl. Opt."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"44994","DOI":"10.1038\/srep44994","article-title":"An in-line Mach-Zehnder interferometer using thin-core fiber for ammonia gas sensing with high sensitivity","volume":"7","author":"Huang","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"324","DOI":"10.1016\/j.snb.2015.09.083","article-title":"Photonic crystal fiber long-period grating absorption gas sensor based on a tunable erbium-doped fiber ring laser","volume":"223","author":"Zheng","year":"2016","journal-title":"Sens. Actuator B Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1858","DOI":"10.1364\/OME.7.001858","article-title":"Room temperature ammonia sensor using side-polished optical fiber coated with graphene\/polyaniline nanocomposite","volume":"7","author":"Khalaf","year":"2017","journal-title":"Opt. Mater. Express"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1016\/j.optcom.2014.11.092","article-title":"Ammonia sensing properties of tapered plastic optical fiber coated with silver nanoparticles\/PVP\/PVA hybrid","volume":"340","author":"Raj","year":"2015","journal-title":"Opt. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"8712","DOI":"10.1364\/AO.54.008712","article-title":"Fiber-optic ammonia sensor using Ag\/SnO2 thin films: Optimization of thickness of SnO2 film using electric field distribution and reaction factor","volume":"54","author":"Pathak","year":"2017","journal-title":"Appl. Optics"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1016\/j.snb.2006.09.055","article-title":"Silver nanoparticles doped silica nanocomposites coated on an optical fiber for ammonia sensing","volume":"123","author":"Guo","year":"2007","journal-title":"Sens. Actuator B Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2864","DOI":"10.1109\/JLT.2017.2701404","article-title":"High sensitivity ammonia gas sensor based on a silica-gel-coated microfiber coupler","volume":"35","author":"Sun","year":"2017","journal-title":"J. Lightwave Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"7924","DOI":"10.1364\/AO.57.007924","article-title":"Fabrication of three-dimensional zinc oxide nanoflowers for high-sensitivity fiber-optic ammonia gas sensors","volume":"57","author":"Zhu","year":"2018","journal-title":"Appl. Opt."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4402","DOI":"10.1021\/acsphotonics.8b00828","article-title":"Hypersensitive and selective interferometric nose for ultratrace ammonia detection with fast response utilizing PANI@SnO2 Nanocomposite","volume":"5","author":"Shrivastav","year":"2018","journal-title":"ACS Photonics"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1016\/j.snb.2013.12.085","article-title":"All-optical Mach-Zehnder interferometric NH3 gas sensor based on graphene\/microfiber hybrid waveguide","volume":"194","author":"Yao","year":"2014","journal-title":"Sens. Actuator B Chem."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1235","DOI":"10.1364\/OL.39.001235","article-title":"Graphene-coated microfiber Bragg grating for high-sensitivity gas sensing","volume":"39","author":"Wu","year":"2014","journal-title":"Opt. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.snb.2016.12.126","article-title":"Miniature fiber-optic NH3 gas sensor based on Pt nanoparticle-incorporated graphene oxide","volume":"244","author":"Yu","year":"2017","journal-title":"Sens. Actuator B Chem."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1016\/j.snb.2017.06.067","article-title":"Zinc oxide nanoparticle incorporated graphene oxide as sensing coating for interferometric optical microfiber for ammonia gas detection","volume":"254","author":"Fu","year":"2018","journal-title":"Sens. Actuator B Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"9232","DOI":"10.1364\/OE.27.009232","article-title":"Graphene oxide-film-coated splitting ratio-adjustable Mach-Zehnder interferometer for relative humidity sensing","volume":"27","author":"Deng","year":"2019","journal-title":"Opt. Express"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.snb.2016.05.020","article-title":"Polarization-dependent humidity sensor based on an in-fiber Mach-Zehnder interferometer coated with graphene oxide","volume":"234","author":"Wang","year":"2016","journal-title":"Sens. Actuator B Chem."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"131110","DOI":"10.1063\/1.3115029","article-title":"Tapered fiber Mach-Zehnder interferometer for simultaneous measurement of refractive index and temperature","volume":"94","author":"Lu","year":"2009","journal-title":"Appl. Phys. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"626","DOI":"10.1109\/LPT.2008.919507","article-title":"Refractive index sensing with Mach-Zehnder interferometer based on concatenating two single-mode fiber tapers","volume":"20","author":"Tian","year":"2008","journal-title":"IEEE Photonic. Tech. Lett."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2035","DOI":"10.1109\/LPT.2017.2761981","article-title":"Graphene-based ammonia-gas sensor using in-fiber Mach-Zehnder interferometer","volume":"29","author":"Hao","year":"2017","journal-title":"IEEE Photonic. Tech. Lett."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1038\/nmat1849","article-title":"The rise of graphene","volume":"6","author":"Geim","year":"2007","journal-title":"Nat. Mater."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/j.ssc.2008.02.024","article-title":"Ultrahigh electron mobility in suspended graphene","volume":"146","author":"Bolotin","year":"2008","journal-title":"Solid State Commun."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"125416","DOI":"10.1103\/PhysRevB.77.125416","article-title":"Adsorption of H2O, NH3, CO, NO2, and NO on graphene: A first principles study","volume":"77","author":"Leenaerts","year":"2008","journal-title":"Phys. Rev. B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3906","DOI":"10.1002\/adma.201001068","article-title":"Graphene and graphene oxide: Synthesis, properties, and applications","volume":"22","author":"Zhu","year":"2010","journal-title":"Adv. Mater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2604","DOI":"10.1021\/jp907979v","article-title":"Dynamics of water intercalated in graphite oxide","volume":"114","author":"Cerveny","year":"2010","journal-title":"J. Phys. Chem. C"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"3298","DOI":"10.1002\/adma.201200373","article-title":"Graphene oxide as an optical biosensing platform","volume":"24","author":"Merkoci","year":"2012","journal-title":"Adv. Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1038\/nature04969","article-title":"Graphene-based composite materials","volume":"442","author":"Stankovich","year":"2006","journal-title":"Nature"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1039\/B917103G","article-title":"The chemistry of graphene oxide","volume":"39","author":"Dreyer","year":"2010","journal-title":"Chem. Soc. Rev."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1007\/s11783-013-0491-6","article-title":"Ammonia adsorption on graphene and graphene oxide: A first-principles study","volume":"7","author":"Peng","year":"2013","journal-title":"Front. Environ. Sci. Eng."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Girei, S.H., Alkhabet, M.M., Kamil, Y.M., Lim, H.N., Mahdi, M.A., and Yaacob, M.H. (2021). Wavelength dependent graphene oxide-based optical microfiber sensor for ammonia gas. Sensors, 21.","DOI":"10.3390\/s21020556"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"8778","DOI":"10.1021\/jp212218w","article-title":"Adsorption and dissociation of ammonia on graphene oxides: A first-principles study","volume":"116","author":"Tang","year":"2012","journal-title":"J. Phys. Chem. C"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"652","DOI":"10.1038\/nmat1967","article-title":"Detection of individual gas molecules adsorbed on graphene","volume":"6","author":"Schedin","year":"2007","journal-title":"Nat. Mater."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1109\/JSTQE.2013.2263117","article-title":"Hybrid graphene-microfiber waveguide for chemical gas sensing","volume":"20","author":"Wu","year":"2013","journal-title":"IEEE J. Sel. Top. Quantum Electron."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1016\/j.optcom.2015.11.015","article-title":"Simultaneous measurement of refractive index and temperature based on asymmetric structures modal interference","volume":"364","author":"Wang","year":"2016","journal-title":"Opt. Commun."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"11369","DOI":"10.1364\/OE.16.011369","article-title":"High temperature fiber sensor with high sensitivity based on core diameter mismatch","volume":"16","author":"Nguyen","year":"2008","journal-title":"Opt. Express"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"5711","DOI":"10.1364\/OE.15.005711","article-title":"All-fiber Mach-Zehnder type interferometers formed in photonic crystal fiber","volume":"15","author":"Choi","year":"2007","journal-title":"Opt. Express"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/11\/3886\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:10:57Z","timestamp":1760163057000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/11\/3886"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,6,4]]},"references-count":44,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2021,6]]}},"alternative-id":["s21113886"],"URL":"https:\/\/doi.org\/10.3390\/s21113886","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,6,4]]}}}