{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,7]],"date-time":"2026-05-07T11:56:50Z","timestamp":1778155010196,"version":"3.51.4"},"reference-count":34,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,14]],"date-time":"2021-01-14T00:00:00Z","timestamp":1610582400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003093","name":"Ministry of Higher Education, Malaysia","doi-asserted-by":"publisher","award":["PRGS\/2\/2019\/STG05\/UPM\/03\/1"],"award-info":[{"award-number":["PRGS\/2\/2019\/STG05\/UPM\/03\/1"]}],"id":[{"id":"10.13039\/501100003093","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Ammonia detection in ambient air is critical, given its implication on the environment and human health. In this work, an optical fiber tapered to a 20 \u00b5m diameter and coated with graphene oxide was developed for absorbance response monitoring of ammonia at visible (500\u2013700 nm) and near-infrared wavelength regions (700\u2013900 nm). The morphology, surface characteristics, and chemical composition of the graphene oxide samples were confirmed by a field emission scanning electron microscope, an atomic force microscope, X-ray diffraction, and an energy dispersion X-ray. The sensing performance of the graphene oxide-coated optical microfiber sensor towards ammonia at room temperature revealed better absorbance response at the near-infrared wavelength region compared to the visible region. The sensitivity, response and recovery times at the near-infrared wavelength region were 61.78 AU\/%, 385 s, and 288 s, respectively. The sensitivity, response and recovery times at the visible wavelength region were 26.99 AU\/%, 497 s, and 192 s, respectively. The selectivity of the sensor towards ammonia was affirmed with no response towards other gases.<\/jats:p>","DOI":"10.3390\/s21020556","type":"journal-article","created":{"date-parts":[[2021,1,15]],"date-time":"2021-01-15T01:33:29Z","timestamp":1610674409000},"page":"556","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Wavelength Dependent Graphene Oxide-Based Optical Microfiber Sensor for Ammonia Gas"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7038-0972","authenticated-orcid":false,"given":"Saad Hayatu","family":"Girei","sequence":"first","affiliation":[{"name":"Wireless and Photonics Networks Research Centre, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"},{"name":"Department of Computer Engineering, Federal Polytechnic Mubi, Mubi 650113, Adamawa State, Nigeria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7989-5809","authenticated-orcid":false,"given":"Mohammed Majeed","family":"Alkhabet","sequence":"additional","affiliation":[{"name":"Wireless and Photonics Networks Research Centre, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4958-8303","authenticated-orcid":false,"given":"Yasmin Mustapha","family":"Kamil","sequence":"additional","affiliation":[{"name":"Wireless and Photonics Networks Research Centre, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2436-8953","authenticated-orcid":false,"given":"Hong Ngee","family":"Lim","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"}]},{"given":"Mohd Adzir","family":"Mahdi","sequence":"additional","affiliation":[{"name":"Wireless and Photonics Networks Research Centre, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3026-3202","authenticated-orcid":false,"given":"Mohd Hanif","family":"Yaacob","sequence":"additional","affiliation":[{"name":"Wireless and Photonics Networks Research Centre, University Putra Malaysia, Serdang 43400, Selangor, Malaysia"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2837","DOI":"10.1364\/OE.23.002837","article-title":"Room temperature ammonia sensing using tapered multimode fiber coated with polyaniline nanofibers","volume":"23","author":"Ibrahim","year":"2015","journal-title":"Opt. 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