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accelerating the corrosion process. Conventional methods for monitoring chloride ions typically require in situ drilling for sample collection, thereby compromising efficiency and accuracy. Additionally, real-time monitoring and early warning cannot be achieved. To address these challenges, this work introduces a fluorescent-probe-based fiber optic sensor for monitoring chloride levels in concrete structures. Quinine sulfate was chosen as the fluorescent material due to its exceptional sensitivity to chloride ions and its stability in concrete environments. The proposed sensor was manufactured using sol\u2013gel and 3D-printing techniques. Tests were conducted using concrete simulation fluid and cement mortar specimens. The results demonstrate that the sensitivity of the proposed sensor is greater than 0.01 M, and its accuracy in penetration depth measurement is better than 3 mm. The findings confirm that the designed fiber optic sensor based on quinine sulfate enables real-time monitoring of chloride ions in concrete structures, offering high sensitivity (0.1% in concentration and 2.7 mm in terms of penetration depth), unique selectivity (as it is immune to other ions whose concentrations are 10 times higher than those of Cl\u2212), and a compact size (10 \u00d7 20 mm). These attributes render it promising for practical engineering applications.<\/jats:p>","DOI":"10.3390\/s24123700","type":"journal-article","created":{"date-parts":[[2024,6,7]],"date-time":"2024-06-07T04:38:56Z","timestamp":1717735136000},"page":"3700","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Fluorescent Probe-Based Fiber Optic Sensor for Real-Time Monitoring of Chloride Ions in Coastal Concrete Structures"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9936-4784","authenticated-orcid":false,"given":"Zhen","family":"Lin","sequence":"first","affiliation":[{"name":"College of Civil and Transportation Engineering, Institute of Urban Smart Transportation & Safety Maintenance, Shenzhen University, Shenzhen 518060, China"},{"name":"National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment (Shenzhen), Shenzhen 518060, China"},{"name":"Shenzhen Key Laboratory of Safety and Health Monitoring of Marine Infrastructures, Shenzhen 518060, China"},{"name":"Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Quanfeng","family":"Ouyang","sequence":"additional","affiliation":[{"name":"College of Civil and Transportation Engineering, Institute of Urban Smart Transportation & Safety Maintenance, Shenzhen University, Shenzhen 518060, China"},{"name":"National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment (Shenzhen), Shenzhen 518060, China"},{"name":"Shenzhen Key Laboratory of Safety and Health Monitoring of Marine Infrastructures, Shenzhen 518060, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7141-2972","authenticated-orcid":false,"given":"Chuanrui","family":"Guo","sequence":"additional","affiliation":[{"name":"College of Civil and Transportation Engineering, Institute of Urban Smart Transportation & Safety Maintenance, Shenzhen University, Shenzhen 518060, China"},{"name":"National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment (Shenzhen), Shenzhen 518060, China"},{"name":"Shenzhen Key Laboratory of Safety and Health Monitoring of Marine Infrastructures, Shenzhen 518060, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yiqing","family":"Ni","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2024,6,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4113","DOI":"10.1016\/j.corsci.2007.05.007","article-title":"Chloride threshold level for corrosion of steel in concrete","volume":"49","author":"Ann","year":"2007","journal-title":"Corros. 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Sichuan Univ."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"3108","DOI":"10.1021\/acs.accounts.9b00292","article-title":"The chemistry of boronic acids in nanomaterials for drug delivery","volume":"52","author":"Stubelius","year":"2019","journal-title":"Acc. Chem. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"8550","DOI":"10.3390\/s110908550","article-title":"A microfluidic long-period fiber grating sensor platform for chloride ion concentration measurement","volume":"11","author":"Wang","year":"2011","journal-title":"Sensors"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1275","DOI":"10.1016\/j.buildenv.2004.10.005","article-title":"Studies on the aspects of chloride ion determination in different types of concrete under macro-cell corrosion conditions","volume":"40","author":"Muralidharan","year":"2005","journal-title":"Build. Environ."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/S0963-8695(00)00033-5","article-title":"Fiber optic sensors in concrete: The future?","volume":"34","author":"Leung","year":"2001","journal-title":"NDT E Int."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S1452-3981(23)17049-0","article-title":"Corrosion monitoring of reinforced concrete structures\u2014A review","volume":"2","author":"Song","year":"2007","journal-title":"Int. J. Electrochem. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"7527","DOI":"10.1007\/s10853-018-2083-0","article-title":"Microstructure, surface chemistry and electrochemical response of Ag | AgCl sensors in alkaline media","volume":"53","author":"Pargar","year":"2018","journal-title":"J. Mater. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/j.cemconcomp.2006.01.005","article-title":"Multiprobe chloride sensor for in situ monitoring of reinforced concrete structures","volume":"28","author":"Montemor","year":"2006","journal-title":"Cem. Concr. Compos."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1016\/j.aca.2015.06.047","article-title":"Sensor\u2013actuator system for dynamic chloride ion determination","volume":"888","author":"Abbas","year":"2015","journal-title":"Anal. Chim. Acta"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1007\/s13320-011-0011-x","article-title":"Fiber-optic sensor applications in civil and geotechnical engineering","volume":"1","author":"Habel","year":"2011","journal-title":"Photonic Sens."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"334","DOI":"10.1016\/j.snb.2018.12.059","article-title":"Ultrasensitive LPFG corrosion sensor with Fe-C coating electroplated on a Gr\/AgNW film","volume":"283","author":"Guo","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"104029","DOI":"10.1016\/j.cemconcomp.2021.104029","article-title":"Review of fiber optic sensors for corrosion monitoring in reinforced concrete","volume":"120","author":"Fan","year":"2021","journal-title":"Cem. Concr. Compos."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"109467","DOI":"10.1016\/j.optmat.2019.109467","article-title":"Preparation of lucigenin-doped silica nanoparticles and their application in fiber optic chloride ion sensor","volume":"98","author":"Xiao","year":"2019","journal-title":"Opt. Mater."},{"key":"ref_17","first-page":"964","article-title":"An optical fiber salinity sensor based on fluorescence quenching mechanism","volume":"Volume 8421","author":"Nguyen","year":"2012","journal-title":"Proceedings of the OFS2012 22nd International Conference on Optical Fiber Sensors"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.aca.2016.08.049","article-title":"Fluorescence based fiber optic and planar waveguide biosensors","volume":"943","year":"2016","journal-title":"A review. Anal. Chim. Acta"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"330","DOI":"10.1016\/S0925-4005(97)80228-6","article-title":"Studies on quenching of fluorescence of reagents in aqueous solution leading to an optical chloride-ion sensor","volume":"39","author":"Martin","year":"1997","journal-title":"Sens. Actuators B Chem."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Demchenko, A.P. (2015). Introduction to Fluorescence Sensing, Springer International Publishing.","DOI":"10.1007\/978-3-319-20780-3"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/S0301-4622(00)00146-0","article-title":"Quenching mechanism of quinolinium-type chloride-sensitive fluorescent indicators","volume":"85","author":"Jayaraman","year":"2000","journal-title":"Biophys. Chem."},{"key":"ref_22","unstructured":"Li, Z.J. (2018). Study of Optical Fiber Sensor for Monitoring Chloride Concentration on Concrete Environment, Wuhan University of Technology."},{"key":"ref_23","unstructured":"(2009). Sampling and Testing for Chloride Ion in Concrete and Concrete Raw Materials (Standard No. AASHTO T260-97)."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/12\/3700\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:55:07Z","timestamp":1760108107000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/12\/3700"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,6,7]]},"references-count":23,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2024,6]]}},"alternative-id":["s24123700"],"URL":"https:\/\/doi.org\/10.3390\/s24123700","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,6,7]]}}}