{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T17:36:58Z","timestamp":1773337018312,"version":"3.50.1"},"reference-count":20,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2021,8,21]],"date-time":"2021-08-21T00:00:00Z","timestamp":1629504000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["PTDC\/EME-SIS\/1960\/2020"],"award-info":[{"award-number":["PTDC\/EME-SIS\/1960\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["NORTE-01-0145-FEDER-000032 \u2013 NextSea"],"award-info":[{"award-number":["NORTE-01-0145-FEDER-000032 \u2013 NextSea"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]},{"name":"European Regional Development Fund, through INTERREG V-A Spain-Portugal Programme (POCTEP) 2014-2020","award":["0591_FOODSENS_1_E"],"award-info":[{"award-number":["0591_FOODSENS_1_E"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The advanced and widespread use of microfluidic devices, which are usually fabricated in polydimethylsiloxane (PDMS), requires the integration of many sensors, always compatible with microfluidic fabrication processes. Moreover, current limitations of the existing optical and electrochemical oxygen sensors regarding long-term stability due to sensor degradation, biofouling, fabrication processes and cost have led to the development of new approaches. Thus, this manuscript reports the development, fabrication and characterization of a low-cost and highly sensitive dissolved oxygen optical sensor based on a membrane of PDMS doped with platinum octaethylporphyrin (PtOEP) film, fabricated using standard microfluidic materials and processes. The excellent mechanical and chemical properties (high permeability to oxygen, anti-biofouling characteristics) of PDMS result in membranes with superior sensitivity compared with other matrix materials. The wide use of PtOEP in sensing applications, due to its advantage of being easily synthesized using microtechnologies, its strong phosphorescence at room temperature with a quantum yield close to 50%, its excellent Strokes Shift as well as its relatively long lifetime (75 \u00b5s), provide the suitable conditions for the development of a miniaturized luminescence optical oxygen sensor allowing long-term applications. The influence of the PDMS film thickness (0.1\u20132.5 mm) and the PtOEP concentration (363, 545, 727 ppm) in luminescent properties are presented. This enables to achieve low detection levels in a gas media range from 0.5% up to 20%, and in liquid media from 0.5 mg\/L up to 3.3 mg\/L at 1 atm, 25 \u00b0C. As a result, we propose a simple and cost-effective system based on a LED membrane photodiode system to detect low oxygen concentrations for in situ applications.<\/jats:p>","DOI":"10.3390\/s21165645","type":"journal-article","created":{"date-parts":[[2021,8,22]],"date-time":"2021-08-22T22:59:27Z","timestamp":1629673167000},"page":"5645","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["PtOEP\u2013PDMS-Based Optical Oxygen Sensor"],"prefix":"10.3390","volume":"21","author":[{"given":"Camila M.","family":"Penso","sequence":"first","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"given":"Jo\u00e3o L.","family":"Rocha","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1120-9312","authenticated-orcid":false,"given":"Marcos S.","family":"Martins","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2290-808X","authenticated-orcid":false,"given":"Paulo J.","family":"Sousa","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3395-1251","authenticated-orcid":false,"given":"V\u00e2nia C.","family":"Pinto","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2460-0556","authenticated-orcid":false,"given":"Gra\u00e7a","family":"Minas","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5230-639X","authenticated-orcid":false,"given":"Maria M.","family":"Silva","sequence":"additional","affiliation":[{"name":"Chemistry Department and Center of Chemistry, University of Minho, Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8441-3264","authenticated-orcid":false,"given":"Lu\u00eds M.","family":"Goncalves","sequence":"additional","affiliation":[{"name":"Center for MicroElectromechanical Systems (CMEMS-UMinho), University of Minho, Azur\u00e9m, 4800-058 Guimar\u00e3es, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1007\/s10661-018-6692-5","article-title":"Comparative validation of amperometric and optical analyzers of dissolved oxygen: A case study","volume":"190","author":"Helm","year":"2018","journal-title":"Environ. Monit. Assess."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/S0925-4005(97)80168-2","article-title":"Optical measurement of oxygen and temperature in microscale: Strategies and biological applications","volume":"38","author":"Klimant","year":"1997","journal-title":"Sens. Actuators B Chem."},{"key":"ref_3","unstructured":"Ferreira, M.A.C. (2021, January 15). Development of Dissolved Oxygen Sensors Using Electrochemical and Optic Methods for Real Time Monitoring of Water Quality. Available online: http:\/\/www.teses.usp.br\/teses\/disponiveis\/3\/3140\/tde-08012008-161104\/."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"568","DOI":"10.1016\/j.snb.2006.09.062","article-title":"Optical oxygen sensing based on luminescence quenching of platinum porphyrin dyes doped in ormosil coatings","volume":"123","author":"Basu","year":"2007","journal-title":"Sens. Actuators B Chem."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"100338","DOI":"10.1016\/j.jphotochemrev.2019.100338","article-title":"The centenary of the Stern-Volmer equation of fluorescence quenching: From the single line plot to the SV quenching map","volume":"42","author":"Gehlen","year":"2020","journal-title":"J. Photochem. Photobiol. C Photochem. Rev."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1021\/ac00004a006","article-title":"Luminescence quenching mechanism for microheterogeneous systems","volume":"63","author":"Carraway","year":"1991","journal-title":"Anal. Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1007\/s12566-012-0032-y","article-title":"Indicators for optical oxygen sensors","volume":"4","author":"Quaranta","year":"2012","journal-title":"Bioanal. Rev."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1531","DOI":"10.1002\/ejic.201100089","article-title":"Strongly phosphorescent iridium(III)-porphyrins\u2014New oxygen indicators with tuneable photophysical properties and functionalities","volume":"2011","author":"Koren","year":"2011","journal-title":"Eur. J. Inorg. Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2795","DOI":"10.1002\/1097-4628(20000923)77:13<2795::AID-APP1>3.0.CO;2-K","article-title":"Ideality of pressure-sensitive paint. I. Platinum tetra(pentafluorophenyl)porphine in fluoroacrylic polymer","volume":"77","author":"Puklin","year":"2000","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"705","DOI":"10.1002\/1099-1581(200008\/12)11:8\/12<705::AID-PAT23>3.0.CO;2-L","article-title":"Novel optical oxygen sensing material: Platinum porphyrin-fluoropolymer film","volume":"11","author":"Amao","year":"2000","journal-title":"Polym. Adv. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"200","DOI":"10.1016\/S0925-4005(01)01006-1","article-title":"Response characteristics of thin film oxygen sensors, Pt and Pd octaethylporphyrins in polymer films","volume":"82","author":"Douglas","year":"2002","journal-title":"Sens. Actuators B Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"871","DOI":"10.1039\/b000702l","article-title":"Optical oxygen sensing based on the luminescence change of metalloporphyrins immobilized in styrene-pentafluorostyrene copolymer film","volume":"125","author":"Amao","year":"2000","journal-title":"Analyst"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1917","DOI":"10.1021\/ma001454j","article-title":"Polymer\/silica composite films as luminescent oxygen sensors","volume":"34","author":"Lu","year":"2001","journal-title":"Macromolecules"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1911","DOI":"10.1039\/b005838f","article-title":"Platinum porphyrin embedded in poly(1-trimethylsilyl-1-propyne) film as an optical sensor for trace analysis of oxygen","volume":"125","author":"Amao","year":"2000","journal-title":"Analyst"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"3724","DOI":"10.1021\/ic049902h","article-title":"Electronic spectroscopy, photophysical properties, and emission quenching studies of an oxidatively robust perfluorinated platinum porphyrin","volume":"43","author":"Lai","year":"2004","journal-title":"Inorg. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1111","DOI":"10.1142\/S1088424609001455","article-title":"Optical oxygen sensor devices using metalloporphyrins","volume":"13","author":"Amao","year":"2009","journal-title":"J. Porphyr. Phthalocyanines"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1002\/polb.1995.090330214","article-title":"Gas permeability and stability of poly(1-trimethylsilyl-1-propyne-co-1-phenyl-1-propyne) membranes","volume":"33","author":"Nagai","year":"1995","journal-title":"J. Polym. Sci. Part B Polym. Phys."},{"key":"ref_18","unstructured":"Brandrup, J., Immergut, E.H., and Grulke, E.A. (1999). Polymer Handbook, Wiley-Interscience Publication. [4th ed.]."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"274","DOI":"10.1016\/j.molstruc.2010.03.054","article-title":"Raman, mid-infrared, near-infrared and ultraviolet-visible spectroscopy of PDMS silicone rubber for characterization of polymer optical waveguide materials","volume":"976","author":"Cai","year":"2010","journal-title":"J. Mol. Struct."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1883","DOI":"10.1002\/adfm.200500737","article-title":"Mesostructured Silica Chemically Doped with RuII as a Superior Optical Oxygen Sensor","volume":"16","author":"Lei","year":"2006","journal-title":"Adv. Funct. Mater."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5645\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:48:55Z","timestamp":1760165335000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5645"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,21]]},"references-count":20,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["s21165645"],"URL":"https:\/\/doi.org\/10.3390\/s21165645","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,21]]}}}