{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T16:36:33Z","timestamp":1774629393436,"version":"3.50.1"},"reference-count":36,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2024,1,30]],"date-time":"2024-01-30T00:00:00Z","timestamp":1706572800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Wellcome Trust","award":["WT223940\/Z\/21\/Z"],"award-info":[{"award-number":["WT223940\/Z\/21\/Z"]}]},{"name":"Wellcome Trust","award":["2020.00044"],"award-info":[{"award-number":["2020.00044"]}]},{"name":"FCT-Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["WT223940\/Z\/21\/Z"],"award-info":[{"award-number":["WT223940\/Z\/21\/Z"]}]},{"name":"FCT-Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["2020.00044"],"award-info":[{"award-number":["2020.00044"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper presents an approach to enhancing sensitivity in optical sensors by integrating self-image theory and graphene oxide coating. The sensor is specifically engineered to quantitatively assess glucose concentrations in aqueous solutions that simulate the spectrum of glucose levels typically encountered in human saliva. Prior to sensor fabrication, the theoretical self-image points were rigorously validated using Multiphysics COMSOL 6.0 software. Subsequently, the sensor was fabricated to a length corresponding to the second self-image point (29.12 mm) and coated with an 80 \u00b5m\/mL graphene oxide film using the Layer-by-Layer technique. The sensor characterization in refractive index demonstrated a wavelength sensitivity of 200 \u00b1 6 nm\/RIU. Comparative evaluations of uncoated and graphene oxide-coated sensors applied to measure glucose in solutions ranging from 25 to 200 mg\/dL showed an eightfold sensitivity improvement with one bilayer of Polyethyleneimine\/graphene. The final graphene oxide-based sensor exhibited a sensitivity of 10.403 \u00b1 0.004 pm\/(mg\/dL) and demonstrated stability with a low standard deviation of 0.46 pm\/min and a maximum theoretical resolution of 1.90 mg\/dL.<\/jats:p>","DOI":"10.3390\/s24030891","type":"journal-article","created":{"date-parts":[[2024,1,30]],"date-time":"2024-01-30T12:06:58Z","timestamp":1706616418000},"page":"891","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Enhanced Sensitivity in Optical Sensors through Self-Image Theory and Graphene Oxide Coating"],"prefix":"10.3390","volume":"24","author":[{"given":"Cristina","family":"Cunha","sequence":"first","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Sciences, University of Porto, 4150-179 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0463-9894","authenticated-orcid":false,"given":"Catarina","family":"Monteiro","sequence":"additional","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"}]},{"given":"Ant\u00f3nio","family":"Vaz","sequence":"additional","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7555-361X","authenticated-orcid":false,"given":"Susana","family":"Silva","sequence":"additional","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"}]},{"given":"Orlando","family":"Fraz\u00e3o","sequence":"additional","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8295-3259","authenticated-orcid":false,"given":"Susana","family":"Novais","sequence":"additional","affiliation":[{"name":"INESC TEC\u2014Institute for Systems and Computer Engineering, Technology and Science, 4150-179 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,30]]},"reference":[{"key":"ref_1","first-page":"15","article-title":"Review on developments in fiber optical sensors and applications","volume":"Volume 7677","author":"Annamdas","year":"2010","journal-title":"Fiber Optic Sensors and Applications VII"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1064","DOI":"10.1109\/JLT.0082.921915","article-title":"Fiber-Optic Sensing: A Historical Perspective","volume":"26","author":"Culshaw","year":"2008","journal-title":"J. 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