Optimization of Reversible Photochromic Coatings Based on Methylene Blue: Formulation Screening, Performance Characterization, and Mechanistic Insights

Optimization of Reversible Photochromic Coatings Based on Methylene Blue: Formulation Screening, Performance Characterization, and Mechanistic Insights | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Short Report Optimization of Reversible Photochromic Coatings Based on Methylene Blue: Formulation Screening, Performance Characterization, and Mechanistic Insights Yiming Zou, Jianqi Chen, Yaolin Zhang, Xia Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8226451/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Reversible photochromic coatings have emerged as promising materials for optical information storage, smart packaging, and UV detection, yet commercial products often suffer from high fabrication costs, poor color-switching sensitivity, and narrow absorption ranges. In this study, a methylene blue (MB) based reversible photochromic coating was developed via systematic single-factor optimization, focusing on seven critical variables: color-changing agent type, reducing agent type, oxidizing agent dosage, catalyst type, system temperature, UV wavelength, and auxiliary material type. The optimal formulation was determined as 0.02 g MB (color-changing agent), 0.2 g SnCl2 (reducing agent), and 20 g SiO2 (auxiliary material) in 0.5 mol/L HCl medium. Under 365 nm UV irradiation, this coating exhibited rapid color switching (blue → colorless → blue) with a color-changing time of 15-19 s and recovery time of 10-13 s over 8 cycles. Spectroscopic characterization via a V-1600 spectrophotometer revealed a broad absorption range of 330-685 nm, with a maximum absorption peak at 664 nm (consistent with MB’s characteristic absorption). Cost analysis showed the optimized coating cost only 12.66 CNY/kg, which is 85.8% lower than commercial photochromic coatings (87.71 CNY/kg). Additionally, incorporating 0.5 g tris(2,2′-bipyridine)ruthenium chloride hexahydrate ([Ru(bpy)3]Cl2·6H2O) as a catalyst expanded the color transition to orange-to-black, enhancing the material’s versatility. Mechanistic studies suggested that Sn2+ mediates MB’s reduction to leucomethylene blue (colorless), while UV irradiation (365 nm) drives reoxidation to MB (blue); SiO2 acts as a dispersant to improve coating uniformity and stability. This low-cost, high-performance MB-based coating provides a scalable solution for practical photochromic applications. Materials Chemistry Reversible photochromism Methylene blue Stan nous chloride Coating optimization Performance characterization Full Text Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8226451","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":552041939,"identity":"dc26876c-0282-4670-a950-045e0be354db","order_by":0,"name":"Yiming Zou","email":"","orcid":"","institution":"Jinan University","correspondingAuthor":false,"prefix":"","firstName":"Yiming","middleName":"","lastName":"Zou","suffix":""},{"id":552041940,"identity":"94f1a6f7-2e9e-411e-ab64-76c1391f4ee7","order_by":1,"name":"Jianqi Chen","email":"","orcid":"","institution":"Jinan 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04:36:49","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-8226451/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8226451/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":97250425,"identity":"cefef2c6-5030-48fc-9344-0a15b3f5151c","added_by":"auto","created_at":"2025-12-02 13:14:30","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":739046,"visible":true,"origin":"","legend":"","description":"","filename":"MehtyleneBlue.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8226451/v1_covered_fd02da89-66ea-432a-aa70-bed04dfbeb4b.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eOptimization of Reversible Photochromic Coatings Based on Methylene Blue: Formulation Screening, Performance Characterization, and Mechanistic Insights\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Jinan University","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Reversible photochromism, Methylene blue, Stan nous chloride, Coating optimization, Performance characterization","lastPublishedDoi":"10.21203/rs.3.rs-8226451/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8226451/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eReversible photochromic coatings have \u0026nbsp;emerged as promising materials for optical information \u0026nbsp;storage, smart packaging, and UV detection, yet \u0026nbsp;commercial products often suffer from high fabrication \u0026nbsp;costs, poor color-switching sensitivity, and narrow \u0026nbsp;absorption ranges. In this study, a methylene blue (MB) based reversible photochromic coating was developed via \u0026nbsp;systematic single-factor optimization, focusing on seven \u0026nbsp;critical variables: color-changing agent type, reducing \u0026nbsp;agent type, oxidizing agent dosage, catalyst type, system \u0026nbsp;temperature, UV wavelength, and auxiliary material type. \u0026nbsp;The optimal formulation was determined as 0.02 g MB \u0026nbsp;(color-changing agent), 0.2 g SnCl2 (reducing agent), and \u0026nbsp;20 g SiO2 (auxiliary material) in 0.5 mol/L HCl medium. \u0026nbsp;Under 365 nm UV irradiation, this coating exhibited \u0026nbsp;rapid color switching (blue → colorless → blue) with \u0026nbsp;a color-changing time of 15-19 s and recovery time of \u0026nbsp;10-13 s over 8 cycles. Spectroscopic characterization via \u0026nbsp;a V-1600 spectrophotometer revealed a broad absorption \u0026nbsp;range of 330-685 nm, with a maximum absorption peak at \u0026nbsp;664 nm (consistent with MB’s characteristic absorption). \u0026nbsp;Cost analysis showed the optimized coating cost only \u0026nbsp;12.66 CNY/kg, which is 85.8% lower than commercial \u0026nbsp;photochromic coatings (87.71 CNY/kg). Additionally, \u0026nbsp;incorporating 0.5 g tris(2,2′-bipyridine)ruthenium chloride \u0026nbsp;hexahydrate ([Ru(bpy)3]Cl2·6H2O) as a catalyst expanded \u0026nbsp;the color transition to orange-to-black, enhancing the \u0026nbsp;material’s versatility. Mechanistic studies suggested \u0026nbsp;that Sn2+ mediates MB’s reduction to leucomethylene \u0026nbsp;blue (colorless), while UV irradiation (365 nm) drives \u0026nbsp;reoxidation to MB (blue); SiO2 acts as a dispersant to \u0026nbsp;improve coating uniformity and stability. This low-cost, \u0026nbsp;high-performance MB-based coating provides a scalable \u0026nbsp;solution for practical photochromic applications.\u003c/p\u003e","manuscriptTitle":"Optimization of Reversible Photochromic Coatings Based on Methylene Blue: Formulation Screening, Performance Characterization, and Mechanistic Insights","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-02 11:26:02","doi":"10.21203/rs.3.rs-8226451/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"109c11af-64f2-4fb9-b9c3-21b0528e9b9e","owner":[],"postedDate":"December 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":58745909,"name":"Materials Chemistry"}],"tags":[],"updatedAt":"2025-12-02T11:26:02+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-02 11:26:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8226451","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8226451","identity":"rs-8226451","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}