Synergistic Photothermal Antibacterial Effects of Silver-Coated Upconversion Nanoparticles: Experimental Insights and DFT Calculations

Synergistic Photothermal Antibacterial Effects of Silver-Coated Upconversion Nanoparticles: Experimental Insights and DFT Calculations | 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 Research Article Synergistic Photothermal Antibacterial Effects of Silver-Coated Upconversion Nanoparticles: Experimental Insights and DFT Calculations Zhou You, Ali Mohsin, Reesha Khan, Ali Hussain, Sobia Niazi, Muhammad Sajjad, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7765354/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 The rise of antibiotic-resistant bacterial infections presents a significant global health challenge, contributing to higher mortality rates and prolonged hospitalizations. A promising solution is the development of localized hyperthermia for bacterial inactivation. In this study, we investigate the fabrication of silver-coated upconversion nanoparticles (UCNP@Ag NPs) that convert near-infrared (NIR) light into localized heat, offering an alternative to traditional antibiotic treatments. UCNP@Ag NPs were successfully synthesized and showed high photothermal conversion efficiency when irradiated with a 980 nm NIR laser. At a concentration of 100 µg/mL, the nanoparticles increased the solution temperature to 58.9°C within 6 minutes under 1.0 W/cm² NIR laser irradiation, which was sufficient to kill the bacteria. The inhibition rates for E. coli and S. aureus were 93.9% and 96.2%, respectively. The core-shell nanostructure exhibited superior antibacterial performance compared to silver nanoparticles (Ag NPs) and non-irradiated groups. Additionally, DFT calculations confirmed that the adsorption energy of Ag clusters on the NaYF₄:Yb,Tm host was thermodynamically favorable (−1.23 eV), ensuring stable integration. The calculated projected density of states (PDOS) and dielectric function analyses showed that Ag doping modifies the electronic structure near the Fermi level, enhancing NIR absorption and localized heating, which were critical for the nanoparticle’s effective antibacterial performance. This work demonstrates a highly efficient approach for antibacterial therapy through photothermal conversion using silver-coated upconversion nanoparticles. The synergy between the thermal and silver effects presents a promising alternative to traditional antibiotics, with potential applications in combating resistant bacterial strain Upconversion NPs Silver coating Photothermal Antibacterial activity Density Functional Theory Full Text Additional Declarations No competing interests reported. Supplementary Files supportinginformation.docx GraphicalAbstract.tif 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-7765354","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":532165093,"identity":"adbe0be4-fb6a-4ff2-94d1-144cbbfdddee","order_by":0,"name":"Zhou You","email":"","orcid":"","institution":"Research Center of Food Intelligent Detection and Quality Control, School of Food and Biological Engineering, Jiangsu University, Zhenjiang 213013, P. R. 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A promising solution is the development of localized hyperthermia for bacterial inactivation. In this study, we investigate the fabrication of silver-coated upconversion nanoparticles (UCNP@Ag NPs) that convert near-infrared (NIR) light into localized heat, offering an alternative to traditional antibiotic treatments. UCNP@Ag NPs were successfully synthesized and showed high photothermal conversion efficiency when irradiated with a 980 nm NIR laser. At a concentration of 100 µg/mL, the nanoparticles increased the solution temperature to 58.9°C within 6 minutes under 1.0 W/cm² NIR laser irradiation, which was sufficient to kill the bacteria. The inhibition rates for E. coli and S. aureus were 93.9% and 96.2%, respectively. The core-shell nanostructure exhibited superior antibacterial performance compared to silver nanoparticles (Ag NPs) and non-irradiated groups. Additionally, DFT calculations confirmed that the adsorption energy of Ag clusters on the NaYF₄:Yb,Tm host was thermodynamically favorable (−1.23 eV), ensuring stable integration. The calculated projected density of states (PDOS) and dielectric function analyses showed that Ag doping modifies the electronic structure near the Fermi level, enhancing NIR absorption and localized heating, which were critical for the nanoparticle’s effective antibacterial performance. This work demonstrates a highly efficient approach for antibacterial therapy through photothermal conversion using silver-coated upconversion nanoparticles. The synergy between the thermal and silver effects presents a promising alternative to traditional antibiotics, with potential applications in combating resistant bacterial strain\u003c/p\u003e","manuscriptTitle":"Synergistic Photothermal Antibacterial Effects of Silver-Coated Upconversion Nanoparticles: Experimental Insights and DFT Calculations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-22 11:12:52","doi":"10.21203/rs.3.rs-7765354/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":"e77504db-f6c3-48d2-977c-b2097c85bf91","owner":[],"postedDate":"October 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-25T21:38:27+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-22 11:12:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7765354","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7765354","identity":"rs-7765354","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}