{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,8]],"date-time":"2026-02-08T11:18:14Z","timestamp":1770549494879,"version":"3.49.0"},"reference-count":36,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2022,2,17]],"date-time":"2022-02-17T00:00:00Z","timestamp":1645056000000},"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 Tecnologia","doi-asserted-by":"publisher","award":["UID-B\/50025\/2020"],"award-info":[{"award-number":["UID-B\/50025\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UID-P\/50025\/2020"],"award-info":[{"award-number":["UID-P\/50025\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UID-B\/50011\/2020"],"award-info":[{"award-number":["UID-B\/50011\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UID-P\/50011\/2020"],"award-info":[{"award-number":["UID-P\/50011\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["PTDC\/CTM-CTM\/3553\/2020"],"award-info":[{"award-number":["PTDC\/CTM-CTM\/3553\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>Zn1+xGa2\u22122xGexO4 (ZGGO:Cr)-persistent phosphor, with a molar fraction, x, of x = 0.1, doped with a 0.5% molar of chromium, was synthesised via solid-state reaction at 1350 \u00b0C for 36 h. X-ray diffraction measurements and Raman spectroscopy evidence a single crystalline phase corresponding to the cubic spinel structure. Room temperature (RT) photoluminescence (PL) and afterglow decay profiles were investigated using above and below bandgap excitation. In both cases, persistent PL was observed for almost 8 h, mainly originating from a Cr3+ defect, the so-called N2 optical centre. RT PL excitation and diffuse reflectance allow identification of the best pathways of Cr3+ red\/NIR emission, as well as estimation of the ZGGO bandgap energy at 4.82 eV. An in-depth investigation of the observed luminescence at 15 K and temperature-dependent PL under site-selective excitation reveals the spectral complexity of the presence of several optically active Cr3+ centres in the ZGGO host that emit in almost the same spectral region. Furthermore, the temperature dependence of the R-lines\u2019 intensity indicates the existence of thermal populating processes between the different optical centres. Such observations well account for a wide distribution of defect trap levels available for carrier capture\/release, as measured by the persistent luminescence decay, from which the carriers are released preferentially to the N2 Cr3+-related optical centre.<\/jats:p>","DOI":"10.3390\/app12042104","type":"journal-article","created":{"date-parts":[[2022,2,17]],"date-time":"2022-02-17T20:24:26Z","timestamp":1645129466000},"page":"2104","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Optical Studies in Red\/NIR Persistent Luminescent Cr-Doped Zinc Gallogermanate (ZGGO:Cr)"],"prefix":"10.3390","volume":"12","author":[{"given":"Maria S.","family":"Batista","sequence":"first","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0424-3248","authenticated-orcid":false,"given":"Joana","family":"Rodrigues","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Maria S.","family":"Relvas","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"J\u00falia","family":"Zanoni","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2699-646X","authenticated-orcid":false,"given":"Ana V.","family":"Gir\u00e3o","sequence":"additional","affiliation":[{"name":"CICECO-Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Ana","family":"Pimentel","sequence":"additional","affiliation":[{"name":"i3N\/CENIMAT, Department of Materials Science, NOVA School of Science and Technology, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8729-714X","authenticated-orcid":false,"given":"Florinda M.","family":"Costa","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4174-7253","authenticated-orcid":false,"given":"S\u00f3nia O.","family":"Pereira","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6945-2759","authenticated-orcid":false,"given":"Teresa","family":"Monteiro","sequence":"additional","affiliation":[{"name":"i3N, Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,2,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1906068","DOI":"10.1002\/adfm.201906068","article-title":"Multistimuli-Responsive Display Materials to Encrypt Differentiated Information in Bright and Dark Fields","volume":"29","author":"Jiang","year":"2019","journal-title":"Adv. Funct. Mater."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1705769","DOI":"10.1002\/adfm.201705769","article-title":"Optical Data Storage and Multicolor Emission Readout on Flexible Films Using Deep-Trap Persistent Luminescence Materials","volume":"28","author":"Zhuang","year":"2018","journal-title":"Adv. Funct. Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"152119","DOI":"10.1016\/j.jallcom.2019.152119","article-title":"Photostimulated near-infrared persistent luminescence Cr3+-doped Zn-Ga-Ge-O phosphor with high QE for optical information storage","volume":"812","author":"Wang","year":"2020","journal-title":"J. Alloys Compd."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1854","DOI":"10.1021\/acsami.7b17271","article-title":"Trap Depth Engineering of SrSi2O2N2:Ln2+, Ln3+ (Ln2+ = Yb, Eu; Ln3+ = Dy, Ho, Er) Persistent Luminescence Materials for Information Storage Applications","volume":"10","author":"Zhuang","year":"2018","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1900526","DOI":"10.1002\/adom.201900526","article-title":"Super-Long Persistent Luminescence in the Ultraviolet A Region from a Bi3+ -Doped LiYGeO4 Phosphor","volume":"7","author":"Shi","year":"2019","journal-title":"Adv. Opt. Mater."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"9096","DOI":"10.1021\/acs.jpcc.1c00999","article-title":"Afterglow-Catalysis and Self-Reporting of Pollutant Degradation by Ethylenediaminetetraacetic Acid Disodium-Etched Cr:ZnGa2O4","volume":"125","author":"Zhang","year":"2021","journal-title":"J. Phys. Chem. C"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1038\/nmat3908","article-title":"The in vivo activation of persistent nanophosphors for optical imaging of vascularization, tumours and grafted cells","volume":"13","author":"Maldiney","year":"2014","journal-title":"Nat. Mater."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"10131","DOI":"10.1364\/OE.19.010131","article-title":"ZnGa2O4:Cr3+: A new red long-lasting phosphor with high brightness","volume":"19","author":"Jacquart","year":"2011","journal-title":"Opt. Express"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1365","DOI":"10.1021\/cm403050q","article-title":"Storage of Visible Light for Long-Lasting Phosphorescence in Chromium-Doped Zinc Gallate","volume":"26","author":"Sharma","year":"2014","journal-title":"Chem. Mater."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"826","DOI":"10.1016\/j.jpcs.2014.03.005","article-title":"Origin of the visible light induced persistent luminescence of Cr3+-doped zinc gallate","volume":"75","author":"Gourier","year":"2014","journal-title":"J. Phys. Chem. Solids"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1016\/j.jpcs.2019.01.022","article-title":"Trends in Cr3+ red emissions from ZnGa2O4 nanostructures produced by pulsed laser ablation in a liquid medium","volume":"129","author":"Relvas","year":"2019","journal-title":"J. Phys. Chem. Solids"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1038\/nmat3173","article-title":"Sunlight-activated long-persistent luminescence in the near-infrared from Cr3+-doped zinc gallogermanates","volume":"11","author":"Pan","year":"2012","journal-title":"Nat. Mater."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1600","DOI":"10.1021\/cm304101n","article-title":"Considerable Improvement of Long-Persistent Luminescence in Germanium and Tin Substituted ZnGa2O4","volume":"25","author":"Allix","year":"2013","journal-title":"Chem. Mater."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3197","DOI":"10.1111\/jace.13103","article-title":"Novel Self-Activated Zinc Gallogermanate Phosphor: The Origin of its Photoluminescence","volume":"97","author":"Ren","year":"2014","journal-title":"J. Am. Ceram. Soc."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1077","DOI":"10.1063\/1.110937","article-title":"New ultraviolet-transport electroconductive oxide, ZnGa2O4 spinel","volume":"64","author":"Omata","year":"1994","journal-title":"Appl. Phys. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2535","DOI":"10.1021\/acs.cgd.9b01669","article-title":"p-Type Ultrawide-Band-Gap Spinel ZnGa2O4: New Perspectives for Energy Electronics","volume":"20","author":"Chikoidze","year":"2020","journal-title":"Cryst. Growth Des."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"252104","DOI":"10.1063\/5.0014827","article-title":"Electrical and optical properties of degenerate and semi-insulating ZnGa2O4: Electron\/phonon scattering elucidated by quantum magnetoconductivity","volume":"116","author":"Look","year":"2020","journal-title":"Appl. Phys. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"5197","DOI":"10.1063\/1.1674815","article-title":"Optical and Microwave Spectra of Cr3+ in the Spinel ZnGa2O4","volume":"54","author":"Kahan","year":"1971","journal-title":"J. Chem. Phys."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"751","DOI":"10.1107\/S0567739476001551","article-title":"Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides","volume":"32","author":"Shannon","year":"1976","journal-title":"Acta Crystallogr. Sect. A"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1039\/df9582600043","article-title":"The line spectra of Cr3+ ion in crystals","volume":"26","author":"Sugano","year":"1958","journal-title":"Discuss. Faraday Soc."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"753","DOI":"10.1143\/JPSJ.9.753","article-title":"On the Absorption Spectra of Complex Ions. I","volume":"9","author":"Tanabe","year":"1954","journal-title":"J. Phys. Soc. Japan"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"955","DOI":"10.1103\/PhysRevB.8.955","article-title":"Optical Spectra of Cr3+ Pairs in the Spinel ZnGa2O4","volume":"8","author":"Henning","year":"1973","journal-title":"Phys. Rev. B"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/0022-2313(81)90169-1","article-title":"N-lines in the luminescence spectra of Cr3+ -doped spinels (I) identification of N-lines","volume":"26","author":"Mikenda","year":"1981","journal-title":"J. Lumin."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1016\/0022-2313(81)90170-8","article-title":"N-lines in the luminescence spectra of Cr3+ -doped spinels (II) origins of N-lines","volume":"26","author":"Mikenda","year":"1981","journal-title":"J. Lumin."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1790","DOI":"10.1039\/C4CP03866E","article-title":"The importance of inversion disorder in the visible light induced persistent luminescence in Cr3+ doped AB2O4 (A = Zn or Mg and B = Ga or Al)","volume":"17","author":"Basavaraju","year":"2015","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2402","DOI":"10.1021\/acs.inorgchem.5b02805","article-title":"First-Principles Study of Antisite Defect Configurations in ZnGa2O4:Cr Persistent Phosphors","volume":"55","author":"Lejaeghere","year":"2016","journal-title":"Inorg. Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"710","DOI":"10.1038\/nnano.2009.326","article-title":"Second window for in vivo imaging","volume":"4","author":"Smith","year":"2009","journal-title":"Nat. Nanotechnol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1002\/adfm.201401612","article-title":"Gadolinium-Doped Persistent Nanophosphors as Versatile Tool for Multimodal In Vivo Imaging","volume":"25","author":"Maldiney","year":"2015","journal-title":"Adv. Funct. Mater."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1149\/2.F06094IF","article-title":"Persistent Luminescence Beats the Afterglow: 400 Years of Persistent Luminescence","volume":"18","year":"2009","journal-title":"Electrochem. Soc. Interface"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1002\/andp.201000096","article-title":"Lattice dynamics of ZnAl2O4 and ZnGa2O4 under high pressure","volume":"523","author":"Romero","year":"2011","journal-title":"Ann. Phys."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Manjon, F.J., Tiginyanu, I., and Ursaki, V. (2014). Pressure-Induced Phase Transitions in AB2X4 Chalcogenide Compounds, Springer.","DOI":"10.1007\/978-3-642-40367-5"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"903","DOI":"10.1016\/j.jeurceramsoc.2006.04.057","article-title":"Spectroscopic study of spinel ZnCr2O4 obtained from mechanically activated ZnO\u2013Cr2O3 mixtures","volume":"27","year":"2007","journal-title":"J. Eur. Ceram. Soc."},{"key":"ref_33","first-page":"97","article-title":"Luminescence from Chromium Doped Yttrium Aluminium Garnet","volume":"75","author":"Henry","year":"1975","journal-title":"Proc. R. Irish Acad. Sect. A Math. Phys. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"063522","DOI":"10.1063\/1.4754517","article-title":"Photoluminescence spectroscopy and energy-level analysis of metal-organic-deposited Ga2O3:Cr3+ films","volume":"112","author":"Tokida","year":"2012","journal-title":"J. Appl. Phys."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"582","DOI":"10.1016\/j.jlumin.2013.08.041","article-title":"Eu3+ luminescence in aluminophosphate glasses","volume":"145","author":"Nico","year":"2014","journal-title":"J. Lumin."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Pelant, I., and Valenta, J. (2012). Luminescence Spectroscopy of Semiconductors, Oxford University Press Inc.","DOI":"10.1093\/acprof:oso\/9780199588336.001.0001"}],"container-title":["Applied Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-3417\/12\/4\/2104\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:21:40Z","timestamp":1760134900000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-3417\/12\/4\/2104"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,2,17]]},"references-count":36,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2022,2]]}},"alternative-id":["app12042104"],"URL":"https:\/\/doi.org\/10.3390\/app12042104","relation":{},"ISSN":["2076-3417"],"issn-type":[{"value":"2076-3417","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,2,17]]}}}