{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T18:23:17Z","timestamp":1773339797863,"version":"3.50.1"},"reference-count":29,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,3,8]],"date-time":"2021-03-08T00:00:00Z","timestamp":1615161600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>Tetragonal Er0.5Nb0.5O2 and monoclinic ErNbO4 micro- and nanoparticles were prepared by the citrate sol\u2013gel method and heat-treated at temperatures between 700 and 1600 \u00b0C. ErNbO4 revealed a spherical-shaped crystallite, whose size increased with heat treatment temperatures. To assess their optical properties at room temperature (RT), a thorough spectroscopic study was conducted. RT photoluminescence (PL) spectroscopy revealed that Er3+ optical activation was achieved in all samples. The photoluminescence spectra show the green\/yellow 2H11\/2, 4S3\/2\u21924I15\/2 and red 4F9\/2\u21924I15\/2 intraionic transitions as the main visible recombination, with the number of the crystal field splitting Er3+ multiplets reflecting the ion site symmetry in the crystalline phases. PL excitation allows the identification of Er3+ high-energy excited multiplets as the preferential population paths of the emitting levels. Independently of the crystalline structure, the intensity ratio between the green\/yellow and red intraionic transitions was found to be strongly sensitive to the excitation energy. After pumping the samples with a resonant excitation into the 4G11\/2 excited multiplet, a green\/yellow transition stronger than the red one was observed, whereas the reverse occurred for higher excitation photon energies. Thus, a controllable selective excited tunable green to red color was achieved, which endows new opportunities for photonic and optoelectronic applications.<\/jats:p>","DOI":"10.3390\/nano11030660","type":"journal-article","created":{"date-parts":[[2021,3,8]],"date-time":"2021-03-08T12:12:18Z","timestamp":1615205538000},"page":"660","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Tuning Green to Red Color in Erbium Niobate Micro- and Nanoparticles"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2217-4584","authenticated-orcid":false,"given":"Susana","family":"Devesa","sequence":"first","affiliation":[{"name":"Centre for Physics University of Coimbra (CFisUC), Physics Department, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal"},{"name":"i3N and Physics Department, 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 and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"S\u00edlvia Soreto","family":"Teixeira","sequence":"additional","affiliation":[{"name":"i3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Aidan P.","family":"Rooney","sequence":"additional","affiliation":[{"name":"CEA LETI-Minatec, 17 Rue des Martyrs, 38054 Grenoble CEDEX 9, France"}]},{"given":"Manuel P. F.","family":"Gra\u00e7a","sequence":"additional","affiliation":[{"name":"i3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"David","family":"Cooper","sequence":"additional","affiliation":[{"name":"CEA LETI-Minatec, 17 Rue des Martyrs, 38054 Grenoble CEDEX 9, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6945-2759","authenticated-orcid":false,"given":"Teresa","family":"Monteiro","sequence":"additional","affiliation":[{"name":"i3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7666-4741","authenticated-orcid":false,"given":"Lu\u00eds C.","family":"Costa","sequence":"additional","affiliation":[{"name":"i3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,3,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1455","DOI":"10.1039\/C7CE02072D","article-title":"Growth, structural and thermophysical properties of TbNbO4 crystals","volume":"20","author":"Guo","year":"2018","journal-title":"CrystEngComm"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"062024","DOI":"10.1088\/1742-6596\/917\/6\/062024","article-title":"Transparent glass-ceramics with Yb3+,Ho3+:YNbO4 nanocrystals for green phosphors","volume":"917","author":"Volokitina","year":"2017","journal-title":"J. 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