{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T04:54:18Z","timestamp":1787028858441,"version":"build-2736575974"},"reference-count":53,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,12,20]],"date-time":"2025-12-20T00:00:00Z","timestamp":1766188800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Bulgarian NSF","award":["K\u03a0-06-H89\/07"],"award-info":[{"award-number":["K\u03a0-06-H89\/07"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>This study explores the sol\u2013gel synthesis, structural characterization, and photocatalytic performance of Ho3+-doped TiO2 nanopowders at two dopant levels (0.5 and 2 mol%). Transparent, homogeneous gels were prepared using titanium (IV) butoxide and holmium (III) nitrate pentahydrate in ethanol, followed by drying and optional annealing at 500 \u00b0C. X-ray diffraction confirmed anatase TiO2 as the dominant crystalline phase, with Ho incorporation suppressing crystal growth and yielding smaller crystallite sizes than undoped TiO2. FT-IR and UV-Vis spectroscopy verified complete hydrolysis\u2013condensation during gel formation, while diffuse reflectance spectra revealed a red-shifted absorption edge, indicating reduced band gaps. SEM analysis showed nanoscale particles with agglomeration, which intensified after annealing. Photocatalytic activity was tested under UV irradiation using Crystal Violet (anionic dye) and Carmoisine (cationic dye). Annealed Ho-doped powders exhibited markedly higher degradation rates, with the 2 mol% sample achieving the greatest efficiency, particularly against Crystal Violet. These findings demonstrate that Ho3+ doping enhances TiO2\u2019s UV-driven photocatalytic activity by tailoring its structural and optical properties.<\/jats:p>","DOI":"10.3390\/ma19010017","type":"journal-article","created":{"date-parts":[[2025,12,22]],"date-time":"2025-12-22T07:01:33Z","timestamp":1766386893000},"page":"17","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Photocatalytic Decomposition of Carmoisine and Crystal Violet by Ho-Doped TiO2 Sol-Gel Powders"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2010-7118","authenticated-orcid":false,"given":"Nina","family":"Kaneva","sequence":"first","affiliation":[{"name":"Laboratory of Nanoparticle Science and Technology, Department of General and Inorganic Chemistry, Faculty of Chemistry and Pharmacy, University of Sofia, 1 James Bourchier Blvd., 1164 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-1943-7197","authenticated-orcid":false,"given":"Stefani","family":"Petrova","sequence":"additional","affiliation":[{"name":"Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev, Str., bl. 11, 1113 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7697-466X","authenticated-orcid":false,"given":"Albena","family":"Bachvarova-Nedelcheva","sequence":"additional","affiliation":[{"name":"Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev, Str., bl. 11, 1113 Sofia, Bulgaria"},{"name":"National Centre of Excellence Mechatronics and Clean Technologies, 8 bul., Kl. Ohridski, 1756 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"120103","DOI":"10.1016\/j.jenvman.2024.120103","article-title":"Contamination of Textile Dyes in Aquatic Environment: Adverse Impacts on Aquatic Ecosystem and Human Health, and Its Management Using Bioremediation","volume":"353","author":"Dutta","year":"2024","journal-title":"J. Environ. Manag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"108639","DOI":"10.1016\/j.jece.2022.108639","article-title":"A Review on Selective Dye Adsorption by Different Mechanisms","volume":"10","author":"Shi","year":"2022","journal-title":"J. Environ. Chem. 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