{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T23:19:29Z","timestamp":1768000769641,"version":"3.49.0"},"reference-count":34,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2023,5,22]],"date-time":"2023-05-22T00:00:00Z","timestamp":1684713600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"national funds (OE)","award":["57\/2016"],"award-info":[{"award-number":["57\/2016"]}]},{"name":"national funds (OE)","award":["57\/2017"],"award-info":[{"award-number":["57\/2017"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Ferrites have been widely studied for their use in the biomedical area, mostly due to their magnetic properties, which gives them the potential to be used in diagnostics, drug delivery, and in treatment with magnetic hyperthermia, for example. In this work, KFeO2 particles were synthesized with a proteic sol-gel method using powdered coconut water as a precursor; this method is based on the principles of green chemistry. To improve its properties, the base powder obtained was subjected to multiple heat treatments at temperatures between 350 and 1300 \u00b0C. The samples obtained underwent structural, morphological, biocompatibility, and magnetic characterization. The results show that upon raising the heat treatment temperature, not only is the wanted phase detected, but also the secondary phases. To overcome these secondary phases, several different heat treatments were carried out. Using scanning electron microscopy, grains in the micrometric range were observed. Saturation magnetizations between 15.5 and 24.1 emu\/g were observed for the samples containing KFeO2 with an applied field of 50 kOe at 300 K. From cellular compatibility (cytotoxicity) assays, for concentrations up to 5 mg\/mL, only the samples treated at 350 \u00b0C were cytotoxic. However, the samples containing KFeO2, while being biocompatible, had low specific absorption rates (1.55\u20135.76 W\/g).<\/jats:p>","DOI":"10.3390\/ma16103880","type":"journal-article","created":{"date-parts":[[2023,5,22]],"date-time":"2023-05-22T05:04:44Z","timestamp":1684731884000},"page":"3880","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Potassium Ferrite for Biomedical Applications"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2416-9081","authenticated-orcid":false,"given":"Jo\u00e3o P. F.","family":"Carvalho","sequence":"first","affiliation":[{"name":"i3N and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"T\u00e2nia","family":"Vieira","sequence":"additional","affiliation":[{"name":"i3N\/CENIMAT, Physics Department, NOVA School of Science and Technology, Campus de Caparica, NOVA University Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9959-4272","authenticated-orcid":false,"given":"Jorge Carvalho","family":"Silva","sequence":"additional","affiliation":[{"name":"i3N\/CENIMAT, Physics Department, NOVA School of Science and Technology, Campus de Caparica, NOVA University Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4975-7480","authenticated-orcid":false,"given":"Paula I. P.","family":"Soares","sequence":"additional","affiliation":[{"name":"i3N\/CENIMAT, Materials Science Department, NOVA School of Science and Technology, Campus de Caparica, NOVA University Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4398-9256","authenticated-orcid":false,"given":"Nuno M.","family":"Ferreira","sequence":"additional","affiliation":[{"name":"i3N and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4148-4374","authenticated-orcid":false,"given":"Carlos O.","family":"Amorim","sequence":"additional","affiliation":[{"name":"CICECO-Aveiro Institute of Materials and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4084-5764","authenticated-orcid":false,"given":"S\u00edlvia Soreto","family":"Teixeira","sequence":"additional","affiliation":[{"name":"i3N and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6858-9507","authenticated-orcid":false,"given":"Manuel P. F.","family":"Gra\u00e7a","sequence":"additional","affiliation":[{"name":"i3N and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1316","DOI":"10.1080\/02656736.2018.1430867","article-title":"Magnetic hyperthermia therapy for the treatment of glioblastoma: A review of the therapy\u2019s history, efficacy and application in humans","volume":"34","author":"Mahmoudi","year":"2018","journal-title":"Int. J. Hyperth."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Kumar, P., Burman, U., and Kaul, R.K. (2018). Nanomaterials in Plants, Algae, and Microorganisms, Elsevier.","DOI":"10.1016\/B978-0-12-811487-2.00009-8"},{"key":"ref_3","unstructured":"Hussain, M.I., Xia, M., Na Ren, X., Akhtar, K., Nawaz, A., Sharma, S.K., and Javed, Y. (2020). Magnetic Nanoheterostructures: Diagnostic, Imaging and Treatment, Springer."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1016\/j.rpor.2013.09.011","article-title":"Magnetic nanoparticle-based hyperthermia for cancer treatment","volume":"18","author":"Teijeiro","year":"2013","journal-title":"Rep. Pract. Oncol. Radiother."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/j.jab.2014.05.003","article-title":"Study on novel, superparamagnetic and biocompatible PEG\/KFeO2 nanocomposite","volume":"13","author":"Khanna","year":"2015","journal-title":"J. Appl. Biomed."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/j.jmst.2013.10.008","article-title":"Synthesis, Characterization and Biocompatibility of Potassium Ferrite Nanoparticles","volume":"30","author":"Khanna","year":"2014","journal-title":"J. Mater. Sci. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Moon, S., Shim, I., and Kim, C. (2006, January 8\u201312). Crystallographic and Magnetic Properties of KFeO2. Proceedings of the 2006 IEEE International Magnetics Conference (INTERMAG), San Diego, CA, USA.","DOI":"10.1109\/INTMAG.2006.375457"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4620","DOI":"10.1039\/D1CP05171G","article-title":"K+ extraction induced phase evolution of KFeO2","volume":"24","author":"Zhang","year":"2022","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1117","DOI":"10.1016\/0022-3697(77)90037-3","article-title":"Crystal and magnetic structure of KFeO2","volume":"38","author":"Tomkowicz","year":"1977","journal-title":"J. Phys. Chem. Solids"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"11232","DOI":"10.1007\/s10854-021-05793-x","article-title":"Investigation of cytotoxicity of superparamagnetic KFeO2 nanoparticles on MCF-7 cell lines for biomedical applications","volume":"32","author":"Tangra","year":"2021","journal-title":"J. Mater. Sci. Mater. Electron."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1039\/B918763B","article-title":"Green Chemistry: Principles and Practice","volume":"39","author":"Anastas","year":"2010","journal-title":"Chem. Soc. Rev."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1007\/s10971-012-2829-0","article-title":"Structural and dielectric characterization of LiNbO3 nano-size powders obtained by Pechini method","volume":"64","author":"Prezas","year":"2012","journal-title":"J. Sol-Gel Sci. Tech."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"11346","DOI":"10.1007\/s10854-019-01482-y","article-title":"Niobium oxide prepared by sol\u2013gel using powder coconut water","volume":"30","author":"Lucas","year":"2019","journal-title":"J. Mat. Sci. Mater. Electron."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1016\/j.jallcom.2009.06.052","article-title":"Spectroscopy studies of NiFe2O4 nanosized powders obtained using coconut water","volume":"485","author":"Monteiro","year":"2009","journal-title":"J. Alloys Compds."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"88","DOI":"10.1016\/j.physb.2006.05.158","article-title":"Nanocrystals of BaFe12O19 obtained by the proteic sol\u2013gel process","volume":"384","author":"Fortes","year":"2006","journal-title":"Phys. B Condens. Matter"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.physb.2006.05.159","article-title":"SrFe12O19 prepared by the proteic sol\u2013gel process","volume":"384","author":"Brito","year":"2006","journal-title":"Phys. B Condens. Matter"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"467","DOI":"10.1016\/j.matchemphys.2014.10.047","article-title":"Magnetic, Raman and M\u00f6ssbauer properties of double-doping LaFeO3 perovskite oxides","volume":"149\u2013150","author":"Benali","year":"2015","journal-title":"Mat. Chem. Phys."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"105602","DOI":"10.1088\/1361-6501\/ac0d23","article-title":"A geometry-independent moment correction method for the MPMS3 SQUID-based magnetometer","volume":"32","author":"Amorim","year":"2021","journal-title":"Meas. Sci. Technol."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Teixeira, S.S., Gra\u00e7a, M.P.F., Lucas, J., Valente, M.A., Soares, P.I.P., Lan\u00e7a, M.C., Vieira, T., Silva, J.C., Borges, J.P., and Jinga, L.-I. (2021). Nanostructured LiFe5O8 by a Biogenic Method for Applications from Electronics to Medicine. Nanomaterials, 11.","DOI":"10.3390\/nano11010193"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1154\/1.2179804","article-title":"R factors in Rietveld analysis: How good is good enough?","volume":"21","author":"Toby","year":"2006","journal-title":"Powder Diffr."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"114830","DOI":"10.1016\/j.mseb.2020.114830","article-title":"Williamson-hall analysis in estimation of crystallite size and lattice strain in Bi1.34Fe0.66Nb1.34O6.35 prepared by the sol-gel method","volume":"263","author":"Devesa","year":"2021","journal-title":"Mater. Sci. Eng. B Solid State Mater. Adv. Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.jallcom.2018.11.059","article-title":"Investigation of structural, Raman and photoluminescence properties of novel material: KFeO2 nanoparticles","volume":"778","author":"Tangra","year":"2019","journal-title":"J. Alloys Compd."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1018","DOI":"10.1016\/j.gsf.2020.03.002","article-title":"Raman and infrared spectroscopic quantification of the carbonate concentration in K2CO3 aqueous solutions with water as an internal standard","volume":"12","author":"Ma","year":"2021","journal-title":"Geosci. Front."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"873","DOI":"10.1002\/(SICI)1097-4555(199711)28:11<873::AID-JRS177>3.0.CO;2-B","article-title":"Raman microspectroscopy of some iron oxides and oxyhydroxides","volume":"28","year":"1997","journal-title":"J. Raman Spectrosc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"012036","DOI":"10.1088\/1757-899X\/743\/1\/012036","article-title":"Production of Iron Oxide Nanoparticles by Co-Precipitation method with Optimization Studies of Processing Temperature, pH and Stirring Rate","volume":"743","author":"Hui","year":"2020","journal-title":"IOP Conf. Ser. Mater. Sci. Eng."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"264","DOI":"10.1016\/j.matchemphys.2010.06.029","article-title":"Micelle based synthesis of cobalt ferrite nanoparticles and its characterization using Fourier Transform Infrared Transmission Spectrometry and Thermogravimetry","volume":"124","author":"Rana","year":"2010","journal-title":"Mater. Chem. Phys."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"151","DOI":"10.3103\/S0967091220030055","article-title":"Structure, Morphology and Magnetic Properties of Hematite and Maghemite Nanopowders Produced from Rolling Mill Scale","volume":"50","author":"Kargin","year":"2020","journal-title":"Steel Transl."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3135","DOI":"10.1007\/s10008-019-04407-1","article-title":"KFeO2 with corner-shared FeO4 frameworks as a new type of cathode material in potassium-ion batteries","volume":"23","author":"Han","year":"2019","journal-title":"J. Solid State Electrochem."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Gavinho, S.R., P\u00e1dua, A.S., S\u00e1-Nogueira, I., Silva, J.C., Borges, J.P., Costa, L.C., and Gra\u00e7a, M.P.F. (2022). Biocompatibility, Bioactivity, and Antibacterial Behaviour of Cerium-Containing Bioglass\u00ae. Nanomaterials, 12.","DOI":"10.3390\/nano12244479"},{"key":"ref_30","unstructured":"Gavinho, S.R., Prezas, P.R., and Gra\u00e7a, M.P.F. (2017). Electrical Measurements: Introduction, Concepts and Applications, Nova Science Publishers Inc."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1885","DOI":"10.1111\/ijac.13243","article-title":"Nontoxic glasses: Preparation, structural, electrical and biological properties","volume":"16","author":"Gavinho","year":"2019","journal-title":"Int. J. App. Ceram. Tech."},{"key":"ref_32","first-page":"2","article-title":"High saturation magnetization of \u03b3-Fe2O3 nano-particles by a facile one-step synthesis approach","volume":"6","author":"Cao","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Haynes, W.M., Lide, D.R., and Bruno, T.J. (2016). CRC Handbook of Chemistry and Physics, CRC Press.","DOI":"10.1201\/9781315380476"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"S2919","DOI":"10.1088\/0953-8984\/18\/38\/S26","article-title":"Magnetic particle hyperthermia: Nanoparticle magnetism and materials development for cancer therapy","volume":"18","author":"Hergt","year":"2006","journal-title":"J. Phys. Condens. Matter"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/10\/3880\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:39:47Z","timestamp":1760125187000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/10\/3880"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,5,22]]},"references-count":34,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2023,5]]}},"alternative-id":["ma16103880"],"URL":"https:\/\/doi.org\/10.3390\/ma16103880","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,5,22]]}}}