resumo
Superparamagnetic ferrite nanoparticles (MFe2O4, where M = Fe, Co, Mn) were synthesized through a novel one-step aqueous coprecipitation method based on the use of a new type of alkaline agent: the alkanolamines isopropanolamine and diisopropanolamine. The role played by the bases on the particles' size, chemical composition, and magnetic properties was investigated and compared directly with the effect of the traditional inorganic base NaOH, The novel MFe2O4 nanomaterials exhibited high colloidal stability, particle sizes in the range of 4-12 nm, and superparamagnetic properties. More remarkably, they presented smaller particle sizes (up to 6 times) and enhanced saturation magnetization (up to 1.3 times) relative to those prepared with NaOH. Furthermore, the nanomaterials exhibited improved magnetic properties when compared with nanoferrites of similar size synthesized by coprecipitation with other bases or by other methods reported in the literature. The alkanolamines were responsible for these achievements by acting both as alkaline agents and as complexing agents that controlled the particle size during the synthesis process and improved the spin rearrangement at the surface (thinner magnetic "dead" layers). These results open new horizons for the design of water-dispersible MFe2O4 nanoparticles with tuned properties through a versatile and easily scalable coprecipitation route.
palavras-chave
IRON-OXIDE NANOPARTICLES; FERRITE NANOCRYSTALS; COBALT FERRITE; MAGHEMITE NANOPARTICLES; TEMPERATURE-DEPENDENCE; COFE2O4 NANOPARTICLES; CONTRAST AGENTS; DIGESTION TIME; DRUG-DELIVERY; OLEIC-ACID
categoria
Chemistry; Materials Science
autores
Pereira, C; Pereira, AM; Fernandes, C; Rocha, M; Mendes, R; Fernandez-Garcia, MP; Guedes, A; Tavares, PB; Greneche, JM; Araujo, JP; Freire, C
nossos autores
Ricardo Faria Mendes
Investigador Júnioragradecimentos
This work was funded by Fundacao para a Ciencia e a Tecnologia (FCT) and FEDER through Grant PEst-C/EQB/LA0006/2011 and Project PTDC/QUI-QUI/105304/2008 in the framework of Program COMPETE. The authors also acknowledge funding from the University of Porto and Santander Totta through Projects of Scientific Research in Pre-Graduation 2009 and 2010. The authors thank Prof. J. L. Figueiredo and Prof. M. F. R. Pereira from LSRE/LCM for access to the TGA equipment. C.P. and A.M.P. thank FCT for postdoctoral grants (SFRH/BPD/79606/2011 and SFRH/BPD/63150/2009, respectively). M.P.F.-G. acknowledges the Spanish "Programa Clarin" of "Gobierno del Principado de Asturias" for a postdoctoral grant (POST10-31).