En el presente trabajo, sintesizamos y caracterizamos nanopartículas magnéticas de maghemita & gamma;-Fe2O3utiles para aplicaciones biomédicas. En el proceso químico de co-precipitación, una solución precursora de magnetita fue oxidizada ajustando el pH=3.5 a 80℃ en un ambiente ácido. El diámetro de los granos de las nanopartículas obtenidas de maghemita fueron calculados de las mediciones TEM y muestran nanopartículas de menos de 12 nm de tamaño. Las curvas de magnetización FC y ZFC medidas a 1 kOe indican una temperatura de bloqueo de 95 K. La curva M-H revela una coercitividad de cero a temperatura ambiente. La función paramagnética de Langevin fue usada para ajustar la curva de histéresis a 300 K para estimar el diámetro de los granos en la nanomuestra.

Vacancy ordered maghemite (γ-Fe2O3) nanoparticles functionalized with nanohydroxyapatite (HAp – Ca10(PO4) 6(OH)2) have been successfully synthesized using an inexpensive co-precipitation chemical route. Evidence for the presence of vacancy order in maghemite was shown by the superstructure lines observed in X-ray diffraction. The adsorption of carboxyl groups of citric acid (C6H8O7) onto γ-Fe2O3 nanoparticles was investigated by FTIR, XPS and Mössbauer spectroscopy. From XPS surface analysis, two binding energies related to oxygen were attributed to bindings between C6H8O7/γ- Fe2O3 and C6H8O7/HAp from an interfacial reaction promoted by strongly adsorbed H2O molecules at the surface of these nanomaterials.

This research was funded by Fondo Nacional de Desarrollo Cient?fico, Tecnol?gico y de Innovaci?n Tecnol?gica (FONDECYT-CONCYTEC), Project number 177-2020-FONDECYT.

The authors thank the Fondo Nacional de Desarrollo Cient?fico, Tecnol?gico y de Inno-vaci?n Tecnol?gica (PROCIENCIA-CONCYTEC), project number: 177-2020-FONDECYT (PROCIEN-CIA), project CLEAN NANOMAGNETIC. The APC was funded by PROCIENCIA. Acknowledgments: Edson C. Passamani is also thankful to FAPES and CNPq for their financial support in the infrastructure of Ufes?s laboratory under his supervision. We finally thank Jean-Marc Greneche for supporting us with the in-field M?ssbauer measurement of NPEDTA samples.

Magnetic properties of maghemite (?-Fe2O3 ) nanoparticles grown on activated multiwall carbon nanotubes have been studied by alternating current (AC) magnetic susceptibility experiments performed under different temperatures, frequencies, and applied magnetic fields. Transmission elec-tron images have suggested that the ?-Fe2O3 nanoparticles are not isolated and have an average size of 9 nm, but with a relatively broad size distribution. The activation energies of these 9 nm ?-Fe2O3 nanoparticles, determined from the generalized Vogel–Fulcher relation, are reduced upon increasing the direct current (DC) field magnitude. The large activation energy values have indi-cated the formation of a superspinglass state in the ?-Fe2O3 nanoparticle ensemble, which were not observed for pure ?-Fe2O3 nanoparticles, concluding that the multiwall carbon nanotubes favored the appearance of highly conce...

This work was supported by a grant (No. 013-2013) from the National Council of Science, Technology and Technological Innovation (CONCYTEC/FONDECYT-Peru). Ramos Guivar Juan A. is also grateful to FONDECYT (Grant No. 0218-2014).

Funding: The authors thank the Fondo Nacional de Desarrollo Científico, Tecnológico y de Inno-vación Tecnológica (PROCIENCIA-CONCYTEC), project number: 177-2020-FONDECYT (PROCIEN-CIA), project CLEAN NANOMAGNETIC. “The APC was funded by PROCIENCIA”.