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.

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...

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.

Bare maghemite nanoparticles (Nps), binary, and ternary magnetic nanocomposites made with titanium dioxide (TiO2) and graphene oxide (GO) were synthesized by a facile and cheap coprecipitation chemical route, and used as magnetic nanoadsorbents to remove arsenite (As(III)) and arsenate (As(V)) from water. The structural, morphological, magnetic and surface properties were analyzed by XRD, TEM microscopy, FTIR and Raman vibrational spectroscopy, Mössbauer technique and N2 adsorption-desorption measurements. It was found that materials were composed of maghemite nanoparticles with crystallites diameters varying from 9 to 13 nm for bare Nps, binary and ternary nanocomposites, with these nanocomposites having a high percentage of maghemite phase (80%). The presence of TiO2 and GO in the binary and ternary materials was also confirmed. All the samples were found to show magnetic properties a...

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”.