63 research outputs found
Gold-decorated magnetic nanoparticles design for hyperthermia applications and as a potential platform for their surface-functionalization
The integration of noble metal and magnetic nanoparticles with controlled structures that can couple various specific effects to the different nanocomposite in multifunctional nanosystems have been found interesting in the field of medicine. In this work, we show synthesis route to prepare small Au nanoparticles of sizes <d> = 3.9 ± 0.2 nm attached to Fe 3 O 4 nanoparticle cores (<d> = 49.2 ± 3.5 nm) in aqueous medium for potential application as a nano-heater. Remarkably, the resulted Au decorated PEI-Fe 3 O 4 (Au@PEI-Fe 3 O 4 ) nanoparticles are able to retain bulk magnetic moment M S = 82–84 Am 2 /kg Fe3O4 , with the Verwey transition observed at T V = 98 K. In addition, the in vitro cytotoxicity analysis of the nanosystem microglial BV2 cells showed high viability (>97.5%) to concentrate up to 100 µg/mL in comparison to the control samples. In vitro heating experiments on microglial BV2 cells under an ac magnetic field (H 0 = 23.87 kA/m; f = 571 kHz) yielded specific power absorption (SPA) values of SPA = 43 ± 3 and 49 ± 1 µW/cell for PEI-Fe 3 O 4 and Au@PEI-Fe 3 O 4 NPs, respectively. These similar intracellular SPA values imply that functionalization of the magnetic particles with Au did not change the heating efficiency, providing at the same time a more flexible platform for multifunctional functionalization
Structural and magnetic properties of core-shell Au/Fe 3 O 4 nanoparticles
We present a systematic study of core-shell Au/Fe 3 O 4 nanoparticles produced by thermal decomposition under mild conditions. The morphology and crystal structure of the nanoparticles revealed the presence of Au core of d = (6.9 ± 1.0) nm surrounded by Fe 3 O 4 shell with a thickness of ~3.5 nm, epitaxially grown onto the Au core surface. The Au/Fe 3 O 4 core-shell structure was demonstrated by high angle annular dark field scanning transmission electron microscopy analysis. The magnetite shell grown on top of the Au nanoparticle displayed a thermal blocking state at temperatures below T B = 59 K and a relaxed state well above T B. Remarkably, an exchange bias effect was observed when cooling down the samples below room temperature under an external magnetic field. Moreover, the exchange bias field (H EX) started to appear at T~40 K and its value increased by decreasing the temperature. This effect has been assigned to the interaction of spins located in the magnetically disordered regions (in the inner and outer surface of the Fe 3 O 4 shell) and spins located in the ordered region of the Fe 3 O 4 shell
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Preparation and crystallization of hollow α-Fe<inf>2</inf>O<inf>3</inf> microspheres following the gas-bubble template method
In this work we report the formation of hollow α-Fe2O3 (hematite) microspheres by the gas-bubble template method. This technique is simple and it does not require hard templates, surfactants, special conditions of atmosphere or complex steps. After reacting Fe(NO3)3.9H2O and citric acid in water by sol-gel, the precursor was annealed in air at different temperatures between 180 and 600 ºC. Annealing at 550 and 600 ºC generates bubbles on the melt which crystallize and oxidizes to form hematite hollow spheres after condensation. The morphology and crystal evolution are studied by means of X-ray diffraction and scanning electron microscopy. We found that after annealing at 250-400 ºC, the sample consist of a mixture of magnetite, maghemite and hematite. Single hematite phase in the form of hollow microspheres is obtained after annealing at 500 and 600 ºC. The crystallization and crystal size of the hematite shells increase with annealing temperature. A possible mechanism for hollow sphere formation is presented.This work was supported by the Engineering and Physical Science Research Council (EPSRC No. EP/J003638/1). The work in Peru has been supported by CONCYTEC. The work in Brazil was supported by CNPq (307552/2012-8), CAPES (PNPD- 230.007518/2011-11) and FACEPE (APQ-0589-1.05/08).This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.matchemphys.2015.11.02
Gold-decorated magnetic nanoparticles design for hyperthermia applications and as a potential platform for their surface-functionalization
The integration of noble metal and magnetic nanoparticles with controlled structures that can couple various specific effects to the different nanocomposite in multifunctional nanosystems have been found interesting in the field of medicine. In this work, we show synthesis route to prepare small Au nanoparticles of sizes = 3.9 ± 0.2 nm attached to Fe 3 O 4 nanoparticle cores ( = 49.2 ± 3.5 nm) in aqueous medium for potential application as a nano-heater. Remarkably, the resulted Au decorated PEI-Fe 3 O 4 (Au@PEI-Fe 3 O 4 ) nanoparticles are able to retain bulk magnetic moment M S = 82–84 Am 2 /kg Fe3O4 , with the Verwey transition observed at T V = 98 K. In addition, the in vitro cytotoxicity analysis of the nanosystem microglial BV2 cells showed high viability (>97.5%) to concentrate up to 100 µg/mL in comparison to the control samples. In vitro heating experiments on microglial BV2 cells under an ac magnetic field (H 0 = 23.87 kA/m; f = 571 kHz) yielded specific power absorption (SPA) values of SPA = 43 ± 3 and 49 ± 1 μW/cell for PEI-Fe 3 O 4 and Au@PEI-Fe 3 O 4 NPs, respectively. These similar intracellular SPA values imply that functionalization of the magnetic particles with Au did not change the heating efficiency, providing at the same time a more flexible platform for multifunctional functionalization.Fil: León Félix, L.. Universidade do Brasília; Brasil. Universidad de Zaragoza; EspañaFil: Sanz, B.. Nb Nanoscale Biomagnetics S.l.; EspañaFil: Sebastián, V.. Universidad de Zaragoza; España. Centro de Investigación en Red en Bioingeniería; EspañaFil: Torres Molina, Teobaldo Enrique. Universidad de Zaragoza; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Sousa, Marcelo Henrique. Universidade do Brasília; BrasilFil: Coaquira, J. A. H.. Universidade do Brasília; BrasilFil: Ibarra, M.R.. Universidad de Zaragoza; EspañaFil: Goya, Gerardo Fabian. Universidad de Zaragoza; Españ
Assessing the internal uppermost crustal structure of the central pyrenees by gravity-constrained cross sections
The Pyrenees constitutes an exceptional example of an Alpine orogenic belt characterized by basement thrust sheets involving Paleozoic rocks and Mesozoic and Cenozoic cover units detached on the Triassic evaporites, the main décollement level. This work is located in the Central Pyrenees, where gravity data help to better constrain the internal architecture of the upper crust of the southern half of the Axial Zone and the northern part of the South Pyrenean Zone, a key area to understand the orogenic evolution of the chain. Previous and new gravity, petrophysical and geological data have been used to obtain the Bouguer and residual anomaly maps of the study area and six serial gravity-constrained cross sections perpendicular to the main structural trend. The residual anomaly map shows a good correlation between basement units involved in thrust sheets of the study area and gravity highs whereas negative anomalies are interpreted to correspond with Mesozoic/Cenozoic basins, Triassic evaporites, Late Variscan igneous bodies, and Ordovician gneisses. The six gravity-constrained cross sections highlight strong along-strike variations on the gravity signal due to lateral differences of the superficial and subsurface occurrence of Triassic evaporites, different geometry at depth of the Late Variscan igneous bodies outcropping in the study area, and geometric lateral variations of the basement thrust sheets and their relationship with the Mesozoic-Cenozoic units.This work was funded by projects CGL2017-84901-C2-2-P funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, PID2020-114273GB-C22 funded by MCIN/AEI/10.13039/501100011033 from the Spanish Ministry of Science and Innovation, and "Severo Ochoa” extraordinary grants for excellence IGME-CSIC (AECEX2021).Peer reviewe
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Structural and magnetic properties of core-shell Au/FeO nanoparticles
We present a systematic study of core-shell Au/FeO nanoparticles produced by thermal decomposition under mild conditions. The morphology and crystal structure of the nanoparticles revealed the presence of Au core of = (6.9 ± 1.0) nm surrounded by FeO shell with a thickness of ~3.5 nm, epitaxially grown onto the Au core surface. The Au/FeO core-shell structure was demonstrated by high angle annular dark field scanning transmission electron microscopy analysis. The magnetite shell grown on top of the Au nanoparticle displayed a thermal blocking state at temperatures below = 59 K and a relaxed state well above . Remarkably, an exchange bias effect was observed when cooling down the samples below room temperature under an external magnetic field. Moreover, the exchange bias field () started to appear at ~40 K and its value increased by decreasing the temperature. This effect has been assigned to the interaction of spins located in the magnetically disordered regions (in the inner and outer surface of the FeO shell) and spins located in the ordered region of the FeO shell.This work was supported by the Brazilian agencies CNPq and CAPES (BEX 6932/15-0) through a financial support in the PhD Student Exchange Program performed in the Institute of Nanoscience of Aragón. The work in Spain was also supported by the Spanish Ministerio de Economia y Competitividad (MINECO) through project MAT2013-42551 and the Aragon Regional Government (DGA, Project No. E26) Technical support from LMAINA and SAI-UZ is acknowledged
Ayotzinapa y la crisis del estado neoliberal mexicano
¿Qué pasó en Ayotzinapa? Es la pregunta que surgió el 26 de septiembre de 2014, que no encuentra una respuesta satisfactoria pese a la intervención de actores de distintas instancias, niveles y nacionalidades, y al esbozo de múltiples hipótesis sobre los enfrentamientos registrados en Iguala, Guerrero, que derivaron en la muerte de varias personas y la desaparición de 43 estudiantes de la Normal Rural “Isidro Burgos”, en una tragedia que evidenció la crisis que atraviesa el estado mexicano y que afecta a todo el país.
A partir de lo acontecido en Ayotzinapa y con base en la teoría general de los campos de Pierre Bourdieu y su propuesta de análisis teórico metodológico sobre el estado, en esta obra se realiza un análisis de la práctica sistemática y generalizada de las desapariciones forzadas en México, con el fin de ofrecer otra manera de comprender el entretejido político–económico–social que hace posible este grave fenómeno, que desgarra tanto a familias como a la comunidad.
La herida abierta por Ayotzinapa sangra y el objetivo último de este libro es contribuir a evitar que se cierre en tanto no se responda la interrogante de qué pasó ahí y que crímenes de lesa humanidad como este sigan aconteciendo en México.ITESO, A.C
Developing a new innovative methodology to integrate geophysical techniques into characterization of potential CO2 storage sites: Lopín structure (Southern Ebro basin, Spain)
Abstract:One of the main challenges facing geological storage is to identify cost-effective methodologicalworkflows for characterizing and monitoring geological storage sites. In the framework of the ALGECO2 pro-ject, led by the IGME (Geological and Mining Institute, Spain), a preliminary study of the Lopín site in the NEof Spain indicated conditions were promising for geological storage of CO2. However, the poor quality of thelegacy seismic reflection data precluded thorough characterization. Within the H2020 PilotSTRATEGY pro-ject, one of the possible selected target reservoirs was the Lopín structure. In order to characterize its geometryand physical properties as required to properly evaluate its storage potential, IGME applied a new emergingmethodology that integrates reinterpreted reflection seismic data with newly acquired and interpreted gravity,passive seismic and petrophysical data. This methodology was successfully applied along one seismic profile. Inthis paper, we present the results of this integration as thefirst step towards characterizing the site and evaluatingits suitability for storage.Funding for this research came from the Horizon 2020 Framework Programme (European Climate,Infrastructure and Environment Executive Agency (CINEA), award 101022664
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