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Moya C, Escoda-Torroella M, Rodríguez-Álvarez J, Figueroa AI, García Í, Ferrer-Vidal IB, Gallo-Cordova A, Puerto Morales M, Aballe L, Fraile Rodríguez A, Labarta A, Batlle X. Unveiling the crystal and magnetic texture of iron oxide nanoflowers. Nanoscale 2024; 16:1942-1951. [PMID: 38170857 DOI: 10.1039/d3nr04608g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Iron oxide nanoflowers (IONF) are densely packed multi-core aggregates known for their high saturation magnetization and initial susceptibility, as well as low remanence and coercive field. This study reports on how the local magnetic texture originating at the crystalline correlations among the cores determines the special magnetic properties of individual IONF over a wide size range from 40 to 400 nm. Regardless of this significant size variation in the aggregates, all samples exhibit a consistent crystalline correlation that extends well beyond the IONF cores. Furthermore, a nearly zero remnant magnetization, together with the presence of a persistently blocked state, and almost temperature-independent field-cooled magnetization, support the existence of a 3D magnetic texture throughout the IONF. This is confirmed by magnetic transmission X-ray microscopy images of tens of individual IONF, showing, in all cases, a nearly demagnetized state caused by the vorticity of the magnetic texture. Micromagnetic simulations agree well with these experimental findings, showing that the interplay between the inter-core direct exchange coupling and the demagnetizing field is responsible for the highly vortex-like spin configuration that stabilizes at low magnetic fields and appears to have partial topological protection. Overall, this comprehensive study provides valuable insights into the impact of crystalline texture on the magnetic properties of IONF over a wide size range, offering a deeper understanding of their potential applications in fields such as biomedicine and water remediation.
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Affiliation(s)
- Carlos Moya
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Mariona Escoda-Torroella
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Adriana I Figueroa
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Íker García
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
| | - Inés Batalla Ferrer-Vidal
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
| | - A Gallo-Cordova
- Department of Nanoscience and Nanotechnology, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - M Puerto Morales
- Department of Nanoscience and Nanotechnology, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - Lucía Aballe
- ALBA Synchrotron Light Facility, CELLS, 08290 Barcelona, Spain
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
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Rodríguez-Álvarez J, Labarta A, Idrobo JC, Dell'Anna R, Cian A, Giubertoni D, Borrisé X, Guerrero A, Perez-Murano F, Fraile Rodríguez A, Batlle X. Imaging of Antiferroelectric Dark Modes in an Inverted Plasmonic Lattice. ACS Nano 2023; 17:8123-8132. [PMID: 37089111 PMCID: PMC10173685 DOI: 10.1021/acsnano.2c11016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Plasmonic lattice nanostructures are of technological interest because of their capacity to manipulate light below the diffraction limit. Here, we present a detailed study of dark and bright modes in the visible and near-infrared energy regime of an inverted plasmonic honeycomb lattice by a combination of Au+ focused ion beam lithography with nanometric resolution, optical and electron spectroscopy, and finite-difference time-domain simulations. The lattice consists of slits carved in a gold thin film, exhibiting hotspots and a set of bright and dark modes. We proposed that some of the dark modes detected by electron energy-loss spectroscopy are caused by antiferroelectric arrangements of the slit polarizations with two times the size of the hexagonal unit cell. The plasmonic resonances take place within the 0.5-2 eV energy range, indicating that they could be suitable for a synergistic coupling with excitons in two-dimensional transition metal dichalcogenides materials or for designing nanoscale sensing platforms based on near-field enhancement over a metallic surface.
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Affiliation(s)
- Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
| | - Juan Carlos Idrobo
- Materials Science and Engineering Department, University of Washington, Seattle, Washington 98195, United States
| | - Rossana Dell'Anna
- Sensors & Devices Center, FBK - Bruno Kessler Foundation, via Sommarive, 18, Povo, TN 38123, Italy
| | - Alessandro Cian
- Sensors & Devices Center, FBK - Bruno Kessler Foundation, via Sommarive, 18, Povo, TN 38123, Italy
| | - Damiano Giubertoni
- Sensors & Devices Center, FBK - Bruno Kessler Foundation, via Sommarive, 18, Povo, TN 38123, Italy
| | - Xavier Borrisé
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain
| | - Albert Guerrero
- Institut de Microelectrònica de Barcelona (IMB-CNM, CSIC), Bellaterra 08193, Spain
| | | | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
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Escoda-Torroella M, Moya C, Ruiz-Torres JA, Fraile Rodríguez A, Labarta A, Batlle X. Selective anisotropic growth of Bi 2S 3 nanoparticles with adjustable optical properties. Phys Chem Chem Phys 2023; 25:3900-3911. [PMID: 36648114 DOI: 10.1039/d2cp05437j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We report on the controlled synthesis and functionalization in two steps of elongated Bi2S3 nanoparticles within a wide range of sizes. First, we show the effect of the temperature and reaction time on the synthesis of two series of nanoparticles by the reaction of thioacetamide with bismuth(III) neodecanoate in the presence of organic surfactants. At 105 °C and long reaction times, nanoneedles of about 45 nm in length containing larger crystallites are obtained, while highly crystalline nanorods of about 30 nm in length are dominant at 165 °C, regardless of the reaction time. The optical properties of both types of nanoparticles show an enhancement of the band gap compared to bulk Bi2S3. This is likely to arise from quantum confinement effects caused by the small particle dimensions relative to the typical exciton size, together with an increase in near-infrared absorption due to the anisotropic particle shape. Second, a ligand exchange approach has been developed to transfer the Bi2S3 nanoparticles to aqueous solutions by grafting dimercaptosuccinic acid onto the surface of the particles. The as-prepared coated nanoparticles show good stability in water, in a wide biological pH range, and in phosphate-buffered saline solutions. Overall, this work highlights the controlled design at all levels - from the inorganic core to the organic surface coating - of elongated Bi2S3 nanoparticles, leading to a tunable optical response by tuning their morphology and size.
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Affiliation(s)
- Mariona Escoda-Torroella
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
| | - Carlos Moya
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
| | - José A Ruiz-Torres
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Barcelona, Spain
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Rodríguez-Álvarez J, García-Martín A, Fraile Rodríguez A, Batlle X, Labarta A. Tunable circular dichroism through absorption in coupled optical modes of twisted triskelia nanostructures. Sci Rep 2022; 12:26. [PMID: 34996969 PMCID: PMC8742006 DOI: 10.1038/s41598-021-03908-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 12/10/2021] [Indexed: 11/25/2022] Open
Abstract
We present a system consisting of two stacked chiral plasmonic nanoelements, so-called triskelia, that exhibits a high degree of circular dichroism. The optical modes arising from the interactions between the two elements are the main responsible for the dichroic signal. Their excitation in the absorption cross section is favored when the circular polarization of the light is opposite to the helicity of the system, so that an intense near-field distribution with 3D character is excited between the two triskelia, which in turn causes the dichroic response. Therefore, the stacking, in itself, provides a simple way to tune both the value of the circular dichroism, up to 60%, and its spectral distribution in the visible and near infrared range. We show how these interaction-driven modes can be controlled by finely tuning the distance and the relative twist angle between the triskelia, yielding maximum values of the dichroism at 20° and 100° for left- and right-handed circularly polarized light, respectively. Despite the three-fold symmetry of the elements, these two situations are not completely equivalent since the interplay between the handedness of the stack and the chirality of each single element breaks the symmetry between clockwise and anticlockwise rotation angles around 0°. This reveals the occurrence of clear helicity-dependent resonances. The proposed structure can be thus finely tuned to tailor the dichroic signal for applications at will, such as highly efficient helicity-sensitive surface spectroscopies or single-photon polarization detectors, among others.
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Affiliation(s)
- Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028, Barcelona, Spain. .,Institut de Nanociència i Nanotecnologia (IN2UB), 08028, Barcelona, Spain.
| | - Antonio García-Martín
- Instituto de Micro y Nanotecnología IMN-CNM, CSIC, CEI UAM + CSIC, Isaac Newton 8, 28760, Tres Cantos, Madrid, Spain
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028, Barcelona, Spain.,Institut de Nanociència i Nanotecnologia (IN2UB), 08028, Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028, Barcelona, Spain.,Institut de Nanociència i Nanotecnologia (IN2UB), 08028, Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028, Barcelona, Spain.,Institut de Nanociència i Nanotecnologia (IN2UB), 08028, Barcelona, Spain
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Bugallo D, Langenberg E, Ferreiro-Vila E, Smith EH, Stefani C, Batlle X, Catalan G, Domingo N, Schlom DG, Rivadulla F. Deconvolution of Phonon Scattering by Ferroelectric Domain Walls and Point Defects in a PbTiO 3 Thin Film Deposited in a Composition-Spread Geometry. ACS Appl Mater Interfaces 2021; 13:45679-45685. [PMID: 34523338 DOI: 10.1021/acsami.1c08758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We present a detailed analysis of the temperature dependence of the thermal conductivity of a ferroelectric PbTiO3 thin film deposited in a composition-spread geometry enabling a continuous range of compositions from ∼25% titanium deficient to ∼20% titanium rich to be studied. By fitting the experimental results to the Debye model we deconvolute and quantify the two main phonon-scattering sources in the system: ferroelectric domain walls (DWs) and point defects. Our results prove that ferroelectric DWs are the main agent limiting the thermal conductivity in this system, not only in the stoichiometric region of the thin film ([Pb]/[Ti] ≈ 1) but also when the concentration of the cation point defects is significant (up to ∼15%). Hence, DWs in ferroelectric materials are a source of phonon scattering at least as effective as point defects. Our results demonstrate the viability and effectiveness of using reconfigurable DWs to control the thermal conductivity in solid-state devices.
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Affiliation(s)
- David Bugallo
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
| | - Eric Langenberg
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
- Department de Física de la Matèria Condensada and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
| | - Elias Ferreiro-Vila
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
| | - Eva H Smith
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Christina Stefani
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of Science and Technology, Campus Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193 Spain
| | - Xavier Batlle
- Department de Física de la Matèria Condensada and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona 08028, Spain
| | - Gustau Catalan
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of Science and Technology, Campus Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193 Spain
| | - Neus Domingo
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of Science and Technology, Campus Universitat Autònoma de Barcelona, Bellaterra, Barcelona 08193 Spain
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States
- Leibniz-Institut für Kristallzüchtung, Max-Born-Strasse 2, 12489 Berlin, Germany
| | - Francisco Rivadulla
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
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Rodríguez-Álvarez J, Gnoatto L, Martínez-Castells M, Guerrero A, Borrisé X, Fraile Rodríguez A, Batlle X, Labarta A. An Inverted Honeycomb Plasmonic Lattice as an Efficient Refractive Index Sensor. Nanomaterials (Basel) 2021; 11:nano11051217. [PMID: 34064520 PMCID: PMC8147928 DOI: 10.3390/nano11051217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 04/26/2021] [Accepted: 05/01/2021] [Indexed: 11/16/2022]
Abstract
We present an efficient refractive index sensor consisting of a heterostructure that contains an Au inverted honeycomb lattice as a main sensing element. Our design aims at maximizing the out-of-plane near-field distributions of the collective modes of the lattice mapping the sensor surroundings. These modes are further enhanced by a patterned SiO2 layer with the same inverted honeycomb lattice, an SiO2 spacer, and an Au mirror underneath the Au sensing layer that contribute to achieving a high performance. The optical response of the heterostructure was studied by numerical simulation. The results corresponding to one of the collective modes showed high sensitivity values ranging from 99 to 395 nm/RIU for relatively thin layers of test materials within 50 and 200 nm. In addition, the figure of merit of the sensor detecting slight changes of the refractive index of a water medium at a fixed wavelength was as high as 199 RIU-1. As an experimental proof of concept, the heterostructure was manufactured by a simple method based on electron beam lithography and the measured optical response reproduces the simulations. This work paves the way for improving both the sensitivity of plasmonic sensors and the signal of some enhanced surface spectroscopies.
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Affiliation(s)
- Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
- Institut de Nanociència i Nanotecnologia (IN2UB), 08028 Barcelona, Spain
- Correspondence:
| | - Lorenzo Gnoatto
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
| | - Marc Martínez-Castells
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
| | - Albert Guerrero
- Institut de Microelectrónica de Barcelona (IMB-CNM, CSIC), 08193 Bellaterra, Spain;
| | - Xavier Borrisé
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193 Barcelona, Spain;
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
- Institut de Nanociència i Nanotecnologia (IN2UB), 08028 Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
- Institut de Nanociència i Nanotecnologia (IN2UB), 08028 Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain; (L.G.); (M.M.-C.); (A.F.R.); (X.B.); (A.L.)
- Institut de Nanociència i Nanotecnologia (IN2UB), 08028 Barcelona, Spain
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Valmianski I, Rodríguez AF, Rodríguez-Álvarez J, García Del Muro M, Wolowiec C, Kronast F, Ramírez JG, Schuller IK, Labarta A, Batlle X. Driving magnetic domains at the nanoscale by interfacial strain-induced proximity. Nanoscale 2021; 13:4985-4994. [PMID: 33634814 DOI: 10.1039/d0nr08253h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We investigate the local nanoscale changes of the magnetic anisotropy of a Ni film subject to an inverse magnetostrictive effect by proximity to a V2O3 layer. Using temperature-dependent photoemission electron microscopy (PEEM) combined with X-ray magnetic circular dichroism (XMCD), direct images of the Ni spin alignment across the first-order structural phase transition (SPT) of V2O3 were obtained. We find an abrupt temperature-driven reorientation of the Ni magnetic domains across the SPT, which is associated with a large increase of the coercive field. Moreover, angular dependent ferromagnetic resonance (FMR) shows a remarkable change in the magnetic anisotropy of the Ni film across the SPT of V2O3. Micromagnetic simulations based on these results are in quantitative agreement with the PEEM data. Direct measurements of the lateral correlation length of the Ni domains from XMCD images show an increase of almost one order of magnitude at the SPT compared to room temperature, as well as a broad spatial distribution of the local transition temperatures, thus corroborating the phase coexistence of Ni anisotropies caused by the V2O3 SPT. We show that the rearrangement of the Ni domains is due to strain induced by the oxide layers' structural domains across the SPT. Our results illustrate the use of alternative hybrid systems to manipulate magnetic domains at the nanoscale, which allows for engineering of coercive fields for novel data storage architectures.
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Affiliation(s)
- Ilya Valmianski
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
| | - Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
| | - Montserrat García Del Muro
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
| | - Christian Wolowiec
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Florian Kronast
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | | | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
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8
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Escoda-Torroella M, Moya C, Rodríguez AF, Batlle X, Labarta A. Selective Control over the Morphology and the Oxidation State of Iron Oxide Nanoparticles. Langmuir 2021; 37:35-45. [PMID: 33301314 DOI: 10.1021/acs.langmuir.0c02221] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Iron oxide nanoparticles (NPs) have been extensively used for both health and technological applications. The control over their morphology, crystal microstructure, and oxidation state is of great importance to optimize their final use. However, while mature in understanding, it is still far from complete. Here we report on the effect of the amount of 1,2-hexadecanediol and/or 1-octadecene in the reaction mixture on the thermal decomposition of iron(III) acetylacetonate in oleic acid for two series of iron oxide NPs with sizes ranging from 6 to 48 nm. We show that a low amount of either compound leads to both large, mixed-phase NPs composed of magnetite (Fe3O4) and wüstite (FeO) and high reaction yields. In contrast, a higher amount of either 1,2-hexadecanediol or 1-octadecene gives rise to smaller, single-phase NPs with moderate reaction yields. By infrared spectroscopy, we have elucidated the role of 1,2-hexadecanediol, which mediates the particle nucleation and growth. Finally, we have correlated the magnetic response and the structural features of the NPs for the two series of samples.
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Affiliation(s)
- Mariona Escoda-Torroella
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Carlos Moya
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
- Université libre de Bruxelles (ULB), Engineering of Molecular Nanosystems, 50 Avenue F. D. Roosevelt, 1050 Bruxelles, Belgium
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
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9
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Conde-Rubio A, Rodríguez AF, Borrisé X, Perez-Murano F, Batlle X, Labarta A. Geometric frustration in a hexagonal lattice of plasmonic nanoelements. Opt Express 2018; 26:20211-20224. [PMID: 30119347 DOI: 10.1364/oe.26.020211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 07/10/2018] [Indexed: 06/08/2023]
Abstract
We introduce the concept of geometric frustration in plasmonic arrays of nanoelements. In particular, we present the case of a hexagonal lattice of Au nanoasterisks arranged so that the gaps between neighboring elements are small and lead to a strong near-field dipolar coupling. Besides, far-field interactions yield higher-order collective modes around the visible region that follow the translational symmetry of the lattice. However, dipolar excitations of the gaps in the hexagonal array are geometrically frustrated for interactions beyond nearest neighbors, yielding the destabilization of the low energy modes in the near infrared. This in turn results in a slow dynamics of the optical response and a complex interplay between localized and collective modes, a behavior that shares features with geometrically frustrated magnetic systems.
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Moya C, Iglesias-Freire Ó, Batlle X, Labarta A, Asenjo A. Superparamagnetic versus blocked states in aggregates of Fe(3-x)O₄ nanoparticles studied by MFM. Nanoscale 2015; 7:17764-17770. [PMID: 26456633 DOI: 10.1039/c5nr04424c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Magnetic domain configurations in two samples containing small aggregates of Fe(3-x)O4 nanoparticles of about 11 and 49 nm in size, respectively, were characterized by magnetic force microscopy (MFM). Two distinct magnetic behaviors were observed depending on the particle size. The aggregates constituted of nanoparticles of about 11 nm in size showed a uniform dark contrast on MFM images, reflecting the predominant superparamagnetic character of these particles and arising from the coherent rotation of the spins within the aggregate as the latter align along the tip stray-field. By applying a variable in-plane field, it is possible to induce magnetic polarization yielding an increasing dark/bright contrast as the strength of the applied field overcomes the stray-field of the tip, although this polarization completely disappears as the remanent state is recovered when the magnetic field is switched off. On the contrary, for aggregates of NPs of about 49 nm in size, dark/bright contrast associated with the existence of magnetic domains and magnetic polarization prevails in MFM images all along the magnetic cycle due to the blocking state of the magnetization of these larger particles, even in the absence of an applied field. All in all, we unambiguously demonstrate the capabilities of magnetic force microscopy to distinguish between blocked and superparamagnetic states in the aggregates of magnetic nanoparticles. Micromagnetic simulations strongly support the conclusions stated from the MFM experiments.
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Affiliation(s)
- Carlos Moya
- Departament de Física Fonamental, Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona, 08028, Spain.
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Alayo N, Conde-Rubio A, Bausells J, Borrisé X, Labarta A, Batlle X, Pérez-Murano F. Nanoparticles with tunable shape and composition fabricated by nanoimprint lithography. Nanotechnology 2015; 26:445302. [PMID: 26469372 DOI: 10.1088/0957-4484/26/44/445302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Cone-like and empty cup-shaped nanoparticles of noble metals have been demonstrated to provide extraordinary optical properties for use as optical nanoanntenas or nanoresonators. However, their large-scale production is difficult via standard nanofabrication methods. We present a fabrication approach to achieve arrays of nanoparticles with tunable shape and composition by a combination of nanoimprint lithography, hard-mask definition and various forms of metal deposition. In particular, we have obtained arrays of empty cup-shaped Au nanoparticles showing an optical response with distinguishable features associated with the excitations of localized surface plasmons. Finally, this route avoids the most common drawbacks found in the fabrication of nanoparticles by conventional top-down methods, such as aspect ratio limitation, blurring, and low throughput, and it can be used to fabricate nanoparticles with heterogeneous composition.
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Affiliation(s)
- Nerea Alayo
- Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, 08193 Bellaterra, Spain
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Moya C, Iglesias-Freire Ó, Pérez N, Batlle X, Labarta A, Asenjo A. Direct imaging of the magnetic polarity and reversal mechanism in individual Fe(3-x)O4 nanoparticles. Nanoscale 2015; 7:8110-8114. [PMID: 25873128 DOI: 10.1039/c5nr00592b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This work reports on the experimental characterization of the magnetic domain configurations in cubic, isolated Fe3-xO4 nanoparticles with a lateral size of 25-30 nm. The magnetic polarity at remanence of single domain ferrimagnetic Fe3-xO4 nanoparticles deposited onto a carbon-silicon wafer is observed by magnetic force microscopy. The orientations of these domains provide a direct observation of the magneto-crystalline easy axes in each individual nanoparticle. Furthermore, the change in the domain orientation with an external magnetic field gives evidence of particle magnetization reversal mediated by a coherent rotation process that is also theoretically predicted by micromagnetic calculations.
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Affiliation(s)
- Carlos Moya
- Departament de Física Fonamental, Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona, 08028, Spain.
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Morales R, Basaran AC, Villegas JE, Navas D, Soriano N, Mora B, Redondo C, Batlle X, Schuller IK. Exchange-bias phenomenon: the role of the ferromagnetic spin structure. Phys Rev Lett 2015; 114:097202. [PMID: 25793846 DOI: 10.1103/physrevlett.114.097202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Indexed: 06/04/2023]
Abstract
The exchange bias of antiferromagnetic-ferromagnetic (AFM-FM) bilayers is found to be strongly dependent on the ferromagnetic spin configuration. The widely accepted inverse proportionality of the exchange bias field with the ferromagnetic thickness is broken in FM layers thinner than the FM correlation length. Moreover, an anomalous thermal dependence of both exchange bias field and coercivity is also found. A model based on springlike domain walls parallel to the AFM-FM interface quantitatively accounts for the experimental results and, in particular, for the deviation from the inverse proportionality law. These results reveal the active role the ferromagnetic spin structure plays in AFM-FM hybrids which leads to a new paradigm of the exchange bias phenomenon.
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Affiliation(s)
- R Morales
- Department of Chemical-Physics & BCMaterials, University of the Basque Country UPV/EHU, 48940 Leioa, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Ali C Basaran
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
| | - J E Villegas
- Unité Mixte de Physique CNRS/Thales, 91767 Palaiseau, France and Université Paris Sud, 91405 Orsay, France
| | - D Navas
- IFIMUP-IN and Departamento Física e Astronomia, Universidade do Porto, 4169-007 Porto, Portugal
| | - N Soriano
- Department of Chemical-Physics, University of the Basque Country UPV/EHU, 48940 Leioa, Spain
| | - B Mora
- Department of Chemical-Physics, University of the Basque Country UPV/EHU, 48940 Leioa, Spain
| | - C Redondo
- Department of Chemical-Physics, University of the Basque Country UPV/EHU, 48940 Leioa, Spain
| | - X Batlle
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
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Moya C, Morales MDP, Batlle X, Labarta A. Tuning the magnetic properties of Co-ferrite nanoparticles through the 1,2-hexadecanediol concentration in the reaction mixture. Phys Chem Chem Phys 2015; 17:13143-9. [DOI: 10.1039/c5cp01052g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work reports on the effect of the 1,2-hexadecanediol content on the structural and magnetic properties of CoFe2O4 nanoparticles synthesized by thermal decomposition of metal–organic precursors in 1-octadecene.
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Affiliation(s)
- Carlos Moya
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona
- Spain
| | | | - Xavier Batlle
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona
- Spain
| | - Amílcar Labarta
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona
- Spain
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15
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Abstract
This work reports on the effect of the oleic acid concentration on the magnetic and structural properties of Fe3−xO4 nanoparticles synthesized by thermal decomposition of Fe(acac)3 in benzyl-ether.
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Affiliation(s)
- Carlos Moya
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona 08028
- Spain
| | - Xavier Batlle
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona 08028
- Spain
| | - Amílcar Labarta
- Departament de Física Fonamental
- Institut de Nanociència i Nanotecnologia
- Universitat de Barcelona
- Barcelona 08028
- Spain
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16
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Figueroa AI, Moya C, Bartolomé J, Bartolomé F, García LM, Pérez N, Labarta A, Batlle X. SiO2 coating effects in the magnetic anisotropy of Fe3-xO4 nanoparticles suitable for bio-applications. Nanotechnology 2013; 24:155705. [PMID: 23518930 DOI: 10.1088/0957-4484/24/15/155705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present radio frequency transverse susceptibility (TS) measurements on oleic acid-coated and SiO2-coated Fe3-xO4 magnetite nanoparticles. The effects of the type of coating on the interparticle interactions and magnetic anisotropy are evaluated for two different particle sizes in powder samples. On the one hand, SiO2 coating reduces the interparticle interactions as compared to oleic acid coating, the reduction being more effective for 5 nm than for 14 nm diameter particles. On the other hand, the magnetic anisotropy field at low temperature is lower than 1 kOe in all cases and independent of the coating used. Our results are relevant concerning applications in biomedicine, since the SiO2 coating renders 5 and 14 nm hydrophilic particles with very limited agglomeration, low anisotropy, and superparamagnetic behavior at room temperature. The TS technique also allows us to discriminate the influence on the anisotropy field of interparticle interactions from that of the thermal fluctuations.
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Affiliation(s)
- A I Figueroa
- Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Zaragoza, Spain.
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Salafranca J, Gazquez J, Pérez N, Labarta A, Pantelides ST, Pennycook SJ, Batlle X, Varela M. Surfactant organic molecules restore magnetism in metal-oxide nanoparticle surfaces. Nano Lett 2012; 12:2499-503. [PMID: 22497711 DOI: 10.1021/nl300665z] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The properties of magnetic nanoparticles tend to be depressed by the unavoidable presence of a magnetically inactive surface layer. However, outstanding magnetic properties with a room-temperature magnetization near the bulk value can be produced by high-temperature synthesis methods involving capping with organic acid. The capping molecules are not magnetic, so the origin of the enhanced magnetization remains elusive. In this work, we present a real-space characterization on the subnanometer scale of the magnetic, chemical, and structural properties of iron-oxide nanoparticles via aberration-corrected scanning transmission electron microscopy. For the first time, electron magnetic chiral dichroism is used to map the magnetization of nanoparticles in real space with subnanometer spatial resolution. We find that the surface of the nanoparticles is magnetically ordered. Combining the results with density functional calculations, we establish how magnetization is restored in the surface layer. The bonding with the acid's O atoms results in O-Fe atomic configuration and distances close to bulk values. We conclude that the nature and number of molecules in the capping layer is an essential ingredient in the fabrication of nanoparticles with optimal magnetic properties.
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Affiliation(s)
- Juan Salafranca
- Dpt. Física Aplicada III, Universidad Complutense de Madrid, Madrid, 28040 Spain.
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Pérez N, López-Calahorra F, Labarta A, Batlle X. Reduction of iron by decarboxylation in the formation of magnetite nanoparticles. Phys Chem Chem Phys 2011; 13:19485-9. [DOI: 10.1039/c1cp20457b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Guardia P, Pérez-Juste J, Labarta A, Batlle X, Liz-Marzán LM. Heating rate influence on the synthesis of iron oxide nanoparticles: the case of decanoic acid. Chem Commun (Camb) 2010; 46:6108-10. [PMID: 20661498 DOI: 10.1039/c0cc01179g] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Iron oxide nanoparticles with uniform sizes between 13 nm and 180 nm can be selectively prepared through the "heating up" thermal decomposition method by using decanoic acid and carefully tuning the heating rate.
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Affiliation(s)
- Pablo Guardia
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
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20
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Mejías R, Pérez-Yagüe S, Roca AG, Pérez N, Villanueva A, Cañete M, Mañes S, Ruiz-Cabello J, Benito M, Labarta A, Batlle X, Veintemillas-Verdaguer S, Morales MP, Barber DF, Serna CJ. Liver and brain imaging through dimercaptosuccinic acid-coated iron oxide nanoparticles. Nanomedicine (Lond) 2010; 5:397-408. [PMID: 20394533 DOI: 10.2217/nnm.10.15] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND & AIM Uptake, cytotoxicity and interaction of improved superparamagnetic iron oxide nanoparticles were studied in cells, tissues and organs after single and multiple exposures. MATERIAL & METHOD We prepared dimercaptosuccinic acid-coated iron oxide nanoparticles by thermal decomposition in organic medium, resulting in aqueous suspensions with a small hydrodynamic size (< 100 nm), high saturation magnetization and susceptibility, high nuclear magnetic resonance contrast and low cytotoxicity. RESULTS In vitro and in vivo behavior showed that these nanoparticles are efficient carriers for drug delivery to the liver and brain that can be combined with MRI detection.
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Kovylina M, Erekhinsky M, Morales R, Schuller IK, Labarta A, Batlle X. The fabrication of ordered arrays of exchange biased Ni/FeF2 nanostructures. Nanotechnology 2010; 21:175301. [PMID: 20357410 DOI: 10.1088/0957-4484/21/17/175301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The fabrication of ordered arrays of exchange biased Ni/FeF(2) nanostructures by focused ion beam lithography is reported. High quality nano-elements, with controlled removal depth and no significant re-deposition, were carved using small ion beam currents (30 pA), moderate dwell times (1 micros) and repeated passages over the same area. Two types of nanostructures were fabricated: square arrays of circular dots with diameters from 125 +/- 8 to 500 +/- 12 nm and periodicities ranging from 200 +/- 8 to 1000 +/- 12 nm, and square arrays of square antidots (207 +/- 8 nm in edge length) with periodicities ranging from 300 +/- 8 to 1200 +/- 12 nm. The arrays were characterized using scanning ion and electron microscopy, and atomic force microscopy. The effect of the patterning on the exchange bias field (i.e., the shift in the hysteresis loop of ferromagnetic Ni due to proximity to antiferromagnetic FeF(2)) was studied using magneto-transport measurements. These high quality nanostructures offer a unique method to address some of the open questions regarding the microscopic origin of exchange bias. This is not only of major relevance in the fabrication and miniaturization of magnetic devices but it is also one of the important proximity phenomena in nanoscience and materials science.
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Affiliation(s)
- M Kovylina
- Departament de Física Fonamental, Universitat de Barcelona, Barcelona, Catalonia, Spain.
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22
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Abstract
We report on the effect of using decanoic acid as capping ligand on the synthesis of iron oxide nanoparticles by thermal decomposition of an organic iron precursor in organic medium. This procedure allowed us to control the particle size within 5 nm and about 30 nm by modifying the precursor-to-capping ligand ratio in a systematic fashion and to further expand the particle size range up to about 50 nm by adjusting the final synthesis temperature. The nanoparticles also showed high saturation magnetization of about 80-83 emu/g at low temperature, almost size-independent and close to the value for the bulk counterpart. Decanoic acid-coated nanoparticles were transferred to water by using tetramethylammonium hydroxide, which allowed further coating with silica in a tetraethyl orthosilicate solution. Consequently, these iron oxide nanoparticles are tunable in size and highly magnetic, and they could become suitable candidates for various biomedical applications such as contrast agents for magnetic resonance imaging and magnetic carriers for drug delivery.
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Affiliation(s)
- Pablo Guardia
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain.
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Kovylina M, del Muro MG, Konstantinović Z, Varela M, Iglesias O, Labarta A, Batlle X. Controlling exchange bias in Co-CoOx nanoparticles by oxygen content. Nanotechnology 2009; 20:175702. [PMID: 19420597 DOI: 10.1088/0957-4484/20/17/175702] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report on the occurrence of exchange bias on laser-ablated granular thin films composed of Co nanoparticles embedded in an amorphous zirconia matrix. The deposition method allows one to control the degree of oxidation of the Co particles by tuning the oxygen pressure at the vacuum chamber (from 2 x 10(-5) to 10(-1) mbar). The nature of the nanoparticles embedded in the nonmagnetic matrix is monitored from metallic, ferromagnetic (FM) Co to antiferromagnetic (AFM) CoO(x), with a FM/AFM intermediate regime for which the percentage of the AFM phase can be increased at the expense of the FM phase, leading to the occurrence of exchange bias in particles of about 2 nm in size. For an oxygen pressure of about 10(-3) mbar the ratio between the FM and AFM phases is optimum with an exchange bias field of about 900 Oe at 1.8 K. The mutual exchange coupling between the AFM and FM is also at the origin of the induced exchange anisotropy on the FM leading to high irreversible hysteresis loops, and the blocking of the AFM clusters due to proximity to the FM phase.
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Affiliation(s)
- Miroslavna Kovylina
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona, Spain
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Pérez N, Guardia P, Roca AG, Morales MP, Serna CJ, Iglesias O, Bartolomé F, García LM, Batlle X, Labarta A. Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles. Nanotechnology 2008; 19:475704. [PMID: 21836285 DOI: 10.1088/0957-4484/19/47/475704] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The effect of surface anisotropy on the distribution of energy barriers in magnetic fine particles of nanometer size is discussed within the framework of the Tln(t/τ(0)) scaling approach. The comparison between the distributions of the anisotropy energy of the particle cores, calculated by multiplying the volume distribution by the core anisotropy, and of the total anisotropy energy, deduced by deriving the master curve of the magnetic relaxation with respect to the scaling variable Tln(t/τ(0)), enables the determination of the surface anisotropy as a function of the particle size. We show that the contribution of the particle surface to the total anisotropy energy can be well described by a size-independent value of the surface energy per unit area which permits the superimposition of the distributions corresponding to the particle core and effective anisotropy energies. The method is applied to a ferrofluid composed of non-interacting Fe(3-x)O(4) particles of 4.9 nm average size and x about 0.07. Even though the size distribution is quite narrow in this system, a relatively small value of the effective surface anisotropy constant K(s) = 2.9 × 10(-2) erg cm(-2) gives rise to a dramatic broadening of the total energy distribution. The reliability of the average value of the effective anisotropy constant, deduced from magnetic relaxation data, is verified by comparing it to that obtained from the analysis of the shift of the ac susceptibility peaks as a function of the frequency.
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Affiliation(s)
- N Pérez
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, Martíi Franqués 1, E-08028 Barcelona, Catalonia, Spain
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25
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Iglesias O, Labarta A, Batlle X. Exchange bias phenomenology and models of core/shell nanoparticles. J Nanosci Nanotechnol 2008; 8:2761-2780. [PMID: 18681014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Some of the main experimental observations related to the occurrence of exchange bias in magnetic systems are reviewed, focusing the attention on the peculiar phenomenology associated to nanoparticles with core/shell structure as compared to thin film bilayers. The main open questions posed by the experimental observations are presented and contrasted to existing theories and models for exchange bias formulated up to date. We also present results of simulations based on a simple model of a core/shell nanoparticle in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and at the interfacial regions, offering new insight on the microscopic origin of the experimental phenomenology. A detailed study of the magnetic order of the interfacial spins shows compelling evidence that most of the experimentally observed effects can be qualitatively accounted within the context of this model and allows also to quantify the magnitude of the loop shifts in striking agreement with the macroscopic observed values.
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Affiliation(s)
- Oscar Iglesias
- Departament de Física Fonamental, Universitat de Barcelona, Barcelona, Spain
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Abstract
We present an atomistic model of a single nanoparticle with core/shell structure that takes into account its lattice structure and spherical geometry, and in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and interfacial regions. By means of Monte Carlo simulations of the hysteresis loops based on this model, we have determined the range of microscopic parameters for which loop shifts after field cooling can be observed. The study of the magnetic order of the interfacial spins for different particle sizes and values of the interfacial exchange coupling have allowed us to correlate the appearance of loop asymmetries and vertical displacements to the existence of a fraction of uncompensated spins at the shell interface that remain pinned during field cycling, offering new insight on the microscopic origin of the experimental phenomenology.
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Affiliation(s)
- Oscar Iglesias
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia de la UB (IN2UB), Universitat de Barcelona, Avenida Diagonal 647, 08028 Barcelona, Spain
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Calderón-Moreno JM, Labarta A, Batlle X, Pradell T, Crespo D, Binh VT. Magnetic properties of dense carbon nanospheres prepared by chemical vapor deposition. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.09.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Konstantinović Z, Muro MGD, Varela M, Batlle X, Labarta A. Particle growth mechanisms in Ag-ZrO(2) and Au-ZrO(2) granular films obtained by pulsed laser deposition. Nanotechnology 2006; 17:4106-4111. [PMID: 21727545 DOI: 10.1088/0957-4484/17/16/019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thin films consisting of Ag and Au nanoparticles embedded in amorphous ZrO(2) matrix were grown by pulsed laser deposition in a wide range of metal volume concentrations in the dielectric regime (0.08<x(Ag)<0.28 and 0.08<x(Au)<0.52). High resolution transmission electron microscopy (TEM) showed regular distribution of spherical Au and Ag nanoparticles having very sharp interfaces with the amorphous matrix. Mean particle size determined from x-ray diffraction agreed with direct TEM observation. The silver mean diameter increases more abruptly with metal volume content than that corresponding to gold particles prepared under the same conditions. Two mechanisms of particle growth are observed: nucleation and particle coalescence, their relative significance being different in both granular systems, which yields very different values of the percolation threshold (x(c)(Ag)∼0.28 and x(c)(Au)∼0.52).
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Affiliation(s)
- Zorica Konstantinović
- Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Martíi Franquès 1, 08028 Barcelona, Spain
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Li ZP, Petracic O, Morales R, Olamit J, Batlle X, Liu K, Schuller IK. Asymmetric reversal in inhomogeneous magnetic heterostructures. Phys Rev Lett 2006; 96:217205. [PMID: 16803273 DOI: 10.1103/physrevlett.96.217205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Indexed: 05/10/2023]
Abstract
Asymmetric magnetization reversal is an unusual phenomenon in antiferromagnet/ferromagnet (AF/FM) exchange biased bilayers. We investigated this phenomenon in a simple model system experimentally and by simulation assuming inhomogeneously distributed interfacial AF moments. The results suggest that the observed asymmetry originates from the intrinsic broken symmetry of the system, which results in local incomplete domain walls parallel to the interface in reversal to negative saturation of the FM. The magneto-optical Kerr effect unambiguously confirms such an asymmetric reversal and a depth-dependent FM domain wall in accord with the magnetometry and simulations.
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Affiliation(s)
- Zhi-Pan Li
- Physics Department, University of California - San Diego, La Jolla, California, 92093-0319, USA
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Barea E, Batlle X, Bourges P, Corma A, Fornés V, Labarta A, Puntes VF. Synthesis and Characterization of Stabilized Subnanometric Cobalt Metal Particles. J Am Chem Soc 2005; 127:18026-30. [PMID: 16366553 DOI: 10.1021/ja053746b] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Subnanometric cobalt metallic particles, with an average size of 0.8 nm and an estimated number of 50 atoms, have been stabilized in the confined spaces within the nanopores of crystalline molecular sieves. Remarkably, these clusters show a rapid vanishing of the magnetization as the temperature is increased from 10 to 20 K because of the ferromagnetic-paramagnetic transition together with thermal fluctuations of the remaining moment. This dramatic reduction of the transition temperature is due to strong finite size effects. Such behavior, predicted for very small metallic particles, was never observed before due to the inherent difficulty in achieving subnanometric stable metallic particles.
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Affiliation(s)
- Eva Barea
- Instituto de Tecnología Química, UPV-CSIC, Av. los Naranjos s/n, Valencia, Departament de Física Fonamental, Universitat de Barcelona, 647 Av Diagonal, 08028 Barcelona, Spain
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Roy S, Fitzsimmons MR, Park S, Dorn M, Petracic O, Roshchin IV, Li ZP, Batlle X, Morales R, Misra A, Zhang X, Chesnel K, Kortright JB, Sinha SK, Schuller IK. Depth profile of uncompensated spins in an exchange bias system. Phys Rev Lett 2005; 95:047201. [PMID: 16090835 DOI: 10.1103/physrevlett.95.047201] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Indexed: 05/03/2023]
Abstract
We have used the unique spatial sensitivity of polarized neutron and soft x-ray beams in reflection geometry to measure the depth dependence of magnetization across the interface between a ferromagnet and an antiferromagnet. The net uncompensated magnetization near the interface responds to applied field, while uncompensated spins in the antiferromagnet bulk are pinned, thus providing a means to establish exchange bias.
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Affiliation(s)
- S Roy
- Department of Physics, University of California at San Diego, La Jolla, California 92093, USA
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Marcos J, Mañosa L, Planes A, Casanova F, Batlle X, Labarta A, Matínez B. Magnetocaloric and shape-memory effects in Ni-Mn-Ga ferro-magnetic alloys. ACTA ACUST UNITED AC 2004. [DOI: 10.1051/jp4:2004115013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Tella R, Gaig P, Lombardero M, García-Ortega P, Bartra J, Papo M, Batlle X. Allergic eosinophilic gastroenteritis in a child with Crohn's disease. J Investig Allergol Clin Immunol 2004; 14:159-61. [PMID: 15301307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
A case of a child with Crohn's disease who developed an eosinophilic gastroenteritis is reported. Although symptoms of eosinophilic gastroenteritis at age 8 could mimic those of Crohn's disease, laboratory, radiographic and histologically studies are clearly different. Peripheral blood eosinophilia (7,476 cells per mm3), high serum IgE level (1,050 kU/l) and normal C-reactive protein and erythrocyte sedimentation rate are common in eosinophilic gastroenteritis and uncommon in Crohn's disease. Eosinophilic gastroenteritis was due to bovine serum albumin (BSA) hypersensitivity, confirmed with skin tests, serum levels to specific IgE and a SDS-PAGE IgE-immunoblotting. A strict meat-free diet was started, with progressive relief of symptoms and decrease of eosinophil count twelve months later; the patient became fully symptom-free and eosinophil count was normal.
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Affiliation(s)
- R Tella
- Allergy Unit, Hospital Universitari Joan XXIII, Institut d'Estudis Avancats, Universitat Rovira i Virgili, Tarragona
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Medarde M, Rodríguez-Carvajal J, Martínez B, Batlle X, Obradors X. Magnetic ordering and spin reorientations in Nd1.8Sr0.2NiO3.72. Phys Rev B Condens Matter 1994; 49:9138-9149. [PMID: 10009696 DOI: 10.1103/physrevb.49.9138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Labarta A, Batlle X, Martínez B, Obradors X. Magnetic study of spin freezing in the spin glass BaCo6Ti6O19: Static and dynamic analysis. Phys Rev B Condens Matter 1992; 46:8994-9001. [PMID: 10002683 DOI: 10.1103/physrevb.46.8994] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Batlle X, Obradors X, Martnez B. Magnetic interactions, weak ferromagnetism, and field-induced transitions in Nd2NiO4. Phys Rev B Condens Matter 1992; 45:2830-2843. [PMID: 10001832 DOI: 10.1103/physrevb.45.2830] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Obradors X, Batlle X, Rodrguez-Carvajal J, Martnez JL, Vallet M, González-Calbet J, Alonso J. Magnetic transitions in Nd2NiO4. Phys Rev B Condens Matter 1991; 43:10451-10454. [PMID: 9996768 DOI: 10.1103/physrevb.43.10451] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Barrios L, Caballín MR, Mirò R, Fuster C, Berrozpe G, Subías A, Batlle X, Egozcue J. Chromosome abnormalities in peripheral blood lymphocytes from untreated Hodgkin's patients. A possible evidence for chromosome instability. Hum Genet 1988; 78:320-4. [PMID: 3360446 DOI: 10.1007/bf00291727] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We describe the presence of a high frequency of spontaneous chromosome aberrations in lymphocytes from six untreated patients with Hodgkin's disease. The characteristics of the chromosome abnormalities observed suggest the existence of a certain degree of chromosome instability in these cases, that could be a predisposing factor for the development of malignancies.
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Affiliation(s)
- L Barrios
- Departament de Biologia Cel.lular i Fisiologia, Universitat Autònoma de Barcelona, Bellaterra, Spain
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