Strategies to tailor the architecture of dual Ag/Fe-oxide nano-heterocrystals—interfacial and morphology effects on the magnetic behavior

Bifunctional nanostructured architectures have shown appealing properties, since a single entity can combine the diverse properties of its individual constituents. Particularly, by growing Fe-oxide domains over Ag nanoparticles, the plasmonic and superparamagnetic properties can be combined in a single particle. Beyond the multifunctionality of this system, there are several properties that emerge from intrinsic factors, such as: interface and/or morphology. In this study, we present the synthesis protocols to obtain two sets of heterocrystals, each one with different morphology: dimer and flower-like. In addition, the magnetization behavior of these hybrid nano-heterocrystals is investigated and discussed. These nanomaterials were built by a seed assisted heterogeneous nucleation process, carried out in organic solvents of high boiling point, using the same batch of silver nanoparticles with a mean size of 6 nm as seeds, and tuning the electron-donor capacity of the reaction environment at the thermal decomposition of the iron precursor. Ag/Fe3O4 heterocrystals with dimer and flower-like morphologies were obtained. The synthesis protocols for generating these types of nanomaterials are discussed step-by-step. Structural and morphological properties were determined by transmission electron microscopy, x-ray diffraction and x-ray absorption fine structure. DC magnetization results suggest that the silver/magnetite coupling generates an increase of the blocking temperature in comparison to those obtained from pure magnetite. This behavior could be linked to a possible increase in the magnetic anisotropy produced by an additional disorder at the Ag–Fe3O4 interface. The higher interface area of the Ag/Fe3O4 heterocrystals with flower-like architecture leads to a higher blocking temperature and a stronger magnetic anisotropy. These results are supported by AC susceptibility data.Fil: Tancredi Gentili, Pablo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Moscoso Londoño, Oscar. Universidad Autónoma de Manizales; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade Estadual de Campinas; BrasilFil: Rivas Rojas, Patricia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Sólidos Amorfos; ArgentinaFil: Wolff, U.. Leibniz Institute for Solid State and Materials Research; AlemaniaFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Knobel, M.. Universidade Estadual de Campinas; BrasilFil: Muraca, D.. Universidade Estadual de Campinas; Brasi

Nanopartículas de óxidos de hierro: preparación, caracterización e integración en nanoestructuras multicomponentes

Grado obtenido: Doctor de la Universidad de Buenos Aires. Área IngenieríaDisciplina: IngenieríaFil: Tancredi Gentili, Pablo. Universidad de Buenos Aires. Facultad de IngenieríaLugar de trabajo: Laboratorio de Sólidos Amorfos - INTECIN, Facultad de Ingeniería – UBA, en el marco de la beca doctoral CONICE

Polymer-assisted size control of water-dispersible iron oxide nanoparticles in range between 15 and 100 nm

Starch-coated Fe3O4 nanoparticles were synthesized by the precipitation–oxidation of ferrous hydroxide method. Starch was employed as a kinetic control agent, and the effect of the polymer on both size and aggregation of the Fe3O4 nanoparticles was studied. The size of the as-prepared magnetite nanoparticles was tuned from 15 to 100 nm by changing the time of addition of a starch solution on the reaction system. Also, the starch-coating over Fe3O4 nanoparticles assures good water-dispersibility, stability, and possible biocompatibility. Transmission and scanning electron microscopies (TEM, SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and magnetic measurements were used to characterize the prepared samples. Kinetic control assays were also done with polyethylene glycol and polyvinyl alcohol in order to study the influence of the polymer nature in the size and aggregation process of the Fe3O4 nanoparticles. For this work, the effect is more pronounced for voluminous polymers, with large electrosteric hindrance produced by increased polar groups per monomer, like starch.Fil: Tancredi Gentili, Pablo. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; ArgentinaFil: Botasini, Santiago. Universidad de la República; UruguayFil: Moscoso Londoño, Oscar. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; ArgentinaFil: Méndez, Eduardo. Universidad de la República; UruguayFil: Socolovsky, Leandro Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; Argentina. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Sólidos Amorfos; Argentin

Radial Distribution Function Analysis and Molecular Simulation of Graphene Nanoplatelets Obtained by Mechanical Ball Milling

Graphene nanoplatelets have been synthesized by ball milling of synthetic graphite and its structural features studied by x-ray analysis using Mo Kα radiation followed by the proposal of a possible molecular arrangement using AVOGADRO® software. Additional characterization using complementary techniques was also performed. The radial and total distribution functions of the coordination number, as well as atomic distances within short-range order, revealed that oxygen atoms were incorporated into the material produced after 24 h of grinding. The structural disorder parameter (ξ) was found to be ~ 3.5, as well as superposition between the second and third coordination spheres (r ~ 2.4 × 10−1 nm), which can be attributed to the presence of oxygen atoms, as suggested by localized defects.Fil: Pagnola, Marcelo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Morales Alvarez, Fabiana Nakary. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Tancredi Gentili, Pablo. Instituto Nacional de Tecnologia Industrial. Gerencia Operativa de Desarrollo Tecnologico E Innovacion. Sub Gerencia Areas del Conocimiento. Direccion Tecnica de Micro y Nanotecnologias. Departamento Nanomateriales Funcionales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; Argentin

Mass-production of water-based ferrofluids capable of developing spike-like structures

Ferrofluids are among the most popular and engaging materials related to the nanotechnology field, with applications ranging from studies of basic science phenomena to educational and outreach activities. Therefore, there is a continuous interest in the synthesis strategies used to fabricate these systems, especially those that can lead to simple procedures able to be reproduced under a wide spectrum of laboratory conditions. The ferrofluids described in this work are systems composed of iron oxide nanoparticles synthesized by the coprecipitation method and functionalized with citrate molecules to ensure the dispersion in an aqueous medium. During the experimental work we evaluated different operations and synthesis conditions, in order to arrive to a unique procedure that optimizes the functionalization results and the scaling potential. The optimized synthesis route has two main features that are worth to highlight. The first is the possibility of using readily available commercial products as chemical precursors; the second is the overall reduction of the procedure difficulties, as we show that several operations that are usually used in similar reports can be avoided, such as sonication, centrifugation, dialysis, inert atmospheres of Ar/N2 or heating of large volumes of liquid. Both features can be included in the synthesis route without compromising the ferrofluid quality. The procedure can be used to successfully prepare nearly 30 g of functionalized nanoparticles per synthesis batch. Furthermore, this production has the potential to increase due to the absence of significant limitations in the scaling process. We show that the synthesized nanoparticles can produce a stable colloid even at extremely high concentrations (above 50% wt), leading to the formation of ferrofluids that can develop static peak patterns, known as Rosensweig instabilities, when exposed to an external magnetic field. In turn, we show that the extent of these disturbances can be modified both with the concentration of nanoparticles and with the surface tension of the ferrofluid, as expected for this type of system.Fil: Jara, Denisse. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Veiga, Lionel S.. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Garate, Octavio Federico. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Ybarra, Gabriel Omar. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Tancredi Gentili, Pablo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingenieria "Hilario Fernandez Long". Grupo Vinculado al Intecin - Grupo Interdisciplinario en Materiales; Argentin

Step-by-step synthesis of iron-oxide nanoparticles attached to graphene oxide: A study on the composite properties and architecture

A set of nanocomposites made of iron oxide nanoparticles covalently bonded to graphene oxide and reduced graphene oxide was successfully prepared. The synthesis was carried out in a precise step-by-step process in order to carefully control the nanocomposite formation. The nanocomposites were characterized by a range of techniques to verify the components arrangement according to the proposed strategy. Over the different samples, an in-depth study by Small Angle X-Ray Scattering (SAXS) and DC-Magnetometry was accomplished to analyze in detail the structure and properties of the systems. The results from this work indicate that the increase of the nanoparticle to graphene oxide ratio and the chemical reduction from graphene oxide to reduced graphene oxide modify the spatial distribution and the architecture of the nanoparticles over the sheets, leading to the formation of localized assemblies and bundle-like structures that have a significant impact on the macroscopicmagnetic behavior.Fil: Tancredi Gentili, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Moscoso Londoño, Oscar. Universidad Autónoma de Manizales; Colombia. Universidade Estadual de Campinas; BrasilFil: Rivas Rojas, Patricia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Knobel, Marcelo. Universidade Estadual de Campinas; BrasilFil: Socolovsky, Leandro Martín. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Tuning dipolar magnetic interactions by controlling individual silica coating of iron oxide nanoparticles

Single and fixed size core, core–shell nanoparticles of iron oxides coated with a silica layer of tunable thickness were prepared by chemical routes, aiming to generate a frame of study of magnetic nanoparticles with controlled dipolar interactions. The batch of iron oxides nanoparticles of 4.5 nm radii, were employed as cores for all the coated samples. The latter was obtained via thermal decomposition of organic precursors, resulting on nanoparticles covered with an organic layer that was subsequently used to promote the ligand exchange in the inverse microemulsion process, employed to coat each nanoparticle with silica. The amount of precursor and times of reaction was varied to obtain different silica shell thicknesses, ranging from 0.5 nm to 19 nm. The formation of the desired structures was corroborated by TEM and SAXS measurements, the core single-phase spinel structure was confirmed by XRD, and superparamagnetic features with gradual change related to dipolar interaction effects were obtained by the study of the applied field and temperature dependence of the magnetization. To illustrate that dipolar interactions are consistently controlled, the main magnetic properties are presented and analyzed as a function of center to center minimum distance between the magnetic cores.Fil: Rivas Rojas, Patricia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Tancredi Gentili, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Moscoso Londoño, Oscar. Universidade Estadual de Campinas; Brasil. Universidad Autónoma de Manizales; ColombiaFil: Knobel, M.. Universidade Estadual de Campinas; BrasilFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentin

Synthesis process, size and composition effects of spherical Fe 3 O 4 and FeO@Fe 3 O 4 core/shell nanoparticles

In this work, we investigate the size, composition and magnetic behavior of a series of iron oxide nanoparticles prepared by means of high temperature decomposition of an iron oleate precursor. Different synthesis conditions, such as gas atmosphere, precursor ratio and heating rate were tested to obtain a direct correlation between the final sample structure and the varied parameter. The synthesis products were characterized by X-ray diffraction, transmission electron microscopy and small-angle X-ray scattering, respectively. We studied six samples with rather narrow size distribution and mean diameters from 8 nm to 16 nm. The particles with diameter below 11 nm were found to be spinel-type, monocrystalline, and their magnetic response can be ascribed to a single domain framework. On the other hand, two-phase core–shell FeO@Fe3O4 of mean sizes of 15 nm and 16 nm were obtained by increasing the amount of oleic acid and the heating rate. The magnetic behavior of these samples exhibits interesting interface features, related to the exchange coupling phenomenon between the FeO and Fe3O4. We discuss how the different synthesis conditions may lead to the presence of this FeO phase, and how the core–shell configuration and other structural features affect the macroscopic magnetic behavior.Fil: Tancredi Gentili, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Rivas Rojas, Patricia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Moscoso Londoño, Oscar. Universidad Autónoma de Manizales; Colombia. Universidade Estadual de Campinas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wolff, Ulrike. Leibniz Institute for Solid State and Materials Research Dresden; AlemaniaFil: Neu, Volker. Leibniz Institute for Solid State and Materials Research Dresden; AlemaniaFil: Damm, Christine. Leibniz Institute for Solid State and Materials Research Dresden; AlemaniaFil: Rellinghaus, Bernd. Leibniz Institute for Solid State and Materials Research Dresden; AlemaniaFil: Knobel, Marcelo. Universidade Estadual de Campinas; BrasilFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentin

Exploring the synthesis conditions to control the morphology of gold-iron oxide heterostructures

Gold–iron oxide nano-heterostructures with a clear and well-defined morphology were prepared via a seed-assisted method. The synthesis process and the events of heterogeneous nucleation during the decomposition of the iron precursor were carefully studied in order to understand the mechanism of the reaction and to tailor the architecture of the fabricated heterostructures. When employing Au seeds of 3 and 5 nm, nanoparticles with a dimer-like morphology were produced due to the occurrence of a single iron oxide nucleation event. Otherwise, multi-nucleation events could be favored by two mechanisms: (i) by the incorporation of a reducing agent and the slowing down of the heating protocol, leading to a core–shell system; (ii) by the increase of the Au seed size to 8 nm, leading to a flower-like system. Further increase of the Au seed size to 12 nm using similar synthesis conditions promotes the homogeneous nucleation and growth of the iron oxide phase, without formation of heterostructures. An in-depth study was performed on the gold–iron oxide heterostructures to confirm the epitaxial growth of the oxide domain over the Au seed and to analyze the elemental distribution of the components within the heterostructures. Finally, it was found that the modification of the plasmonic properties of the Au nanoparticles are strongly influenced by the architecture of the heterostructure, with a more pronounced damping effect for the systems produced after multi-nucleation events.[Figure not available: see fulltext.].Fil: Tancredi Gentili, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: da Costa, Luelc Souza. Universidade Estadual de Campinas; Brasil. Brazilian Nanotechnology National Laboratory; BrasilFil: Calderon, Sebastian. International Iberian Nanotechnology Laboratory; PortugalFil: Moscoso Londoño, Oscar. Universidade Estadual de Campinas; Brasil. Autonomous University of Manizales; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Socolovsky, Leandro Martín. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferreira, Paulo J.. International Iberian Nanotechnology Laboratory; Portugal. University of Texas at Austin; Estados UnidosFil: Muraca, Diego. Universidade Estadual de Campinas; BrasilFil: Zanchet, Daniela. Universidade Estadual de Campinas; BrasilFil: Knobel, Marcelo. Universidade Estadual de Campinas; Brasi