ABSTRACT
In the present work, we have reported the effect of Ag NPs seeds on the growth and magnetic properties of Ag-Fe3O4 heterodimer nanoparticles prepared using a two step chemical approach. Three different Ag NPs concentrations have been tried and thoroughly characterized using small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), X-ray diffraction (XRD), dc magnetization, and X-ray absorption near edge spectroscopy (XANES). It is observed that at low concentration, the "flower" types of nanoparticles are more favorable whereas the higher concentration of Ag NPs seeds promotes the growth of dimer type of structures. Our dc magnetization results are well correlated to the structural ones. The sample with lower amount of starting Ag NPs seeds possesses highest blocking and irreversibility temperature. On the other hand, the sample with highest concentration of Ag NPs seeds, the blocking temperature is lowered.
ABSTRACT
Magnetoliposomes consist of vesicles composed of a phospholipid membrane encapsulating magnetic nanoparticles. These systems have several important applications, such as in MRI contrast agents, drug and gene carriers, and cancer treatment devices. For all of these applications, controlling the number of encapsulated magnetic nanoparticles is a key issue. In this work, we used a magneto-optical technique to obtain information about the efficiency of encapsulation, the number of nanoparticles encapsulated per liposome and also about the formation of the nanoparticle structures. The parameters studied included the effect of the duration of sonication, the presence of cholesterol in the liposome membrane, as well as time-related stability. For the liposomal vesicles prepared in this work, we found between 35 and 300 nanoparticles encapsulated per liposome, depending on the experimental conditions, consisting of small linear chains of nanoparticles, basically trimers and tetramers. The methodology developed might be useful for the investigation and improvement of the properties of several magnetic nanocarrier systems.
Subject(s)
Ferrosoferric Oxide/chemistry , Liposomes/chemistry , Nanoparticles/chemistry , Electromagnetic FieldsABSTRACT
Using the first-principles real-space linear muffin-tin orbital method within the atomic sphere approximation (RS-LMTO-ASA) we study hyperfine and local magnetic properties of substituted pure Fe and Fe-Cu clusters in an fcc Cu matrix. Spin and orbital contributions to magnetic moments, hyperfine fields and the Mössbauer isomer shifts at the Fe sites in Fe precipitates and Fe-Cu alloy clusters of sizes up to 60 Fe atoms embedded in the Cu matrix are calculated and the influence of the local environment on these properties is discussed.
ABSTRACT
An overview on magnetic of nanostructured magnetic materials is presented, with particular emphasis on the basic features displayed by granular nanomagnetic solids. Besides a review of the basic concepts and experimental techniques, the role of structural disorder (mainly the distribution of grain sizes), interparticle magnetic interactions and surface effects are also discussed with some detail. Recent results, models and trends on the area are also discussed.
ABSTRACT
Morphological, structural and magnetic properties of 4.8 nm iron oxide nanoparticles have been investigated after annealing under inert atmosphere at different temperatures. The as-prepared iron oxide nanoparticles have been synthesized by chemical route from high temperature reaction of Fe(acac)3 solution in presence of oleic acid and oleylamine surfactant. Annealing the particles at low temperatures (Tann = 573 K) produces an increment of the mean size from 4.8 nm to 6.0 nm, preserving the same morphology. The coercive field of the annealed sample has a small increasing with respect to the as-prepared sample in agreement with the mean particle volume change. Annealing at higher temperature (Tann = 823 K) leads to a bimodal size distribution of the iron oxide nanoparticles with 6.0 nm and 17 nm mean sizes respectively, where the bigger particles dominate the observed magnetic properties.
