Physicochemical Studies of Complex Silver–Magnetite Nanoheterodimers with Controlled Morphology

Abstract

This work discusses the influence of synthesis conditions on self-assembly capability and morphology of obtained Ag–Fe3O4 nanoheterostructures. Samples were synthesized in two steps: first silver nanoparticles were synthesized and then used as seeds for the growth of iron oxide nanoparticles in a second step. The silver nanoparticle size was tuned, changing the oleylamine (OAm) and oleic acid (OA) ratio, which enables us to study the influence of chemical agents and seed size on the final magnetic nanoparticle morphology. The mechanism during the formation of these heterostructures has been discussed by several authors; however, it remains an open issue. In this paper we extend the discussion and advance on the understanding of synthesis conditions, related to silver sizes, chemical agents, and physical properties on the obtained nanoparticles. In our Ag–Fe3O4 system, two types of heterostructures were obtained: dimer, flower, or combination of the two. We have found that the final shape depends on silver seed size, as well as the polarity of the chemical agents used during the synthesis. We made an exhaustive study of the relationship between magnetic properties and structural features. The morphology and size distributions of the heterostructures were analyzed with transmission electron microscopy (TEM).

Synthesis and Characterization of Bifunctionalα-Fe2O3-Ag Nanoparticles

“…To expand the discussion regarding the factors that involved the growing of these nanostructures, the surface charges associated with the active sites of the nanoparticles should be considered [18]. Based on the fact that the particle size and structure type determine the compensation charge in the nanoparticles surface, it can be deduced that mainly the size of decahedral Ag nanoparticles would influence the charge compensation and hence the formation of Fe 2 O 3 heterostructures [24], due the fact that the decahedral nanoparticles exhibit greater reactivity. In this regard, some studies have reported these structures as a function of the -Fe 2 O 3 size/size Ag seed ratio [22,23].…”

“…It is important to highlight the synthesis methodology presented in this research since it offers a simple route for obtaining controlled bimetallic nanostructures. This synthesis is carried out at room temperature while some other methodologies involve temperature (∼400 ∘ C) [22,[24][25][26].…”

Nano-fried-eggs: Structural, optical, and magnetic characterization of physically prepared iron-silver nanoparticles

“…one of the most abundant oxides, magnetite Fe3O4, whereas Ag has a four times higher extinction coefficient than Au at the surface plasmon resonance [13]. The extremely high affinity of iron towards oxidation has, however, hindered the fabrication of purely metallic FeAg nanoparticles and most studies are focused on the fabrication and study of particles combining silver with iron oxides [9,14] as well as their applications in e.g. biomedicine [15], theranostics [16], SERS [17], catalysis and imaging [18].…”

Magnetic hyperthermia in brick-like Ag@Fe3O4 core–shell nanoparticles

“…The synthesis consists on a decomposition of an organometallic precursor in presence of surfactants [22]. Silver-magnetite dimer synthesis was carried out using the same synthesis method on previously formed Ag seed colloid solution, as described in [22][23][24][25]. The shape of the heating curve of this two-step process can be seen in Figure 1-b.…”

“…Typical relationship between size and geometry is observed: for smaller diameters, NPs tend to be more spherical in order to minimize their surface energy. On the other hand, nanoparticles of larger sizes can have different shapes, such as cubes, parallelepipeds or hexagons [25].…”