Colloidal Flower‐Shaped Iron Oxide Nanoparticles: Synthesis Strategies and Coatings

Abstract

The assembly of magnetic cores into regular structures may notably influence the properties displayed by a magnetic colloid. Here, key synthesis parameters driving the self‐assembly process capable of organizing colloidal magnetic cores into highly regular and reproducible multi‐core nanoparticles are determined. In addition, a self‐consistent picture that explains the collective magnetic properties exhibited by these complex assemblies is achieved through structural, colloidal, and magnetic means. For this purpose, different strategies to obtain flower‐shaped iron oxide assemblies in the size range 25–100 nm are examined. The routes are based on the partial oxidation of Fe(OH)2, polyol‐mediated synthesis or the reduction of iron acetylacetonate. The nanoparticles are functionalized either with dextran, citric acid, or alternatively embedded in polystyrene and their long‐term stability is assessed. The core size is measured, calculated, and modeled using both structural and magnetic means, while the Debye model and multi‐core extended model are used to study interparticle interactions. This is the first step toward standardized protocols of synthesis and characterization of flower‐shaped nanoparticles.

Shape Anisotropic Iron Oxide-Based Magnetic Nanoparticles: Synthesis and Biomedical Applications

“…A different particle architecture was developed by Wang et al [119] through the solvothermal route, using CTAB and sodium acetate in ethylene glycol (200 • C, 24 h), that afforded hollow microspheres with a M s of 80 emu/g. Other flower-like architecture is exhibited by the multicore particles, in which the interaction between the cores leads to a large magnetic moment and weak remanence magnetization [120]. Gavilán et al [120] developed different methods to synthesize multi-core nanoparticles through the use of polyols as reducing agents, obtaining nanoflowers as small as 50 nm and M s value of 100 emu/g.…”

“…Other flower-like architecture is exhibited by the multicore particles, in which the interaction between the cores leads to a large magnetic moment and weak remanence magnetization [120]. Gavilán et al [120] developed different methods to synthesize multi-core nanoparticles through the use of polyols as reducing agents, obtaining nanoflowers as small as 50 nm and M s value of 100 emu/g. Through the use of succinic acid, urea and FeCl 3 .6H 2 O in a solvothermal route, Cheng et al [121] were also able to synthesize flower-like multi-core nanoparticles with ca.…”

Formation of Fe and Fe2O3 Microspirals via Interfacial Synthesis

“…The technique has been previously applied to obtaining inorganic and composite microtubes. Fe(OH) 3 microspirals were chosen as a research object because they are suitable precursors that can be transformed into microstructures of other iron compounds, Fe 2 O 3 and Fe, for example, without any significant morphology change . Iron‐based compounds are widely used as magnetic and catalytic materials .…”

Ferrofluid Leidenfrost droplets

“…1, the Langevin law does not perfectly fit the magnetization curve. This can be explained by the fact that the magnetization mechanism of the ferrofluid composed of multicore nanoclusters is much more complicated than the one of individual single-domain nanoparticles 17 . Since the precise magnetization mechanism of a ferrofluid composed of nanoclusters is still not completely established, it is reasonable to fit the magnetization curve by an empirical magnetization law, such as the Fröhlich-Kennely one 18 ,…”