Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2–30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25:1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application.

Synthesis of Ni nanoparticles with controllable magnetic properties by atmospheric pressure microplasma assisted process

“…First, the effect of discharge power was investigated, when the plasma power was varied from 1.3 to 3.4 W while keeping a constant precursor concentration (35 ppm, condition 1-4). Next, the influence of precursor concentration was studied by operating the plasmas in the same power range but with half the precursor concentrations (17.5 ppm, condition [5][6][7][8]. The typical procedure was as follows: a discharge was ignited in pure argon.…”

“…6 Iron oxide nanoparticles of maghemite structure (c-Fe 2 O 3 ) show excellent superparamagnetic behavior, in contrast to the antiferromagnetic nature of hematite (a-Fe 2 O 3 ). 7 Also, the hyperthermia therapy efficacy of Ni nanoparticles is affected by several parameters: (1) Composition. The existence of impurities will significantly reduce their magnetic performance.…”

Lock-in thermography as a rapid and reproducible thermal characterization method for magnetic nanoparticles

“…MNP-5 exhibits a broader size distribution due to variances in the synthesis. As demonstrated by Hufschmid et al [29] adding oleic acid or reducing iron concentration broadens the size distribution. Since the mean size is close to MNP-6 it was interesting to investigate in which way a broader dispersity influences the heating slope of the materials.…”

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

“…[130] Actually, this non-hydrolytic method has been devoted to the fabrication of uniform MNPs by inspiration from semiconductor nanocrystals and oxide formation in non-aqueous media. [46a,131] As its name implies, it involves breaking down of materials to form new compositions at various temperatures.…”

“…[145] In a recent study, Hufschmid et al evaluated and compared synthesis of iron oxide nanoparticles from decomposition of different precursors for their capability to produce iron oxide nanoparticles with specific size and phase-purity requirements. [130] It was www.advancedsciencenews.com www.advhealthmat.de concluded that pentacarbonyl synthesis is suited for synthesis of small (<10 nm) SPIONs, while both iron oleate and oxyhydroxide surpass the thermal decomposition method for production of larger (10-30 nm) particles. Particle size plays an important role on the blocking temperature of nanomagnets, thus a narrow size distribution of magnetic particles prevents polydispersion in a resulted sample.…”