Advances in the Synthesis and Long‐Term Protection of Zero‐Valent Iron Nanoparticles

Abstract

Core@shell Fe@Fe3O4 nanoparticles (NPs) are synthesized via the thermal decomposition of iron pentacarbonyl (Fe(CO)5) in the presence either of oleylamine (OAm) or a mixture of OAm and oleic acid (OA). The heterostructured nanocomposites formed do so by a postsynthetic modification of isolated Fe seeds. This proves the versatility of the coating procedure and represents a significant advantage over previous work with Co seeds owing to the higher magnetic susceptibility, reduced toxicity, and excellent biocompatibility of Fe. Furthermore, the latter system allows the synthetic methodology to be developed from a two‐pot scenario where seeds are isolated then coated, to an easier and more efficient direct one‐pot scenario. The two‐pot method yields proportionately larger cores. However, in both cases, the monodisperse product reveals a carbonaceous interface between the Fe core and oxide shell. Meanwhile for the one‐pot synthesis, the OA:OAm ratio influences both the morphology and dispersity of the product. This is interpreted in terms of competing interactions of the ligands with the iron precursor. Superparamagnetism (SPM) is observed, and microscopic studies reveal oxidative stability of the Fe(0) cores achieved by either method for >6 months. It is proposed that the carbonaceous interface is critical to this sustained oxidative stability.

Rapid Millifluidic Synthesis of Stable High Magnetic Moment FexCy Nanoparticles for Hyperthermia

“…The dependence of coercivity on the C content has been reported by Meffre et al and Yu et al In particular, a minimum coercive field of ∼150 Οe at an iron percentage composition near 80% was found for iron carbide-based NPs . In addition, the coercivity is size dependent . No exchange coupling is noticed because both iron carbide and iron oxide phases are soft magnetic materials with comparable coercivity values in the nanoscale …”

Superior CdSe/ZnS@Fe2O3 Yolk‐Shell Nanoparticles as Optically Active MRI Contrast Agents**

“…Based on this, iron holds great potential for targeted drug delivery and MRI . [11] Regarding MRI applications, paramagnetic nanomaterials offer advantages over conventional coordination complexes. As an example, their size, shape and composition can be engieered easily.…”

“…After passive oxidation, nanoparticles coated with an oxide shell maintain a stable core. Also, since it is ferromagnetic, the application of a metal oxide shell increases the magnetic susceptibility of non‐magnetic materials [11] …”

“…[12] It is known that the thermal decomposition of Fe(CO) 5 used in the production of advanced composite nanostructures is one of the most successful and frequently used techniques. [11] Generally, the coating can be achieved by temperature change. [18] Fe(CO) 5 and oleyamine (OAm) reaction is in the group containing less CO.…”

Magnetic Nanomaterials for Magnetically-Aided Drug Delivery and Hyperthermia

“…Magnetic nanoparticles play a big role in cancer detection [7][8][9], drug delivery [2,3], as well as hyperthermia treatment [10][11][12]. During the last decade, bi-magnetic core/shell nanoparticles featuring an iron core and an iron oxide (Fe 3 O 4 ) shell have become widely used [13][14][15][16][17][18][19], due to their superior magnetic properties [20,21].…”