Correlating Size and Composition-Dependent Effects with Magnetic, Mössbauer, and Pair Distribution Function Measurements in a Family of Catalytically Active Ferrite Nanoparticles

Abstract

The magnetic spinel ferrites, MFe 2 O 4 (wherein 'M' = a divalent metal ion such as but not limited to Mn, Co, Zn, and Ni), represent a unique class of magnetic materials in which the rational introduction of different 'M's can yield correspondingly unique and interesting magnetic behaviors. Herein we present a generalized hydrothermal method for the synthesis of single-crystalline ferrite nanoparticles with 'M' = Mg, Fe, Co, Ni, Cu, and Zn), which can be systematically and efficaciously produced simply by changing the metal precursor. Our protocol can moreover lead to reproducible size control by judicious selection of various surfactants. As such, we have probed the effects of both (i) size and (ii) chemical composition upon the magnetic properties of these nanomaterials using complementary magnetometry and Mössbauer spectroscopy techniques. The structure of the samples was confirmed by atomic PDF analysis of X-ray and electron powder diffraction data as a function of particle size. These materials retain the bulk spinel structure to the smallest size (i.e. 3 nm). In addition, we have explored the catalytic potential of our ferrites as both (a) magnetically recoverable photocatalysts and (b) biological catalysts, and noted that many of our asprepared ferrite systems evinced intrinsically higher activities as compared with their iron oxide counterparts.

Synthesis, characterization, and evaluation of PEGylated first-row transition metal ferrite nanoparticles as T2contrast agents for high-field MRI

“…A slight shi in peak positions for the substituted spinel NPs with respect to unsubstituted Fe 3 O 4 NPs could be noted; this change is well-recorded in literature, and is in agreement with the ionic radii of the divalent cations, indicating a successful incorporation of divalent cations into the lattice. 45 In general, the powder X-ray diffractograms of all the MFe 2 O 4 NPs are in excellent agreement with their theoretical counterparts, as can be seen from Fig. 2 Fig.…”

“…For all samples, the behavior is typical of superparamagnetism, which is expected for nanoscaled magnetic NPs. 45 The exception is CoFe 2 O 4 , whose T B is slightly below room temperature. Upon closer inspection, the room- NPs synthesized by Yang et al The reduced saturation magnetization of NPs is attributed to the existence of a magnetically 'dead' surface layer for each particle in which magnetic moments do not contribute to the magnetization.…”

“…43 The T B for these NPs, at $280 K, is also signicantly greater than that of the other ferrite NPs; this is expected for CoFe 2 O 4 NPs. 45,52 The Co 2+ ion -with a d 7 cong-uration -imparts a high magnetocrystalline anisotropy from the presence of spin-orbit coupling. The M s values recorded were 52.8 emu g À1 at 1.9 K and 33.7 emu g À1 at 300 K.…”

A low-cost preparation of waste-based PANI/NiFe2O4 composite for photocatalytic hydrogen evolution

“…However, NiFe 2 O 4 exhibits low visible-light-induced photocatalytic activity owing to the fast recombination of photoelectron-hole pairs [23]. Several methods, such as structure-design, metallic and non-metallic elements loading, and fabrication of semiconductor heterojunction have been reported to improve the photocatalytic activity and stability of NiFe 2 O 4 [24][25][26]. Thereby, NiFe 2 O 4 -based novel photocatalyst was designed to enhance the photocatalytic hydrogen production efficiency.…”

An X-ray magnetic circular dichroism (XMCD) study of Fe ordering in a synthetic MgAl2O4-Fe3O4(spinel-magnetite) solid-solution series: Implications for magnetic properties and cation site ordering

“…Because of their physical and electronic properties, they are widely used as technological and medical materials (e.g., magnetic recording media, batteries, catalysts, gas sensors, pigments, pharmaceuticals and magnetic resonance imaging 'targets'). The superparamagnetic properties of ferrite nanoparticles are the subject of expanding research (Pellegrin et al, 1999;Liu et al, 2000;Gunjakar et al, 2008;Pearce et al, 2012;Byrne et al, 2013;Tiano et al, 2015). The most common natural spinel is magnetite (Fe 2+ Fe 3+ 2 O 4 ) but other minerals include spinel (ss, MgAl 2 O 4 ), and complex solid solutions (e.g., franklinite…”