A thermolysis approach to simultaneously achieve crystal phase- and shape-control of ternary M–Fe–O metal oxide nanoparticles

Abstract

Significant studies have achieved beautiful control in particle size, while the shape- and phase-control synthesis of nanoparticles remains an open challenge. In this study, we have developed a generalized methodology to selectively prepare either NaCl-type (reduced form) or spinel-type ferrite (oxidized form) M-Fe-O (M = Mn, Co) crystallites with high reproducibility. A two-step heating process was able to control formation of two types of crystal phase, either a thermodynamic spinel-type under air or a kinetic-control of NaCl-type (rock salt structure) under Ar in a cubic morphology. On the other hand, the three-step heating procedure in air obtained the spinel-type with a thermodynamic equilibrium octahedral shape exclusively. Either using metal acetates (M(ac)(2)) or metal acetylacetonates (M(acac)(2)) as the starting precursors (M = Mn, Co) can be introduced to prepare NaCl-type (reduced form) or spinel-type ferrite (oxidized form) crystallites with identical experimental parameters, including precursor concentration, reaction temperature, reaction time, and heating rate. The oleic acid molecule, reaction temperature, and heating rate employed in the synthesis were carefully examined and found acting as determined roles behind the reaction processes. Apart from the previous literature reports as shape-directed and/or stabilizing agents, the oleic acid molecule played an additional phase-tuning role.

Selective Magnetic Evolution of MnxFe1–xO Nanoplates

“…In addition, saturation is hard to achieve and M S (10. 29 The other transition at 59 K is thought from the interaction between AFM and FM. In many AFM/FM materials, this broad transition at low temperature is observed.…”

“…Several shapes of Mn x Fe 1-x O nanoparticles were prepared by thermal decomposition method, such as nanospheres, 26 concave shape nanoparticles, 27 nanocubes, 28,29 and hexagonal shape nanoparticles. 30 The advantage of Mn x Fe 1-x O is its resistance to oxidation in air compared to MnO and FeO, which makes it a good candidate for magnetic contrast agent.…”

Magnetic nanoparticle-based immunoassay for rapid detection of influenza infections by using an integrated microfluidic system

“…In order to target influenza viruses that infected on mock cells, the targeted materials (the surface of MnFe 2 O 4 nanoparticles will be conjugated with influenza A anti-body) must be hydrophilic. Based on the process reported in the literature, 37 the method of MnFeO nanoparticles synthesis is in hydrophobic phase. Therefore, the hydrophobic MnFeO nanoparticles must be transferred to the hydrophilic phase and then conjugated with influenza A anti-body.…”

Microfluidic system for rapid detection of influenza infection by utilizing magnetic MnFe2O4 nanoparticle-based immunoassay

“…3. These nanoparticles were produced through serial chemical heating generation using Fe (acac) 3 , Mn (ac)z, oleic acid and trioctylamine as starting materials [11]. The synthesized nanoparticle has an average size of 98 ± 19.5 nm.…”