Magnetite preparation

At an AI/O4 mol ratio of approximately 0.4, Al preferentially replaces tetrahedral Fe (A-site). Ardizzone et al. (1983) reported that magnetite prepared in sodium acetate buffer solution contains up to 2.3 mg g Na in the structure. 

Since the spinel phase must be prepared at low temperatures (by hydrothermal synthesis or by careful oxidation of magnetite at a temperature T < 300 C, for example) it has been widely suspected that some incorporation of hydrogen is needed to stabilize it. However, Schrader and Buttner have shown that pure y-Fe203 does exist, and Coey et al. have been able to prepare Fe3 j04 in the compositional range 0 < x < 0.08 by quenching non-stoichiometric magnetite prepared at 1450 °C. There is no evidence that hydrogen is needed to stabilize the system. 

Single-bilayer phosphatidylcholine (14) surfactant vesicles Magnetite prepared from equimolar Fe2+/Fe3+ and NaOH and sonicated with the lipid X-ray analysis established the presence of magnetite in the vesicles 787, 788... 

Fig. 9 High resolution TEM images of (a) nanocubes and (b) nanospheres of magnetite prepared by the solventless decomposition of ferrocene in the presence of PVP. Variation of molar ratio of ferrocene and PVP (a) 1 1 and (b) 1 5, together with thermal decomposition treatment at 350 °C for (a) 2 hours and (b) 4 hours afforded particles of varying morphologies. 2012 Royal Society of Chemistry.

Wan, J., Cai, W., Meng, X. and Liu, E. (2007) Monodisperse water-soluble magnetite nanoparticles prepared by polyol process for high-performance magnetic resonance imaging. Chemical Communications, (47), 5004—5006. 

Li, Z Sun, Q. and Gao, M.Y. (2005) Preparation of water-soluble magnetite nanocrystals from hydrated ferric salts in 2-pyrrolidone mechanism leading to Fe304. Angewandte Chemie International Edition, 44 (1), 123-126. 

PEG is hydrophilic and is widely used in biological research because it protects surfaces from interacting with cells or proteins. Thus, coated particles may result in increased blood circulation time. For their preparation, 10-mg magnetite particles were dispersed in 1.0 mU of deoxygenated water by sonication for 30 min. The aqueous dispersion of MNPs was dissolved in the aqueous cores of reverse micelles... 

Micro- and nanobeads with magnetic properties have recently become popular since these tools can be manipulated, e.g., collected in the region of interest. Magnetite nanoparticles are introduced in order to render the polymeric beads magnetic. Preparation and application of magnetic beads will be discussed in more detail in Sect 5.5. 

Precipitation was found to be a very useful method for preparation of nanobeads with magnetic properties [17] since not only indicators but also small lipophilic magnetite nanobeads (having diameter of a few nanometers) can be incorporated inside the polymeric beads. Such multifunctional magnetic beads can be guided to the region of interest, be collected and manipulated there. 

Mandemack KW, Bazylinski DA, Shanks III WC, Bullen TD (1999) Oxygen and iron isotope studies of magnetite produced by magnetotactic bacteria. Science 285 1892-189 Mann S, Sparks NHC, Couling SB, Larcombe MC, Franke RB (1989) Crystallochemical characterization of magnetite spinels prepared from aqueous solution. J Chem Soc Far Trans 85 3033-3044 Matthews A, Zhu XK, O Nions K (2001) Kinetic iron stable isotope fractionation between iron (-II) and (-III) complexes in solution. Earth Planet Sci Lett 192 81-92... 

Zhao et al. prepared magnetite (FesO nanoparticles modified with electroactive Prussian Blue [44]. These modified NPs were drop-cast onto glassy-carbon electrodes. They observed the redox processes commonly observed for PB (similar to that seen in Figure 4.8), and also demonstrated that the Prussian White material produced by PB reduction at 0.2 V served as an electrocatalyst for Fi202 reduction. They also prepared LbL films in which PB NPs and glucose oxidase were alternated between PD DA layers [99]. These were demonstrated to act as electrocatalysts for Fi202 reduction. Based on the ability to sense the product of the enzymatic reaction, these structures were shown to act as glucose sensors. 

Fig. 4. Composition of magnetite and hematite grains from the till samples prepared by ODM. Larger symbol is the average composition for all analyses for each sample.

Still following the macro-structural hypothesis which we favored at that time, we abondoned the idea of a specific favorable influence of flux promoters and assumed instead that the cause for the success of the magnetite experiment was the compact porous structure of the iron sponge which was formed in the test oven by the reduction of the Swedish ore. An apparent support of this idea was that contrary to the favorable action of the dense iron sponge obtained from magnetite, catalysts of a looser structure such as, e.g., iron asbestos preparations had always been particularly ineffective. 

With the aim of becoming independent of the individual origins and compositions of the various materials, we attempted to prepare, synthetically, an iron-containing catalyst equivalent in structure and in composition to the Magnetite of Gallivare (Sweden) which had proved, in repeated tests, to be an efficient and dependable catalyst. 

The preparation of metals from their oxides by reaction in reducing atmospheres. For example, iron is prepared from crushed and sized magnetite... 

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