Inorganic magnetite

The mostly used methods to monitor LbL deposition on monodisperse PS-latex particles for various substances are SPLS method and microelectrophoresis. Inorganic (magnetite, silica, titania and fluorescent quantum dots) nanoparticles [32-34], lipids [35-37] and proteins (albumin, immunoglobulin and others) [29, 38, 39] were incorporated as building block for shell formation on colloidal particles. In paper [39] the construction of enzyme multilayer films on colloidal particles for biocatalysis was demonstrated. The enzyme multilayers were assembled on submicrometer-sized polystyrene spheres via the alternate adsorption of poly(ethyleneimine) and glucose oxidase. The high surface area bio-multilayer coated particles formed were subsequently utilized in enzymatic catalysis. The step-wise coating of different lipids alternated with polyelectrolytes was performed by adsorption of preformed vesicles onto... 

Fig. 9 XMCD spectra of bionanomagnetite before and after interaction with the azo dye. (A) shows the XMCD spectra (inset showing TEM image of the nanoparticles) for inorganic magnetite and (B) for biogenic nanomagnetite. The latter shows reduction of the octahedral Fe component, as indicated (black curves are before interaction, grey (red) curves are after interaction).

Magnetite deserves further investigation as robust inorganic sorbent material. 

Blesa MA, Marinovich HA, Baumgartner EC, Maroto AJG. 1987. Mechanism of dissolution of magnetite by oxalic acid ferrous iron solutions. Inorganic Chemistry 26 3713-3717. 

The magnetite is considered to form from a ferrihydrite precursor by interaction of this phase with dissolved Fe" ions (Kirschvink Lowenstam, 1979 Lowenstam, 1981 Nesson Lowenstam, 1985). The same mechanism operates for inorganic synthesis at around pH 7 (see chap. 13). Most probably the other iron oxides in the teeth form by a similar mechanism, but under conditions of slightly lower pH and/ or higher redox potential. The separation of these minerals in time and space suggests local variations in growth conditions. 

Ferrihydrite has indeed been found in association with magnetite in Magnetospirillum magnetotacticum (Frankel et ah, 1983). It seems essential that the cell solution is sufficiently buffered to maintain a neutral pH and thus ensure that the solubility product of magnetite is always exceeded. This is a reaction which easily takes place in a purely inorganic system at ambient temperature (see chap. 14). Lepidocrocite has also been suggested as a magnetite precursor (Abe et al. 1983). 

Couling, S.B. Mann, S. (1985) The influence of inorganic phosphate on the crystallization of magnetite (Fe304 from aqueous solution. 

A.J.G. Blesa, M.A. (1988) The dissolution of magnetite by nitrilotriacetatoferrate(II). J. Chem. Soc. Earaday Trans. I. 84 9-18 Delgado, A. Torrent, J. (2000) Phosphorus forms and desorption patterns in heavily fertilized calcareous and limed acid soils. Soil Sci. Soc. Am. J. 64 2031-2037 Delgado, A.V. Gonzalez-Caballero, F. (1998) Inorganic particles as colloidal models. Effects of size and shape on the electrokinetics of hematite (a-Fe203). Croatica Chemica Acta 71 1087-1104... 

As summarized in Table 14.1, teeth, bones, shells, etc. are indispensable components, consisting of inorganic mineral crystals and protein film, with sizes, morphologies, and textures suitable to fulfil the function of the particular organs involved. In this section we will look at hydroxyapatite, aragonite and calcite (two polymorphs of CaCO ), and magnetite in greater detail. 

Suspended solid surfaces (particles or colloids) in waters play a prominent role in controlling the concentration of dissolved trace elements. Most of these elements are eliminated by sedimentation after incorporation on to or into particles, generally by complexation with the surface sites. The most common inorganic particles and colloids are non-clay silicates (quartz, potash feldspar, plagioclase, opaline silica (diatoms)) clays (illite, smectite) carbonates (calcite, dolomite) Fe-Mn oxides (goethite, magnetite) phosphates (apatite) sulfides (mackinawite). Particles and colloids in a water body may be classified as a function of their origin ... 

The encapsulation of magnetite particles into polystyrene particles was efficiently achieved by a miniemulsion process using oleoyl sarcosine acid [ 109] or the more efficient oleic acid as first surfactant system to handle the interface magnetite/styrene, and SDS to stabilize the interface styrene/water, thus creating a polymer-coated ferrofluid (Fig. 15b). Since the magnetite particles were very small (ca. 10 nm), each polymer particle was able to incorporate many inorganic nanoparticles. A content of 20 wt% could be incorporated in this way. 

Carboxylic acids can be used as the media for the solvothermal synthesis of inorganic materials. Synthesis of magnetite by thermal decomposition of an iron... 

Redox reactions are of importance in the dissolution of Fe-bearing minerals. Reductive dissolution of Fe(III)(hydr)oxides can be accomplished with many reductants especially organic and inorganic reductants, such as ascorbate, phenols, dithionite, and HS. Fe(II) in the presence of complex formers can readily dissolve Fe(III)(hydr)oxides. The Fe(II) bound in magnetite and silicate and adsorbed to oxides can reduce O2 (White, 1990 White and Yee, 1985). 

Detritus, both organic and inorganic, often settles in morphological depressions on varnish. These pieces are sometimes trapped by accreting rock varnish, leading to a wide variety of other minerals that are sometimes found in varnish samples such as quartz, feldspars and magnetite (Potter and Rossman, 1979a Dorn, 1998, p. 198 Mancinelli et al., 2002). 

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