Phyllosilicates magnesium

Fujii and coworkers reported the synthesis and detailed structural analyses of alkylammonium/magnesium phyllosilicate hybrids [88], which were prepared by hydrothermal reaction from a mixture ofoctadecyldimethyl(3-trimethoxysilylpropyl)-ammonium chloride, silica sol, and magnesium hydroxide Mg(OH)2. The structure of the hybrid compound was studied by XRD, TEM, electron diffraction, high-resolution solid-state NMR, TG-DTA/MS, and elemental analysis. The resulting analytical information confirmed the unit structure, which consists of a 2 1... 

Fig. 2.17 Three structure candidates (A, B, and C) of alkyl-ammonium/magnesium phyllosilicate hybrids. Reprinted with permission from [88], K. Fuji etal., Chem. Mater., 2003, 75,1189.

This chapter reviews recent work on the fabrication and characterization of bio-inorganic nanomaterials based on organically functionalized magnesium phyllosilicate materials. We begin with the general procedures used to synthesize and characterize these organodays (Section 8.2), and then describe how higher-order... 

Synthesis and Characterization of Organically Functionalized 2 1 Magnesium Phyllosilicates... 

Fig. 8.2 PXRD pattern of ethlyenediamine-functionalized magnesium phyllosilicate showing reflections indexed according to the 2 1 trioctahedral phyl losi I icate structure of talc.

Fig. 8.3 SEM images of hexadecyl-functionalized magnesium phyllosilicate showing (A) intact spheroids (scale bar = 20pm) and (B) fractured spheroid with foam like interior (scale bar = 20pm). (C) TEM image of a wall fragment showing lattice fringes corresponding to a periodic lamellar structure (scale bar = 50 nm).

Fig. 8.5 SEM images of (A) close packed array of latex beads (scale bar= 1 tm) and (B) macroporous aminopropyl-functionalized magnesium phyllosilicate monolith obtained after infiltration and extraction of colloidal template (scale bar= 1 pm).

Intercalation of Biomolecules within Organically Modified Magnesium Phyllosilicates 247... 

In the next section, we demonstrate how exfoliation and ordered restacking of aminopropyl-derivatized magnesium phyllosilicates in the presence of proteins, enzymes or DNA can be used to prepare new types of bio-inorganic layered nanocomposites. 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

In conclusion, we have highlighted in this and the preceding section two versatile synthetic strategies to bio-inorganic layered nanocomposites based on the self-assembly of organically functionalized magnesium phyllosilicates (Figure 8.18). 

Fig. 8.18 Schematic diagram showing the potential scope of organically functionalized magnesium phyllosilicate (shown in top centre of figure) for the preparation of functional bioinorganic nanomaterials. (A) biomolecule-induced co-assembly of exfoliated aminopro-pyl-functionalized organoclay sheets to produce layered nanocomposites containing functional protein molecules (top left) or DNA (bottom left). (B) molecular wrapping...

Fukushima, Y. and Tani M. (1995) An organic/inorganic hybrid layered polymer methacrylate-magnesium (nickel) phyllosilicate. Chemical Communications, 241—242. 

Whilton. N.T., Burkett, S.L. and Mann, S. (1998) Hybrid lamellar nanocomposite based on organically functionalized magnesium phyllosilicate days with interlayer... 

Fonseca, M.G. and Airoldi C. (2000) Mercaptopropyl magnesium phyllosilicate-thermodynamic data on the interaction with divalent cations in aqueous solution. Thermochimica Acta, 359, 1-9. 

Patil, A.J., Muthusamy, E. and Mann, S. (2005) Fabrication of functional protein-organoclay lamellar nanocomposites by biomolecule-induced assembly of exfoliated aminopropyl-functionalized magnesium phyllosilicates. Journal of Materials Chemistry, 15, 3838-3843. 

Soapstone or steatite are names generally applied to any soft, waxy or greasy, massive metamorphic rock. The dominant mineral is usually talc, a light-colored magnesium silicate. Other phyllosilicate minerals or mixtures of minerals are used in similar ways, since their relative softness makes them attractive to carvers. Massive soft soapstone has also been used to make sinks, electrical switchboards, and ovens. 

The crystal lattice of montmorillonite, similar to other 2 1 phyllosilicates, may have isomorphic substitutions both in the tetrahedral and octahedral positions. In the tetrahedral positions, the central tetravalent silicon can be substituted by trivalent aluminum ions in the octahedral positions, the trivalent aluminum ions can be substituted by bivalent (usually magnesium and iron(II)) cations of similar... 

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