Lamellar silica , synthesis

Simple silica matrices To further illustrate the limit of this chapter, we briefly discuss one type of materials that will not be systematically reviewed layered lanthanide silicates obtained by hydrothermal synthesis. An alkaline solution of sodium silicate and lanthanide chlorides was stirred to produce a gel which was subsequently put into an autoclave under pressure at 230 °C during seven days, a procedure during which lamellar photoluminescent silicates... 

Titanium Silicalite-2 (TS-2), structurally similar to TS-1, could be prepared likewise using tetrabutylammonium hydroxide as the template [13, 14]. Titanium aluminum Beta (Ti,Al-[3) was prepared by hydrothermal synthesis from amorphous silica, sodium aluminate, tetraethyltitanate and tetraethylammonium hydroxide [15]. The presence of A1 was necessary for the crystallization of the product. Al-free Titanium Beta (Ti-[3) could be obtained in the presence of particular templates, such as dibenzyldimethylammonium hydroxide [16]. Titanium Mordenite (Ti-MOR), conversely, was obtained by post-synthesis insertion of Ti to dealuminated Mordenite [17]. Ti-MWW (Ti-MCM-22) was obtained by the synthesis of the lamellar precursor of Ti,B-MCM-22 followed by acid treatment to remove most of the boron and extra-framework Ti and finally calcination to burn out the template and bring about the condensation of lamellae into the three-dimensional MWW structure [18]. Ti is present in a number of different environ-... 

Amphiphilic inorganic-organic block copolymers (PDMS-h-PEO) with variable block lengths were successfully syndiesized. The obtained polymers revealed predominantly lamellar phases in their aqueous solutions. At low concentrations the spcmtaneous fisrmation of vesicles was obsaved. The polymers can be applied as structure-directing agents in the synthesis of mesostmctured silica-based thin films. 

This mediated (S+X I+)-synthesis model is supported by the following evidence (i) the cationic silica species which are present at pH < 2 (ii) the near 1 1 surfactant-to-chlorine ratio in the hexagonal and lamellar products (iii) the easy removal of the surfactant with ethanol (iv) the observation that TEOS and SiC L hydrolyse and form mesophase products, while Cab-O-Sil, which does not readily hydrolyse in acidic conditions, forms no mesophase products and (v) the anion dependence of the synthesis, e.g., the different products obtained with Cl, Br, and oxyanions. 

T. Dabadie, A. Ayral, C. Guizard, L. Cot, C. Lurin, W. Nie and D. Rioult, Synthesis of inorganic gels in lyyotropic liquid crystal medium. I. Synthesis of silica gels in lamellar phases obtained from non-ionic surfactants. /. Sol-Gel Sci. TechnoL, 4 (1995) 107. 

Synthesis of MCM-48 31 g of silica, 57 g of 25 % tetramethylammonium hydroxide and 165 g water are digested at 100°C. 172 g of 29 % hexadecyltrimethylammonium chloride solution is added and the mixture reacted for 12 hrs. at 150°C yielding MCM-48. The desired product is transient and upon prolonged heating slowly transforms into the lamellar MCM-50. The latter is initially difficult to observe since its most prominent XRD peak overlaps with the MCM-48 s (220) reflection. The lamellar impurity in MCM-48 can be detected and... 

Recently, we (82) and others (82-84) have shown that similar hetero-structures can be prepared by using two-dimensional inorganic sheets (made by exfoliation of various lamellar solids) in place of the organic polyanion. This technique offers a potentially powerful alternative to the construction of multi-component electron transfer systems, because it can, in principle, be used to stack up an arbitrary number of redox-active polymers without interpenetration (85). This chapter describes the preparation and photochemistry of simple multilayer composites on high-surface-area silica. Specifically, the synthesis and electron transfer kinetics of systems containing a polycationic sensitizer, poly-[Ru(bpy)2(vbpy)(Cl)2] (1), (abbreviated [Ru(bpy)3 ]n bpy = 2,2 -bipytidine and vbpy = 4-vinyl-4 -methyl-2,2 -bipyridine), and an electron-acceptor polycation poly[(styrene-co-]V-vinylbenzyl-N -methyl-4,4 -bipyridine)(Cl)2] (2), (PS-MV ) are presented. Using a solution-phase electron donor, 3, as the third electroactive component, it was possible to prepare and study the photoinduced electron transfer reactions of several different diad and triad combinations. 

There are some excellent review articles on different aspects of mesostructured materials, such as synthesis, properties, and applications. " Extensive research effort has been devoted to the exploitation of new phases (lamellar, cubic, hexagonal structures), expansion of the pore sizes (about 2-50 nm are accessible), and variable framework compositions (from pure silica, through mixed metal oxides to purely metal oxide-based frameworks, and inorganic-organic hybrid mesostructures). Another research focus is on the formation of mesostructured materials in other morphologies than powders, e.g. monolithic materials and films, which are required for a variety of applications including, but not limited to, sensors (based on piezoelectric mass balances or surface acoustic wave devices), catalyst supports, (size- and shape-selective) filtration membranes or (opto)electronic devices. The current article is focused... 

The application of a 11-ferrocenylundecyl-ammonium bromide/hexa-decylammonium bromide surfactant mixture as structure-directing agent resulted in a lamellar mesostructured silica film, which showed electronic conductivity due to electron transport in the ferrocenyl chains. Lyotropic lithium triflate-silicate liquid crystals have been utilized as supramolecular templates in the synthesis of ionically conducting nanocomposite films. ... 

Figure 36.3. Synthesis field diagrams for the synthesis of mesostructures (CmTMA surfactant, 0.33 M KOH, 2 days). The reactions were carried out at 90 °C (left column), 110 °C (center column), and 130 °C (right column). Top row 100 % TEOS as a silica source bottom row 90% TEOS and 10 % PTMOS as silica source. H hexagonal MCM-41-type phase, C cubic MCM-48-type phase, LMU-1 LMU-1 or KIT-1, L lamellar phase.

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