Tetramethyl orthosilicate

The use of sol-gel techniques to prepare ceramic powders has recently attracted much interest in academia and industry. Sol-gel techniques involve dissolving a ceramic precursor (e g., tetramethyl orthosilicate) in a solvent and... 

Fig. 1.2 Scanning electron micrographs of (A) the silica wall of the diatom Stephcmopyxis turns (reproduced from [21] by permission ofWiley-VCH) and (B-D) singular morphologies of silica synthesized using poly-L-lysine and pre-hydro-lyzed tetramethyl orthosilicate (TMOS) under...

Some non-silica sol-gel materials have also been developed to immobilize bioactive molecules for the construction of biosensors and to synthesize new catalysts for the functional devices. Liu et al. [33] proved that alumina sol-gel was a suitable matrix to improve the immobilization of tyrosinase for detection of trace phenols. Titania is another kind of non-silica material easily obtained from the sol-gel process [34, 35], Luckarift et al. [36] introduced a new method for enzyme immobilization in a bio-mimetic silica support. In this biosilicification process precipitation was catalyzed by the R5 peptide, the repeat unit of the silaffin, which was identified from the diatom Cylindrotheca fusiformis. During the enzyme immobilization in biosilicification the reaction mixture consisted of silicic acid (hydrolyzed tetramethyl orthosilicate) and R5 peptide and enzyme. In the process of precipitation the reaction enzyme was entrapped and nm-sized biosilica-immobilized spheres were formed. Carturan et al. [11] developed a biosil method for the encapsulation of plant and animal cells. 

Synonyms Tetramethoxysilane tetramethyl orthosilicate methyl orthosilicate tetramethyl silicate... 

An optode based on Meldola Blue immobilized in tetramethyl orthosilicate gel can be used to evaluate the concentration of H2O2 in the pH range from 5 to 12, in the dynamic... 

Very little accurate structural information about esters of the oxygen acids of the heavier elements has been reported. The molecule of tetramethyl orthosilicate, Si(OCH3)4, has21 Si—C = 1.64 0.03 A, C—O = 1.42 0.04 A, and angle Si—O— C = 113° 2°. These values are approximately those expected from the foregoing considerations the amount of double-bond character of the Si—O bonds is indi-... 

Abbreviations p, ratio between ionic radii of cation and anion TBHP, rm-butyl hydroperoxide EBHP, ethylbenzene hydroperoxide PO, propylene oxide TBOT, tetrabutyl orthotitanate TEOT, tetraethyl orthotitanate TIOT, tetraisopropyl orthotitanate TEOS, tetraethyl orthosilicate THF, tetrahydrofuran TPA-OH, tetrapropylammonium hydroxide TMOS, tetramethyl orthosilicate TBA-OH, tetrabutylammonium hydroxide TBP-OH, tetrabutylphophonium hydroxide TEA-OH, tetraethylammonium hydroxide TMA-OH, tetramethylammonium hydroxide. 

A difference in the relationship between UCV and degree of substitution x has recently been reported in connection with the use of tetramethyl orthosilicate (TMOS) as the silicon source instead of TEOS. The Ti content can be increased up to a value of 0.05 without evidence for extra-framework titanium species in the UV-visible spectra. However the UCV increases do not follow the relationship of Eq. (5) and the maximum value obtained, 5390 A3 at x = 0.05, is the... 

The formation of a sol-gel porous material is through a hydrolysis-polycondensation reaction. An example is given in equation 1 with the methoxide of silicon (tetramethyl-orthosilicate, TMOS), but many other alkoxides, aryl oxides and acyl oxides can be used, as well as Si—N and Si—Cl compounds. 

Since the use of alcohol in the sol-gel process can lead to aggregation of the colloidal metal, Au/SiC>2 catalysts have been prepared without alcoholic solution, using tetramethyl orthosilicate (TMOS) as a water-soluble silicic precursor and colloidal gold by reducing aqueous HAuCLi with magnesium citrate.114 However, the size of the gold particles was not reported, but reduction by citrate ion does not usually produce small particles. 

PER = Tosoh Perrierite TMOS = tetramethyl orthosilicate, source of Si AI2Q3 -mixed with 40% Dispal powder, then extruded. = 100 cc/min. 

Narang, U. Wang, R. Prasad, P. N. Bright, F. V., Effects of aging on the dynamics of rhodamine 6G in tetramethyl orthosilicate-derived sol-gels. Journal of Physical Chemistry 1994, 98(1), 17-22... 

The chemistry involved in the formation of mesoporous silica thin films is qualitatively well understood. However, specific reaction mechanisms of the individual steps are still debated. In addition, owing to the complexity of the sol-gel reaction pathways and cooperative self-assembly, full kinetic models have not been developed. From the time of mixing, hydrolysis reactions, condensation reactions, protonation and deprotonation, dynamic exchange with solution nucleophiles, complexation with solution ions and surfactants, and self-assembly, all occur in parallel and are discussed here. Although the sol-gel reactions involved may be acid or base catalyzed, mesoporous silica film formation is carried out under acidic conditions, as silica species are metastable and the relative rates of hydrolysis and condensation reactions lead to interconnected structures as opposed to the stable sols produced at higher pH. Silicon alkoxides are the primary silica source (tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, etc.) and are abbreviated TMOS, TEOS, and TPOS, respectively. Starting from the alkoxide, Si(OR)4, in ROH and H2O solution, some of the general reactions are ... 

From Ethoxides A mixture of tetramethyl orthosilicate and zirconium w-propoxide was hydrolyzed in 4 (mol water/mol Zr -t Si) parts of water at room temperature. The precipitate was washed in warm water and calcined at 500°C for 3 h. 

Of the available silicon alkoxides, tetraethyl orthosilicate (TEOS) appears to be the most popular. This is because it reacts more slowly with water than tetramethyl orthosilicate, comes to equilibrium as a complex silanol and in a partially hydrolyzed state is stable over longer periods of time. The clear TEOS liquid is the product of the reaction of SiCl4 with ethanol. The reaction produces HCl along with the ester Si(0C2H5)4 (1). This colorless liquid of a density of about 0.9 g/cm is easy to handle and through multiple distillation extremely pure. 

CAS-No [681-84-5] methyl orthosllicate silicic acid tetramethyl ester tetramethoxysilane tetramethyl orthosilicate... 

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