Silica sol-gel

Exposure to fiime and the precipitated silica (amorphous silica) causes fatal bronchial response as these are respirable. Repeated exposure dries the skin and causes mechanical irritation to eyes. Sol-gel silica, as an alternative to this, ceases the floating problem and avoids unnecessary contamination. 

The effects of restructuring at short length scales are evident in several studies of sol-gel silica polymerization. Based on... 

Hench, L.L. (1998) Sol-Gel Silica. Properties, Processing and Technology Transfer, Noyes Publications, Westwood, New Jersey, USA. 

Carturan, G., Dal Toso, R., Boninsegna, S. and Dal Monte, R. (2004) Encapsulation of functional cells by sol-gel silica actual progress and perspectives for cell therapy. Journal of Materials Chemistry, 14, 2087-2098. 

Rayss J., Sudolski G., Ion absorption in the porous sol-gel silica layer in the fibre optic pH sensor, Sens. Actuat B 2002 87 397-405. 

J.D. Badjic and N.M. Kostic, Unexpected interactions between sol-gel silica glass and guest molecules. Extraction of aromatic hydrocarbons into polar silica from hydrophobic solvents. J. Phy. Chem. B 4, 11081-11087 (2000)... 

D. Badjic and N.M. Kostic, Behavior of organic compounds confined in monoliths of sol-gel silica glass. Effects of guest-host hydrogen bonding on uptake, release, and isomerization of the guest compounds. J. Mater. Chem. 11, 408 118 (2001). 

C. Shen and N.M. Kostic. Kinetics of photoinduced electron-transfer reactions within sol-gel silica glass doped with zinc cytochrome c. Study of electrostatic effects in confined liquids. J. Am. Chem. Soc. 119, 1304-1312 (1997). 

J.D. Badjic and N.M. Kostic, Effects of encapsulation in sol-gel silica glass on esterase activity, conformational stability, and unfolding of bovine carbonic anhydrase II. Chem. Mater. 11, 3671-3679 (1999). 

Synthetic methods include the use of silanes bearing a chiral group for silylating the surface of the porous sol-gel silica, the use of such silanes as monomers or co-monomers in the polycondensation, the physical entrapment of chiral molecules, the imprinting of SG materials with chiral templates and the creation of chiral pores, and the induction of chirality in the matrix skeleton itself 48... 

The concept is general and one-pot acid/base and enzyme/catalyst enantioselective solid-state syntheses are easily achieved by entrapment of the mutually destructive reagents in two different sol-gel silicas. It is worth pointing out that while acids and bases adsorbed at the surface of polymers are left partly exposed and consequently require acid/base solid-state... 

Figure 5.20 Sol-gel silica entrapped cells such as those of Saccharomyces cerevisiae shown here are highly stabilized and freely accessible to external nutrients acting as potent bioreactors. (Photo courtesy of Giovanni Carturan.)...

The chemical inertness and optical transparency of Si02 sol-gel matrices make the doping methodology ideal for sensor developments, even if leaching is an issue that must be often addressed. Another attractive, unique feature is that non-toxic sol-gel silicas can be made in... 

M. L. Ferrer and F. del Monte, Study of the Adsorption Process of Sulforhodamine B on the Internal Surface of Porous Sol-Gel Silica Glasses through Fluorescence Means, Langmuir, 2003, 19, 650. 

Figure 2.7 Sol-gel silica microparticles biodegrade faster than commercial silica. (Reproduced from DelsiTech.com, with permission.)...

Sol-gel reversibility, of hydrogels, 13 730 Sol—gel silica—PDMS hybrids, 23 81 Sol—gel silica system, chemical additions to, 23 62... 

Immobilizing DENs within a sol-gel matrix is another potential method for preparing new supported catalysts. PAMAM and PPI dendrimers can be added to sol-gel preparations of silicas " and zinc arsenates to template mesopores. In one early report, the dendrimer bound Cu + ions were added to sol-gel silica and calcined to yield supported copper oxide nanoparticles. Sol-gel chemistry can also be used to prepare titania supported Pd, Au, and Pd-Au nanoparticle catalysts. Aqueous solutions of Pd and Au DENs were added to titanium isopropoxide to coprecipitate the DENs with Ti02. Activation at 500°C resulted in particles approximately 4 nm in diameter. In this preparation, the PAMAM dendrimers served two roles, templating both nanoparticles and the pores of the titania support. 

L. Beakley, R. Cheng, S. Yost, andB. D. Chandler, Immobilization of dilute dendrimer encapsulated Pt nanoparticles in a sol-gel silica matrix, Appl. Catal. A Gen. 292, 124-129 (2005). 

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