Silica sol-gel matrix

Colloids embedded in a silica sol-gel matrix were prepared by using fully alloyed Pd-Au particles. The Mossbauer data have yielded evidence that alloying Pd with Au in bimetallic colloids leads to enhanced catalytic hydrogenation and also to improved selectivity [426]. 

The two water-soluble porphyrins, 5,10,15,20-tetra(4-N-methyl-pyridiniumyl) porphyrin (H2TMPyP4+) and 5,10,15,20-tetra(4-sulfonato) porphyrin (H2TPPS4 ), were immobilized in the silica sol-gel matrix and served as the pH sensors as well65. The sol-gels doped with porphyrin were... 

Diffusion of different amines led to changes in the spectra of the silica sol-gel matrix containing the Co(III)porphyrin104. This phenomenon was... 

Center for Healthcare Technologies at Lawrence Livermore National Laboratory in Livermore, potentially capable to measure pH at or near the stroke site29. The probe is the distal end of a 125 pm fibre tapered up to a diameter of 50 pm. A fluorescent pH-indicator, seminaphthorhodamine-1-carboxylate, is embedded inside a silica sol-gel matrix which is fixed to the fibre tip. Excitation of the dye takes place at 533 nm and the emission in correspondence of the acid (580 nm) and basic (640 nm) bands are separately detected. The use of this ratiometric technique obviates worrying about source fluctuations, which have the same effects on the two detected signals. The pH sensor developed was first characterised in the laboratory, where it showed fast response time (of the order of tens of seconds) and an accuracy of 0.05 pH units, well below the limit of detection necessary for this clinical application (0.1 pH units). The pH sensor was also tested in vivo on rats, by placing the pH sensor in the brain of a Spraque-Dawley rat at a depth of approximately 5 mm30. 

Coupling reactions. Various coupling reactions involving nonpolar substrates may be carried out with hydrophobicized silica sol-gel matrix in which Pd(OAc)2 is trapped. The substrates form microemulsions in water with SDS and ROH. The catalyst is leach-proof and reusable. ... 

Samples of the pure silica sol-gel matrix and encapsulated CGTase were taken for TGA with a TGA-50 Shimadzu Thermogravimetric Analyzer, and the mass loss as a function of temperature was registered at a heating rate of 20 °C/min fiom room temperature to 1,000 °C. Initial mass samples varied from 2 to 6 mg. 

Cu-mordenite in silica sol-gel films. The fabrication procedure of Cu-mordenite-doped sol-gel films was modified as compared with the above Cu-doped ones by the change of copper nitrate onto Cu-modrenite. The subsequent deposition of the sol onto quartz substrate resulted in formation of thin films similar to simple Cu-doped ones. Amount of Cu-mordenite was adjusted for fabrication of the films with sufficient optical quality. The films were heated in air at 500 C followed by heating in hydrogen atmosphere at 150-450 C. The latter temperature variance determined different reduction of Cu-mordenite, and similarly different results were obtained with mordenite within the silica sol-gel matrix. 

Li et al have prepared an amperometric biosensor for hydrogen peroxide using a sol-gel immobilisation of horseradish peroxidase. HRP was entrapped in a thin silica sol-gel matrix made from tetramethoxysilane polymerised on carbon paste electrodes. The hydrogen peroxide detection was performed in the presence of hexacyanoferrate (II). Under optimised conditions, the linear range for detection of hydrogen peroxide was 2 x 10 - 2.6 x 10 M. The enzyme electrode maintained up to 65% of its activity for the period of 35 days. 

In a more direct translation of current macroscale, silica-based, SPE protocols other, microchip-based purification systems have focused on utilizing a packed silica-bead bed or silica sol-gel matrix solid phase for purification. This type of extraction was first miniaturized in a capillary format, to demonstrate the utility of the proposed method in the microscale, by Tian et al., who utilized a 500 nL capillary-based chamber packed with silica particles to establish that PCR-amplifiable DNA (with 80-90% of proteins removed during the load and wash steps) could be obtained from white blood cells with high extraction efficiencies (70%). This demonstrated the feasibility of incorporating such silica-based column purification methods into microfabricated devices and the effectiveness of such methods for the purification of DNA from a wide variety of biological species (white blood cells, cultured cells, and whole blood). 

In the same idea, it is worth mentioning that the electrochemical behavior of PTh grown by a template electrosynthesis in a silica sol-gel matrix is rather different from the one of a classical PTh... 

Adsorption PMMA chip modified with zeolite nanopartides silanol functional groups introduced to PMMA and modified with silicalite-1 nanoparticle Trypsin immobilized using silica-sol-gel matrix (Si—O—Si bridge via tethering to silanol, groups) Cyt-C and BSA digestion at 4 ftl/min for 5 s... 

In one case a strong synergistic effect has been observed when equimolar amounts of [Rh(cod)Cl]2 and Na2HRu3(CO)n have been co-entrapped in a silica sol-gel matrix. Whether under these conditions the two metallic complexes form a heteronuclear cluster or been activated by a remote control effect (Ojeda, 2003) has not been proven. The entrapped mixture ofthe two complexes promote at 80°C under 16 atm. H2 the hydrogenation of aromatic C-C bonds. 1,4-Xylene, e.g., forms within 4 h 1,4-dimethylcyclohexane (mainly as the cw-isomer) in quantitative yield (Scheme 24-35). 

Li, J. P, and T. Z. Peng, 2003. Cholesterol biosensors based on cholesterol oxidase immobilized in a silica sol-gel matrix on a Prussian Blue modified electrode. Chem J Chinese Universities-Chinese 24 798-802. 

The approach is general, and was demonstrated quite widely. For instance, Talhami et al. [5] have physically entrapped dichlorobis(triphenylphosphine)pal-ladium(II) within a silica sol-gel matrix, resulting in efficient catalysts for crosscoupling of aryl iodides, bromides, and triflates with intramolecularly stabilized... 

Figure 31.7 Synergetic effect obtained by entrapping two catalysts in the same silica sol-gel matrix highly efficient detoxification of chlorinated environmental pollutants by the combined action of Pd nanoparticles and [Rh(cod)CI)2.

Scratch resistance of the coating can be increased by adopting a dual-layer reinforced coating strategy with the nanofillers added from a water-based solution [33] to a hybrid silica sol-gel matrix. The first consequence of adding the... 

Chon, J.W.M., Bullen, C., Zijlstra, P., and Gu, M. (2007) Spectral encoding on gold nanorods doped in a silica sol-gel matrix and its application to high-density optical data storage. Adv. Funct. Mater., 17, 875-880. 

Maduraiveeran, G. and Ramaraj, R. (2007) Gold nanoparticles embedded in silica sol-gel matrix as an amperometric sensor for hydrogen peroxide. /. Electroanal. Chem., 608 (1), 52-58. 

Catalytic Membranes Ion gel membranes have been reported to be used as catalytic membranes or as a reaction media in biocatalysis. Liu et al. have reported the encapsulation of horseradish peroxidase (HRP) into an ionic liquid [C4mim][BF4]-based silica sol-gel matrix [138]. The specific activity of HRP enhanced dramatically, about... 

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