Modified Gels

the APD process yields aerogels that offer identical properties to those dried supercritically. However, the elaboration of every synthetic method starts with arduous trials and optimization studies until this point is reached. From that point of view, the supercritical drying method is certainly less labor-intensive because there are fewer steps to the final product and the drying is not as sensitive to process parameter changes as in the APD case. 

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The dried polyoxazoline-modified silica gel was immersed into distilled water. The adsorption property of the resulting gel was estimated by the water content. The water uptake was calculated from an expression of (W -W)jW, where Wis the weight of dried gel and W is the weight of water-absorbed gel. The modified gel showed a higher water-adsorption property than that of untreated silica gel, which absorbed 10.8 multiples of water. The water uptake of modified gel was up to 13.7 multiples of the weight of dried gel. Thus, silica gel has been made more hydrophilic by a polyoxazoline segment. 

Pack modified gel into column and adsorb sample containing a mixture of components A, C, and D ... 

Evans, G., 3ohnson, P.E., Brushmiiler and Ames, R.W., 1979. Detection of labile zincbinding ligands in biological fluids by modified gel filtration chromatography. Anal. Chem., 51 839-843. 

Zinc-binding components of urine were examined using modified gel chromatography (15). Urine (3 ml) was chromatographed on Sephadex G-25 columns (2.5 x 40 cm) equilibrated with a buffer containing 10 ppm Zn as Zn(N03)2 and 10 mM Tris buffer, pH 7.4. Fractions of 3 ml were analyzed by atomic absorption spectroscopy. Void volume of the column was determined with blue dextran. 

The NMR and X-ray diffraction data are only consistent with substitution of boron into the framework structure of the mordenite. Although we prepared boron substituted mordenite directly from modified gels, direct synthesis has severe limitations. The solution chemistry of the substituting element can interfere with zeolite nucleation and crystallization, as... 

Figure 1 Scanning transmission electron micrograph of a Pd-silica composite formed via an organically modified gel. The average particle size is 3.8nm, and the distribution range is 2.8-5.2nm. (Reprinted with permission from Ref. 10. 1991 American Chemical Society)...

The smface chemistry of the as-synthesized NCs has been exploited in order to develop methods for anchoring the semicondnctor NCs directly to the sol-gel network. The approaches investigated are analogous to methods discussed in Section 2 with respect to organically modified gels, with one major exception - the colloidal NC, and not jnst the starting metal salt, is directly tethered to the metal-oxide network ... 

Human endothelial cells isolated from umbilical cord (HUVECs) were seeded on pure and RGD modified gels to determine the cell-adhesive characteristics of the compared materials. Cell adhesion and proliferation (or apoptosis) were observed by means of microscopic and colorimetric techniques. 

Fig. 9 Viability of human endothelial cells isolated from umbilical cord on RGD modified gels (here shown for Type B) monitored by the live/dead assay. Representative pictures shows live (fluorescein di-O-acetate, viable cells visible as light spots, left) and dead (propidium iodide, no dead cells visible, right) staining. Image after 1 day culture. Scale bar 200 pm...

Ordinary chromatographic techniques depend for their effectiveness on differences (often small) in adsorption, partition, ionic charge, or size, between solute molecules of similar chemical character. A modified gel technique in which use is made of the high specificity of biochemical reactions is affinity chromatography [54,55]. 

For the above reasons, most efforts in the design and production of pH sensors have focused on the development of high-precision sensors for industrial process streams owing to the diverse and often difficult conditions that are experienced in these media. These pH sensors are designed to have long-term stability and extended life, based on the use of industrial-grade electrodes with silver/silver chloride reference electrodes incorporated into gel-polymer electrolytes. Some of the industrial-grade pH sensors use modified gel-solid electrolyte, which is free of silver chloride and, hence, can be used in presence of sulfides. 

Bulk titania wet gels, prepared by hydrolysis of TNB in ethanol solution with addition of EACAC using acid catalyst, were aged at 90°C for 1 h, and the wet gels were immersed into an ethanol solution of surfactants, CTAC oxBTAC, at 60°C for 1 h, and dried at 90°C for 24 h (surfactant-modified gels) [28, 29]. The dried gels were annealed at 500°C for 2 h. 

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