On colloidal silica

Lower and coworkers [199] have investigated the adsorption of T4 lysozyme on colloidal silica. It was observed that the enzymatic activity decreased upon adsorption due to the differences in adsorbed enzyme structure and orientation as well as the electrostatic effects. 

Braun et al. [258] used a combination of tert-butyllithium (t-BuLi) and tetramefhy-lethylenediamine to create initiator sites at the surface of carbon black for the LASIP of styrene. Schomaker et al. [259] first immobilized a methyl methacrylate derivative on colloidal silica and after activation by a Grignard reagent polymerized MMA. 

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

Fig. 12.1.4 Immobilization of bovine serum albumin on colloidal silica grafted with poly (maleic anhydride-styrene) (O), poly(maleic anhydride-methyl methacrylate) ( ), and poly (ethylene glycol)-poly(maleic anhydride-styrene) (A). (Front Ref. 42.)...

The accompanying data give the volume of N2 at STP adsorbed on colloidal silica at the temperature of liquid nitrogen as a function of the ratio p/p0. Plot these results according to the linear form of the BET equation. Evaluate c, Vm, and Asp from these results, using 16.2 A2 as the value for o°. 

Figure 6. Sorption capacity and surface coverage by hydrolyzed AJ(H1) on colloidal silica as function of pH...

Heilweil EJ, Casassa MP, Cavanagh RR, Stephenson JC. Vibrational energy relaxation of surface hydroxyl groups on colloidal silica. J Chem Phys 1984 81 2856-2859. 

WHEELER AND THOMAS Photochemistry on Colloidal Silica Solutions 99... 

Figure 35. Schematic representation of the Ru(bpy)3 /a-ZrP/viologen onion structure grown on colloidal silica particles. The sequence of fast (1, 2) and slow (3) electron-transfer steps that follow photoexcitation of Ru(Me-vpy)(bpy)2 " polymer is shown. Reproduced from D.M. Kaschak, S.A. Johnson, C.C. Waraksa, J. Pogue and T.E. Mallouk, Coord. Chem. Rev. 1999, 185-186, 403, with permission from Elsevier Science.

Phan, T.N.T., et al., Adsoption of zinc on colloidal silica, triple layer modelization and aggregation data. Colloids Surf. A, 244, 131, 2004. 

The symposium was exceptional because it gathered together for the first time many of the world s outstanding silica scientists, who presented close to 200 selected papers. Forty of the most prominent silica researchers from the former Soviet republics, who could not attend the symposium, sent papers to be discussed at the meeting. On this basis Iler s book and the symposium can be considered landmarks in the history of exchange of information on colloidal silica systems. A most valuable source of information published before the symposium was the excellent textbook by Brinker and Scherer printed in 1990 (8). 

Subsequent work on colloidal silica with sedimentation FFF was reported by Kirkland and co-workers (7,12) and by Yonker et al. (13), who used various organic liquids as the FFF carrier. 

To explore this analogy, we will review previous work on the influence of stoichiometry as well as present new results on the effect of neutralization on macromolecular complex formation. In addition, we will review very recent results for adsorption on colloidal silica and present preliminary results for the adsorption on colloidal polystyrene. The excimer to monomer emission intensity ratio, the excitation spectra, and the lifetimes of the excimer and monomer are the observable experimental parameters. 

When temperature is increased growth rate increases. Therefore the decision of when to increase temperature based on colloidal silica concentration should be made by previously analyzing the effect of SSn on the process at the selected temperature. 

Just like in the case of coating formulations for jet ink receptors, intensive efforts have been made in the last 15 to 20 years to develop polishing formulations for microelectronic products containing colloidal particles of different compositions. The final step in most pohshing processes usually employs colloidal particles of silica. We have summarized information on colloidal silica as polishing agent from an number of recent patents in a table. Table 57.9. 

Gierszal KP, Jaroniec M (2006) Carbons with extremely large volume of uniform mesopores synthesized by carbonization of phenolic resin film formed on colloidal silica template. J Am Chem Soc 128 10026-10027... 

S.A. Khan, K.E. Jensen, Microfluidic synthesis of titania shells on colloidal silica. Advanced Materials, 2007, 19, 2556. 

Both head- and tail-type cationic vinyl monomers with long methylene chains in THF or chloroform had the maximum adsorption on colloidal silica on the respective adsorption isotherm. Above the monomer concentration giving maximum adsorption, the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from the silica surface. At the monomer concentration giving maximum adsorption, the adsorbed monomer was spontaneously polymerised on the silica surface in THF or chloroform without an initiator at 40C or 60C. The polymerisation mechanism was discussed. Adsorption of an anion-type monomer with a carboxyl group on delta-alumina which showed a positive zeta potential in neutral aqueous solution was higher than that on colloidal silica, but spontaneous polymerisation did not occur on alumina. 19 refs. lAPAN... 

In this paper, we present a study in which combustion catalysts based on silica-coated metal monoliths were prepared. The aim of this study was to prepare washcoated metal monoliths with controlled properties. The properties varied are specific surface area of the washcoat and washcoat thickness or washcoat loading. Furthermore, we discuss how the preparation procedure affects the resulting catalyst properties and related performance. We deposited washcoats based on colloidal silica sols. Colloidal silica sols give porous materials with rather narrow pore size distributions when dried and calcined. This gives us excellent control over the pore size distribution of the washcoat, as will be discussed. The technique presented here, allows deposition of washcoats with controllable thickness in one step, unlike techniques based on pure silica sols, reported elsewhere [7,8]. Washcoats were impregnated with paUadium salts to make active catalysts that were tested in methane combustion. The effects of the preparation procedure of the silica and of the impregnation procedure were studied using particulate catalysts. 

In depositing silica on colloidal silica nuclei to increase the size of the particles, Mindick and Vassos (267) set a maximum rate of addition of silica (molecular weight less than 90,000) to avoid forming new nuclei by a formula that gives 5.0 grams silica per 1000 m hr. In this case no sodium salt is present in the system, so that the maximum rate is only half of what could be used when salt was present. 

Coagulation of silver halide by hydrolyzed aluminum salts was shown by Matijevi6, Kratohvil, and Sticles (267) to be inhibited by fluoride ion which formed complex ions with aluminum. Similar reduction in coagulation effectiveness of other metal cations such as Fe and Th on colloidal silica may be anticipated. 

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