Silica nanosphere material

A further example of a cooperative catalytic system is a bifunctionalized mesoporous silica nanosphere material (MSN) containing the ureidopropyl group (UDP) and 3-[2-(2-aminoethylamino)ethylamino]propyl group (AEP). All catalysts were synthesized by a sol-gel procedure similar to the previously mentioned one by using different AEP/UDP molar ratios. The MSN-AEP/ UDP catalyst was employed for the aldol, Henry and cyanosilylation reactions (Scheme 3.8 R = NO2, R" = H, Schemes 3.35 and 3.36, respectively) and TON values were compared with those observed by using MSN-AEP and MSN-UDP catalysts (Table 3.10). 

Recently, we reported on a new cooperative catalytic system comprised of a series of bifunctionalized mesoporous silica nanosphere materials with various relative... 

Radu, D. R. Lai, C.-Y Huang, J. Shu, X. Lin, V. S. Y, Fine-tuning the degree of organic functionalization of mesoporous silica nanosphere materials via an interfacially designed co-condensation method. Chemical Communications (10), 1264-1266, 2005. 

Following this approach, Kopelman and coworkers have prepared a pH sensor72 using as magnetic material barium ferrite nanocrystals (BaM) and as dye the dextran-linked carboxy SNARF-1, a commercially available fluorescein derivative with a convenient pKa of 7.5 and dual excitation and emission, which allows for ratiometric pH sensing. The two components were incorporated in silica nanospheres of 300 nm... 

Lin et al. have developed a new nucleophilic catalytic system for the MBH reaction that consists of dialkylaminopyridine-functionalized mesoporous silica nanospheres (DMAP-MSN). This material is an efficient heterogeneous catalyst for MBH reactions, exhibiting good reactivity, product selectivity and recyclability to give the corresponding adducts in moderate to excellent yields (Scheme 2.235). ... 

Gaharwar, A.K., Rivera, C., Wu, C.J., Chan, B.K., Schmidt, G., 2013. Photocrosslinked nanocomposite hydrogels from PEG and silica nanospheres structural, mechanical and cell adhesion characteristics. Materials Science and Engineering C Materials 33, 1800—1807. 

T. (2007) Hollow silica nanospheres in situ, semi-in situ, and two-step synthesis. Chemistry of Materials, 19(7), 1700-3. 

N., Tourne-Peteilh, C. et al. (2004) Characterization of a phospholipid bilayer entrapped into non-porous silica nanospheres. Journal of Materials Chemistry, 14,1316-20. 

The major differences between biological and biomimetic silica formation mainly lies in precursor concentrations (undersaturated in biosilicification), time required for biosilica deposition, involvement of other molecules (ions, organic molecules, and membranes), and the presence of a confined environment in diatoms. Nonetheless, proteins that direct biomineralization in nature can be used to control the production of nanostructured materials and fecilitate the febrica-tion of new structures in vitro under ambient conditions. Indeed, polycationic silaffins and silicateins isolated from diatoms and sponges, respectively, were shown to generate networlcs of silica nanospheres within seconds when added to a solution of silicic acid. 

Gao, T., Jelle, B.P., Sandberg, L.I.C., and Gustavsen, A. (2013) Monodisperse hollow silica nanospheres for nano insulation materials synthesis, characterization, and life cycle assessment. ACS Appl. Mater. Interface, 5, 761-767. 

Wang, J. X., Wen, L. X., Wang, Z. H. Chen, J. F. (2006). Immobilization of silver on hollow silica nanospheres and nanotubes and their antimicrobial effects. Materials Chemistry and Physics, 96, 90-97. 

Because the forces of attraction prevail when molecules are brought into sufficiently dose proximity under normal conditions, release is best effected if both the strength of the interaction and the degree of contact are minimized. Aliphatic hydrocarbons and fluorocarbons achieve the former effect, finely divided solids the latter. Materials such as microcrystalline wax [64742 42-3] and hydrophobic silica [7631-86-9] combine both effects. Some authors refer to this combined effect as the ball bearing mechanism. A perfluoroalkylated fullerene nanosphere would perhaps be the ultimate example of this combined effect (17). These very general mechanistic remarks can be supplemented by publications on the mechanism of specific classes of release agents such as metallic stearates (18), fatty acids and fluorinated compounds (19), and silicone-coated rdease papers (20,21). The mechanism of release of certain problem adherents, eg, polyurethanes, has also been addressed (22,23). 

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