Silica gels ORMOSILs

J.H. Harreld, T. Ebina, N. Tsubo, and G. Stocky, Manipulation of pore size distributions in silica and ormosil gels dried under ambient pressure conditions. J. Non-Cryst. Solids 298, 241—251 (2002). 

Figure 5.13 Yields in the Montanari-Anelli oxidation of 1-nonanol to give nonanal in the presence of silica-supported TEMPO (SG-TMP-O, front row), and in the presence of sol gel ORMOSIL doped with TEMPO [SG-TEMPO-1 is 25% and SG-TEMPO-2 is 100% methylated (middle and back row, respectively)]. (Reproduced from ref. 25, with permission.)...

Marino IG, Bersani D, Lottici PP. 2000. Photo induced birefringence in drl doped sol gel silica and ormosils thin films. Opt Mater 15 175 180. 

Green W.H., Le K.P., Grey J., Au T.T., Sailor M.J. White phosphors from a silicate-carboxylate sol-gel precursor that lack metal activator ions. Science 1997 276 1826-1828 Harreld J.H., Ebina T., Tsubo N., Stucky G. Manipulation of pore size disUibutions in silica and ormosil gels dried under ambient pressure conditions. J. Non-Cryst. Sohds 2002 298 241-251 Hazenkamp M.F., Blasse G. Rare-earth ions adsorbed onto porous ass luminescence as a characterizing tool. Chem. Mater. 1990 2 105-110... 

Manipulation of pore size distributions in silica and ormosil gels dried under ambient pressure conditions. 

Furthermore, the same sol-gel matrices have been used in a system where acid and base catalysis occur in the same pot without quenching either catalyst [29]. In this case, the acids were either entrapped Nafion (perfluorinated resin sulfonic super acid, a3) or entrapped molybdic acid (M03-Si02, a2), while the bases were two ORMOSILs (organically modified silica sol-gel materials), one with H2N (CH2)2NH(CH2)3 groups (bi) and the other guanidine base residues (b2) (Scheme 5.12). 

On the basis of the sol-gel process, much more attention has been paid to silicate-containing Class II hybrids, also referred to as organically modified silicas, ormosils. In this section, the synthesis of some of the most characteristic ormosils for bone and dental applications are described. 

In recent years, silica sol-gel-based inorganic-organic hybrid materials have also been reported. The introduction of various functional groups into organic alkoxide has led to organically modified sol-gel glasses (ormosils). Some of the ormosil monomers and ormosil formations can be found in Fig. 16.3. Redox molecules can be coupled with the ormosil monomer functional group. The immobilized redox molecules can... 

In other cases, organic modification of the sol gel cages markedly protects the entrapped molecular dopant from degradation by external reactants, as shown for instance by the entrapment of the radical 2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPO). This is a highly active catalyst which in the NaOCl oxidation of alcohols to carbonyls in a CH2CI2-H20 biphasic system becomes highly stabilized upon sol gel entrapment in an ORMOSIL matrix it progressively loses it activity when entrapped at the external surface of commercial silica.25... 

Ormosil-TEMPO is a sol-gel hydrophobized nanostructured silica matrix... 

Keywords Biosensors Dyes Fluorescence Glass Immunosensors Luminescence Nanocomposites Optodes Optosensors Ormosils PVC Silica Siloxanes Sol-gel... 

The confinement of a relatively large number of dye molecules in the small volume of a nanoparticle may trigger collective phenomena otherwise not observable in bulk solution. This has been demonstrated by Prasad and coworkers in the case of an ORMOSIL pH sensor.69 The PEBBLEs contain a naphthalenylvinylpyridine derivative (NVP) as pH-sensitive fluorescent dye which has been functionalized with a triethoxysilane anchor by reaction with an excess of (3-isocyanatopropyl)triethoxysi-lane (ICTES). The sol-gel polymerization in aqueous micellar solution of the NVP-ICTES derivative with VTES gives spherically shaped 33 nm silica nanoparticles in which the dye is covalently linked to the silica matrix and uniformly distributed in the nanoparticle volume. The NVP dye responds ratiometrically to protons, with a... 

The second example involves straightforward doping of methyl modified silica, denoted as ormosil, with tetrapropylammonium perruthenate via the sol-gel process [102] (Table 3). A serious disadvantage of this system are the low TOFs of 1.0 and 1.8 h 1 observed for a primary aliphatic alcohol and allylic alcohol, respectively. 

Recently two heterogeneous TPAP-catalysts were developed, which could be recycled successfully and displayed no leaching In the first example the tetra-alkylammonium perruthenate was tethered to the internal surface of mesopor-ous silica (MCM-41) and was shown [153] to catalyze the selective aerobic oxidation of primary and secondary allylic and benzylic alcohols. Surprisingly, both cyclohexanol and cyclohexenol were unreactive although these substrates can easily be accommodated in the pores of MCM-41. The second example involves straightforward doping of methyl modified silica, denoted as ormosil, with tetra-propylammonium perruthenate via the sol-gel process [154]. A serious disadvantage of this system is the low-turnover frequency (1.0 and 1.8 h-1) observed for primary aliphatic alcohol and allylic alcohol respectively. 

In this chapter, recent progress in several key areas is reviewed. These areas are catagorized by material classification rather than by end-use application (1) bulk silica optics (2) optically active doped silica glasses (3) gel-polymer composites (4) organically modified silicates (ormosils) and (5) gradient-index glasses. These represent the five most significant developments in the area of bulk optical materials by the sol-gel process to date. 

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