Silica sol-gel materials

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). 

Preparation and physisorption characterization of D-glucose-templated mesoporous silica sol-gel materials. Chemistry of Materials, 11, 2023-2029. 

Some non-silica sol-gel materials have also been developed to immobilize bioactive molecules for the construction of biosensors and to synthesize new catalysts for the functional devices. Liu et al. [33] proved that alumina sol-gel was a suitable matrix to improve the immobilization of tyrosinase for detection of trace phenols. Titania is another kind of non-silica material easily obtained from the sol-gel process [34, 35], Luckarift et al. [36] introduced a new method for enzyme immobilization in a bio-mimetic silica support. In this biosilicification process precipitation was catalyzed by the R5 peptide, the repeat unit of the silaffin, which was identified from the diatom Cylindrotheca fusiformis. During the enzyme immobilization in biosilicification the reaction mixture consisted of silicic acid (hydrolyzed tetramethyl orthosilicate) and R5 peptide and enzyme. In the process of precipitation the reaction enzyme was entrapped and nm-sized biosilica-immobilized spheres were formed. Carturan et al. [11] developed a biosil method for the encapsulation of plant and animal cells. 

D. Avnir, L. C. Klein, D. Levy, U. Schubert and A. B. Wojcik, Organo-silica sol-gel materials, in Organic Silicon Compounds, ed. Z. Rappoport and Y. Apeloig, John Wiley Sons, 1998, vol. 2. 

The incorporation of Ru(II) chelates in various types of silica sol-gel-based composite films is another mode of immobilization.262,280-284 Silica sol-gel materials provide some advantages over organic polymers such as the ease with which they can be prepared, modified, and doped with various reagents. Particularly, silica sol-gel films are stable upon continuous electrochemical oxidation or upon drying the gels in a high humidity environment. 

Y. Wei, J. Xu, H. Dong, J. Dong, K. Qiu, S. Jansen-Vamum, Preparation and Physisorption Characterization of D-Glucose-Templated Mesoporous Silica Sol-Gel Materials Chem. Mater. 1999,11, 2023-2029. 

Baccile, N. Babonneau, F. Thomas, B. Coradin, T., Introducing Ecodesign in Silica Sol-Gel Materials. J. Mater. Chem. 2009,19, 8537-8559. 

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