Sol-Gel Composites

Korotcenkov, Handbook of Gas Sensor Materials, Integrated Analytical Systems, 

Ru(dpp) trimethyl-silylpropane-sulfonate (=TMS) Silicone E4, silicone E41 Chloroform 

Ormosil phenyl-trimethoxysUane-co-tetramethoxysilane, TMOS tetramethoxysilane, TriMOS phenyl-trimethoxysilane, TMMS trimethylmethoxysilane 

For example, it was found that organically modified sol-gel precursors, such as phenyl-trimethoxysilane (Ph-SiOMej) and its copolymers with other triaUcoxysilanes, display distinctly improved properties in terms of long-term stability, gas permeability, and ease of deposition on waveguide optics. Several sol-gel-based cocktails used for making oxygen sensors are presented in Table 15.1. 

---

A strain of yeast and a strain of bacterium were co-immobilized to fabricate a biochemical oxygen demand (BOD) sensor based on sol-gel derived composite materials97. This novel type of biosensor was developed for water monitoring and was used to determine the BOD values of OECD synthetic wastewater, domestic wastewater, and lake waters. The microorganisms Trichosporon cutaneum and Bacillus subtilis were coimmobilized in the sol-gel composite material, which was composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)). 

Y. Guo, A.R. Guadalupe, O. Resto, L.F. Fonseca, and S.Z. Weisz, Chemically derived Prussian blue sol-gel composite thin films. Chem. Mater. 11,135-140 (1999). 

V.G. Gavalas, S.A. Law, J.C. Ball, R. Andrews, and L.G. Bachasa, Carbon nanotube aqueous sol-gel composites enzyme-friendly platforms for the development of stable biosensors. Anal. Biochem. 329, 247-252 (2004). 

B. Wang and S.J. Dong, Organic-phase enzyme electrode for phenolic determination based on a functionalized sol-gel composite. J. Electroanal. Chem. 487, 45-50 (2000). 

Initially, the sol gel compositions were optimized using Congo red dye as the dopant because of its optical properties. This facilitates monitoring of the release process by optical spectroscopy. Next, the gels were evaluated for their stabilization and release of subtilisin. These sol gel matrices bring about controlled release of the encapsulated enzyme molecules as a response to a change in the water content of the medium (Figure 2.20).15... 

Fig. 15. Electrochromatograms obtained in columns coated with sol-gel composites (A) TEOS and (B) C8-TEOS/TEOS. (Reprinted with permission from [80]. Copyright 1999 American Chemical Society). Separation conditions fused silica capillary, 12 pm i.d., 60 cm total length, 40 cm active length, mobile phase 60/40 methanol/1 mmol/1 phosphate buffer, voltage 30 kV, electrokinetic injection 5 s at 6 kV, UV detection at 214 nm. Peaks toluene (1), naphthalene (2), and biphenyl (3)...

Table 2. Physico-chemical and catalytic properties of M-P0M/Si02 sol-gel composites...

These reactions usually are slow at room temperature, and the adhesives must be cured with heat. Tertiary amines or amidines can be used to catalyze the reaction whereby the car-boxylate anion is the nucleophile and the ammonium or amidinium ion act as hydrogen-bond donors. Dusek et al. have shown that transesterification only occurs after essentially complete consumption of the carboxylic acid in compositions initially having equivalent amounts of acid and epoxy groups.40 41 The transesterification leads to an equilibrium sol-gel composition. 

Colloidal metal NCs can be directly introduced to the sol precursors to fashion metal NC-sol-gel composites. Silica glasses fabricated from TMOS with Au NCs as the dopant and ammonia as the catalyst contained NCs with diameters... 

The micropore structure of the sol-gel composite could be controlled by varying the pH value of the sol. As the pH value increases, the pore volume of the composite decreases. This is the result of zeolite aggregations caused by the highly alkaline sol. 

Gordeeva, L.G. Mrowiec-Bialon, J. Jarzebski, A.B. Lachowski, A.I. Malinowski, J. Aristov, Y.I. Selective water sorbents for multiple applications, 8. Sorption properties of CaCl2-Si02 sol-gel composites. React. Kinet. Catal. Lett. 1999, 66 (1), 113-120. 

Keywords. Coumarin dye Methanol Porphyrin J-aggregate Sol-gel Composite film Optical sensor... 

EVA, adhesives adhesion promoter for solv., water-based, solventless, and povwJ. coaling systems pigment treatment copolymerized with styrene in formation of sol-gel composites RegiiaUxy SARA 313 reportable Manuf./Distrib. AP Resources Aldrich Fluka GelesI Sigma Trade Names Dow Coming Z-6030 Silane PC4100 Silane SilquesI A-174... 

Enzymes were immobilized using various conducting materials such as sol-gel composites with integrated graphite particles [195] however, there are still problems regarding a low sensitivity and undefined electron transfer. Moreover, in the case of the entrapment of enzymes into conducting-polymer films, possible direct electron transfer [150, 151] is stiU under discussion [196-198]. 

ECL response of allopurinol in aqueous media over a wide pH range (pH 2-13) was studied by Chi et al. [97] They found that allopurinol itself does not have ECL activity but could generate the ECL of Ru(bpy)3 in alkaline media giving rise to a sensitive Fl-ECL response. Humic acid (HA) was used as modifier to prepare the organic-inorganic hybrid modified glassy carbon electrode based on HA-silica-PVA (poly(vinyl alcohol)) sol-gel composite. Electroactive species of Ru(bpy)3 interact with the HA-sUica-PVA films to form Ru(bpy)3 modified electrodes [98]. 

The work performed in Task lA first centered around developing robotic spray parameters for both the enamel and sol-gel compositions. Enamel and sol-gel coatings have been... 

---