Triethoxysilane layers

American scientists prepared the organo-silica sol-gel membranes60 and demonstrated in a single layer format for pH measurement and multiple-layer format for both C02 and NH3. The sensors used a hydroxypyrenetrisulfonic acid (HPTS) as the indicator immobilizes in a base-catalyzed sol-gel containing poly(dimethyl)siloxane, aminopropyl-triethoxysilane (APTES) and tetraethylorthosilicate (TEOS). This indicator gel was over coated with a hydrophobic sol-gel to reduce cross reactivity to pH when either carbon dioxide or ammonia were examined. 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

Acetylcholineesterase The surface photovoltage technique was applied to the fabrication of a biosensor based on immobilized cholineesterase. The type of the cholineesterase used depends on the type of substrate. On the surface of the silicon wafer the cholineesterase layers were immobilized by using 3-aminopropyl triethoxysilane and glutaraldehyde. Characteristics of the sensor were studied in phosphate buffered saline containing 15 mM NaCl and 1 mM phosphate buffer (pH 7). 

The surface silanols can still catalyze the polymerization of triethoxysilane molecules even if there is one or more adsorbed layers of water on the surface. Presumably the triethoxysilane molecule H-bonds to the surface via water molecules after which it requires only an electron shift to make a silanol proton available to the alkoxysilane molecule. This sequence is illustrated by the following structures ... 

Besides the researches on the triethoxysilane hydrolysis on the silica surface which were discussed earlier [45,46], there are studies [56,69,74] concentrating upon the chemical reactions of HSi(OC2H5)3 with silanol groups. It was established by Petrova, Tertykh, and Pavlov [56] that this chemical reaction is accelerated not only in the presence of organic bases but also in the case of the introduction of hydrogen chloride into the reaction volume. The possible causes of the catalytic effect of electron- and proton-donors on the proceeding of chemical reactions in a silica surface layer has been discussed in more detail in our monograph [1]. 

Abel and co-workers [106] at Ciba-Geigy Ltd. have reported an automated optical biosensor system. Their device utilizes 5 -biotinylated-16-mer oligonucleotide probes bound to an optical fiber functionalised with avidin to detect complementary oligonucleotides pre-labeled with fluorescein moieties in a total internal reflection fluorescence (TIRF) evanescent wave motif similar to that of Squirrell. Immobilization of nucleic acid probes onto the optical fiber substrate was achieved by functionalisation of the surface with (3-aminopropyl)triethoxysilane (APTES) or mercaptomethyldimethylethoxysilane (MDS). Onto the short alkylsilane layer was... 

Materials. NADH (> 98%, Sigma Chemical Co.), HRP, (Funakoshi), bovine serum albumin (BSA, Wako Pure Chemical Industries), glutarddehyde (GA, 25%, Wako Pure Chemical Industries), (3-aminopropyl)triethoxysilane (GR gr e, Tokyo Chemical Industry), n-octadecyltrichlorosUane (GR grade, Tokyo Chemical Industry), and Tween 20 (Kanto Chemical Co.) were used as received. Ferrocenylmethanol (FMA) was synthesized by reduction of ferrocenecarboxyaldehyde (98%, Aldrich Chemical Co.). Completion of the reaction was confiimed with thin-layer chromatography. Diaphorase purified from Bacillus stearothermophilus (EC 1. 6. 99. -) was donated by Unitika. CEA, HCG, HPL, anti-CEA, anti-HCG, anti-HPL, HRP-labeled anti-CEA, HRP-labeled anti-HCG, and HRP-labeled anti-HPL were donated by Mochida Pharmaceutical Co. CEA is a glycoprotein and its molar mass is ca. 180,000 to 200,000 Da. Both HCG and HPL are polypeptide hormones, and their molar masses are 38,000 and 22,000 Da, resp tively. 

M. Okamoto, F. Yamada, and T. Omori, Preparation and evaluation of 3-Aminopropyl-triethoxysilane treated plates for high performance thin-layer chromatography, /. Hihg Resolut, Chromatogr, Croma-togr,Commun, 5 163-164 (1982). 

Lu et al. reported an MIP-coated SiO -based flow injection chemiluminescence sensor for dapsone. The SiO particles were initially modified through grafting amino groups by (3-aminopropyl)triethoxysilane to enhance the cohesion of the MIP layer to the particles. The MIP-coated particles were used for flow injection chemiluminescence analysis of the analyte in the linear range of 1.0 X 10 -1.0 X M with a detection limit of 5.27 X 10" M [375]. 

The requirement for anchoring of L-B films can be achieved by the use of phospholipids bearing photoactivatable head groups, v ich covalently bind to surfaces on illumination. For glass or silicon substrates the surface must be first coated with an organic layer using, for example, 3-aminopropyl triethoxysilane or similar material. 

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