Layered organosilanes

The first category is layered organosilanes. Layered alkylsilanes are synthesized from akyltrialkoxysilane [CH3(CH2) iSi(OR)3, R is often CH3 or C2H5] and tetraethyl orthosilicate (TEOS) [62-66]. Alkoxy groups are hydrolyzed and condensed into... 

Keywords R metal particles, sihca layer, organosilane, dehydrogenation of cyclohexane 1. Introduction... 

Chemically bonded layers are prepared by reacting silica gel with various functionalized organosilane reagents forming siloxane Ssonds with some of the silanol groups originally present on the silica surface (10,23,71-77). Chemically bonded siloxane layers... 

Figure 5.9 TEMPO DE is obtained by electrodeposition of a thin layer of orga-nosilica doped with TEMPO (2,2,6,6-tetramethylpiperidine-l-oxyl) upon application of — 1.1 V (v.v. Ag/AgCl) for 15 min to a solution of suitable organosilanes (left). The electrocatalytic film thereby obtained selectively converts benzyl alcohol dissolved in 0.2 M NaHC03 (right). 

Aluminum coating (for surface fluorescence quenching see Section 13.5.5) can be accomplished in a standard vacuum evaporator the amount of deposition can be made reproducible by completely evaporating a premeasured constant amount of aluminum. After deposition, the upper surface of the aluminum film spontaneously oxidizes in air very rapidly. This aluminum oxide layer appears to have some similar chemical properties to the silicon dioxide of a glass surface it can be derivatized by organosilanes in much the same manner. 

The self-assembly of an imprinted layer on the surface of a transducer was realized through the adsorption of the template on gold, Si02, or ln02 surfaces followed by treatment with an alkylthiol or organosilane (Hirsch et al. 2003). The first example of this type of sensor was reported in 1987 by Tabushi and coworkers (1987). Octadecylchlorosilane was chemisorbed in the presence of n-hexadecane onto tin dioxide or silicon dioxide for electrochemical detection of phylloquinone, menaqui-none, topopherol, cholesterol, and adamantane. Another MlP-based sensor was... 

Organosilanes are particularly effective as positive ultraviolet photoresists (Section 3.5.1). The oxide layer exposed where the resist has been removed may then be etched with an appropriate solution (buffered aqueous HF in the case of a silica layer) to expose the silicon underneath. Application of the desired metal over the whole surface is then followed by removal of the remaining photoresist, taking the unwanted parts of the metal layer with it and leaving the metal contact on the Si that had been exposed by etching. Variations on this approach can be used to attach shaped deposits of other electronically active materials. 

ESCA results of treated polysilicon substrates indicate that the polysilicon surface, like that of the blank single-crystal Si wafer, is covered with a thin layer of SiOz (<20A). For this substrate, surface layer changes are detected by observing the SiOx/Si ratio vs. that of the blank. VTS/HMDS and VTS/6208 treated surfaces have increased SiOx/Si ratios of 6.8-7.0, while the blank exhibits values of 2.5-2.6. Concomitantly, increases also occur in the carbon concentration. The increases in SiOx/Si ratio and carbon content after surface treatment are interpreted as due to the formation of an additional surface layer through the reaction of the organosilanes and surface —SiOH groups. If a thicker layer had resulted, no Si° would have been detected, because it would have been out of the ESCA detection depth therefore, the reactions are restricted primarily to the first few surface layers. 

The concept of using the functional groups of electrode surfaces themselves to attach reagents by means of covalent bonding offers synthetic diversity and has been developed for mono- and multi-layer modifications. The electrode surface can be activated by reagents such as organosilanes [5] which can be used to covalently bond electroactive species to the activated electrode surface. Recently, thermally induced free-radical polymerization reactions at the surfaces of silica gel have been demonstrated [21]. This procedure has been applied to Pt and carbon electrode surfaces. These thermally initiated polymer macromolecules have the surface Of the electrode as one of their terminal groups. Preliminary studies indicate that the... 

This type of material is commonly used in the production of semiconductor devices.57 The silica layer is used as a starting layer for integrated circuit (IC) build-up. IC layer materials range from single crystals and doped polycrystalline silicon, silicon nitride, thermally-grown oxide to vapour deposited or sputtered metal or metal silicide layers. Structural adhesion of the various layers is obtained by the application of organosilanes, such as AEAPTS, APTS and GPTS. 

This reaction is generally applicable for organosilanes. However, APTS solutions are more stable towards polymerization than non-aminated silanes. This effect and the consequences of the APTS solute structure on the eventual modified layer structure will be discussed in this paragraph. 

The higher order alkylchlorosilanes (C8 and C18) have historically been treated in the same way as organosilanes. The reaction inevitably occurs in the liquid phase and is usually followed by a curing step. The extremely low surface of the silicon wafers and the deposited Si02 layers, used for self-assembled-monolayers does not allow a spectroscopic quantification of the surface species. A completely different type of analysis techniques is used here mainly to determine the quality (roughness and uniformity), the adherence (parallel or at random) and the hydrofobicity of the coated layer. 

In analogy to the organosilicon method for the production of bulk carbides, the formation of ceramic coatings by pyrolysis of organosilane layers on silica gel is studied. As a ceramic precursor, the aminosilane APTS is used. 

FIGURE 10.1 Organosilane coupling agents react with water in aqueous solutions to form hydrolyzed silanes that react with the surface of inorganic fillers or the adherend. The bound silane polymerizes, building up layers outward, with the organic functionality oriented to the resin matrix.3... 

Corriu s group has reported another possibility to form layered materials by direct hydrolyis/polycondensation of functional monosilylated organosilanes. In the case of CN-(CH3) -Si(OEt)3 hydrolysis/polycondensation of the ethoxy groups simultaneously with the formation of the carboxylic functions from the cyano groups lead... 

Yan Y and Bein T. Molecular recognition on acoustic wave devices Zeolite thin films coated with organosilane gate layers. Micropor Mesopor Mater 1993 1 413-422. 

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