Interference layer

Fig. 4.51. SIMS (a) and IBSCA (b) depth profiles of an interference layer system used for automotive application...

Potential CVD applications are beam splitter and interference layer in optical devices and detector for ethyl alcohol. 

Figure 1.2 Electrochemical deposition of glucose oxidase (GOx) followed by electropolymerization of the polyphenol interference layer. Reprinted with permission from Ref. 40. Copyright 2002 American Chemical Society.

In biospecific electrodes the eliminating enzymes are directly integrated in the sensor in membrane-immobilized form and separated from the indicator enzyme layer by a semipermeable membrane. The first enzymatic anti-interference layer was developed to enable the electrochemical determination of catecholamines in brain tissue at a graphite... 

Fig. 95. Enzyme sequence electrode for maltose determination containing a hexokinase anti-interference layer for glucose.

Fig. 96. Function of a lactate monooxygenase membrane as anti-interference layer for lactate. The current is a measure of the permeation of lactate through the membrane.

Enzymatic anti-interference layers containing oxidases can also be used to eliminate oxygen or prevent its diffusion into the electrode-near space. This enables the polarographic determination of organic com-... 

Cover picture Metallographic section of the oxide scale and the subsurface zone of a two-phase TiAl alloy after oxidation in air at 1350 °C for 1 h (interference layer metallography)... 

Iron(iii) oxide, a-Fe203, is used as a beam splitter and interference layer in optical devices [10]. a-lron(iii) oxide can be prepared by CVD using iron pentacarbonyl, Fe(CO)5 (10), as a precursor [55, 56]. The decomposition of ferrocene, Cp2Fe, (11) at... 

Interference layers in the form of filled polymers have been used on warships. A simple system is polyester filled with Ti02. It, however, provides protection only within a very narrow frequency range. 

Although IRRAS is a well-established method for studying monolayers on transparent substrates, its sensitivity is almost an order of magnitude lower than on metals. At the same time, transparent IRRAS offers an important advantage that p- and j-polarized spectra of the film can be measured, which is extremely valuable for orientational studies (Section 3.11.5). One can combine the advantages of metalhc and transparent IRRAS by using a complex-substrate transparent layer on a metal (Fig. 2.16), rather than a single-substance substrate. The upper transparent layer, which imitates the surface chemistry of a bulk transparent substrate, is dubbed a buffer or interference layer. The technique that involves such a buffer layer-metal substrate is known as buried metal layer (BML)-IRRAS or interference underlayer IRRAS. 

The use of a buffer (interference) layer between a film and the metallic substrate (the BML-IRRAS technique) allows one to measure the 5-polarized spectra and to avoid the band distortions in the p-polarized spectra. At... 

In ceramic-metal composites, the application of nonmetallic interference layers to polished or etched sections can also be used for purposes of brightness matching. This involves reducing the reflectivity of the phases of the metal component while increasing the reflectivity of the ceramic material. 

Automated preparation of samples of ceramic composites is preferable to manual preparation, as it ensures the reproducibility of the results and the flatness of the sections. Sections of ceramic composites should first be examined in the unetched state, in which it is easier to recognize material separations, porosity, transitions between coatings and substrates, and coating thickness. As a rule, chemical etching is only effective for portions of the composite. It is advisable to increase the contrast by applying interference layers. 

Figure 40 shows a typical interference pattern after an alteration of the refractive index and the thickness of the interference layer. The shift AX, is caused by Ar/ and Ar2 whereas the chance in the modulation depth Ag is caused by A 2 only. 

In this paper the deposition of proteins, principally for a glucose biosensor, in two spatially well controlled ways, one photolilhog and the other electrochemical will be described, as vdll be the electrochemical deposition of a thin anti-interference layer. 

Two principle techniques for electrochemical enzyme deposition have been reported, entrapment in an electrochemically grown polymer and electrochemically aided absorption. A wide range of electrochemically grown polymers have been used. The polymer can function as both an entrapment matrix and as an anti-interference layer (7, 12-20), as a matrix for the immobilisation of the protein with an electron transfer mediator (21-23), and as an electron transfer matrix alone (24, 25), Electrochemically aided adsorption has received comparably less attention (26-30), However, in our experience (31) the latter technique results in larger responses and is more appropriate to microelectrodes. Here we will present results on the electrochemically aided adsorption of GOx and BSA, and also of urease. Furthermore to reduce the interferences at the GOx/ BSA electrode we will describe the deposition of an anti-interference layer of polypyrrole, which is grown on the electrode after the deposition of the proteins. 

The polypyrrole anti-interference layer was deposited after the deposition and... 

The above results demonstrate the use of electrochemical and photolithographic methods for the spatially controlled deposition of enzymatic and anti-interference layers in a controlled way upon the surface of miniature electrodes. Although the results concentrate upon ucose measurement, the example of urease indicates that the electrochemical method should be extendible to other enzymes and we are currently investigating this. We beUeve the measurements made using the electrodes with the thin anti-interference layer are particularly interesting and show that the modified electrodes can be used in complex matrixes such as complex yeast extract medium. 

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