Use in sensor

Ferroelectrics Poly(vynidilene fluoride) undergoes electrostriction when subjected to high ac fields, thus can be made into actuators applied pressure produces a piezoelectric response useful in sensors. 

Figure 3. Emission spectra of continuous light sources used in sensors.

The introduction of 2-[4-(dimethylamino)phenylazo]benzoic acid into a silica sol allows the preparation of pH-sensitive doped coatings upon glass substrates. The behavior of this system was evaluated as the function of pH changes in liquid and gas media68. Optical absorption and sensitivity against pH were monitored by Vis spectroscopy. Chemical and mechanical stability tests carried out with coatings demonstrated that they were resistant enough to be use in sensor devices for pH measurements in laboratories. 

Taking all these prerequisites into account, the use of chemical and physical sensors within household appliances is considerably restricted, and only a few applications are already on the market. In the field of bioanalytics, sensors are already used for bioprocess-monitoring and biomedical applications. In this area highly specific recognition processes can be used in sensors that only require a short lifespan, due to operating conditions etc. [64]. 

In order to make a FPI chemical sensor, the FP cavity needs to be made accessible by the analyte molecules. One way to achieve this is to use a holey sleeve to host the cavity. Xiao et al.7 reported such a fiber FPI gas sensor formed by bonding two endface-polished fibers in a holey sleeve using epoxy. The holey sleeve allows gas to freely enter and leave the cavity. A resolution of 10 5 was estimated in monitoring the changes in the refractive index caused by varying the gas composition. However, the sensor assembly was complicated and required the use of epoxy. In addition, the various components used in sensor construction were made of different materials. As a result, the device had a strong dependence on temperature. 

Hematite is used to coat the red emiting phosphor, Y2O2EU, which is used in cathode ray tubes (Franz et al., 1993 Merckhi and Feldmann, 2000). Hematite is also used in sensors for the detection of hydrocarbon gases and carbon monoxide. The sensitivity of the sensor can be improved by sintering the oxide with 0.09 mol ° mol Al at 850 °C (Han et al., 2001 and references therein). 

Selective complexation of cations by crown ethers 17 [lb, lg] and calixarenes 18 [If] depending on the rings size was proposed to be used in sensors. 

The basic operating principle of enzyme use in sensors is simple an enzyme is immobilized inside a permeable layer, into which the substrate(s) diffuse and from which the product(s) can effuse. Any other species that participate in the reaction, such as buffers, must also diffuse in and out of the layer (see Fig. 2.9). Because of the combined mass transport and chemical reaction, this scheme is often referred to as the diffusion-reaction mechanism. 

Cobaltacarboranes also have been used in sensor technology. The sandwich complex [Co(B9C2Hu)2] can be used as a hpophilic coreceptor instead of tetraarylborate ion additives in ion selective electrodes, producing electrodes that are more selective for specific alkah metal ions. ... 

Preparation of Optical Fiber Prior to Its Use in Sensor Development De-cladding... 

A classification of the recognition elements used in sensors can be made on the basis of their physicochemical/biological/biomimetic origin and catalytic/non-cata-lytic nature (see Table 18.1). 

Very promising can be the use in sensors field of molecular imprinted membrane [41,42], where the memory of a specific substance is imprinted in a polymeric material. 

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