Polymer films sensors

With liquid crystal metal phthalocyanine compounds as mass sensors, the LSER approach has proven useful. Analyte uptake has been measured using QCM methods, and adsorption of volatile organic compounds (VOCs) into the liquid crystalline coating appears to follow similar trends as for organic polymer film sensors. It should be noted that the analytes examined (toluene, chloroform, carbon tetrachloride, benzene, hexane, and methanol) are volatile compounds that are very weak ligands toward metals [167], Thus, the composite sensor response for metal phthalocyanine sensors based on conductivity is a complex property that depends on analyte redox properties, basicity, and sensor crystallinity. 

Starting with a simple analyzer composed of an array of polymer film sensors, it is agreed among some researchers that, despite the inclusion of 10-20 different polymer films in the array, its maximum OCC, or n, is 5 to 6. Next, a microGC might be able to achieve a peak capacity of n = 50, if the time and energy constraints in this MGA Program were relaxed. 

The extent to which the orthogonal channel capacity (OCC) is available for each analysis, as the full capacity cannot always be harnessed, e.g., with an array of polymer film sensors where some polymers may not have any interaction with an analyte, or with some mass values of an analyte mixture not being represented in a mass spectrum. Appropriate OCC discounts may need to be derived. 

Semiconductive polymer film sensors Many organic monomers can be polymerized to yield a linear carbon-carbon bond backbone with alternating single and double bonds, e.g.,... 

Rauen, K.L., Smigh, D.A., Heineman, W.R., Johnson, J., Seguin, R., and Stoughton, R (1993). Humidity sensor based on conductivity measurements of a poly (dimethyl-diallylammonium chloride) polymer film. Sensors Actuators 17 61. 

M. K. Malmros, J. Gulbinski III, and W. B. Gibbs, A semi-conductive polymer film sensor for glucose. Biosensors 3 1 (1987/88). 

H. Dreuth and C. Heiden, Thermoplastic structuring of thin polymer films . Sensors and Acmators, 78, 198-204,1999. 

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Composition materials ineluding indieator reagent and bearer have been investigated as sensor materials. It has been found out that nature of beai er (sorbent or polymer film) is of the main signifieanee. Siliea gel, aluminium oxide, porous glass, polyurethane, polyvinylehloride ete have been investigated as beai ers. 

Yan H.M., Kraus G., Gauglitz G., Detection of Mixtures of Organic Pollutants in Water by Polymer Film Receptors in Fibre-Optical Sensors Based on the Reflectometric Interference Spectrometry, Anal ChimActa 1995 312 1-8. 

We have shown a new concept for selective chemical sensing based on composite core/shell polymer/silica colloidal crystal films. The vapor response selectivity is provided via the multivariate spectral analysis of the fundamental diffraction peak from the colloidal crystal film. Of course, as with any other analytical device, care should be taken not to irreversibly poison this sensor. For example, a prolonged exposure to high concentrations of nonpolar vapors will likely to irreversibly destroy the composite colloidal crystal film. Nevertheless, sensor materials based on the colloidal crystal films promise to have an improved long-term stability over the sensor materials based on organic colorimetric reagents incorporated into polymer films due to the elimination of photobleaching effects. In the experiments... 

Platinum and palladium porphyrins in silicon rubber resins are typical oxygen sensors and carriers, respectively. An analysis of the characteristics of these types of polymer films to sense oxygen is given in Ref. 34. For the sake of simplicity the luminescence decay of most phosphorescence sensors may be fitted to a double exponential function. The first component gives the excited state lifetime of the sensor phosphorescence while the second component, with a zero lifetime, yields the excitation backscatter seen by the detector. The excitation backscatter is usually about three orders of magnitude more intense in small optical fibers (100 than the sensor luminescence. The use of interference filters reduce the excitation substantially but does not eliminate it. The sine and cosine Fourier transforms of/(f) yield the following results ... 

I. Yaropolov, and A. P. Savitsky, Phosphorescent polymer films for optical oxygen sensors, Biosensors Bioelectronics 7, 199-206 (1991). 

This concept is in essence a chromatographic effect similar to that observed in gas chromatography (GC), with the conjugated polymer film acting as the stationary phase. It is possible that like in GC and other candidate technologies for explosive detection, these responses could be empirically standardized for expected analytes of interest and sensory devices caHbrated to deconvolute temporal quenching signals to determine which analytes are present. This would further enhance the selectivity of what is already a very selective sensor for TNT and related compounds. 

While the amount of electricity that can be conducted by polymer films and wires is limited, on a weight basis the conductivity is comparable with that of copper. These polymeric conductors are lighter, some are more flexible, and they can be laid down in wires that approach being one-atom thick. They are being used as cathodes and solid electrolytes in batteries, and potential uses include in fuel cells, smart windows, nonlinear optical materials, LEDs, conductive coatings, sensors, electronic displays, and in electromagnetic shielding. 

Any (bio)chemical reaction is accompanied by energy conversion, most often in the form of heat production, the amount of heat produced being proportional to that of substance converted. Therefore, heat is a highly nonspecific expression of a (bio)chemical reaction but can be used as indicative for a given substance when this is selectively converted (e.g. by effect of a catalyst, particularly an enzyme). This section discusses three types of sensors based on the use of as many types of devices for measurement of the heat involved in a biochemical reaction, namely fibre optics, polymer films and thermistors. 

R.E. DESSY, L. BURGESS, L. ARNEY and J. PETERSEN "Fiber-optic- and polymer film-based enthalpimeters for biosensor applications" in "Chemical Sensor and Microinstrumentation", ACS Symposium series 403, 1989. 

Vinokurov lA. A new kind of redox sensor based on conducting polymer-films. Sens Actual B... 

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