Composite Sensors

In previous sections, carbon materials serve either as sensing materials or as transducers. Many studies also use carbon-polymer composites, where carbon materials serve as both support and transducer. The polymer-coated FET discussed above is one example. Arrays of carbon black/organic polymer composite have also been demonstrated in many studies as chemiresistive vapor detectors 

In summary, carbon materials have a unique structure and unique physical properties. The optimization of these materials for sensing applications depends on how to organize them into the proper configurations. The recent development of one-dimensional nanostmctnres snch as CNTs and CNFs opens up new opportunities that one can electrically wire biomolecules with electronic circuits at molecular levels. Further development in this field is expected to offer highly mnltiplex and miniatnrized sensor arrays with unprecedented sensitivities. 

VENU ARUNAJATESAN, BAOSHU CHEN, KONRAD MOBUS, DANIEL J. OSTGARD, THOMAS TACKE, and DORIT WOLF 

The use of catalysts in the chemical industry is one of the major contributors to the economy of a chemical process. Most of today s chemical production processes utilize a catalytic step. In most cases the catalyst plays the most important role, as it controls the activity and the selectivity of the process and as such has a direct impact on the economics. Especially supported catalysts are of high interest. The typically high-surface-area supports provide a good utilization of the catalytically active metal by means of high dispersion and stabilization of small metallic particles. This is especially true for precious metals, where sometimes up to 100% of the precious metal is accessible for the catalytic reaction. 

In the fine chemical and pharmaceutical industry a relatively large amount of carbon-supported catalysts are used. The advantage of carbon as a support is the stability under acidic and basic conditions, which does not apply for alumina or silica. Alumina and silica are dissolved under basic conditions alumina is also sensitive to acids [1,2]. Another important topic for the overall economy of a process is the recovery, refining, and recycling of the metal. This is especially easy for precious metals supported on carbon catalysts, because the support material can simply be burned to receive highly loaded precious metal containing ashes from where the precious metal can be recovered in high yields [3,4]. 

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This chapter deals with ISE construction, their characteristic properties such as selectivity coefficient, response time, temperature coefficient and drift, as well as electrode calibration and composite sensors containing ISEs. 

Nickel AML, Seker E, Ziemer BP, Ellis AB. Imprinted poly (acrylic acid) films on cadmium selenide. A composite sensor structure that couples selective amine binding with semiconductor substrate photoluminescence. Chem Mater 2001 13 1391-1397. 

Fig 12.4 shows a model for signal transduction in the two-component system of yeast. The SLNl protein of yeast is a composite sensor regulator system in which the... 

Polarization cell Measurement of kinetic data by polarization Electrochemical composition actors (electrolyzers, pumps, windows), electrochemical composition sensors (amperometric, conductometric)... 

Open-circuit cell Measurement of thermodynamic formation data Potentiometric composition sensors... 

There is an extended special literature3,10-16 on applications of solid state electrochemistry and even more on electrochemical devices. According to our objective, in this section applications will be emphasized in which migration and diffusion in the solid state are decisive processes (as discussed in Part I2). We intend to subsume such applications under the headlines composition sensors, composition actors, and energy storage or conversion devices. 

We will begin with a description of electrochemical sensors or more specifically composition sensors based on electrochemical principles (i.e., we refer to an electrochemical detection of composition). Another group of applications refers to devices in which the transference of mass and charge is used primarily to change composition or produce chemicals (electrochemical pumps and electrochemical reactors, or electrochemical filters) we will term such devices composition actors. At the end we will discuss energy conversion and storage devices (which we do not subsume under the term composition actors as here the energy aspect is to the fore). 

In this section we will describe what may be called electrochemical composition actors, in which chemical action—and not mechanical action as usually described by the term actor (or actuator)—is caused by electrical excitation. Unlike electrochemical composition sensors which detect chemical composition via electrochemical methods, they cause changes in chemical composition. It shall not remain unmentioned that at present interesting work is pursued also to realize mechanical action on an electrochemical stimulus ( artifical muscles ).48... 

To maintain the production rate, product quality, and plant safety requires a data acquisition and control system. This system consists of temperature, pressure, liquid level, flow rate, and composition sensors. Computers record data and may control the process. Modem chemical plants use program logic controllers (PLC) extensively. According to Valle-Riestra [20], instrumentation cost is about 15% of purchased equipment cost for little automatic control, 30% for full automatic control, and 40% for computer control. 

Pioggia, G., Francesco, F. Di., Ferro, M., Sorrentino, F., Salvo, P., and Ahluwalia, A. (2008). Characterization of a carbon nanotube polymer composite sensor for an impedimetric electronic tongue. Mikrochim. Acta 163, 57-62. 

Shevade, A.V. Homer, M.L. Taylor, C.J. Zhou, H. Manatt, K. Jewell, A. D. Kisor, A. Yen, S.P.S. Ryan, M.A., Correlating polymer-carbon composite sensor response with molecular descriptors, Journal of Electrochemistry 2006, 153, H209-H21. 

Kachoosangi RT, Musameh MM, Abu-Yousef I et al (2009) Carbon nanotube-ionic liquid composite sensors and biosensors. Anal Chem 81 435-442... 

Zhuiykov, S., Microstructure characterisation and oxygen sensing properties of AljOj—ZrOj—Y2O3 shaped eutectic composites. Sensors and Materials 12 (2000) 117-132. 

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. 

Composition sensors, 249, 252 Compressor control, 37 selective control, 403-4 Computer, digital, 552-57 Computer control, 30-33, 561-66, 634-55... 

Tat, M.E. J.H. Van Gerpen. Biodiesel blend detection using a fuel composition sensor. Appl. Engin. Agric. 2003,19. 125-131. 

An electronic nose consisting of 32 polymer carbon black composite sensors was used to identify two species of Staphylococcus aureus bacteria [methicillin-... 

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