Optochemical sensors

The major part of the volumes consists of a careful description of basic sensors in Chapters 7-13. They include liquid electrolyte sensors, solid electrolyte sensors, electronic conductivity and capacitance sensors, field effect sensors, calorimetric sensors, optochemical sensors, and mass sensitive sensors. 

In particular besides meeting the technical specifications of selectivity, sensitivity, suitable response and recovery time, long term stability in a quite frequently aggressive environment will be the most important feature In view of these requirements two types of chemical sensors, optochemical and mass-sensitive sensors (SAW s) and the concept of the evanescent field absorbance microprobe (ERAS) will be discussed by referring to ongoing microanalyzer system development at the KfK (Kernforschungszentrum Karlsruhe)... 

Optical fiber sensors that use enzymes can operate in the direct or indirect detection mode. In the first case, the optical properties of the reactives, intermediates or products of the biocatalyzed reaction can be monitored using the optical fibers. In the second type, an optochemical transducer generates the optical changes. 

Trinkel M., Trettnak W., Reininger F., Benes R., O Leary P., Wolfbeis O., Study of the performance of an optochemical sensor for ammonia, Anal. Chim. Acta 1996 320 235-243. 

Coated LPGs as Highly Sensitive Optochemical Sensors... 

Optochemical sensors have had a huge expansion during the last few years, and surely the main reason is the wide range of optical phenomena that one can take advantage of for the design of different sensing schemes. 

The fundamental operation of an optochemical sensor consists of three main steps the analyte-recognizing element interaction by means of any of the different mechanisms that are schematized in Fig. 1 [3] the detection and transduction of any physical or chemical variation caused by the recognizing reactions and the signal processing and the acquisition of results. 

Fig. 2 Schematic representation of optochemical sensors depending on the arrangement of the optically active reagents, a Sin-face optodes reagents are directly immobilized over a solid support by (1) covalent bonding, (2) adsorption or (3) electrostatic interactions or a waveguide or are trapped in a porous matrix (4). b Bulk optodes reagents are dissolved in a plasticizer (5)...

Fig. 4 Different optochemical configurations for flow-cell-based sensors. Notice that flow cells are expendable. S source, D detector, Of optical fiber, a Non-guided sensors the transmission of a non-guided collimated radiation beam is measured, b Radiation is guided though optical fibers from the source to the recognition element and from this position to the detector...

Standard single-mode fibers are often 10-p.m-thick and multimodal ones 50- and 62.5- im-thick. The latter are the easiest to apply in the optochem-ical sensor field, because they allow a proper light transmission at medium and short distances and can be employed with a great number of commercial optical components. 

IWAOs have been designed to address some of the weak points concerning absorbance optochemical sensors based on bulk optodes. In order to reach a practical application level, new research is needed to overcome some signifi-... 

These novel sensors are conceived to optimize four essential characteristics that define a high-quality optochemical sensor enhanced and sizable sensitivity (depending on the free propagation region length) an adequate selectivity towards a certain analyte (regulated by an ionophore) low response time and minimization of interference effects caused by the solution matrix. The scheme is presented in Fig. 17. 

The novel water-soluble dye 64 shows sufficient stability for potential application in molecular-based beacons for cancer detection using optical imaging <2005BCC735>. An optochemical ozone sensor with a quantitation limit of 0.03 ppm and accuracy exceeding 8% has been obtained by immobilization of the novel soluble indigo derivative 65 in permeable transparent polymeric films of polydimethylsiloxane-polycarbonate <2005MI1628>. 

Analogous solvent-dependent intramolecular Lewis acid/base equilibria between laetonie and zwitterionie forms have also been found for the xanthene dyes fiuoreseein and eosin [176]. Strueturally related eolourless 3,3-diarylphthalides form highly eoloured triarylearbenium ions by interaetion with acidic compounds such as phenols. This aeid/ base reaetion has been used to design optochemical sensors suitable for the deteetion of vapours of polar solvents in the air or in waste water [271]. 

J. Spadavecchia, G. Ciccarella, P. Siciliano, S. Capone, R. Rella, Spin-coated thin films of metal porphyrin-phthalocyanine blend for an optochemical sensor of alcohol vapors. Sen. Actuators, B, Chem 100, 88-93 (2004). 

Membrane-covered optochemical sensors (optodes) with O2 sensitive or pH sensitive fluorescence indicators (e.g. pyrene butyric acid or hydroxypyrene trisulfonic acid) have been coupled with different enzyme reactions, such as the conversion of glucose, lactate, ethanol, or xanthine, and with antigen-antibody couples (Opitz and Lubbers, 1987). 

Applications of Optochemical Sensors for Measuring Chemical Quantities. . 867 O. Wolfbeis, G. E. Boisde... 

Applications of Optochemical Sensors for Measuring Chemical Quantities... 

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