PROBES AND SENSORS

The chromophore environment can affect the spectral position of the absorption and emission bands, the absorption and emission intensity (eM, r), and the fluorescence lifetime as well as the emission anisotropy, e.g., in the case of rigid matrices or hydrogen bonding. Changes in temperature typically result only in small spectral shifts, yet in considerable changes in the fluorescence quantum yield and lifetime. This sensitivity can be favorably exploited for the design of fluorescent sensors and probes [24, 51], though it can unfortunately also hamper quantification from simple measurements of fluorescence intensity [116], The latter can be, e.g., circumvented by ratiometric measurements [24, 115],... 

Lee JS, Kim YK, Vendrell M et al (2009) Diversity-oriented fluorescence library approach for the discovery of sensors and probes. Mol BioSyst 5 411—421... 

Current PAT approaches depend heavily on in-line/on-line/remote sensing sensors and probes instead of having to extract actual samples from the process . A fair summary of the most popular PAT sensor/probe designs and deployment strategies in a pipeline is illustrated in Figure 3.16 (and similarly for vertical flows). 

Figure 3.16 Illustration of incorrect sensor and probe head design (top), and deployment strategies (bottom). There are numerous variations on the same theme(s), e.g. in vertical flows, but all alternatives need not be shown as the design/deployment problems are identical none are correct - as none eliminates IDE. Indeed none have a field of view larger than a miniscule part of the cross section of the flow. Identical generation of IDE holds also for vertical flow, compare Eigure 3.14. Note that real-world conduit diameters are often significantly larger than shown here, which only exacerbates these IDE issues.

Medical (coatings, adhesives, sensors and probes, prosthetics and biomedical products, and optical fibers)... 

Much of the recent activity has focused on fluorescent sensors and probes and on therapy, particularly photodynamic therapy. 

Choice of sensors and probes. The choice of the sensors should take into account their stabihty as a function of time, so that the necessary calibrations and maintenance can be planned. Initial sensor calibration has to be documented. For remote or inaccessible locations only very robust and durable sensors should be installed. 

Among all the sensors and probes, pressure sensors can provide the most basie information not only on pressure itself but also on voidage, bed height, and flow regime or quality of fluidization. Pressure monitoring is essential in most eases to maintain an appropriate loop pressure pattern or a maeroseopie pressure... 

Optical sensors and probes have become indispensible analytical tools for the detection of a wide range of chemical and biological species in industry, biotechnology, medicine and the environment. The principle behind optical sensing is the change in one or more optical property (e.g. absorbance, luminescence, refractive index) of a smart molecule in the presence of the analyte. This change... 

Wardle B (2009) Principles and applications of photochemistry, Wiley. This book includes some excellent chapters on fluorescence sensors and probes, as well as a detailed description of more advanced fluorescence spectroscopy and imaging techniques. 

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