IR sensitivity

SEC has sometimes been used with off-line IR spectroscopy for the detection of polymer additives, such as dioctylphthalate, as well as on-line [39]. Dissolutions of PVC/DEHP and of PC/pentaerythritoltetrastearate (release agent) were analysed by SEC-FTIR using the thermospray/moving belt/DRIFT interface [40]. The detection limits of the method were in the 100 ng range, depending on the IR sensitivity and volatility of the solutes. This is not extremely sensitive. 

Infrared remote sensing, 23 141 Infrared (ir)-sensitizing polymethine dyes, 20 513... 

FT-IR has a number of advantages for studying chemical reactions involving polymers. Compared to other analytical techniques such as NMR, the FT-IR sensitivity is very high and has the ability to study a wide range of different sample types under a variety of environmental conditions. If the lifetimes of intermediate species are of the order of 3 sec, the complete spectrum can be obtained using FT-IR. In addition, the kinetics of the reactions can also be studied as will be indicated in a later section. 

Various multi-component LA compns or admixtures with LA to alter irs sensitivity... 

How can the actual contact surface be measured One possibility is to measure the electrical resistance between two conductors and calculate the contact area from the measured resistance and the specific resistivity of the materials. Another possibility is to use an IR sensitive microscope to measure hot spots of a transparent solid that is in contact with a hot surface. With these methods it was found that the friction force is, in fact, proportional to the actual contact area. This implies that the true contact area must increase linearly with load. To illustrate how this is possible, we consider two extreme cases. In the first case, purely elastic deformation is considered. In the second case, we assume plastic deformation of the microcontacts. 

The first array-based technique was designed specifically to study reactions on solid phase catalysts as IR thermography.9,19 This approach utilizes IR sensitive FPA detectors to measure the temperature of catalysts under reaction conditions. This approach has the advantages of a theoretical high thermal sensitivity, typically several tens of millikelvin, and the ability to study both endothermic and exothermic reactions. The main disadvantage of this approach, however, is the lack of chemical information. It must be assumed that the temperature change is associated entirely with the desired reaction pathway. The presence of unexpected side reactions will not be detected in this approach, as long as they have similar thermal behavior as the reaction under study. 

GC/IR has previously been utilized in flavor research to analyze aroma components in tropical fruits (5) and apples (6). While a linked GC/IR/MS system was proposed earlier (5), the principal limitation at that time resulted from the inherent lack of IR sensitivity in older light pipe systems. 

George Thomas, K. Thomas, K. J. Das, S. George, M. V. Liu, D. Kamat, P. V. Photochemistry of squaraine dyes. 10. Excited state properties and photosensitization behavior of an IR sensitive cationic squaraine dye, Faraday Trans. 1996, 92, 4913. 

The combination of two photochromic units as in molecules 30, 49, 50 (Scheme 23) can result in very interesting materials. Irradiation of the mixed biphotochromic system 30 leads to a colored form absorbing in the infrared. Thus IR-sensitive materials become available. A detailed description of this new material is given in Ref. 34, 65. The charge, distribution in the colored ring open form can be schematically represented as shown in Scheme 26. 

Applications or potential applications for these molecules have been demonstrated. Molecular switches can be built using supramolecular or LC photochromic materials.1 Photochromic polymers can be used in phototropic glasses or as a basis for information recording. IR-sensitive materials have been made using biphoto-chromic molecules. Light sensitive dental materials have been developed. 

A recent study of Cgo in pulse radiolysis reported a spectral feature at 650 nm, assigned to the radical cation [82], This study apparently did not use a near-IR sensitive detector, so that the strong 980 nm absorption was not observed, and it is possible that this 650 nm absorption is caused by products of radical addition to Ceo- Reaction of triplet Ceo with strong electron acceptors produces an exciplex and the free C o radical cation in benzonitrile [24]. 

As a result, self-scanned solid-state OIDs with and without MCP image intensifications have rapidly replaced OIDs based on vidicon (second generation) television pickup tube technology. Moreover, indications are that in the near future, the progress in silicon-based LSI devices will expand to more exotic materials such as InSb, InAs, HgCdTe, and PbSnTe. This expansion will allow for the development of IR-sensitive OIDs that could eventually replace mechanical multiplex detection systems based on mathematical transformations such as Fourier and Hadamard. 

The advent of fast response detectors with IR sensitivity and high bandwidth, high gain amplifiers has provided the capability of detecting the extremely weak luminescence at 1269 nm [32-37], This has allowed the accurate determination of lifetimes directly from the exponential decay of the IR emission, quenching rate constants by appropriate use of Eq. (15). 

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