Process chemiluminescence

In this work the development of mathematical model is done assuming simplifications of physico-chemical model of peroxide oxidation of the model system with the chemiluminesce intensity as the analytical signal. The mathematical model allows to describe basic stages of chemiluminescence process in vitro, namely spontaneous luminescence, slow and fast flashes due to initiating by chemical substances e.g. Fe +ions, chemiluminescent reaction at different stages of chain reactions evolution. 

A useful division of the contributing mechanistic features of any chemiluminescence process involving excitation of a "spectator" fluorophore is given in Equation 2. To optimize the chemical efficiency > we have also undertaken a systematic investigation of... 

Figure 9 demonstrates the fact that the chemiluminescence process occurs predominantly in the amorphous phase of the polymer. Low molar mass dicaproyl hexamethylene diamide is a fully crystalline compound the chemiluminescence signal under isothermal conditions below the melting point (136°C) at 130°C is very low, but it becomes rather strong after the crystallites of... 

The structure of the fluorescent molecule can also contribute substantially to the overall efficiency of a chemiluminescent process. Excitation and fluorescence can be strongly influenced by the structure of the fluorescer. 

The contemporary trends of dioxetane chemistry include a number of fundamental and applied aspects. The fundamental aspects encompass the stereoselective synthesis and the transformations of novel chiral dioxetanes, as well as the mechanistic studies on the thermal, electron-transfer-induced and catalytic dioxetane decomposition. The emphasis lies on the elucidation of the excited-state generation in these chemiluminescent processes. 

The cleavage of 1,2-dioxetanes constitntes the model chemiluminescent process, which may be initiated thermally, by electron transfer or in catalytic reactions (e.g. in complexes formed between dioxetanes and transition metals). In the subsequent subsections, we review the most recent significant developments in this area. 

Spectroscopic Probes of Cavitation Conditions. Determination of the temperatures reached in a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, MBSL provides a solution. High resolution MBSL spectra from silicone oil under Ar have been reported and analyzed (7). The observed emission comes from excited state C2 and has been modeled with synthetic spectra as a function of rotational and vibrational temperatures, as shown in Figure 7. From comparison of synthetic to observed spectra, the effective cavitation temperature is 5050 =L 150 K. The excellence of the match between the observed MBSL and the synthetic spectra provides definitive proof that the sonoluminescence event is a thermal, chemiluminescence process. The agreement between this spectroscopic determination of the cavitation temperature and that made by comparative rate thermometry of sonochemical reactions is surprisingly dose (6). 

Of most relevance to the present work, however, is the interest in chemiluminescent reactions generated by their relation to fundamental molecular transformations and dynamics. Study of these reactions promises to yield important information concerning these molecular processes. To this end, attention has focused on the extraordinary step of the chemiluminescence process, the chemiexcitation step, the key nonadiabatic process in which a ground-state reactant is transformed into a product in an electronically excited state. It is within this step that much of the mystery and interest in chemiluminescence remains. 

The field of chemiluminescence has experienced tremendous growth and witnessed significant advances in the past decade. To a large extent, the recent progress toward the understanding of chemiluminescent processes can be attributed to achievements in three general areas. 

More recently, direct experimental verification of the existence of radical ions in the reaction of [261 with activators and of their intermediacy in the chemiluminescence process was obtained by applying nanosecond laser spectrophotometric techniques to the study of this reaction (Horn and Schuster, 1979). Excited singlet pyrene was generated by irradiation with a nitrogen laser. The fluorescence of pyrene was quenched by diphenoyl peroxide... 

Carbonyl compounds 12-15 most likely derive from the corresponding intermediate dioxetanes 20, which under the reaction conditions would be expected to decompose thermally and or by direct sensitized photolysis, usually through a chemiluminescent process due to the fluorescence emitted by the singlet electronically excited carbonyl compound [17-20] [Eq. (9)]. 

Chemiluminescent processes occur in most combustion reactions, giving flames many of their characteristic colors. However, hot solid carbon particles in flames emit (usually yellow) thermal radiation in an equilibrium radiative process which therefore is not chemiluminescence,... 

A variant of the crossed-beam geometry, simpler but efficient in some cases, is the beam-gas arrangement. It leads usually to much larger signal than in the crossed-beam configurations, at the expense of a less accurate definition of the reaction kinematics. It is used fairly often to study the total cross-sections of chemiluminescent processes, especially when the species which is to be put into the beam is refractory, as are the transition metals [39, 40]. Reactions of alkaline earth metal atoms have been studied by this technique [41]. 

For the experimental determination of the 0, it is necessary to quantify the light output of the direct chemiluminescent process. The experimental definition of the direct chemiluminescence quantum yield is given in Eq. 36, that is, the initial rate of photon production (/q ) per initial rate of dioxetane decomposition k )[D]o). Alternatively, the total or integrated light intensity per total dioxetane decomposed can be used. The /t )[Z)]o term is readily assessed by following the kinetics of the chemiluminescence decay, which is usually first order. Thus, from a semilogarithmic plot of the emission intensity vs. time, the dioxetane decomposition rate constant kjj is obtained and the initial dioxetane concentration [Z)]o is known,especially if the dioxetanes have been isolated and purified. In those cases in which the dioxetanes are too labile for isolation and purification, [/)]o is determined by quantitative spectroscopic measurements or iodometric titration. 

Figure 7.56. Schematic state correlation diagram a) for a singlet photoreaction and b) for a singlet chemiluminescent process.

Studies of low-pressure flames offer several advantages. In particular, the flame can be maintained flat, and the light from different parts of the reaction zone studied separately the reaction volume from which light is collected is determined with much greater accuracy for such flames. At low pressures, chemiluminescent processes are more important than thermal excitation, collisional quenching of excited species is reduced, and self-absorption is diminished. A typical investigation of the low pressure flame is that of Gaydon and Wolfhard quantitative measurements of the C2 emission were made. 

Hydrogen atoms may be estimated in a similar way by using the titration reaction (36). Nitric oxide formed in this reaction can participate in the chemiluminescent process ... 

The excellence of the match between the observed MBSL and the synthetic spectra provides definitive proof that the sonoluminescence event is a thermal, chemiluminescence process. The agreement among these spectroscopic determinations5,6 of the cavitation temperature and to that made by comparative rate thermometry of sonochemical reactions4 is extremely good. 

Figure 24-4 Emission or chemiluminescence processes. In (a), the sample is excited by the application of thermal, electrical, or chemical energy. These processes do not involve radiant energy and are hence called nonradia-tive processes. In the energy-level diagram (b), the dashed lines with upward-pointing arrows symbolize these nonradiative excitation processes, while the solid lines with downward pointing arrows indicate that the analyte loses its energy by emission of a photon. In (c), the resulting spectrum is shown as a measurement of the radiant power emitted Pg as a function of wavelength, A.

Chemiluminescence processes in thermal and photochemically oxidised poly (ethylene - co - 1,4- cyclohexanedimethylene terephthalate). N. S. Norman, S. Allen, G. Guillaume Rivalle, M. Mchele Edge, T. Teresa Corrales, F. Fernando Catalina/ZPoZjroer degradation and stability (2002), 75, 2, 237 - 246. 

Among different coumarin derivatives used, 7-Amino-4-trifluoromethylcoumarin (ATFMC) revealed the most promising characteristics as an efficient fluorescent emitter. AFTMC is used in the synthesis of a substrate for fluorimetric assay of proteolytic enzymes and for use as a laser dye. We have recently investigated the chemiluminescence reactions of some peroxyoxalate esters, hydrogen peroxide and AFTMC. In this paper we report the solvent effects on the kinetics of the chemiluminescence process of the peroxyoxalate chemiluminescence in the presence of AFTMC. 

The processes described by Eq. (16) are called chemiluminescence processes. A special case of chemiluminescence is that in which one or both of the redox reactants of Eq. (16a) are produced by electrochemical methods (electrochemiluminescence, eel) [116]. 

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