Electrochemically generated chemiluminescence

It may be added that generator/collector cells can be implemented without convection. Double microbands [65] and interdigitated bands [294,447, 500] have been considered for this purpose, for titrations [458, 541] and for studies in electrochemically generated chemiluminescence (ECL) [539], See also the review by Amatore [46] with more references therein. 

Elect regenerated chemiluminescence (ECL) — (-> electrochemiluminescence or electrochemically generated chemiluminescence) The generation of light in an electrochemical cell by an energetic electron transfer reaction, often between radical ions in an aprotic solvent. In a typical experiment in a solution of rubrene (R) and N,N,N, N -tetramethyl-p-phenylenediamine (TMPD) in dimethylformamide initially radical anions of rubrene are formed by electroreduction... 

Phull, S.S. The development and Evaluation of an Electrochemically Generated Chemiluminescent Immunoassay System. Ph.D. Thesis, University of Warwick (1990) and references therein. 

The octahedral Ru complex [Ru(bipy)3] (bipy=2,2 -bipyridyl) exhibits efficient photoluminescence, electroluminescence, and also electrochemically-generated chemiluminescence (quantum yields up to 5-7%) through the reactions shown in Eqs. 2.18a and 2.18b, respectively (excited states are labelled ) [68-70]. These properties have led to a range of studies on polymers with appended polypyridyl and related complexes. 

Legg KD, Hercules DM (1969) Electrochemically generated chemiluminescence of lucigenin. J Am Chem Soc 91(8) 1902-1907... 

Much of the study of ECL reactions has centered on two areas electron transfer reactions between certain transition metal complexes, and radical ion-annihilation reactions between polyaromatic hydrocarbons. ECL also encompasses the electrochemical generation of conventional chemiluminescence (CL) reactions, such as the electrochemical oxidation of luminol. Cathodic luminescence from oxide-covered valve metal electrodes is also termed ECL in the literature, and has found applications in analytical chemistry. Hence this type of ECL will also be covered here. 

A slightly different application is where species produced electrochem-ically lead to photon emission in the visible spectrum, via the formation of organic radicals by homogeneous reaction from electrochemically generated precursors. The electrode controls the quantity of precursor, enabling quantitative parameters of the homogeneous reaction to be elucidated. This is known as electrogenerated chemiluminescence or electrochemiluminescence (ECL). 

Chemiluminescence, under the action of electrochemically generated solvated electrons, was also observed in a mixture of ammonia and tetrahydrofurane At a volume ratio of 2 1 the system behaves essentially as would pure ammonia and the tetrahydrofurane ensures good solubility of the organic compounds. In such a mixture, a- and P-naptholtosylates and also N-tosylcarbazol (R—Ts) react with the solvated electrons by emitting light R—Ts -I- e - R—Ts" -> R Ts- R -p ef -> R ... 

Wang, X. and Bobbitt, D. R., In situ cell for electrochemically generated Ru(bpy)33-t-based chemiluminescence detection in capillary electrophoresis. Anal. Chim. Acta, 383, 213,1999. 

Electrochemistry can be coupled with other physical methods such as fluorescence spectroscopy. An XO-based electrochemiluminescent biosensor for hypoxanthine has been reported. The enzyme was immobilized in a carbon paste electrode with bovine serum albumin cross-linked with glutar-aldehyde. The working principle of the biosensor is illustrated in Scheme 5.6. As already shown (eqn (5.3a)), H2O2 is produced by the catalytic reaction between hypoxanthine and XO immobilized on the electrode surface. In an alkaline or neutral solution, luminol is electrochemically oxidized to a compound that reacts spontaneously with H2O2 to generate chemiluminescent luminol and the ensuing luminescence was used to quantify the amount of hypoxanthine present. 

Hercules DM (1964) Chemiluminescence resulting fiom electrochemically generated species. Science (New York, NY) 145 (3634) 808-809. doi 10.1126/science.145.3634.808... 

Wang X, Bobbitt DR (2000) Electrochemically generated Ru(bpy)3 -based chemiluminescence detection in micellar electrokinetic chromatography. Talanta 53(2) 337-345... 

When a solution of Pt2(pop)4 is subjected to alternating current electrolysis with variable frequency, the 514-nm luminescence is observed at one electrode. This observation of chemiluminescence has been explained by the generation of triplet Pt2(pop)4 from the electron transfer reaction between electrochemically generated Pt2(pop)4 and Pt2(pop)4 [Eq. 4.16)]. ... 

R. Lei, L. Stratmann, D. Schafer, T. Erichsen, S. Nengebaner, N. Li, W. Schnhmann. Imaging biocatalytic activity of enzyme-polymer spots by means of combined scanning electrochemical microscopy/electro-generated chemiluminescence. Ana/ Chem. 81 5070 (2009). 

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