Cathodic luminescence

Although the ECL phenomenon is associated with many compounds, only four major chemical systems have so far been used for analytical purposes [9, 10], i.e., (1) the ECL of polyaromatic hydrocarbons in aqueous and nonaqueous media (2) methods based on the luminol reaction in an alkaline solution where the luminol can be electrochemically produced in the presence of the other ingredients of the CL reaction (3) methods based on the ECL reactions of rutheni-um(II) tra(2,2 -bipyridinc) complex, which is used as an ECL label for other non-ECL compounds such as tertiary amines or for the quantitation of persulfates and oxalate (this is the most interesting type of chemical system of the four) and (4) systems based on analytical properties of cathodic luminescence at an oxide-coated aluminum electrode. 

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. 

The mechanism of cathodic luminescence is distinctly different from other ECL systems. Light is emitted from oxide-covered, so-called valve metal, electrodes, namely aluminium and tantalum, during the reduction of peroxodisulfate, hydrogen peroxide, or oxygen, in aqueous solution, at relatively low potentials (<10 V). The mechanism involving persulfate, for example, is as follows. A conduc-... 

The purpose of this study is to determine the relative timing of Au mineralization in the context of the regional tectonic history. This was accomplished buy using cathode-luminescence to study gangue quartz in auriferous sulfide-quartz-carbonate veins. 

Nickel E (1978) The present status of cathode luminescence as a tool in sedimentology. MineralsSci Eng 10 73-... 

Thus, the formation of free radicals appears to be a prerequisite of the cathodic luminescence of aryl tosylates16 in HMPA ... 

CL Cathode Luminescence Insulators, semiconductors Electrons 5-50 keV Photons 0.1-5 eV 1 nm-2 pn 1 or 2 nm Energy levels of impurities and point defects 30... 

Analysis of the images occurred from the secondary electrons (SEI), backscattered electrons (BSE) and cathode luminescence (CL). 

To determine the band gap of the alloys, electron beam cathode luminescence measurements were made on pressed bars of the powder. The band gap value assigned to each semiconductor corresponded to the energy of the maximum in the cathodoluminescence spectrum. 

Unlike optical microscopes, SEM does not use light to examine a surface. Instead, SEM sends a beam of electrons over the surface to be studied. These electrons interact with the sample to produce various signals x-rays, back-scattered electrons, secondary electron emissions, and cathode luminescence. Each of these signals has slightly different characteristics when they are detected and photographed. SEM has very high depth of focus, which makes it a powerful tool for studying the contours of surfaces. 

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