Electro-luminescence

Luminescence has been used in conjunction with flow cells to detect electro-generated intennediates downstream of the electrode. The teclmique lends itself especially to the investigation of photoelectrochemical processes, since it can yield mfonnation about excited states of reactive species and their lifetimes. It has become an attractive detection method for various organic and inorganic compounds, and highly sensitive assays for several clinically important analytes such as oxalate, NADH, amino acids and various aliphatic and cyclic amines have been developed. It has also found use in microelectrode fundamental studies in low-dielectric-constant organic solvents. 

One of the problems in the design of organic (electro)luminescent materials is the decrease of the QE of fluorescence in the solid state due to the formation of ir-aggregates. Earlier we... 

U.S. 6,361,884 Partially conjugated polymers with spiro centers and their use as electro-luminescent materials... 

Table 10.6 Assignments for the photo- and electro-induced luminescence spectra of PEN... 

An IR study of electro-oxidized PS showed a decrease in the OH signal and an increase in the SiO signal with anodization time. This can be interpreted as oxide formation on the PS surface and a removal of electrolyte from the pores. Furthermore a correlation in intensity of localized carrier IR absorption and luminescence indicates that localized states are involved in the red EL [Du4]. 

Luminescence is the emission of light at RT under the influence of various physical agents as mechanical(tribo-l), electrical (electro-1), radiant (photo-1), thermal (thermo-1), or chemical (chemo-1) means. The exciting source also may consist of moving charged particles, such as alpha-, beta-, or gamma-. Certain substances luminesce on crystallization, as,... 

Customarily, semiconductor surfaces are chemically or physically prepared to optimize their chemical and/or electro-optical properties. For chemical sensing applications, a freshly etched surface often provides greater chemical sensitivity. A Br2/MeOH etch of n-CdSe, for example, has typically yielded larger luminescence responses to analytes than have polished samples. Additionally, transducing films have been used to modify semiconductor surfaces to enhance the selectivity of CdSe for particular analytes [2]. 

The transducing mechanism of semiconductor luminescence involves the modification of the semiconductors surface electrical properties through molecular adsorption. Changes in solid-state electro-optical properties result from adsorption of the molecule of interest onto the semiconductor surface. 

The formation of boundary layers at the surface interface between semiconductor and gas influences also the luminescence and the electro-optical qualities of semiconductors. These effects offer interesting possibilities for studying experimentally the mechanism of chemisorption, the stationary state of chemisorption, and electron defects in the catalyst during catalysis. Experiments along this line have been carried out by some investigators (40,41) who have studied in a qualitative way the factors influencing the oxidation of phenols catalyzed by zinc oxide under the influence of light. Further work on this subject is desirable. 

The quinone-hydroquinone redox couple built into complexes 124 and 125 fulfils the requirements for the design of a bistable electro-photoswitch both the oxidized and reduced forms are isolable and stable the reduced form 125 is luminescent, whereas the oxidized form 124 is quenched the electrochemical interconversion of the two species is reversible [8.256]. 

Goulle, V., Harriman, A., Lehn, J. M., An electro-photoswitch - redox switching of the luminescence of a bipyridine metal-complex. J. Chem. Soc., Chem. Commun. 1993, 1034-1036. 

Device motivation for interface studies, and Optical absorption and emission in conjugated oligomers and polymers. The principles of device physics of metal insulator field-effect transistors (MISFETs) and light emitting diodes (LEDs) are oudined mainly as motivation for the contents of the chapters which follow, but also to point out certain features relevant to developing an understanding of the nature of the polymer-metal interface (chapters 5 and 6). The basic principles of electro-luminescence are reviewed here, at the level consistent with the aims of this work. 

This is the process studied experimentally in Refs. 191 and 192 through the luminescence coming from the triplet excited state D. The quantum yield of excitations 4>es can be extracted from the electro-chemiluminescence quantum yield 4>ecl if the emission quantum yield from the excited state < )e is known [191] ... 

Many alternative techniques, both qualitative and quantitative, have been investigated either for screening purposes or as primary methods. Such techniques include atomic absorption spectrophotometry, molecular luminescence, electron spin resonance spectrometry, X-ray analysis methods, and electro analytical methods. Flameless atomic absorption spectrophotometry (FAAS) is the technique that has almost completely replaced NAA. 

Both differential electro-absorption and photo-voltage measurements performed by Chichibu et al on GalnN/GaN SQW LEDs and an MQW LD structure [12] also consistently show the main absorption feature at energies well above the dominating luminescence peak. This was interpreted in terms of localisation of excitons at potential fluctuations due to a partial phase separation of GaN and InN. 

Nobel Prize Chemistry to Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa for their discovery and development of conductive polymers (i.e. electro-luminescent conjugated polymers)... 

Recently, attention have been paid to the properties nano-porous silicon. Canham observed the strong luminescence from porous siliconl. A number of photo-luminescent (PL) and/or electro-luminescent(EL) devices have been reported. Steiner et al. reported not only red/orange luminescence but also green/blue electro luminescence from the devicesI L The quantum confinement or the localized centers at the surface have been reported as the luminescence mechanism. They suggested that the luminescence mechanism depends of the fabrication process of the porous silicon s ll. 

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