Colored light emitters

When small amounts of alkaU metals, alkaline earth metals, or their salts are introduced into a gaseous flame, flame reactions occur relatively easily at low temperatures.liberated metal atoms are promoted to excited states and then return to their normal states. Radiation corresponding to the characteristic Une spectra of the individual metal atoms is emitted as a result of this energy transition. Colored radiation discernible by the human eye, ranging from red to blue, is dependent on the type of metal atoms, as shown in Table 12.4P-  

In general, color emitters used as components of pyrolants are metallic compounds rather than metal particles. Metal particles agglomerate to form liquid metal droplets and liberation of metal atoms in flames occurs only at the surface of the droplets. On the other hand, metallic compounds decompose at relahvely low temperatures compared with metal particles and liberate dispersed metal atoms. Table 12.5 shows typical salts used to obtain emissions of the requisite colors. 

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The fluorescence color converter technique [32] can, in principle, overcome much of this power loss by replacing the white light emitter with a blue-emitting organic stack, and the absorbing filters with green and red fluorescent dyes. Thus when a green pixel is desired, the OLED underneath is turned on and the blui... 

Because luciferyl adenylate emitted a red chemiluminescence in the presence of base, coinciding with the red fluorescence of 5,5-dimethyloxylucferin, the keto-form monoanion Cl in its excited state is considered to be the emitter of the red light. Thus, the emitter of the yellow-green light is probably the enol-form dianion C2 in its excited state, provided that the enolization takes place within the life-time of the excited state. Although the evidence had not been conclusive, especially on the chemical structures of the light emitters that emit two different colors, the mechanism shown in Fig. 1.12 was widely believed and cited until about 1990. 

According to Branchini et al. (2004), luciferase modulates the emission color by controlling the resonance-based charge delocalization of the anionic keto-form of oxyluciferin in the excited state. They proposed the structure C5 as the yellow-green light emitter, and the structure C6 as the red light emitter. 

Firefly bioluminescence, 3-19 characteristics, 12 color of luminescence, 12 effect of pH, 13 effect of temperature, 14 factors required, 3, 4 light emitter, 17-19 mechanism, 15-17 overall reaction, 5... 

In addition to green- and red-light emitters, white PLEDs have also received great attention due to their potential applications in backlight for full-color displays and lighting. 

As mentioned above, quantum dots can be used to produce light emitters of various colors. Although, this application, like many others in the nanoworld, seems attractive, it is technologically very demanding. Among other characteristics, the quantum dots must be stable and their surface must be passivated. To circumvent the inherent reactivity and instability (of all nanoparticles) they should be embedded (above. Fig. 

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