Red-light emitters

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. 

It should be pointed out that the structure C5 (yellow-green emitter) is identical to the structure Cl that was previously assigned to the red light emitter. 

Light-Emitting Thiophene Homopolymers 2.4.2.1 Polythiophenes as Red-Light Emitters... 

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. 

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. 

The light emitter in Latia luminescence. The purple protein is strongly fluorescent in red. Thus, at first glance, it would appear to be a most probable candidate for the light emitter or its precursor. However, this possibility was ruled out when we found that there is no way to relate the fluorescence of the purple protein to the bioluminescence spectrum. Thus, the luciferase must contain a chromophore that produces the light emitter. 

A number of other up-conversion processes are known. The blue emission from a Yb3+/Tm3+ couple in which the active emitters are defect Tm3+ centers is mainly due to the efficient excitation ET process from Yb3+ centers. Two-frequency up-conversion has been investigated using Pr3+ defects in a fluoride glass matrix. Illumination with one pump wavelength results in GSA, while simultaneous irradiation with a second pump wavelength further excites the GSA centers via ESA. The doubly excited defects emit red light. Up-conversion and visible output only takes place at the intersection of the two beams. 

C. Yang, C. Tai, and I. Sun, Synthesis of a high-efficiency red phosphorescent emitter for organic light emitting diodes, J. Mater. Chem., 14 947-950 (2004). 

Kido, J., Hayase, H., Honggawa, K., et al (1994) Bright red light- emitting organic electroluminescent devices having a europium complex as an emitter. Applied Physics Letter, 65, 2124—2126. 

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