Blue emission

Electron-Deficient Polymers - Luminescent Transport Layers 16 Other Electron-Deficient PPV Derivatives 19 Electron-Deficient Aromatic Systems 19 Full Color Displays - The Search for Blue Emitters 21 Isolated Chromophores - Towards Blue Emission 21 Comb Polymers with Chromophores on the Side-Chain 22 Chiral PPV - Polarized Emission 23 Poly(thienylene vinylene)s —... 

The absorption spectrum of the photoprotein showed a small peak (Xmax 423 nm, with a shoulder at about 450 nm) in addition to the protein peak at 280nm (Fig. 10.1.2). The peak at 423nm decreased slightly upon the FI202-triggered luminescence reaction. The photoprotein is fluorescent in greenish-blue (emission A.max 482 nm), which coincides exactly with the luminescence spectrum of the photoprotein... 

Weakly fluorescent zones were visible under long-wavelength UV light (X = 365 i (Fig. 1). Cortisone (h/ f 0-5), dienestrol (h/ f 10-15), 4-androstene-3,17-dione (It 50-55) and 4-cholesten-3-one (h/ f 60-65) had an ochre fluorescence. Diethylsti estrol (h/ f 10-15), 17a-ethinyl-l,3,5-estratriene-3,17B-diol (h/ f 25-30) and estro (h/ f 35-40) had a blue emission. 

Blue luminescence of zinc complexes of pyridyl-containing complexes is an area of current interest.277 Design of blue luminescent materials is of relevance to display applications, as blue-light-emitting diodes, and to this end Che examined solution luminescence of zinc pyridylamine complexes.73,278 Che and co-workers studied the complex Zn40(7-azaindoyl)6 which has a blue emission at 433 nm in the solid state.279,280 In an attempt to improve on stability Wang et al. examined compounds with neutral 7-azaindole and an A-functionalized pyridyl derivative.281 In contrast with other metal complexes of the neutral 7-azaindole (32), Zn(7-azaindole)2(OAc)2 is a blue luminescent compound and a A-(2-pyridyl) 2-azaindole (33) and its complexes were also... 

CaW04 Pb2+ CaS04-2H20, W03, Pb(N03)2 Blue emission used in blends for fluorescent lamps... 

Whitaker, J.E., fdaugland, R.P., Moore, P.L., Hewitt, P.C., Reese, M., and Haugland, R.P. (1991) Cascade blue derivatives Water soluble, reactive, blue emission dyes evaluated as fluorescent labels and tracers. 

SN)X can act as an efficient barrier electrode in ZnS junctions, increasing the quantum efficiency of the blue emission by a factor of 100 over gold.14 It can also be used to increase the efficiency of GaAs solar cells by up to 35%. Metal ions interact more strongly with a poly(sulfur nitride) surface than with other metal electrodes. This property has stimulated investigations of possible applications of (SN)X as an electrode material. 

Figure 5.1 depicts filamentation that has been imaged during the propagation of ultrashort pulses through a crystal of BaF2. The spectrum associated with the filaments that are seen shows a predominantly blue emission [39] that is centered on 330 nm, one of the two luminescence bands (the other one... 

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. 

Blends of yellowish-green-light emissive carbazole-containing PPV-based copolymer 105 (Apl = 490, 520 nm, AEL = 533 nm) with blue-emissive oxadiazole- poly-/ -phenylene (PPP) copolymer 106 (AEL = 426 nm) allowed to tune the emission of PLEDs (ITO/polymer blend/Al) from AEL = 533 nm to AEL = 451 nm, although the device turn-on voltage was essentially higher for the blends with increased content of 106 [149] (Chart 2.22). 

Burn and coworkers [173] synthesized copolymer 143, containing a similar electron deficient moiety (triazole) incorporated in the PPV backbone. They have reported an efficient blue emission from this polymer (APL = 466 nm (solution), 486 nm (film), PL = 33% (film)) although the efficiency of the PLED fabricated as ITO/PPV/143/A1 was not very high (CT>j ) reached 0.08% at a luminance of 250 cd/m2). 

The Problem of Pure Blue Emission in Polyfluorenes Excimer and Aggregate Formation or Fluorenone Defects ... 

The polarized emission experiments on partially photooxidized aligned PF films indicate that the emission from the keto defects exhibits a somewhat smaller polarization ratio than the blue emission from the defect-free chains [263]. This observation was explained with the support of quantum mechanical calculations, which showed that the polarization of the fluorenone emission is influenced by local disorder [263]. 

Many studies on side-chain modifications in PF were initially based on the idea of excimer formation, resulting in the green emission during LED operation or in solid-state PL on annealing PF films. This resulted in several proposed strategies for the design of fluorene side-chain homopolymers, where bulky substituents at position 9 of the fluorene moiety should sterically prevent (hinder) interchain interaction and thus improve the stability of blue emission. 

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