Blue-green emission

Not only the absorption behaviour, but also all the physical properties of derivatives (32) are related to the nature of the 2,5-substitution pattern. For example, a blue-green emission is observed for di(2-pyridyl)phosphole (32b) whereas the emission of di(2-thienyl)phosphole (32a) is red-shifted (AAj,nj= 35 nm) [36]. Likewise, cyclic voltammetry (CV) revealed that derivative (32a), featuring electron-rich thienyl substituents, is more easily oxidised than compound (32b), which possesses electron-deficient pyridyl substituents [36]. 

MgW04 W 3MgC03.Mg(0H)2-3H20, W03 Blue-green emission used in white blends for fluorescent lamps... 

Introduction of electron-accepting hi thieno[3,2-6 2, 3 -e]pyri dine units resulted in copolymer 308 with ca. 0.5 V lower reduction potential compared to the parent homopolymer PFO 195 [398]. Upon excitation at 420 nm (A ax =415 nm), copolymer 308 exhibited blue-green emission with two peaks at 481 and 536 nm. Preliminary EL studies of an ITO/PEDOT/308/A1 device showed two peaks positioned as in the PL spectra. The PLED exhibited low turn-on voltage ( 4 V) but at higher voltages of 6-9 V, a slight increase in the green component was observed (Chart 2.83). 

Rousseau and Leroi studied the two-photon-induced chemical reaction in AgCl by 30 kW ruby-laser pulses which results in a decomposition of AgCl into collodial silver and chlorine. The resultant blue-green emission was proportional to the square of the laser intensity and the measured quantum yield was 10". ... 

The spectral-kinetic parameters of the narrow band at 375 nm enable its confident identification as Eu + luminescence, which is confirmed by emission of synthetic BaS04 artificially activated by Eu (Fig. 5.15a). Such emission was also detected and interpreted by steady-state spectroscopy (Tarashchan 1978). It is interesting to note that very often such a band is absent in natural barite and appears only after heating in air at 600-700 °C (Fig. 4.31b). Such a transformation is reversible, at least partly. Under X-ray excitation the intensity of the UV band diminishes, and a new blue-green emission appears (Fig. 5.16). This shows some kind of transformation, which takes place in the barite lattice under these conditions. Several possibihties exist. It is possible that in barite the luminescence is quenched by the components with high-energy phonons. The water and organic matter may represent the latter. They are removed after... 

Fig. 12. Room-temperature blue-green emissions spectra of BIG Yb, Tm (1%) fluoride glass and energy level diagram of Tm + and Yb ions. Excitation is at 975 nm, into the Yb absorption band, for various pumping densities, (a) 0.06 (b) 0.5 (c) 2 (d) 6, in kW cm-- units (reproduced with permission from Adv. Mat. Res., 1-2 (1994) 101 [133]).

Treatment of the poly(dibenzoylphenylene)s 115 and 116 with boron sulfide gives polymers 117 and 118 with ethene bridges (Scheme 53) [160,161]. These also show blue-green emission (A.max = 478 nm and 484 nm respectively) with some long wavelength emission in the solid state which has been attributed to aggregates. Their EL efficiency is reported to be very low (<0.1%) [162]. 

Figure 4 shows the EL spectra of the copolymers 1-3, which closely resemble the PL spectra shown in Figure 3 green emission occurs from 1 and 2, whereas blue-green emission occurs from 3e. (An EL spectrum of 4 could not be obtained due to insufficient light emission). The similarity between the PL and EL spectra for 1 confirms that EET via Forster dipole-dipole interaction occurs under conditions leading to EL as well PL. 

Penilla EH, Kodera Y, Garay JE (2013) Blue-green emission in terbium-doped alumina (Tb AI2O3) transparent ceramics. Adv Funct Mater 23 6036-6043... 

Both, Hirosaki et al. [292, 295] and Zhou et al. [296] reported a green oxynitride phosphor based on Eu -doped P-sialon. Other suitable host lattices for phosphors include MSi202N2 compounds (M = Ca, Sr, and Ba) for example, SrSi202N2 Eu " emits a green color, BaSi202N2 Eu + yields blue-green emission, while CaSi202N2 ... 

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