Maximum emission

For all compounds, ihe nature of the side-chain has-a strong effect ou the absorption and emission features. The change from alkyl to alkoxy is accompanied by a 0.25 to 0.35 eV red-shilt in the absorption and emission maxima. This result... 

Bioluminescence of firefly luciferin can produce a wide range of colors when catalyzed by different luciferases obtained from various species of fireflies, with their emission maxima ranging from 535 nm (yellow-green) to 638 nm (red). Apparently, each spectrum is emitted from a single emitting species they are not the composites of the yellow-green peak and the red peak (Seliger and McElroy, 1964). 

Energy transfer to fluorescent proteins. There are marked differences among the various bacterial species and strains in terms of the in vivo luminescence spectra. The emission maxima are spread mostly in a range from 472 to 505 nm (Seliger and Morton, 1968), but one of the strains, P. fischeri Y-l, shows a maximum at 545 nm (Ruby and Nealson, 1977), as shown in Fig. 2.3. However, the in vitro luminescence spectra measured with purified luciferases obtained from the various bacterial species and strains are all similar (Amax about 490 nm). The variation in the in vivo luminescence spectra may be due to the occurrence of an intermolecular energy transfer that increases the efficiency of light emission. 

PMs are orange-colored, with an absorption maximum at 488 nm (Fig. 9.6). The absorption characteristics and chemiluminescence activities of those compounds are shown in Table 9.4. All PMs are brightly fluorescent in yellow in organic solvents and also in aqueous solutions containing a surfactant (emission maxima 520-530 nm). The chemiluminescence spectra of PMs are significantly affected by the... 

Luminescence of Pyrosoma. All species of the genus Pyrosoma (about 10 species) are bioluminescent. Pyrosoma is one of the few organisms reported to luminesce in response to light (Bowlby et al., 1990). The luminescence emission spectrum of Pyrosoma atlantica is bimodal according to Kampa and Boden (1957), with the primary peak near 482 nm, and the secondary near 525 nm. Swift et al. (1977) reported the emission maxima of two Pyrosoma species at 485 and 493 nm, respectively, and Bowlby et al. (1990) found an emission peak at 475 nm with P. atlantica. A corrected bioluminescence spectrum of P. atlantica (A.max 485 nm) reported by Herring (1983) is shown in Fig. 10.5.2. 

Table IX. Fluorescence Efficiencies ( j,), Chemiluminescence Efficiencies ( . ), and Emission Maxima (A. ) for...

Figures 3a-f show the emission and excitation spectra for all six humic fractions. The excitation and emission maxima are listed in Table III along with the maxima of the phase-resolved emission spectra. In each case the emission spectrum was scanned with the excitation maximum wavelength held constant, and the excitation spectrum was scanned with the emission maximum wavelength held constant. Several interesting features are noted. The two humic samples ( Figures 3a,b) each have two excitation maxima and it appears that a double peak has been merged into the emission scan as evidenced by the shoulder on the high energy side of the emission peak. Similarly it seems evident that the exaggerated shoulders in the emission spectra of all the fractions point to the inclusion of two emission peaks in each spectrum. This evidence suggests the presence of two chromophores in each humic fraction.

Table III. Humic Fractions Fluorescence Excitation and Emission Maxima and...

Humic Fraction Excitation Maxima (in nm) Emission Maxima (in nm) Emission Maxima Phase Resolved (in nm)... 

The fluorescent signal will change with variation in quantum yield of fluorescence and with molar absorptivity. Not only do fluorescence quantum yields vary with the different dansyl derivatives formed, but so do the molar absorptivities (12). Another problem is exemplified by the 30-nm difference in the emission maxima of the dansyl derivatives of phenol and 2,4,5-trichlorophenol (13). 

Amplification of the natural fluorescence of some pesticides and bathochromic shift of the excitation and emission maxima detection limits 5-100 ng. 

Remarkably, the polymer 38 showed fluorescent properties with an emission maxima at 545 nm and an efficiency of approximately 8% of that for -stilbene [109]. This is the first time fluorescence has been reported for a PPP. 

The complex shown in Figure 3.9 [104] is luminescent in the solid state at 77 K with three emission maxima at 431,448 and 460 nm. The excitation maxima are at 305 and 370 nm. The origin of the luminescence has been attributed to intraligand transitions with contributions of charge transfer character. 

Luminescent Ir complexes of diphosphine and diphosphinite calix[4]arene show emission maxima at 619 nm and 597 nm, respectively, at 77 K. The emission lifetimes are perturbed by addition of Li+, Na+, and U022+. 

Positions of Excitation and Emission Maxima of PL in Anodic Oxide Films Formed in Various Electrolytes by DC Anodization and in Boiling Water... 

Figure 6). The phosphorescence spectra of the copolymer yarns showed excitation in the 305 - 310 nm range with corresponding emission maxima at 480 and about 515 nm, corresponding lifetimes equal 1.2 seconds. In the copolymer yarns containing 0.5 - 2.0 mole percent 4,4 -BPDC a small shoulder was observed at 452 corresponding to the PET homopolymer phosphorescence. 

In the yarns, the fluorescence of the 4,4 -biphenyldicarboxy-late unit is distinct and predominate both at 298 and 77°K. Examination of the phosphorescence spectra of the PET and PET-co-4,41-BPDC yarns revealed three emission maxima. In the PET homopolymer excitation with 310 nm radiation produced an emission at 452 nm from the terephthalate chromophore. In the copolymers excitation with either 305 or 310 nm radiation produced emission spectra with distinct maxima at 480 and 515 nm (t 1.2 sec), and a shoulder near 452 nm (t = 1.2 sec). The maxima in the phosphorescence spectra were assigned as emission from the 4,4 -biphenyldicarboxylate units of the copolymer. The observed emissions are bathochromatically shifted from the emission of 4,4 -BPDC in a glassed solvent. This is supported by the observed emissions from solid 4,4 -BPDC at 520 and 560 nm (t =. 3 sec) when excited with 340 or 356 nm radiation. 

Studies of fluorescence properties of the dye pair (i.e., boron difluoride complexes dye 9a-d and the nonsubstituted one lOa-d) in the BSA/SDS mixture revealed that coumarins 9b and 10c showed two excitation and emission bands, while other heterocycles showed single bands in the corresponding spectra. For all studied compounds, excitation and emission maxima occurred in the range 405-603 nm and 467-680 nm, respectively. 

The resultant bioconjugates displayed absorption and emission maxima in the range 320-349 nm and 393-503 nm, respectively, with high Stokes shifts (73-158 nm), and [Pg.34]

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