Synthetic emission spectra for

Figure 11. Comparison of SH A2X — X2 fluorescence and synthetic emission spectra for a CtHf-Or-Nt (2 2.5 10) flame with 0.5% H,S added to the unburnt gas. Fluorescence excited at 323.76 nm.

Figure 12. Separate emission spectra for in the two Ca sites in synthetic single crystal fluorapatite. Generated by taking advantage of the separate excitation bands for the sites shown in Figure 11. Compare with Figure 8. Modified after Ryan et al. (1970).

The emission of the metal particles may thus originate from a band-to-band transition in the metal particle, which occurs at about 516 nm for gold [60, 119]. As stated above, the nature of the interaction of the dendrimer (PAMAM) host is still uncertain, there could be very strong electrostatic interactions that may play a part in the enhancement of the metal particles quantum efficiency for emission. However, one would expect that this enhancement would result in slightly distorted emission spectra, different from what was observed for the gold dendrimer nanocomposite. Further work is necessary to completely characterize the manner in which the dendrimer encapsulation enhances the emission of the metal nanoparticles. With further synthetic work in preparation of different size nanoparticles (in other words elongated and nonspherical shape particles, including nanorods) it may be possible to develop the accurate description of a... 

Fig. 9. Fluorescence emission spectra of mixtures of nuclease-T-(49,50-149) with nuclease-T-(6-48) or synthetic peptides upon excitation at 295 nm. Samples containing 2 X 10 s M nuclease-T-(49,50-149) and 4 X 10 M nuclease-T-(6-48) or synthetic peptide were in 0.05 M tris, pH 8, with 0.01 M CaCh and 0.0001 M pdTp. The spectrum for nuclease-T-(49,50-149) alone was corrected for the small measured emission exhibited by the buffer solution containing pdTp and Ca2+. The spectra for mixtures of synthetic peptide or nuclease-T-(6-48) with nuclease-T-(49,50-149) were corrected for the measured emission exhibited by the appropriate synthetic peptide tor nuclease-T-(6-48) 1 alone in buffer containing pdTp and Ca t. (0) Nuclcase-T-(6-48), (O) synthetic (6-47), (A) synthetic (9-47), (A) synthetic (18—47), ( ) synthetic (33-47), and ( ) nuclease-T-(49, 50-149) alone. Taken from Ontjes and Anfinsen (87).

The C-Pa-Pb-Q tetrad 46 has recently been reported [102]. This molecule was prepared using the synthetic methodology developed for the C-P-Q triads. The two porphyrin moieties have essentially identical visible spectra, and there is little interaction between the chromophores in absorption. The emission spectra are also essentially identical for the two porphyrins, and their first excited singlet... 

Figure 4. Spectra for a variety of synthetic flux grown and melt pulled forsterites. For both, the positions of the Cr and Mn emissions match closely those of meteoritic forsterites.

Based on the specific affinities to divalent cations, which are often observed for naturally occurring or synthetic macrolides [69], anthraceno maclolides 32 [70] (Structure 18) have been designed for the optical detection of alkaline earth metal cations. Macrolides 32 also display dual fluorescence, whose behavior depend on the number of n and temperature. Moderate addition effects of Sr(C104)2 or Ba(C104)2 on the changes in UV absorption or fluorescence emission spectra were recognized. 

For fluorescence measurements, by far the most versatile and widely used time-resolved emission technique involves time-correlated single-photon counting [8] in conjunction with mode-locked lasers, a typical mo m apparatus being shown in Figure 15.8. The instrument response time of such an apparatus with microchannel plate detectors is of the order of 70 ps, giving an ultimate capability of measurement of decay times in the region of 7 ps. However, it is the phenomenal sensitivity and accuracy which are the main attractive features of the technique, which is widely used for time-resolved fluorescence decay, time-resolved emission spectra, and time-resolved anisotropy measurements. Below ate described three applkations of such time-resolved measurements on synthetic polymers, derived from recent work by the author s group. 

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