Emission spectrum toluene

A with a max at 3800A. The absorption overlap of the nitrocompds is plainly evident. The position and slope of each curve in Fig 1 can be qualitatively correlated with the absorption range and % transmittance at the peak for each compd. Nitro me thane, which absorbs more at shorter wave lengths and exhibits the least overlap of the toluene-PPO emission spectrum, accordingly has the least effect on the count Tate of the pure scintiliator... 

Trace B shows the emission spectrum obtained from a sample of crystals of AuVMeN = COMe)3 after pulsed irradiation, while Trace C shows the spectrum of the light emitted immediately after the addition of chloroform to a previously photo-irradiated sample of Au lMeN = COMe)3 crystals. The spectrum shown in Trace C is that from solvoluminescence. Notice that the emitted light corresponds to the lower energy emission seen for the solid and does not correspond to that seen in solutions of the trimer. Similar emission spectra have been obtained with a number of different solvents including dichloromethane, toluene, methanol, hexane, and even water. In all cases the spectra of the emissions show a maximum at 550 nm. Thus, there is no solvent effect on the emission. However, the intensity of the emission is greatest with those liquids (chloroform, dichloromethane) that are good solvents for the complex and rather feeble in those that are not (hexane, water). 

Figure 3-4. Emission spectrum of toluene and the emission and absorption spectra of PPO. (Courtesy of Beckman Instruments, Inc.)...

Intramolecular Excimer Fluorescence Studies in Polymers Carrying Aromatic Side Chains. Some years ago, it was shown that certain excited aromatic molecules may form a complex with a similar molecule in the ground state, which is characterized by a structureless emission band red-shifted relative to the emission spectrum of the monomer. The formation of such complexes, called "exclmers", requires the two chromophores to lie almost parallel to one another at a distance not exceeding about 3.5A° (11). Later, it was found that Intramolecular excimer formation is also possible. In a series of compounds of the type C5H (CH2)jiC H5, excimer fluorescence, with a maximum at 340nm, was observed only for n 3 -all the other compounds had emission spectra similar to toluene, with a maximum at about 280nm (12). Similar behavior was observed in polystyrene solutions, where the phenyl groups are also separated from one another by three carbon atoms (13). 

It should also be noted that the visible emission spectrum which is shown in Figure 4 was obtained from the 28 MHz. toluene discharge. This spectrum is similar to that which Schuler had previously observed from electrode toluene discharges and assigned to the benzyl radical. Its presence adds additional support to the view that this radical is a major intermediate in the electrodeless radiofrequency powered discharge. 

Figure 21 shows the corrected fluorescence excitation and emission spectra of USql3 in CHCI3. The excitation spectrum is similar to the absorption spectrum and is independent of the monitoring wavelength. In the emission spectrum, an emission maximum at 598 nm, a shoulder at -606 nm, and a number of weaker emission bands from 620 to 740 nm are observed. Very similar multiple emission was also observed in toluene [53]. The major clue for the origin of the multiple emission bands comes from the low-temperature (77 K)... 

Figure 1. Absorption and emission spectra of the CdS NCs. The emission spectrum is recorded at an excitation wavelength of 350 nm. On the right is shown a photograph of CdS NCs dispersed in toluene and illuminated by a UV-lamp (lex = 377 nm).

Fig.4 Change in the emission spectrum of [Pt(dC9bpy)(CN)2] (6, n = 9) (5 X IIT M Aeii = 320nm) in different ratios of CHCl3/toluene, from 100% CHCI3 to 100% toluene in 10% steps [22]...

FIGURE 22.42 Random laser emission spectrum of a DOO-PPV in toluene solution that is infiltrated into an opal photonic crystal. The inset shows the opal, which is composed of silica spheres in an FCC lattice and the laser excitation and collection geometries. (From Poison, R.C., Chipouline, A., and Vardeny, Z.V., Adv. Mater., 13, 760, 2001. With permission.)... 

In a series of papers, Ford and co-workers described the photophysical and photochemical properties of these luminescent clusters in detail [46-58]. In addition to complexes 4a and 4b, time-resolved emission spectra of the tetranu-clear copper(I) iodide clusters [Qi4l4(L)4] with a series of substituted pyridines [L = 4-tert-butylpyridine (4c), 4-benzylpyridine (4d), pyridine-dj (4e), 4-phe-nylpyridine (4f), 3-chloropyridine (4g), piperidine (4h), P"Bu3 (4i)] have also been studied [49]. The photophysical data are summarized in Table 1. In general, in toluene solution at 294 K, the complexes revealed a low-energy emission at 678-698 nm and a weaker, higher energy emission at 473-537 nm. The emission spectrum of 4a in toluene at 294 K is shown in Fig. 2... 

Figure 2 Emission spectrum of 4a in toluene at 294 K. (Adapted from Ref. [49].)...

Forster (1968) points out that R0 is independent of donor radiative lifetime it only depends on the quantum efficiency of its emission. Thus, transfer from the donor triplet state is not forbidden. The slow rate of transfer is partially offset by its long lifetime. The importance of Eq. (4.4) is that it allows calculation in terms of experimentally measured quantities. For a large class of donor-acceptor pairs in inert solvents, Forster reports Rg values in the range 50-100 A. On the other hand, for scintillators such as PPO (diphenyl-2,5-oxazole), pT (p-terphenyl), and DPH (diphenyl hexatriene) in the solvents benzene, toluene, and p-xylene, Voltz et al. (1966) have reported Rg values in the range 15-20 A. Whatever the value of R0 is, it is clear that a moderate red shift of the acceptor spectrum with respect to that of the donor is favorable for resonant energy transfer. 

The fluorescence of TPHA 3 is not a mirror image of its absorption spectrum and the emission intensity is sensitive to concentrations greater than 10 M. The excitation profile of 3 also varies with concentration, believed to be due to aggregation of TPHA in solution and only emulates the ultraviolet-visible (UV-Vis) spectrum at concentrations less than 10 M. The Aem decreased from 633 nm in toluene to 619 nm in dimethyl sulfoxide (DMSO), and this is thought to be indicative of a polar ground state and nonpolar excited state <1998JA2989>. 

The normal (short-lived) fluorescence spectrum of 3 X 10 2M naphthalene at —105 °C. [Fig. 21, curve (a) ] shows not only the band due to the singlet excited monomer but also the broad dimer emission band, with maximum at 400 m which is similar to that observed by Doller and Forster46 in toluene solutions. The spectrum of the delayed emission at the same temperature [Fig. 21, curve (b)] also shows both bands, but the intensity of the dimer band is relatively much greater. When the concentration is reduced to 3 X 10 W, the intensity of the dimer band at —105 °C. is very small in normal fluorescence but is still quite large in delayed fluorescence.45 The behavior of naphthalene solutions at —105° C. is thus qualitatively similar to that of pyrene at room temperature. At temperatures greater than — 67 °C. (Table XII) the proportion of dimer observed in delayed fluorescence is almost the same as that observed in normal fluorescence, and presumably at these temperatures, establishment of equilibrium between the excited dimer and excited monomer is substantially complete before fluorescence occurs to an appreciable extent. The higher the temperature, the lower is the proportion of dimer observed in either normal or delayed fluorescence because the position of equilibrium shifts in favor of the excited monomer. 

The pure-film spectra of the alternating copolymers have been reported only for P(S-fl/t-MMA) and P(2VN-a//-MMA)5S>. For the former polymer, a fluorescence band similar to toluene was observed, distinguished only by a slight broadening at X > 290 nm. The P(2VN-a//-MMA) film spectrum was described as having a maximum at 365 nm, with appreciable fluorescence intensity at 425 nm. This emission, which could not be positively identified as excimer fluorescence, was attributed to an impurity by Fox et al.55). If the results for P(S-a//-MMA) are representative of all the copolymer film spectra, they indicate that very few intermolecular EFS are formed. 

Fig. 8.19 Excitation spectrum of the 8 72 complex in toluene monitoring the emission at 740 nm. Inset—corresponding absorption spectrum of 8 72 in toluene...

Fig. 9.35 Excitation spectrum of 17b (orange) and 17c (pink) in toluene solution monitoring the emission at 530 nm...

Fig. 9.62 a Fluorescence spectra (345 nm excitation) of the oFL reference (pink spectrum), 24a (iorange spectrum) and 24b (brown spectrum) in toluene representing the quenching of the oFL emission, b Fluorescence spectra of the C60 reference (black spectrum), 24a (orange spectrum) and 24b (brown spectrum) in toluene representing the quenching of the C60 emission... 

Fig. 1.27. Normalised UV/VIS absorption (solid lines) and fluorescence excitation spectra of the fullerene emission at 715 nm (dashed lines) of the OPVn-C6o dyads in toluene at 295 K. (a) n = 1, (b) n = 2, (c) n = 3, and (d) n = 4. In each case the fluorescence excitation spectrum shows a close correspondence to the absorption spectrum...

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