Toluene fluorescence

Exciplexes are complexes of the excited fluorophore molecule (which can be electron donor or acceptor) with the solvent molecule. Like many bimolecular processes, the formation of excimers and exciplexes are diffusion controlled processes. The fluorescence of these complexes is detected at relatively high concentrations of excited species, so a sufficient number of contacts should occur during the excited state lifetime and, hence, the characteristics of the dual emission depend strongly on the temperature and viscosity of solvents. A well-known example of exciplex is an excited state complex of anthracene and /V,/V-diethylaniline resulting from the transfer of an electron from an amine molecule to an excited anthracene. Molecules of anthracene in toluene fluoresce at 400 nm with contour having vibronic structure. An addition to the same solution of diethylaniline reveals quenching of anthracene accompanied by appearance of a broad, structureless fluorescence band of the exciplex near 500 nm (Fig. 2 )... 

Fig. 17 Cadmium selenide QDs, dissolved in toluene, fluorescing brightly in the presence of a ultraviolet lamp, in three noticeably different colors (blue 481 nm, green 520 nm, and orange 612 nm). The blue QDs have the smallest particle size, the green dots are slightly larger, and the orange dots are the largest. (Adapted from http //www. amazingrust.com/ experiments/current proj ects / Misc.html)...

Quite similar kinetic data are obtained in two photon laser photolysis with, X 3471 A, of naphthalene in toluene. Fluorescence of the naphthalene excited singlet state and absorption spectra of the excited triplet state were observed, no excited species were observed in similar experiments in cyclohexane (21). This suggests that excitation of toluene is two photon into the Sg state followed by rapid internal conversion to the first excited state S-j, which then leads to energy transfer to Naphthalene N. 

However, Stern Volmer kinetics are obeyed for radiolysis studies of scavenging of toluene fluorescence with benzyl chloride. The electron scavengers CHCl and chlorobenzene reduce the fluorescence yields of arenes in a manner that suggests ... 

The rise time of toluene fluorescence emission was within that of the system, i.e., faster then 15 psec, which gives an upper limit estimation for the time of ion recombination in toluene. Figure 5 also contains similar studies in diethylaniline D.E. and, shows that here the rise time of D.E. fluorescence is 24.4 psec and slower than that in toluene. It was also noted that benzyl chloride reduced the initial yield of D.E. fluorescence, the kinetics being Stern Volmer. 

Acryloid E-10, 40% in mineral thinner (Rohm Haas) fluorescent pigment lactol spirits toluene... 

In C- and T-type gravure systems where oxygenated and aromatic solvents are used, the Radiant P-1700 Series and Day-Glo GT and STX pigments are recommended. A typical formulation for an A-type gravure ink is 30% Acryloid NAD-10 (Rohm Haas), 50% fluorescent pigment, 5% toluene, and 15% heptane (as thinner). 

Diaminoanthraquinone [131-14-6] M 238.3, m 310-320°. Crystd from pyridine. Column-chromatographed on AI2O3 / toluene to remove a fluorescent impurity, then recrystd from EtOH. 

Poly[2,5-dialkoxy-l,4-phenylene) vinylenejs with long solubilizing alkoxy chains dissolve in conventional organic solvents such as chloroform, toluene, or tetrahydrofuran [21, 28, 32-36]. Their emission and absorption spectra are red-shifted relative to PPV itself, and the polymers fluorescence and electroluminescence quantum yields are greater than parent PPV. This benefit may be a consequence of the long alkyl chains isolating the polymer chains from each other. 

A three-step nitration process of toluene is described. The advantages of the modified process are reduced waste, less hazardous operation, reduced oleum requirement, partial replacement of coned HN03 with dil HN03, and higher rate of toluene flow into the reactor (Ref 86) The continuous process of H.C. Prime (Ref 73) for preparing TNT was studied by thin-layer chromatography on silica gel with a starch binder and a fluorescent indicator. The nitration... 

In a recent study, poly(aryl ether) dendritic branches terminated with triethyleneglycol chains were attached to Cgg [66] dendrimer 32 represents the fourth generation. The photophysical properties of these fullerodendrimers have been systematically investigated in three solvents, namely toluene, dichloromethane, and acetonitrile. On increasing dendrimer generation, it has been found that in each solvent (i) the maximum of the fullerene fluorescence band is red-shifted... 

After illumination for 60 min with fluorescent lamps with total intensity of 3750 lux at 20°C, degradation rates of all-trans P-carotene and all-trans lutein, both dissolved in toluene, were very similar 21%, accompanied by only marginally increasing in the levels of cis isomers of P-carotene and lutein. On the other hand. 

Additionally, note that the polarity of the solvent significantly affects not only the positions of absorption and fluorescence spectra but also the fluorescence quantum yields. The largest difference in quantum yield is observed for G19 (eight times larger in toluene) [86]. The effect of solvent polarity on quantum yield and fluorescence lifetime was investigated in mixtures of toluene and ACN (polarity range 0.013-0.306). Polarity dependent quantum yield and lifetime measurements are presented in Fig. 22. 

Fig. 22 (a) Comparison of fluorescence lifetime (blue triangles), calculated from (13), and measured by time-resolved fluorescence red circles) as a function of solvent polarity for G19. (b) Fluorescence quantum yield blue squares) and peak ground state absorption wavelength red circles) as a function of solvent polarity given by the percentage of toluene (T) in toluene-ACN mixtures for G19... 

It is seen that the fluorescence quantum yield and lifetime of G19 gradually decreases with increasing solvent polarity. For example, the insertion of 20% ACN by volume into toluene leads to a decrease of a factor of two. Based on these results we can conclude that G19 is very sensitive to solvent polarity and can be used as an efficient probe to test the polarity of its microenvironment. A reverse trend of the absorption peak at 1 1 mixture of ACN and toluene (50%T in Fig. 22b) corresponds to a change of the sign of due to a transition from a polyene-like structure in nonpolar toluene to a polymethine-like structure in polar ACN. 

The fluorescence and absorption spectra of DTT-A.V-dioxidc 20a with polar covalent bonds was studied in THF, toluene, and decalin. The spectral line and peak energy are almost independent of the solvent polarity. The fluorescence spectra of the decalin and toluene solutions (almost the same polarity) are red-shifted by about 5 nm, with respect to the THF solution of higher polarity. No evident solvatochromism was observed. The absorbance and fluorescence excitation spectra (at the fluorescence peak wavelength) for DTT-3, 3 -dioxide 20a (normalized to peak value) was compared. The fluorescence excitation signal is, in fact, dependent both on the density of the excited state (as the absorbance) and on the efficiency of the relaxation from the excited state of the emitting one <2005PCB6004>. 

Concentrations of radiolabeled proteins, substrates, or products can be quantified by scintillation counters, which detect both emitters of weak (e. g., 3H) and high energy (e.g., 32P) by excitation of an organic solvent (e.g., toluene) which then emits fluorescence fight. In commercial systems the primary fluorescence is transformed via one or two additional fluorescent dyes in the solution into a visible emission signal which can easily be detected by conventional photomultipliers. 

A refined method involving extraction of two aliquots of biological material, buffered at two different pH s, by toluene, and re-extraction into aqueous solution allowed the simultaneous determination of nalidixic and hydroxynalidixic acid(24)(26) by their differential extractabilities and fluorescent intensities. This method was extended to the differential determination of the conjugated forms of nalidixic and hydroxynalidixic acid. 

Figure 6.2 Fluorescence spectra of solutions of pyrene in toluene (a) 1 0"6mol dm"3, (b) KR moldm"3, (c) 10 3moldnr3...

Figure 6.6 Fluorescence spectra of anthracene in toluene in the presence of N,N-diethylaniline of varying concentration...

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