Contents 5 Energy Transfer Processes

Copolymers 15 (Fig. 6) derived from 2,7-fluorene and 2,5-dithienylsilole show red fluorescence via an energy transfer process.31 The APl could be 591 nm for copolymers with higher contents of 2,5-dithienylsilole. The absolute PL quantum yields (<30%) of the copolymers are somewhat lower than the green fluorescent SCPs. A copolymer 16 derived from 2,7-dibenzosilole and 4,7-dithienyl-2,l,3-benzothiadiazole show a better red fluorescence.26 The APL of the copolymer is at 629 nm, with an absolute PL quantum yield of 53%. 

Figure 4 shows that contrarily to what it has been proposed for metal overlayers, the CO (2n) backdonation contribution does not permit to explain the experimental, and also calculated, linear relationship between the interaction energy and the Pd core level shift, pointing out to a different chemical interpretation of the phenomenon in alloys, at least PdCu alloys, and overlayers. Finally, the CSOV and projection analyses permit to explain the C-0 stretch insensitivity to alloy composition. Since charge-transfer processes and Pauli repulsion do not vary significantly with copper content, only the correlation contribution is expected to influence this observable, but... 

Sonochemical homopolymerization of dichlorosilanes in the presence of sodium is successful at ambient temperatures in nonpolar aromatic solvents (toluene or xylenes) only for monomers with a-aryl substituents. Dialky 1-dichlorosilanes do not react with dispersed sodium under these conditions, but they can be copolymerized with phenylmethyldichlorosilane. Copolymers with a 30-45% content of dialkylsilanes were formed from equimolar mixtures of the corresponding comonomers. Copolymerization might indicate anionic intermediates. A chloroterminated chain end in the polymerization of phenylmethyldichlorosilane can participate in a two-electron-transfer process with sodium (or rather two subsequent steps separated by a low-energy barrier). The resulting silyl anion can react with both dichlorosilanes. The presence of a phenyl group in either a or P position in chloroterminated polysilane allows reductive coupling, in contrast to peralkyl species, which do not allow the reaction. Therefore, dialkyl monomers can copolymerize, but they cannot homopolymerize under sonochemical conditions. 

The free energy AG, is expected to decrease with increasing alcohol content. This is because the electron transfer process implies a decrease of the absolute values of the charges of both, the donor and the acceptor. On the other hand, taking into account that the... 

A class of futuristic solar cells, often called hot carrier solar cells, seeks to harvest the full energy of solar photons. Such cells would utilize the additional energy content of a blue photon relative to ared one.126 In present-day solar cells, equilibrated carriers are collected and hence all absorbed photons with energy greater than the bandgap contribute equally to the measured efficiency. The realization of such hot carrier solar cells therefore requires electron transfer processes that are competitive with nonradiative decay of molecules or phonon relaxation in solids.126 Literature data indicate that such relaxation occurs on a femtosecond timescale. The ultrafast... 

The sensitization of fluorescence of an acceptor molecule is considered a concentration-dependent process. The enhancement of chemiluminescence with the Coumarin C337 content was observed in the range of concentration studied. This result would indicate that energy transfer is a diffusion-controlled process. The requirement for donor and acceptor to diffuse to near or actual physical contact with... 

The maximums of liquid product yields (80 and 52.5 mass% in modes 1 and 2, respectively) were observed at the same dose values of about 6 kGy. However, gasoline fractions produced in the two modes considerably differed in their hydrocarbon contents. At the temperature of 375°C, isoalkane yields were comparable with those observed in the catalytic process at the temperatures above 600°C. The unusually high yields of isoparaffins in the RTC modes characterized by relatively low values of temperature and dose rate were attributed to the effects of energy transfer from paraffin to aromatic components of the hydrocarbon mixture. 

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