Energy migration studies

Polymers for Excimer and Energy Migration Study -EOCH2CHCH20CO-R-C03 -E0C2H40C0CHC00C2H40C0NH-R-NHC03j ... 

Based on luminescence studies, we postulated triplet-triplet energy transfer by electron exchange as the mechanism of photostabilization and we calculated an active quenching sphere with a radius, R0, of 19.7 A for 2,6-ND. Because the value of R0 is larger than 15 A, we postulated that energy migration was occurring. 

Fan L-J, Jones WE Jr (2006) Studies of photoinduced electron transfer and energy migration in a conjugated polymer system for fluorescence tum-on chemosensor applications. J Phys Chem B 110 7777-7782... 

ICP analyses of the hardystonite sample in our study confirms a very high Pb content of 5,000 ppm, while the Ce concentration of 55 ppm is two orders of magnitude lower. This elevated Pb concentration may be the reason for a extremely short decay time at room temperature because of energy migration, with a corresponding decrease in decay time. The most Ukely position for Pb " in the hardystonite structure is at the Ca site. The four-coordinated Zn site is less probable. Moreover, the difference between the ionic radii of Zn + and Pb is quite large. 

The rate and extent of electron and hole migration within DNA had been a topic of intense experimental [1] and theoretical [2] interest and dispute. However, as other chapters in this volume point out, the overall picture is now becoming increasingly understood. Several earlier reviews have dealt with the radiation damage to DNA and subsequent chemical processes including electron and hole transfer [3]. This chapter will focus on recent contributions to hole and electron transfer in DNA from high-energy radiation studies. We first present a brief overview on electron transfer processes in DNA from radiation studies and describe in more detail our most recent results on electron and hole transfer in DNA at low temperatures. 

Some additional studies using time-resolved excitation spectroscopy lead these authors to believe that most of it, if not all, the energy migrates from... 

The objective of this review is to characterize the excimer formation and energy migration processes in aryl vinyl polymers sufficiently well that the excimer probe may be used quantitatively to study polymer structure. One such area of application in which some measure of success has already been achieved is in the analysis of the thermodynamics of multicomponent systems and the kinetics of phase separation. In the future, it is likely that the technique will also prove fruitful in the study of structural order in liquid crystalline polymers. 

The photochemical and photophysical processes discussed above provide illustrations and incentives for further studies of photoeffects brought about by the formation of supramolecular species. Such investigations may lead to the development of photoactive molecular and supramolecular devices, based on photoinduced energy migration, electron transfer, substrate release, or chemical transformation. Coupling to recognition processes may allow the transduction of molecular infor-... 

The above studies provide evidence for the donor-to-donor energy migration within the assemblies of the chromophores built from a variety of systems, but they all share a common matrix for assembly. Such systems may be of interest in the construction of artificial light-harvesting antennas [67,72],... 

Many charge-transfer complexes do not fluoresce. Thus, fluorescent probes, either as donor or acceptor, cause fluorescence quenching proportional to the association constant Kc of the complex. Fluorescence quenching may be utilized in the study of small molecules, as well as, particularly, macromolecules, to determine energy migration and transfer [78,79]. The fluorescence yield of the acceptor alone (F0), and that in the presence of... 

Complexes of pyridines, bipyridyls, terpyridyls, and other polypyridines differ considerably from those of NH3 and aliphatic amines. They have been intensively studied because many of them have unusual properties for photoinduced energy migrations and charge separation, luminescence, photocatalytic reactions, and water activation. They are also involved in the construction of double-helical complexes, complexes that bind to DNA, and molecular rods and wires28 for fast electron transfers.29... 

---