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Triplet state dynamics on isolated conjugated polymer chains
Burrows, H. D.; Seixas de Melo, J.; Serpa, C.; Arnaut, L. G.; Miguel, M. da G.; Monkman, A. P.; Hamblett, I.; Navaratnam, S.http://www.sciencedirect.com/science/article/B6TFM-46MD9J0-5/1/ad58ae25c92bd62f507ea5a6a04f467d
Diffusion coefficients of sodium dodecylsulfate in aqueous solutions of sucrose...
Ribeiro, Ana C. F.; Lobo, Victor M. M.; Azevedo, Eduarda F. G.; Miguel, M. da G.; Burrows, H. D.Differential diffusion coefficients of sodium dodecylsulfate (SDS) in aqueous solutions of sucrose and in aqueous solutions at 298.15 K, over the concentration range 0.0018 M to 0.0817 M, have been measured using a conductimetric cell and an automatic apparatus to follow the diffusion. The results are discussed on the basis of the Onsager-Fuoss model. The cell uses an open ended capillary method, while a conduc...
Room temperature and low-temperature absorption and emission spectra of some po...
Silva, M. I.; Burrows, H. D.; Formosinho, S. J.; Miguel, M. da G.Electronic absorption and luminescence spectra are reported for a series of complexes of type [Ru(tpy)(L-L)(py)]2+, where tpy and py are 2,2',2''-terpyridine and pyridine, and L-L represents the bidentate ligands bipyridyl, 4,4'-dimethylbipyridyl, 4-nitrobipyridyl, oxalate and acetylacetonate. The effect of solvent polarity and temperature on their spectral and light emission properties is studied. Energies are...
Transient absorption spectra of triplet states and charge carriers of conjugate...
Burrows, H. D.; Miguel, M. da G.; Monkman, A. P.; Hamblett, I.; Navaratnam, S.The use of pulse radiolysis to study transient species in conjugated polymers in solutions is discussed, with particular reference to poly(2-methoxy-5-(2'-ethylhexoxy)-p-phenylenevinylene) (MEH-PPV). The excited triplet state is specifically generated by energy transfer on radiolysis of benzene solutions in the presence of suitable sensitisers, and its spectrum is reported. The presence of vibronic structure su...
Solvatochromic fluorescent probes in bicontinuous microemulsions
Oliveira, M. E. C. D. R.; Hungerford, G.; Miguel, M. da G.; Burrows, H. D.The fluorescence probes nile red and prodan have been used to study the structure of the bicontinuous phase of C12E5/alkane/water microemulsions. For nile red the steady state fluorescence spectrum show contributions from probe located in alkane and surfactant rich regions, together with indications of surfactant hydration. Fluorescence lifetime measurements show multiexponential decay kinetics consistent with ...
Triplet state dynamics in poly(2,5-pyridine diyl)
Wong, K. S.; Law, Carrie W. Y.; Sun, T.; Monkman, A. P.; Vaschetto, M. E.; Hartwell, L. J.; Horsburgh, L. E.; Burrows, H. D.; Miguel, M. da G.Pulse radiolysis was used to determine the triplet state energy (2.3 eV) of Poly(2,5-pyridine diyl) (PPY) film which was found to be coincident with the emission energy. Detailed time-resolved photoluminescence (PL) and pump-probe measurements have been applied to study the photoexcited state relaxation dynamics. In films, a very large spectral red-shift (~0.35 eV) for the PL occurred within the first 100 ps wh...
Triplet state spectroscopy of conjugated polymers studied by pulse radiolysis
Monkman, A. P.; Burrows, H. D.; Miguel, M. da G.; Hamblett, I.; Navaratnam, S.Using the technique of pulse radiolysis we have elucidated the energies and kinetics of triplet states in soluble luminescent conjugated polymers. Using poly(2-methoxy,5-(2'-ethyl-hexoxy)-p-phenylenevinylene) MEH-PPV as an example we explain this technique and show how it can be used to study the triplet states in conjugated polymers. Triplet energy transfer is used to determine 11Ag-13Bu energy gaps and the ki...
Monitoring the Phase Transition of C12E5/Water/Alkane Microemulsions Through Ex...
Oliveira, M. E. C. D. Real; Hungerford, Graham; Castanheira, E. M. S.; Miguel, M. da G.; Burrows, H. D.The phase transition of microemulsions involving the nonionic surfactant C12E5 [C12H25(OCH2-CH2)5OH], water, and alkanes (heptane, decane and tetradecane) has been investigated through the excimer formation of pyrene. On going to the microemulsion bicontinuous phase, by changing either composition or temperature, pronounced changes in the pyrene excimer-to-monomer fluorescence intensity ratio, IE/IM, are observ...
.beta.-Carboline Photosensitizers. 3. Studies on Ground and Excited State Parti...
Varela, A. P.; Miguel, M. da G.; Maçanita, A. L.; Burrows, Hugh D.; Becker, Ralph S.The photophysical behavior of the P-carbolines norharmane, hmane, and harmine has been studied in waterin- oil (w/o) microemulsions in AOT/cyclohexane. With pure solvents, solubility and partitioning studies indicate that these molecules dissolve preferentially in the organic phase but that their solubility in the aqueous phase increases upon decreasing pH as a consequence of protonation. However, in w/o microe...
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