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Interaction between Poly(9,9-bis(6′-N,N,N-trimethylammonium)hexyl)fluorene phen...
Monteserín, María; Burrows, Hugh D.; Valente, Artur J. M.; Mallavia, Ricardo; Paolo, Roberto E. Di; Maçanita, António L.; Tapia, María J.The interaction between three poly(9,9-bis(6-N,N,N-trimethylammonium)hexyl)fluorene phenylene) bromide (HTMA-PFP) samples of different molecular weights (Mn = 14.5, 30.1 and 61.3 kg/mol) and both dsDNA and ssDNA secondary structures has been studied using UV−visible absorption and fluorescence spectroscopies (including steady-state, time-resolved, and anisotropy measurements for the latter), viscosity, and elec...
Picosecond Structural Relaxation of Abietic Acid Based Amine End Capped Para-Ph...
Paolo, Roberto E. Di; Gigante, Barbara; Esteves, Maria A.; Pires, Natércia; Santos, Célia; Lameiro, Maria H.; Melo, João Seixas de; Burrows, Hugh D.The synthesis and photophysical properties of six new abietic acid based amine end-capped p-phenylenevinylene trimers (AECPV3) in their lowest excited singlet states are presented. The AECPV3 compounds show a large red-shift of both the absorption (25-30 nm) and emission (37-42 nm) maxima with respect to those of the corresponding trimers. Picosecond time-resolved fluorescence data reveal the presence of a fast...
Modulating the Emission Intensity of Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)h...
Monteserín, María; Burrows, Hugh D.; Valente, Artur J. M.; Lobo, Victor M. M.; Mallavia, Ricardo; Tapia, María J.; García-Zubiri, Iñigo X.The interaction between the cationic HTMA-PFP (Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)hexyl-fluorene phenylene) bromide) and oppositely charged sodium n-alkyl sulfonate surfactants of different chain lengths has been studied in DMSO−water solutions (4% v/v) by UV−visible absorption, fluorescence spectroscopy, fluorescence lifetimes, electrical conductivity, and 1H NMR spectroscopy. Polymer−surfactant interact...
Kinetics and Thermodynamics of Poly(9,9-dioctylfluorene) β-Phase Formation in D...
Dias, Fernando B.; Morgado, Jorge; Maçanita, António L.; Costa, Fernando P. da; Burrows, Hugh D.; Monkman, Andrew P.Poly(9,9-dioctylfluorene) (PFO) adopts a particular type of conformation in dilute solutions of the poor solvent methylcyclohexane (MCH) below 273 K, which is revealed by the appearance of a red-shifted absorption peak at 437−438 nm. The formation of this ordered conformation depends on the temperature but is independent of polymer concentration over the range studied (3−25 μg/mL). On the basis of absorption, s...
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation ...
Costa, Fernando Pestana da; Maçanita, António L.; Morgado, Jorge; Dias, Fernando B.; Burrows, Hugh D.; Monkman, Andrew P.Poly(9,9-dioctylfluorene) (PFO) adopts a particular type of conformation in dilute solutions of the poor solvent methylcyclohexane (MCH) below 273 K, which is revealed by the appearance of a red-shifted absorption peak at 437−438 nm. The formation of this ordered conformation depends on the temperature but is independent of polymer concentration over the range studied (3−25 μg/mL). On the basis of absorption, s...
Comprehensive Evaluation of the Absorption, Photophysical, Energy Transfer, Str...
Becker, Ralph S.; Melo, J. Seixas de; Maçanita, António L.; Elisei, FaustoA large basis set of R-oligothiophenes with two to seven rings (R2-R7), also including thiophene, R1, have been investigated in five solvents regarding absorption, fluorescence and phosphorescence, quantum yields of fluorescence ( F) and triplet formation ( T), lifetimes of fluorescence and the triplet state, quantum yields of singlet oxygen production ( ¢), all rate constants kF, kIC, kISC, and several of the ...
Photophysical Behavior of Coumarins as a Function of Substitution and Solvent: ...
Melo, J. Sérgio Seixas de; Becker, Ralph S.; Maçanita, António L.The nature of the lowest excited state for coumarin and some derivatives was investigated using steady-state and time-resolved fluorescence data at room temperature, as well as fluorescence anisotropy at 77 Kin nonpolar and polar solvents in conjunction with theoretical data obtained with different methods: INDO/S-CI, CNDO/ S-CI, MNDO-CI, and AM1-CI. Theresultsshow that SI isactually n,?r* for coumarininanysolv...
The 9-Anthroate chromophore as a fluorescent probe for water
Costa, Fernando Pestana da; Maçanita, António L.; Costa, Sílvia B.; Melo, Eurico C.; Santos, HelenaWater quenches the fluorescence of methyl 9-anthroate with a rate constant showing little dependence on solvent viscosity or polarity. In dioxane, at 20ºC the value of the rate constant is 9.6 X 10^6 M^(-1) s^(-1) , and the activation energy found for the process is 14.1 kJ mol^(-1). The quenching process is entropy-controlled and is likely to involve a hydrogen-bonded complex as an intermediate. Since the fluo...
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