José A. B. Ferreira

Multicriteria decision analysis (MCDA) : Central Porto high-speed railway station

Over recent years, Portugal has been working towards their integration in the trans-European high-speed railway network. While in Spain several new high-speed lines are already under construction or beginning operation, in Portugal the necessary studies are still being carried out. One of these studies concerned the location of one of the high-speed railway stations to be built in the city of Porto, meant to connect the second most populated metropolitan area in Portugal to the high-speed railway network. The goal for the study was to compare alternative siting strategies, defined by the Portuguese high-speed railway authority. These strategies were materialized in a set of location alternatives, which were evaluated from a range of technical, economical, social and environmental criteria. This paper describes the multicriteria decision analysis (MCDA) approach by which the best alternative was identified from the given set of possible alternatives.

Non-Markovian effects in the radiationless decay of rhodamine 3B+ in water : ethanol mixtures

The intramolecular nonradiative decay of the first excited singlet of Rhodamine 3B cation, is studied in the full range of composition of water : ethanol mixtures with different polarities and viscosities. The correlation of experimental data of absorption, emission and rate constants, knr, with the dielectric and shear viscosity parameters of these mixtures shows that friction effects determine the reaction rates. These were modelled using the phenomenological dependence of radiationless decay rates which is expressed in terms of Kramers–Grote–Hynes theory. The reactant well wavenumber (ω0/2πc=30 cm−1) obtained previously for the activated radiationless decay of Rhodamine 3B in a variety of solvents provides a means to estimate the reaction transmission coefficients (κ) in the mixtures. The trend of variation with the composition reflects the dependence on the viscoelastic response of water : ethanol mixtures. The clustering of ethanol molecules at low ethanol content disrupts the water structure and induces enhanced hydrophobicity around the chromophore which manifests in non-Markovian effects on the reaction rates, knr.

RHODAMINE 3B+CLO4- IN WATER:TOLUENE MIXTURES. EVIDENCE OF WATER CLUSTER FORMATION

Abstract Rhodamine 3B perchlorate coexists solubilized in mixtures of water:toluene as a distribution of ion pair (74%) and cation (26%). The quantum yield variation shows that the fluorescence quenching process of the ion pair is diffusion controlled with a rate constant oscillating within the limits of slip and stick boundary conditions. The driving force for the excited-state conversion is the unbalance of electrostatic forces and changes in inter-ionic distances in the water cluster solvation sphere created around the ion pair by dielectric enrichment.

Rhodamine 3B+ ClO4− electronic transitions: reaction field and vibrational structure

Abstract The electronic absorption and emission in the visible region of the spectrum of a xanthene dye, Rhodamine 3B perchlorate, have been studied as a function of solvent and temperature. The spectral shifts correlate well with the function f ( n 2 )=( n 2 −1)/(2 n 2 +1) (Ooshika, Bayliss and McRae theory) and are essentially due to dispersion and induced electronic polarization. A further energy lowering occurs due to orientation polarization giving an estimation of μ e − μ g =1.7 D. The broadenings in absorption reveal the contribution from orbital expansion whilst in emission provide evidence for the opposite effect. The contribution of an electrostriction effect is inferred from the good correlation obtained between a vibronic function containing the elongation of molecular coordinates and the temperature. The double configuration coordinate model describes well the effect of temperature on both the S 1 ↔S 0 transitions Stokes shift and broadening at the vibronic 0↔0 bands.

Solvent effects on the vibronic structure of S1←S0 transition of Rhodamine 3B

Abstract The vibronic pattern of the visible absorption spectra of Rhodamine 3B is studied in terms of Gaussian contributions. The vibronic components 0←0 and 1←0 correlate linearly with Onsagers reaction field function of induced polarisation, f ( n 2 ). The respective solvent dependences follow opposite trends. The spectral shape does not sense significant contributions from orientation polarisation or Boltzmann weighted population redistribution.

Activated radiationless decay of rhodamine-3B: Nonequilibrium polarization effects in viscous solvents

Nonequilibrium polarization effects that arise in high viscous polar solvents are discussed as regards to the rhodamine-3B-activated radiationless process. Rate constants are interpreted using dipole isomerization theories which enable the recovery of a barrier top region wave number identical to that previously obtained in less viscous solvents [J. Phys Chem. A 104, 11909 (2000)]. The Onsager-frequency-dependent reaction field can model the friction effect on the rate constants that in glycerol were estimated also from an adiabatic charge-transfer model. The cusp barrier height is half the electronic coupling, as expected from the equality found for the frequencies of the reactant well and barrier top in this process. Coupling to solvent polarization modes can control the friction effect on the reactive mode. A two-dimensional reaction surface explains the photophysical features detected in the radiationless decay and a state energy diagram is proposed for rhodamine-3B.

Transient photokinetics of Rhodamine 3B+ClO4− in water:toluene mixtures

Abstract The kinetic behavior of the first excited singlet state of an ionic dye, Rhodamine 3B perchlorate, was studied in the region of total miscibility of water:toluene mixtures. The solute exists in two forms: the associated ion pair and cationic, both preferentially solvated by the more polar component (Chem. Phys. Lett. 307 (1999) 139). The transient photokinetics of the excited state hydrated ion pair’s conversion into the cationic species is studied. An anisotropic distribution of the nearest neighbor accounts satisfactorily for the transient effects induced in the diffusional behavior of water molecules in a dielectric cluster solvation sphere around the solute. A kinetic model is proposed to evaluate the dependence of the reactional rate constant k a and the mutual diffusion coefficient D on the water concentration, temperature, and the effect of friction. It is found that both k a and D decrease with the water concentration but, while the overall friction ( k B T / D ) decreases with the temperature, the rate constant k a is not affected. Overall, the kinetic data is in good agreement with the interpretation derived on the basis of steady-state results, and the recovered lifetimes of each individual species are similar to those observed in pure solvents.

Electrophilic reactivity of tetrabromorhodamine 123 is bromine induced: convergent interpretation through complementary molecular descriptors.

Nucleophilic addition of water and of methanol to 3,6-diamino-2,4,5,7-tetrabromo-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, 4BrR123, yields respectively 2-(3,6-diamino-2,4,5,7-tetrabromo-9-hydroxy-9H-xanthen-9-yl)xanthyl benzoate, HO4BrR123 and 2-(3,6-diamino-2,4,5,7-tetrabromo-9-methoxy-9H-xanthen-9-yl)xanthyl benzoate, MeO4BrR123. The novel experimental results are addressed theoretically. The linear free energy relationship, LFER, second-order perturbation theory analysis of the natural bond orbital, NBO, and quantum theory of atoms in molecules, QTAIM, lead to the same conclusion: the electron-withdrawing effect of bonded Br atoms in 4BrR123 extremely enhances the molecular electrophilicity, as compared to 3,6-diamino-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, R123. The reactivity of these diaminoxanthylium cations is discussed in the context of local and global softness in extended conjugated systems.

Thermally induced spectral diffusion of Rhodamine 3B in viscous polyols

Abstract Energy shifts of the ν 00 vibronic near the fluorescence maxima of Rhodamine 3B, in 1,5-pentanediol and glycerol, are studied in the range 275 T

Fluorescence lifetime imaging microscopy and fluorescence resonance energy transfer from cyan to yellow fluorescent protein validates a novel method to cluster proteins on solid surfaces

A novel method to distribute proteins on solid surfaces is proposed. Proteins microencapsulated in the water pool of reverse micelles were used to coat a solid surface with well-individualized round spots of 1 to 3 microm in diameter. The number of spots per unit area can be increased through the concentration of reverse micelles, and networks of spots were obtained at high concentrations of large reverse micelles. Moreover, depending on the pool size of the water reverse micelles, proteins can be deposited far from each other or in close proximity within the range of 50 to 70 A. This proximity obtained with small reverse micelles was proved through fluorescence lifetime imaging microscopy and fluorescence resonance energy transfer (FLIM-FRET) measurements for the most relevant FRET pair in cell biology studies, the cyan and yellow fluorescent proteins. This novel procedure has several advantages and reveals the potential for study of protein-protein interactions on solid surfaces and for developing novel biomaterials and molecular devices based on biorecognition elements.