Robson Valentim Pereira

Modulation of Dye Fluorescence by Photoinduced Intramolecular Charge Transfer with Resonance-Assisted Hydrogen Bond

Fluorescent dyes with photoinduced intramolecular charge-transfer (ICT) process driven by β-enaminone group capable to form resonance-assisted hydrogen bond (RAHB) structure were prepared from aromatic and heterocyclic precursor molecules, such as 1-aminopyrene, 9-amino acridine, and adenine. The electronic ground and excited-state spectral properties of these new dyes are modulated by the type of substituent in the β-enaminone group and solvent interaction as well. The excited-state properties and the complex kinetics observed are results of the interplay between charge and proton transfer, together with the presence of possible conformers or tautomers associated with the keto-amine/enol-imine equilibrium. The applications of such dye derivatives as molecular probes in radical copolymerization with acrylic monomers and as reporters in silver nanoparticles dye interaction in solution are also discussed.

Espectroscopia optogalvânica: alguns aspectos relevantes

In this work we present the optogalvanic effect in ionized gases in an historical perspective. This effect was observed for the first time by Foote and Mohler in 1925, and explained by Penning in 1928 for mixtures (Ne-Ar) and pure gases (or vapours) in 1937. Also, we show some aspects of the contributions of Romenian authors for the development of optogalvanic spectroscopy, which was used as a new technique only after 1964.