Partículas de sílica dopadas com o complexo quercetina-Al3+ foram preparadas através da hidrólise e condensação do tetraetilortossilicato (TEOS) utilizando catálise ácida e básica. A catálise ácida resultou em partículas com diâmetro em torno de 200 nm. A catálise básica com TEOS foi executada sobre um sol de alumina dopado com quercetina utilizado como precursor caroço e com este procedimento foram obtidas partículas fluorescentes de SiO2 na forma de dedos. Os decaimentos de fluorescência do sistema quercetina-alumina-SiO2 são biexponenciais e este caráter é atribuído aos dois tipos de complexos quercetina-Al3+ encapsulados no caroço do sistema.

Silica particles doped with quercetin-Al3+ complex were prepared by hydrolysis and condensation of tetraethylorthosilicate (TEOS) using acid and basic catalysis. The acid catalysis resulted in particles with diameter about 200 nm. Basic catalysis with TEOS was performed over a quercetin doped alumina-sol used as a core precursor, and fluorescent finger-shaped SiO2 particles were obtained. The quercetin-alumina-SiO2 fluorescence decays are biexponential, and this character is ascribed to two types of quercetin-Al3+ complexes entrapped in the core of the system.

Soluções de poli(ácido metacrílico) atático, PAMA com peso molecular na faixa de (1,6 a 3,4) x 10(5) g mol-1, e com corantes fluorescentes 9-aminoacridina ou azul do nilo ligados à cadeia, foram estudados por medidas fotofísicas em função da viscosidade e polaridade do solvente. O comportamento dos segmentos da cadeia do PAMA nas vizinhanças da sonda fluorescente foi descrito pela mudança na rotação difusional dos corantes. O etilenoglicol expande a cadeia polimérica quando comparada com a forma mais compactada do corante-PAMA em 50% água/etilenoglicol. A variação do tempo de relaxação rotacional do corante ligado ao PAMA indica uma expansão progressiva da cadeia polimérica para uma forma aberta em etilenoglicol.

Solutions of atactic poly(methacrylic acid), PMAA, with molecular weights in the range of (1.6 to 3.4) x 10(5) g mol-1, and labeled with the fluorescent dyes 9-aminoacridine or Nile blue were studied by photophysical measurements as a function of solvent viscosity and polarity. The conformational behavior of the PMAA chain segments around the fluorescent probe was reported by the change in the rotational diffusion of the dyes. Ethylene glycol swells the polymer chain compared with the more contracted conformation of PMAA in 50% water/ethylene glycol. The change in the rotational relaxation time of the dye bound to PMAA with the decrease of water content in the solvent mixture indicates a progressive expansion of polymer chain to a more open coil form in solution.

In this work, the energy transfer by dipole-dipole interaction between cationic dyes in n-alcohols (methanol, ethanol, 1-propanol and 1-butanol) is studied by time resolved and steady state fluorescence measurements. The critical radii of energy transfer were determined by three independent methods; the spectral overlap, fluorescence decay profiles, and relative intensity measurements. In all solvents, R0 values of the dye pairs obtained from spectral overlap were between 40 to 90 Å. Steady state and time resolved fluorescence measurements resulted in values of R0 in the range of 50 - 80 Å, with good correlation of values.