The excited states interaction of safranine-O with low generation carboxyl terminated PAMAM dendrimers in aqueous medium.

Carlos M Previtali, Sonia Graciela Bertolotti, Marcela Altamirano, Maria Paula Militello

Index: 10.1039/C8PP00039E

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Abstract

The interaction of the singlet and triplet excited states of the synthetic dye safranine-O with carboxyl-terminated poly(amidoamine) (PAMAM) dendrimers was investigated in buffer solution at pH 8. Low half-generation PAMAM dendrimers (G -0.5; G +0.5: G 1.5) were employed. UV-vis absorption spectrum of the dye presents only a very small red shift in the presence of dendrimers. Fluorescence quenching was detected and it was interpreted by a static mechanism in terms of the association of the dye to the dendrimer. Laser flash photolysis experiments were carried out and the transient absorption spectra of the triplet and radicals were obtained. The triplet state is quenched by the dendrimers with rate constants well below the diffusional limit. The quenching process was characterized as an electron transfer process and the quantum yield of radicals was estimated. It was found that radicals are formed with a high efficiency in the triplet quenching reaction.