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A Comparative Study on the Photophysical and Photochemical Properties of Dyes in the Presence of Low Generation Amino‐terminated Polyamidoamine Dendrimers
Author(s) -
Grassano Micaela E.,
Altamirano Marcela S.,
Militello María P.,
Arbeloa Ernesto M.,
Previtali Carlos M.,
Bertolotti Sonia G.
Publication year - 2018
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.13033
Subject(s) - dendrimer , xanthene , chemistry , photochemistry , quenching (fluorescence) , fluorescence , absorption (acoustics) , reaction rate constant , binding constant , absorption spectroscopy , kinetics , polymer chemistry , binding site , materials science , physics , quantum mechanics , composite material , biochemistry
The photophysical and photochemical properties of the xanthene dyes mercurochrome ( MC r) and eosin‐Y (Eos); and the phenazine dye safranine‐O ( SF ) are evaluated in the presence of amino‐terminated polyamidoamine ( PAMAM ) dendrimers of low generations. The dendrimers produce a red shift in the UV ‐vis absorption spectra of the dyes, which increases with concentration and the size of the PAMAM molecule. The Stern–Volmer plots of fluorescence quenching for xanthenic dyes present a downward curvature. It is ascribed to a static mechanism involving a dye–dendrimer binding. A non‐linear fitting of the SV plots allows the calculation of the binding constants. For SF , the fluorescence is only slightly quenched by PAMAM s and the SV plots are linear. The binding constants are in the order K bind ( SF ) ≪ K bind (Eos) < K bind ( MC r). The difference must be due to important specific structural effects. A decrease in the triplet lifetime and an increase in the absorption of the semireduced form of the dyes are observed in the presence of dendrimers. While for the two xanthene dyes, the rate constants reach the diffusional limit for G2 and G3, for SF they are one order of magnitude lower. This is explained by a different quenching mechanism of the two types of dyes.