Determination of fluorescence lifetimes of fluorescein from fluorescence quenching data

Abstract

The fluorescence quenching of fluorescein by 1,4-benzoquinone (BQ) in five solvents – methanol, ethanol, phosphate buffer saline (PBS, pH 7.4), N,N'-dimethylformamide (DMF) and dimethylsulphoxide (DMSO) is hereby investigated. Fluorescein’s fluorescence was effectively quenched by BQ, and the quenching was dynamic (purely collisional) within the BQ’s concentration range (0.001 to 0.004 M) used in this work. Accordingly, the quenching data were in conformity with the Stern-Volmer’s model. Stern-Volmer’s constant (KSV) values range between 17.4 in DMSO and 43.4 in methanol. KSV values, together with the calculated bimolecular rate constants (kD) in the respective solvents, were used to semi-empirically estimate the fluorescence lifetimes (tF) of fluorescein in the individual solvents. Just as for KSV values, tF values are solvent-viscosity dependent, with the lowest values being obtained in methanol and the highest in DMSO, which are the least and most viscous solvents respectively. tF values obtained in this work are 3.55, 3.71, 3.78, 4.13 and 4.51 ns (in methanol, PBS 7.4, ethanol, DMF and DMSO, respectively).

Aluminum Phthalocyanine−[60]Fullerene Supramolecular Dyads: Synthesis, Photophysical Properties and ROS Photogeneration

“…Precursors of supramolecular dyads were synthesized by the described methods: aluminum phthalocyanine chloride PcAl, [28] cyclopropane fullerene derivativephenyl-C60-butyric acid (I) [29] for dyad III and pyrrolidinofullerene -C60-substituted benzoic acid (II) [30] for dyad IV.…”

“…The attachment of fullerene derivatives to PcAl by extracoordination has practically no effect on the shape and position of the Qband maximum, except for slight differences in the region of its vibrational satellites. Due to the low solubility of PcAl in pyridine, its concentration was additionally determined from the known extinction coefficient (log ε676 = 5.31 in DMF [28] ). The solubility of supramolecular dyads III and IV in pyridine significantly exceeds the solubility of the native dye PcAl.…”