Temperature resolved aggregate states in dialkoxyphenylene-thiophene oligomer

Multi-conformational monomer and dimer steady-states in domains of a few molecules: the consequences on the phosphorescence emission bands

Dropcast films of very low concentration domains of phenazine 1,2,3-triazole molecules, blended in a Zeonex matrix, were studied by steady-state fluorescence as a function of temperature. These domains, randomly spread in the volume of the films, presented emission characteristics of singlet and triplet states coming from different molecular conformations. Emissions of singlet monomers, dimers or more complex aggregates, as well two distinct triplet phosphorescent bands, were observed to appear concomitantly or in isolated forms. From the analysis of the experimental results, the additional red-shifted phosphorescent band appeared as a consequence of the formation of dimer and/or more complex aggregated states. The emission characteristics of both phosphorescent bands were classified as coming from ensembles of a few interactive molecules. This statement was assumed based on the absence of replica modes of vibrational spin-orbit interactions.

Dynamics of aggregated states resolved by gated fluorescence in films of room temperature phosphorescent emitters

Phenazine derivative molecules were studied using steady state and time resolved fluorescence techniques and demonstrated to lead to strong formation of aggregated species, identified as dimers by time dependent density functional theory calculations. Blended films in a matrix of Zeonex®, produced at different concentrations, showed different contributions of dimer and monomer emissions in a prompt time frame, e.g. less than 50 ns. In contrast, the phosphorescence (e.g. emission from the triplet state) shows no significant effect on dimer formation, although strong dependence of the phosphorescence intensity on concentration is observed, leading to phosphorescence being quenched at higher concentration.

Photodynamic therapy evaluation of methoxypolyethyleneglycol-thiol-SPIONs-gold-meso-tetrakis(4-hydroxyphenyl)porphyrin conjugate against breast cancer cells

Magnetic field enhanced photodynamic therapy is an effective non-invasive technique for the eradication of cancer diseases. In this report, magnetic field enhancement of the photodynamic therapy (PDT) efficacy of a novel methoxypolyethyleneglycol-thiol-SPIONs-gold-meso-tetrakis(4-hydroxyphenyl)porphyrin conjugate (nano-drug) against MCF-7 breast cancer cells was evaluated. The nano-drug exhibited excellent blue and red emissions under suitable ultraviolet (380 nm) and visible (430 nm) excitations and was well taken up by the cells without any significant dark cytotoxicity after 24 h post-incubation. However, after exposure of cells to light for about 15 min, high rate of cell death was observed in a dose-dependent manner. In addition, the cells that were exposed to external magnetic field displayed higher phototoxicity than the non-exposed cells. Altogether, these results suggest that the nano-porphyrin drug system can function as a new promising magnetic-field targeting agent for theranostic photodynamic eradication of cancer diseases.