Photophysical and Theoretical Interpretation of the Insensitive Emission to Temperature of a Metallopolymer Containing Europium Ions.

The luminescence and thermochromic properties of a europium-containing metallopolymer were investigated in experimental and theoretical aspects using the same polymer backbone complexed with two different contents of europium ions (25 and 65% molar). The polymer presented an emission insensitive to temperature variation which was attributed to a balance between two factors: the first is the "stiffening effect" on the polymer backbone brought about by ion complexation, and the second is the interconnection of the alkyl chains because of the rotation of the bipyridine sites required for the complexation.

X-rays sensing properties of MEH-PPV, Alq3 and additive components: a new organic dosimeter as a candidate for minimizing the risk of accidents of patients undergoing radiation oncology.

In this paper, we report our experimental design in searching a smart and easy-to-read dosimeter used to detect 6 MV X-rays for improving patient safety in radiation oncology. The device was based on an organic emissive solutions of poly(2-methoxy-5(2'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV), aluminum-tris-(8-hydroxyquinoline) (Alq3) and additive components which were characterized by UV-Vis absorption, photoluminescence and CIE color coordinate diagram. The optical properties of MEH-PPV/Alq3 solutions have been examined as function of radiation dose over the range of 0-100 Gy. It has shown that MEH-PPV/Alq3 solutions are specifically sensitive to X-rays, since the effect of radiation on this organic system is strongly correlated with the efficient spectral overlap between Alq3 emission and the absorption of degraded MEH-PPV, which alters the color and photoemission of MEH-PPV/Alq3 mixtures from red to yellow, and then to green. The rate of this change is more sensitive when MEH-PPV/Alq3 is irradiated in the presence of benzoyl peroxide than when in the presence of hindered phenolic stabilizers, respectively, an accelerator and an inhibitor to activate or inhibit free radical formation. This gives rise to optimize the response curve of the dosimeter. It is clear from the experimental results that organic emissive semiconductors have potential to be used as dedicated and low-cost dosimeters to provide an independent check of beam output of a linear accelerator and therefore to give patients the opportunity to have information on the dose prescription or equipment-related problems a few minutes before being exposed to radiation.

Correlations between conjugation length, macromolecular dynamics, and photophysics of phenylene-vinylene/aliphatic multiblock copolymers.

This work reports a detailed spectroscopy study of a series of multiblock conjugated nonconjugated copolymers built by p-phenylene vinylene type units (PV) and octamethylene spacers, namely, poly(1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-ethenylene) (LaPPS18). The relative proportions of the PV and aliphatic segments were estimated on the basis of solid-state NMR and Raman spectroscopy. The overall structure was characterized by wide angle X-ray diffraction; (1)H wide-line dipolar chemical shift correlation (DIPSHIFT), and centerband-only detection of exchange (CODEX) NMR data, that together with glass transition temperatures allowed us to identify the groups involved in the molecular dynamics. These different structural properties were used to explain the photoluminescence properties in terms of peak position and spectral profile.

Polymer light emitting diode using PFT--poly(9,9'-n-dihexil-2,7-fluorenodiilvinylene-alt-2,5thiophene).

The development of new electroluminescence polymers for specific colour tuning in Polymer Light Emitting Devices (PLEDs) is currently one of the most important fields for organic electronics. This work reports a synthesis of a new electroluminescent polymer and the concomitant test as PLED emissive layer. The polymer, synthesised from fluorene, is poly(9,9'-n-dihexil-2,7-fluorenodiilvinylene-alt-2,5thiophene) or PFT. The luminescence shows large bands with maxima around 480 nm in absorption and 560 nm in emission. The device was made in a three layer structure, with PEDOT:PSS as hole transport layer, PFT as emissive layer and butyl-PBD as electron transport layer. The electroluminescence spectrum shows a strong band peaked at 540 nm. For an applied voltage of 12 Volt, the brightness at normal angle of viewing is near 10 cd/m2 and the luminous efficiency is of 0.01 lm/W. A discussion about carrier transport and the electroluminescence properties is made.