Indirect consequences of exciplex states on the phosphorescence lifetime of phenazine-based 1,2,3-triazole luminescent probes.

The optical properties of phenazine derivative probe solutions involving intersystem crossing from singlet to triplet states were investigated by time resolved spectroscopy. The room temperature phosphorescence emission presented different time responses when Cd2+ ions were bound to the probe chemical structure. The complex exciplex formation observed to occur in this case was not directly responsible for the change in the phosphorescence lifetime. This was more influenced by the new molecular conformation and modified spin-orbit coupling imposed by the binding of the Cd2+ ions to the phenazine molecules.

Selective endocytic trafficking in live cells with fluorescent naphthoxazoles and their boron complexes.

Fluorescent naphthoxazoles and their boron derivatives have been synthesized and applied as superior and selective probes for endocytic pathway tracking in live cancer cells. The best fluorophores were compared with the commercially available acridine orange (co-staining experiments), showing far better selectivity.

Characterization of a sulfonated polycarbonate resistive humidity sensor.

In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11-90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results.

Physicochemical study of floranol, its copper(II) and iron(III) complexes, and their inhibitory effect on LDL oxidation.

The antioxidant activity of floranol (3,5,7,2'-tetrahydroxy-6-methoxy-8-prenylflavanone), a new flavonoid isolated from the roots of Dioclea grandiflora, was evaluated by the inhibition of human low-density lipoprotein (LDL) oxidation. Floranol increased its oxidation lag-phase significantly in a dose-dependent manner. As the antioxidant mechanism may involve metal coordination, we have undertaken a detailed study of floranol interactions with Cu(II) and Fe(III) by combination of UV-visible (UV-Vis) and mass spectrometries and cyclic voltammetry. The acidity constants of the ligand as well as the stability constants of the metal complexes were calculated. The pKa values of 6.58, 11.97 and 13.87 were determined and the following acidity order is proposed 7-OH>5-OH>2'-OH. The best fit between experimental and calculated spectra was obtained assuming the formation of two Cu(II) complexes: [CuL] logbeta=19.34+/-0.05 and [CuL(2)](2-) logbeta=26.4+/-0.10 and three Fe(III) complexes: [FeL(3)](3-) logbeta=44.72+/-0.09, [FeL(2)](-) logbeta=35.32+/-0.08 and [FeL](+) logbeta=19.51+/-0.04. In addition, copper and iron reduction is less favorable in the presence of floranol. These results indicate that floranol can efficiently bind Cu(II) and Fe(III) ions thus preventing their effect on LDL oxidation.

Correlation between thermal, optical and morphological properties of heterogeneous blends of poly(3-hexylthiophene) and thermoplastic polyurethane.

A correlation between thermal, optical and morphological properties of self-sustained films formed from blends of poly(3-hexylthiophene) (P3HT) and thermoplastic polyurethane (TPU), with 1, 10 and 20 wt% of P3HT in TPU, is established. Images of scanning electron microscopy (SEM) show the formation of domains of P3HT into the TPU matrix, characterizing the blend material as heterogeneous. The heat capacity (C(p)) dependence on P3HT contents was investigated in a large temperature interval. In the region of the TPU glass transition, the difference between the experimental and predicted ΔC(p) values is more pronounced for the 1 wt% case, which strongly suggests that in this case there is a higher influence of the P3HT chains on the TPU matrix. The SEM images for the 1 wt% blended film present the formation of the smallest P3HT domains in the TPU matrix. The relatively high reduction of the PL intensity of the pure electronic transition peak in the 1 wt% blended film, in comparison to the other blended films and also to a pure P3HT film, favours the assumption that the smallest P3HT domains are at the origin of a more structural disordered character. This fact is in agreement with the results obtained by Raman spectroscopy and also by photoluminescence resolved by polarization in stretched self-sustained films, showing an ample correlation between morphological, thermal and optical properties of these blended materials. In addition, the thermoplastic properties of the polyurethane configure very good conditions for tensile drawing of P3HT and other conjugated polymer molecules.