Rafik Ben Chaâbane

New anthracene-based soluble polymers: optical and charge carrier transport properties

A series of anthracene-based polymers (P1–3) have been synthesized via the Wittig polycondensation. These organic materials were soluble in common organic solvents and show good film-forming abilities. Their macromolecular structures were characterized by NMR, FT-IR spectroscopies and steric exclusion chromatography, their thermal behaviors were analyzed by differential scanning calorimetry and their HOMO-LUMO energy levels were estimated by cyclic voltammetry. The optical properties of these π-conjugated systems were investigated by UV-visible absorption and photoluminescence spectroscopies. The effect of the spacer-group structure on the photo-physical behavior, π-π stacking ability and charge carrier transport properties of the polymer has been studied.

Density of Grafted Chains in Thioglycerol-Capped CdS Quantum Dots Determines Their Interaction with Aluminum(III) in Water

We aimed to quantify the interaction of water-soluble-functionalized CdS quantum dots (QDs) with metal cations from their composition and physical properties. From the diameter of thioglycerol-capped nanoparticles (TG-CdS QDs) measured by electronic microscopy ( D = 12.3 ± 0.3 nm), we calculated the molecular mass of the individual particle MAQD = (3 ± 0.5) × 106 g·mol-1 and its molar absorption coefficient ε450 = 21 × 106 M-1·cm-1. We built a three-dimensional model of the TG-CdS QDs in agreement with the structural data, which allowed us to quantify the number of thioglycerol grafted chains to ∼2000 per QD. This value fully matches the saturation binding curve of Al3+ cations interacting with TG-CdS QDs. The reaction occurred with a slow association rate ( kon = 2.1 × 103 M-1·s-1), as expected for heavy QDs. The photophysical properties of the functionalized QDs were studied using an absolute QD concentration of 7 nM, which allowed us to investigate the interaction with 14 metallic cations in water. The fluorescence intensity of TG-CdS QDs could be quenched only in the presence of Al3+ ions in the range 0.2-10 μM but not with other cations and was not observed with other kinds of grafting chains.

Use of MPA-capped CdS quantum dots for sensitive detection and quantification of Co 2+ ions in aqueous solution

Water soluble CdS quantum dots (QDs) were synthesized by a simple aqueous chemical route using mercaptopropionic acid (MPA) as a stabilizer. These QDs had a fluorescence emission band maximum at 540 nm with a FWHM ∼130 nm and a quantum yield of ∼12%. Transmission electronic microscopy images were used to determine the QD diameter of 8.9 ± 0.4 nm. From this value we calculated the molecular mass M(QD) = 1.17 × 106 g mol-1 and the extinction coefficient at the band edge (450 nm) ε450 = 4.7 × 106 cm-1 M-1, which allowed to determine the true molar concentration of 17 nM for spectroscopic measurements in solution. The fluorescence intensity of MPA-CdS QDs was quenched only in the presence of Co2+ ions, but not in the presence of thirteen other metal cations. The fluorescence quenching of MPA-CdS QDs appeared proportional to the Co2+ concentration in the range 0.04-2 μM. Based on a fluorescence peak position and a lifetime both independent from Co2+ concentration, the quenching mechanism of MPA-CdS QDs appeared static. Because the strong electronic absorption of Co2+ overlaps the emission of QDs, our results can be explained by Förster energy transfer from QD to the bound Co2+ cations.