Manef Abderrabba

The prolongation of the lifespan of rats by repeated oral administration of [60]fullerene.

Countless studies showed that [60]fullerene (C(60)) and derivatives could have many potential biomedical applications. However, while several independent research groups showed that C(60) has no acute or sub-acute toxicity in various experimental models, more than 25 years after its discovery the in vivo fate and the chronic effects of this fullerene remain unknown. If the potential of C(60) and derivatives in the biomedical field have to be fulfilled these issues must be addressed. Here we show that oral administration of C(60) dissolved in olive oil (0.8 mg/ml) at reiterated doses (1.7 mg/kg of body weight) to rats not only does not entail chronic toxicity but it almost doubles their lifespan. The effects of C(60)-olive oil solutions in an experimental model of CCl(4) intoxication in rat strongly suggest that the effect on lifespan is mainly due to the attenuation of age-associated increases in oxidative stress. Pharmacokinetic studies show that dissolved C(60) is absorbed by the gastro-intestinal tract and eliminated in a few tens of hours. These results of importance in the fields of medicine and toxicology should open the way for the many possible -and waited for- biomedical applications of C(60) including cancer therapy, neurodegenerative disorders, and ageing.

Representation of VLE and liquid phase composition with an electrolyte model: application to H3PO4–H2O and H2SO4–H2O

Abstract The usual approach in modeling electrolyte systems consists in using only VLE experimental data or derived properties values to adjust the thermodynamic model parameters. In the present work it has been showed that this approach, when applied to H3PO4–H2O and H2SO4–H2O systems, fails to represent the real composition of the liquid phase with a good accuracy. In this paper as it was pointed out in our previous work [1] , we present the result of a new modeling approach based on a large experimental database including Raman spectroscopic liquid phase composition. Both the excess properties (osmotic coefficients) and the speciation in terms of H+, HSO4− and SO42− have satisfactorily been modeled with only six parameters of the Pitzer’s model. Furthermore, several chemical equilibria involving ionic and/or molecular species have been taken into account and calculations were led by solving the problem formulated as Gibbs energy minimization. Our results compare well with experimental data within a large domain of acid concentration.

Effective conjugation in conjugated polymers with strongly twisted backbones: a case study on fluorinated MEHPPV

Conjugated polymers with strongly twisted backbones, such as MEHPPV with fluorinated vinylene units (F-MEHPPV), demand a redefinition of the all-important ‘effective conjugation length’ ECL, which we extract here by a facile graphical method. In MEHPPV (being essentially planar), the ECL coincides with the ‘maximum conducive chain length’ MCC and extends over about n ≈ 9 repetition units (RU). In F-MEHPPV, the MCC is similarly long with n ≈ 8, but the ECL localizes on just one RU. The strong twist in F-MEHPPV persists in the excited state, broadening the emission spectrum and quenching the fluorescence with reduced radiative and enhanced non-radiative rates.

Ligand-modified mesoporous silica SBA-15/silver hybrids for the catalyzed reduction of methylene blue

Mesoporous silica SBA-15 was prepared and functionalized by (3-glycidyloxypropyl)trimethoxysilane in order to bind 2-aminothiazole and aminopropyl-triazole ligands. These groups were immobilized through two distinct chemistry routes: reaction of epoxy with amine resulting in AMT-SBA-15 for the former, and epoxy ring opening followed by 1,3-dipolar cycloaddition click reaction providing Tr-SBA-15, for the latter. These ligand-functionalized SBA-15 materials served as reactive platforms for the in situ deposition of silver nanoparticles from the reduction of silver nitrate. The silver-decorated hybrid Ag/AMT-SBA-15 and Ag/Tr-SBA-15 samples, as well as their precursors, were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherms, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The silver-decorated hybrid materials were evaluated as catalysts for the reduction of methylene blue; the results showed excellent catalytic efficiencies with reduction rate constants of 14.3 × 10−3 and 9.4 × 10−3 s−1 for Ag/Tr-SBA-15 and Ag/AMT-SBA-15, respectively. These values are comparable or higher than those claimed in the literature for similar application.

Sonochemical synthesis of Fe3O4@NH2-mesoporous silica@Polypyrrole/Pd: A core/double shell nanocomposite for catalytic applications

There is a growing interest in sonochemistry for either the controlled design of nanostructured materials or for the synthesis of polymers and polymer composites. It is fast and highly efficient method that provides materials with exceptional and enhanced structural and chemical properties. Herein, we take advantage of the versatile sonochemical process in order to design core/double layered shell nanocomposite denoted by Fe3O4@NH2-mesoporous silica@ PPy/Pd. This magnetic, multicomponent material was designed in a three-step sono-process: (i) synthesis of magnetic core, (ii) cure of mesoporous silica, and (iii) sonochemical deposition of PPy/Pd. This last step was achieved within 1 h, a much shorter duration compared to conventional routes which usually take several hours to few days. The final nanocomposite can be recovered with a simple magnetic stick. X-ray diffraction patterns highlighted the presence of zerovalent palladium on the surface of the magnetic nanocomposite. The catalytic activity of the solid support was investigated by the study of the p-nitrophenol (p-NP) reduction and the Methyl Orange (MO) degradation in aqueous media. Results showed a very high catalytic efficiency, a high conversion yield of p-NP into 4-aminophenol (more than 94%) and an almost entire degradation of MO (99%) with a fast kinetics fitting to the first order model. This work demonstrates conclusively the benefits of sonochemistry in the design of metal nanoparticle-decorated inorganic/polymer hybrid system with outstanding performances.

Triazole/Triazine-Functionalized Mesoporous Silica As a Hybrid Material Support for Palladium Nanocatalyst

Noble and precious metal catalysts are sought for their remarkable efficiency in catalyzing numerous reactions in heterogeneous phase. However, they are costly and require the development of high-surface-area supports that favor their strong immobilization, dispersion, and stability. Toward this end, mesoporous silica-based materials can be regarded as unique supports for nanometric-sized noble metal catalysts provided they are functionalized with appropriate ligands. In this work, mesoporous silica SBA-15 was prepared and modified with 3-azidopropyltriethoxysilane and then clicked with alkyne derivatives of 1,3,5-triazine complex ligand. The resulting hybrid material contains triazole and triazine moieties covalently bound to the mesoporous silica network. The triazole/triazine minidendron was immobilized through a 1,3-dipolar cycloaddition click reaction, which was monitored by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The heterocyclic ligand-functionalized SBA-15 material served as a hybrid reactive platform for in situ deposition of palladium nanoparticles whose size is 3.154 ± 0.49 nm as assessed by X-ray diffraction and confirmed by transmission electron microscopy. The catalytic performance of the final palladium-decorated hybrid triazole/triazine-functionalized SBA-15 support was evaluated in the model reduction of 4-nitrophenol to 4-aminophenol by catalytic hydrogenation and stoichiometric reduction. Excellent catalytic performances were achieved, with reduction rate constant (Kapp) of 16.8 × 10-3 s-1 for this model reaction. Moreover, the hybrid catalyst can be produced in high yield and recycled.

Exploring CO dissociation on Fe nanoparticles by density functional theory-based methods: Fe 13 as a case study

The interactions of CO and of C+O with Fe13 have been studied by the PW91, PW91+U, B3LYP density functional theory-based methods. In each case, various possibilities have been explored for Nα–Nβ. All methods predict an icosahedral structure for the naked particle. Moreover, all density functionals predict CO adsorption on threefold hollow site. Depending on the density functional used, the interaction of CO with the Fe13 cluster induces or not a change in the total number of unpaired electrons and, therefore, of the electronic state. The same situation can appear for the dissociation of adsorbed CO to co-adsorbed C+O. In the most stable configuration, C and O are proximate, bound to a common Fe atom that is oxidized. These results suggest the proper description of the reactivity of magnetic metallic nanoparticles toward dissociation of simple diatomic molecules is likely to involve various spin states, which has implications for the search of the corresponding transition states which cannot be restricted to a single potential energy surface.

Salt addition effect on partition coefficient of some phenolic compounds constituents of olive mill wastewater in 1-octanol-water system at 298.15 K

The 1-octanol-water partition coefficient is an important property to measure the hydrophobicity of organic compounds, which has been demonstrated to be a parameter in studying the conformation of biomolecules in aqueous solutions. For biological systems, electrolytes play an important role in thermodynamic properties. The salt addition effect on the distribution of phenolic compounds between water and 1-octanol at 298.15 K has been studied. The phenolic compounds used were vanillic acid, protocatechuic acid, vanillin, tyrosol, cathecol, caffeic acid and syringic acid, and the considered salts were potassium chloride, sodium chloride and lithium chloride. The influence of both the concentration and size of the added salt on the partition coefficient (Kow) have been considered. This study shows a salting in with the following decreasing order: LiCl > NaCl > KCl. The Gibbs energies of transfer of phenolic compounds (168–1) form chloride solutions to organic phase have been calculated using experimental 1-octanol-water partition coefficients.

Photoionization of Benzophenone in the Gas Phase: Theory and Experiment

We report on the single photoionization of jet-cooled benzophenone using a tunable source of VUV synchrotron radiation coupled with a photoion/photoelectron coincidence acquisition device. The assignment and the interpretation of the spectra are based on a characterization by ab initio and density functional theory calculations of the geometry and of the electronic states of the cation. The absence of structures in the slow photoelectron spectrum is explained by a congestion of the spectrum due to the dense vibrational progressions of the very low frequency torsional mode in the cation either in pure form or in combination bands. Also a high density of electronic states has been found in the cation. Presently, we estimate the experimental adiabatic and vertical ionization energy of benzophenone at 8.80 ± 0.01 and 8.878 ± 0.005 eV, respectively. The ionization energy as well as the energies of the excited states are compared to the calculated ones.

Comparison of iso-eluotropic mobile phases at different temperatures for the separation of triacylglycerols in Non-Aqueous Reversed Phase Liquid Chromatography

Triacylglycerols (TAGs) are a large class of neutral lipids that naturally occur in both plant and animal oils and fats. Their analyses in Non-Aqueous Reversed Phase Liquid Chromatography (NARP) require a mixture of weak solvent (mostly acetonitrile) and strong solvent. In the present work, we have established eluotropic solvent strength scale of several binary mobile phases on C18 bonded silica at different temperatures (acetonitrile/methylene chloride, acetonitrile/acetone, acetonitrile/ethyl acetate, acetonitrile/propan-2-ol, and acetonitrile/butan-1-ol at 25°C, 43°C, 63°C and 85°C); it is based on the methylene selectivity and the use of homologous series. We show that this scale is well suited to the TAGs analysis. The analysis of nine seed oils (Aleurites fordii, Calophyllum inophyllum, Glycina max, Olea europea, Orbignya olifeira, Pinus koraiensis, Pistacia lentiscus, Punica granatum and Ribes nigrum) in iso-eluotropic conditions leads to propose unambiguously the couple MeCN/BuOH at 25°C as the best system to separate TAGs. The use of butanol, as strong solvent, provides very good TAGs congeners separations and avoids the use of chlorinated solvents which gave to this day the best separations.