Publications

Abstract Oxidative stress and mitochondrial dysfunction have been associated with metabolic and agerelated diseases. Thus, the prevention of mitochondrial oxidative damage is nowadays a recognized pharmacological strategy to delay disease progression. Epidemiological studies suggested an association between the consumption of polyphenol-rich diet and the prevention of different pathologies, including diseases with a mitochondrial etiology. The development of mitochondrialtargeted antioxidants based on dietary antioxidants may decrease mitochondrial oxidative damage. Herein, we report the design and synthesis of two new mitochondriotropic antioxidants based on hydroxybenzoic acids (AntiOxBENs). The results obtained showed that the novel antioxidants are accumulated inside rat liver mitochondria driven by the organelle transmembrane electric potential and prevented lipid peroxidation, exhibiting low toxicity. Some of the observed effects on mitochondrial bioenergetics resulted from an increase of proton leakage through the mitochondrial inner membrane. The new derivatives present a higher lipophilicity than the parent compounds (protocatechuic and gallic acids) and similar antioxidant and iron chelating properties. AntiOxBENs are valid mitochondriotropic antioxidant prototypes, which can be optimized and used in a next future as drug candidates to prevent or slow mitochondrial oxidative stress associated to several pathologies.

Abstract The paper presents experimental results regarding the electrodeposition and characterization of cobalt and cobalt composites with carbon nanotubes from a choline-chloride-based deep eutectic solvent. Dispersion stability of multi-walled carbon nanotubes (MWCNTs) was excellent in the eutectic solvent used. According to Raman and XRD analysis, the carbon nanotubes were successfully inserted into the metallic matrix. Furthermore, XRD results suggested that the incorporation of CNTs on the deposit promoted a preferred orientation of the Co crystallites on (220) plane. The Co and Co-composites coatings obtained onto a copper substrate are adherent and uniform. Pure Co deposit was formed by sharp edge grains, Co-composites appeared to be less compact and formed by relatively spherical particles connected by MWCNTS. Furthermore, it was found that the presence of MWCNTs contributed to decreasing the deposit's roughness. From corrosion tests, Co-composite films exhibit a comparable or slightly better corrosion performance as compared to pure Co films.

Abstract The self-aggregation, surface properties and foamability of the catanionic surfactant mixture cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate (SOSo) have been investigated to obtain insight on the relation between bulk nanostructures, surfactant packing, and foam stability and aging. Light microscopy, SANS, cryo-TEM, DLS, surface tension, rheometry and direct photography were used to characterize mixtures with varying CTAB molar fraction, xCTAB. In the bulk, self-assembly is richer in the excess CTAB region than in the excess SOSo one. Starting from neat CTAB micelles and on addition of anionic surfactant, there is a change from small ellipsoidal micelles (1 < x(CTAB) <= 0.80) to large rodlike micelles (0.65 <= x(CTAB) < 0.55) and then to vesicles (0 < x(CTAB) <= 0.50), with coexistence regions in between; SOSo-rich mixtures are thus dominated by vesicles. High size polydispersity for the micelles and vesicles is an intrinsic feature of this system. Foam stability is concomitantly impacted by xCTAB. SOSo is a small mobile molecule and so it disrupts foam stability, irrespective of the presence of vesicles. Foams are thus only stable in the CTAB-rich regions, and SANS shows that the shape of micelles and vesicles is unchanged inside the foam. Foam drainage is thereby mostly controlled by the presence of the elongated micelles through the solution viscosity, whereas coarsening is influenced by dense surfactant packing at the gas-liquid interfaces.

Abstract Voltammetric and capacitive studies were carried out on 13 gold single-crystal electrodes, single and stepped faces, in the presence of oxoanions with tetrahedral and planar geometry, but with variable O-O distances, perchlorate, nitrate, sulphate and phosphate. The results indicate that the effect of the introduction of steps on single crystal is seen as “regular” features on surface reconstruction, Au-water interactions, and oxoanion adsorption. When the terraces are wide the predominant effects are related to the orientation of the terrace. However, the relation between terrace-step orientation also plays an important role in the behavior of stepped faces.

Abstract The deposition of Mn and Mn-Sn alloy from two deep eutectic solvents (DES) was investigated. Pure Mn deposits were powdery and amorphous regardless the DES used. In contrast, the manganese-tin deposits obtained from the two DES used were adherent. The morphology of the deposits obtained from the different DES was analyzed by SEM, which showed that pure Mn films were fibrous. The morphology of Mn-Sn deposits changed upon changing on the amount of tin in solution or the DES used. The phase composition of the Mn-Sn films were investigated by X-Ray diffraction, which showed that the deposits were formed by different MnxSny intermetallic phases. The metallic content in the deposit changed upon changing the bath composition or the DES used. Using the urea (U) based DES Mn-Sn deposits with a Sn content between 1.8 and 6.7 wt% were obtained. In contrast, using the ethylene glycol (EG) based DES the Sn content in the deposits varied between 33.2 and 59.0 wt%.

Abstract Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10-60 s, power density similar to 0.002 W mL(-1)), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (similar to 1 W mL(-1)) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1-10(2) pm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (similar to 0.03 W mL(-1)), the flocs break down and re-dispersal occurs. Molecular insight for the mechanism behind this surprising phenomenon is put forth.

Abstract Aqueous micellar two-phase systems (AMTPS) hold a large potential for cloud point extraction of biomolecules but are yet poorly studied and characterized, with few phase diagrams reported for these systems, hence limiting their use in extraction processes. This work reports a systematic investigation of the effect of different surface-active ionic liquids (SAILs) covering a wide range of molecular properties upon the clouding behavior of three nonionic Tergitol surfactants. Two different effects of the SAILs on the cloud points and mixed micelle size have been observed: ILs with a more hydrophilic character and lower critical packing parameter (CPP < 1/2) lead to the formation of smaller micelles and concomitantly increase the cloud points; in contrast, ILs with a more hydrophobic character and higher CPP (CPP >= 1) induce significant micellar growth and a decrease in the cloud points. The latter effect is particularly interesting and unusual for it was accepted that cloud point reduction is only induced by inorganic salts. The effects of nonionic surfactant concentration, SAIL concentration, pH, and micelle zeta potential are also studied and rationalized.

Abstract Numerous reports have shown that the self assembling properties of 12-s-12 bis(quaternary ammonium) gemini surfactants in aqueous solution are significantly influenced by s, the number of methylene groups in the covalent spacer. However, the role played by s on the phase behavior of the single compounds has not been investigated in a similarly systematic way. Here, we report on the thermotropic phase behavior of the anhydrous compounds with s = 2-6, 8, 10, and 12, resorting to differential scanning calorimetry (DSC), polarized light microscopy (PLM), and Xray diffraction (XRD). All of the compounds show a stepwise melting behavior, decomposing at 200 degrees C. As the spacer length increases, nonmonotonic trends are observed for the thermodynamic parameters of the thermotropic phase transitions, mesophase formation, and solid-state door spacings. In particular, the number and type of mesophases (ordered smectic phases and/or fluid smectic liquid crystals) depend critically on s. Further, upon heating molecules with s < 8 decompose before the liquid phase, while those with long spacers, s = 8-12, reach the isotropization (clearing) temperature, hence forming both ionic liquid crystals and ionic liquid phases. We demonstrate that the melting behavior and type of ionic mesophases formed by gemini molecules can be usefully manipulated by a simple structural parameter like the length of the covalent linker.

Abstract This work presents a comprehensive experimental and computational study of the thermodynamic properties of fluorene-2-carboxaldehyde. The crystal vapour pressures of this compound were measured between (335.16 and 355.09) K, using the Knudsen mass-loss effusion method. From these results the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived. The standard molar enthalpy of formation in the crystalline phase at the temperature 298.15 K was derived from the standard molar energy of combustion, determined from combustion calorimetry measurements. This result was combined with the enthalpy of sublimation yielding the standard molar enthalpy of formation in the gaseous phase at T = 298.15 K, that was also derived from a computational study at the G3 and G4 levels. Theoretical calculations were also used to calculate heat capacity and entropy results in the gaseous phase. The enthalpy and temperature of fusion were determined from DSC experiments. From the thermodynamic properties of fusion and sublimation, those of vaporization were derived. The thermodynamic stability of fluorene-2-carboxaldehyde in the crystalline and gaseous phases was evaluated determining the standard Gibbs energies of formation, at the temperature 298.15 K, and compared with the ones reported in the literature for fluorene. (C) 2017 Elsevier Ltd.

Abstract In this work, several simple new equations for predicting important environmental mobility properties, at T = 298.15 K, were derived for halogenated benzenes: standard Gibbs energy of hydration, aqueous solubility, octanol-water partition coefficients, and Henry's law constants. A discussion on our previous estimates of other related properties (standard Gibbs energy and vapor pressure of sublimation and of vaporization) and their relation with entropy of fusion is also presented. As we aimed to estimate these properties for any of the ca. 1500 halogenated benzenes that may exist theoretically, an equation for estimating the temperature of fusion was also derived, since some of the proposed predictive equations (solubility of solids and Gibbs energy of sublimation) require its knowledge. For the other estimated properties just the number of each halogen that replaces hydrogen atoms in the halogenated benzene is needed. It was found that the coefficients that multiply the number of halogen atoms in the predictive equations vary linearly with the volume of the halogen atom.