Publications

Abstract This work aims at providing experimental and theoretical information about the water-perfluorocarbon molecular interactions. For that purpose. experimental solubility results for water in cyclic and aromatic perfluorocarbons (PFCs), over the temperature range between (288.15 and 318.15) K, and at atmospheric pressure. were obtained and are presented. From the experimental solubility dependence on temperature, the partial molar solution and solvation thermodynamic functions such as Gibbs free energy, enthalpy and entropy were determined and are discussed. The process of dissolution of water in PFCs is shown to be spontaneous for cyclic and aromatic compounds. It is demonstrated that the interactions between the non-aromatic PFCs and water are negligible while those between aromatic PFCs and water are favourable. The COSMO-RS predictive capability was explored for the description of the water solubility in PFCs and others substituted fluorocompounds. The COSMO-RS is shown to be a useful model to provide reasonable predictions of the solubility values, as well as to describe their temperature and structural modifications dependence. Moreover, the molar Gibbs free energy and molar enthalpy of solution of water are predicted remarkably well by COSMO-RS while the main deviations appear for the prediction of the molar entropy of solution.

Abstract The present work studied and compared the capacity of four important olive oil polyphenolic compounds, oleuropein, hydroxytyrosol, and the oleuropein aglycones 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA), to protect red blood cells (RBCs) from oxidative hemolysis induced by the physiological initiator H(2)O(2). The amount of hemolysis was evaluated spectrophotometrically. The compounds were also tested in the presence and absence of the naturally occurring antioxidant ascorbic acid. All compounds were revealed to significantly protect RBCs from oxidative hemolysis induced by H(2)O(2) at 40 and 80 mu M, with the order of activity being 3,4-DHPEA-EDA > 3,4-DHPEA-EA > hydroxytyrosol = oleuropein. At 20, 10, and 5 mu M, only 3,4-DHPEA-EDA showed a significant protection against the oxidative injury. In the presence of ascorbic acid at physiological concentration, the addition of individual compounds at 40 mu M increased the stability of erythrocytes. The addition of phenolic compounds at 20 and 10 mu M did not produce further protection when compared with the protection given by ascorbic acid alone, except for 3,4-DHPEA-EDA. This compound was shown to produce further protection even at 5 mu M. In summary, 3,4-DHPEA-EDA plays an important protective role against reactive oxygen species-induced oxidative injury in RBCs, and this effect is more potent than the one evidenced by hydroxytyrosol or oleuropein.

Abstract An optical fiber sensor for Hg(II) in aqueous solution based on sol-gel immobilized carbon dots nanoparticles functionalized with PEG(200) and N-acetyl-t-cysteine is described. This sol-gel method generated a thin (about 750 nm), homogenous and smooth (roughness of 2.7 +/- 0.7 a) film that immobilizes the carbon dots and allows reversible sensing of Hg(II) in aqueous solution. A fast (less than 10 s), reversible and stable (the fluorescence intensity measurements oscillate less than 1% after several calibration cycles) sensor system was obtained. The sensor allow the detection of submicron molar concentrations of Hg(II) in aqueous solution. The fluorescence intensity of the immobilized carbon dots is quenched by the presence of Hg(II) with a Stern-Volmer constant (pH = 6.8) of 5.3 x 10(5) M(-1).

Abstract While cationic/anionic surfactant mixtures have been reported to form strongly non-ideal mixed aggregates in aqueous solution the micellization of true catanionic surfactants i e the salt free ion paired compounds obtained from the mixtures has been much less investigated However if there is a significant solubility mismatch between the paired chains these surfactants may show less conventional aggregation features in water such as a temperature driven vesicle-micelle transition and the coexistence of two lamellar phases in equilibrium In this work we carry out micellization studies for a catanionic surfactant of the type C(16)(+)C(8)(-) cetyltrimethylammonium octylsulfonate (TASo) by surface tension and conductivity measurements For comparison purposes the catanionic mixture cetyltrimethylammonium bromide (CTAB)/sodium octylsulfonate (SOSo) at different mixing ratios and the neat SOSo have also been studied For the non ideal CTAB/SOSo mixture Rubingh s model has been applied to determine the beta interaction parameter and the mixed micelle composition The cmc of TASo has been investigated as a function of temperature salt and excess ionic surfactant displaying some differences with respect to conventional ionic and nonionic surfactants The trends in the thermodynamic parameters of micellization of the three types of systems are comparatively rationalized

Abstract The thermal behavior for three homologous series of cationic geminis surfactants of the type n-2-n, alkanediyl-alpha,omega-bis(alkyldimethylammonium bromide), with n = 12, 14, 16, and 18, and sodium alkyl sulfates, SC (m) S, with m = 12, 14, and 16, is reported here. The cationic/anionic molar ratio is kept at 1:2 (equicharged mixtures), and salt is also present. Polarizing light microscopy and differential scanning calorimetry show a stepwise fusion for the mixtures with appearance of several mesophases between the crystalline structures and the isotropic liquid. A main endothermic transition is observed, associated with partial chain melting and consequent loss of crystalline order, followed by a transition to a smectic liquid crystal. The phase transition thermodynamics is interpreted in terms of an interplay between van der Waals chain-chain interactions and ionic head group interactions.

Abstract Salt-free ion-paired catanionic amphiphiles of the C(m)(+) C(n)(-) type, with a high solubility mismatch (n >> m or m >> n) display a remarkable phase behavior in water. A temperature-driven vesicle-to-micelle transition in the dilute side together with a coexistence of two lamellar phases oil the concentrated side is one of the peculiar effects that have been reported for the hexadecyltrimethylammonium octylsulfonate surfactant, C(16)C(8) or TA(16)So(8) (extensive to C(14)C(8) and C(12)C(8)). In this work, with TA(16)So(8) as a reference, the cationic trimethylammonium (TA(+)) and pyridinium (P(+)) headgroups are combined with the anionic sulfate (S(-)) and sulfonate (So(-)) headgroups to yield other C(16)C(8) compounds: hexadecyltrimethylammonium octylsulfate (TA(16)S(8)) 1-hexadecylpyridinium octylsulfonate (P(16)So(8)), and 1-hexadecylpyridinium octylsulfate (P(16)So(8)). We show that, if the asymmetry of the chain lengths is kept constant at C(16)C(8) and the headgroup chemistry is changed, most of the unusual self-assembly properties are still observed, indicating that they are not system-specific but extensive to other combinations of headgroups and mainly dictated by the ion-pair solubility mismatch. Thus, all the compounds in water quite remarkably show a lamellar-lamellar phase coexistence and spontaneously form vesicles upon solubilization. Moreover, P(16)So(8) undergoes at temperature-driven vesicle-to-micelle transition that involves an intermediate planar lamellar state, similar to TA(16)So(8). Some interesting effects on the global phase behavior, however, do arise when the headgroups are changed, Geometric packing effects are shown to be important, but the differences in phase behavior seem to be mainly dictated by (i) the charge density of the headgroups, which tunes the solubility mismatch of the ion-pair, and (ii) specific interactions between headgroups, which affect the short-range repulsive force that controls the swelling of the concentrated lamellar phase,

Abstract The synthesis and functionalization of carbon nanoparticles with PEG(200) and mercaptosuccinic acid, rendering fluorescent carbon dots, is described. Fluorescent carbon dots (maximum excitation and emission at 320 and 430 nm, respectively) with average dimension 267 nm were obtained. The lifetime decay of the functionalized carbon dots is complex and a three component decay time model originated a good fit with the following lifetimes: tau (1) = 2.71 ns; tau (2) = 7.36 ns; tau (3) = 0.38 ns. The fluorescence intensity of the carbon dots is affected by the solvent, pH (apparent pK (a) of 7.4 +/- 0.2) and iodide (Stern-Volmer constant of 78 +/- 2 M-1).

Abstract The great importance of distinguishing and identifying olive cultivars has been recognized since Roman times. Several classification schemes have been tried based on botanic, ecological, morphological, commercial, and agronomical characteristics. Presently there are a great number of different olive cultivars showing a diversity of morphological and physiological characteristics that result in quite different qualities and uses. However, the olive quality cannot be directly measured, and several indirect measurements, for example fruit and endocarp features, must be correlated with the olive quality and cultivar. This chapter shows that from morphological features of olives (fruit and endocarp) and olive trees (including trees, branches, leaves and flowers) coupled with chemometric multivariate classification techniques, classes of olives from different cultivars are naturally observed. Mixing morphological features from olive fruit and endocarp, classification rules with potential to be applied in the quality control of olives and, consequently, in the Denomination of Protected Origin (DOP) assessment can be developed. Also, it is observed that olive trees can be characterized using classification rules based on leaf and flower features. © 2010 Copyright

Abstract In this work, mutual solubilities of two [PF6]-based ionic liquids (ILs) with water and their thermophysical properties, namely, melting properties of pure ILs and densities and viscosities of both pure and water-saturated ILs, were determined. The selected Its comprise 1-methyl-3-propylimidazolium and 1-methyl-3-propylpyridinium cations combined with the anion hexafluorophosphate. Mutual solubilities with water were measured in the temperature range from (288.15 to 318.15) K. From the experimental solubility data dependence on temperature, the molar thermodynamic functions of solution, such as Gibbs energy, enthalpy, and entropy of the ILs in water were further derived. In addition, a simulation study based on the COSMO-RS methodology was carried out. For both pure ILs and water-equilibrated samples, densities and viscosities were determined in the temperature interval between (303.15 and 373.15) K. The isobaric thermal expansion coefficients for pure and water-saturated ILs were calculated based on the density dependence on temperature.

Abstract A Knudsen mass-loss effusion technique was used for measuring the vapor pressures at different temperatures of the following crystalline compounds: anthraquinone (CAS No. 84-65-1), between (377.06 and 395.03) K; anthrone (CAS No. 90-44-8), between (346.15 and 365.14) K; thianthrene (CAS No. 92-85-3), between (344.27 and 264.06) K; thioxanthone (CAS No. 492-22-8), between (369.12 and 387.20) K; and xanthone (CAS No. 90-47-1), between (342.22 and 362.22) K. From the temperature dependence of the vapor pressure of each crystalline compound, the standard (p degrees = 10(5) Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. The measured thermodynamic properties are compared with literature results for similar compounds, and correlations for estimation of the vapor pressures and enthalpy of sublimation for anthracene-like compounds are presented.