Publications

Abstract In this work, an advanced oxidation process using ozonation combined with hydrogen peroxide (H2O2) and catalyzed by manganese (Mn2+) in alkaline conditions was investigated to degrade the organic matter present in a synthetic dairy wastewater (SDW) with a chemical oxygen demand (COD) of 2.3 g L-1. The effect of independent factors such as pH (7-13), H2O2/O-3 ratio (0-1), and Mn2+ concentration (0-1.71 g L-1) has been evaluated and the process optimized using a factorial design and a central composite design (CCD) in sequence. The experiment has been made in batch trials using 2 L of SDW in which ozone was bubbled during 2 h and samples collected for COD analyses, used as response variable. In the factorial experiment, the effect of H2O2 was not significant for all the ratios tested (p value > 0.10), and the effects of the pH and Mn2+ were positive and significant (p value = 0.05). In the CCD, the linear (positive) and quadratic (negative) effects of pH and Mn2+ were significant (p values = 0.05 and = 0.10, respectively). According to the response optimizer, the optimal condition for the ozonation catalyzed by manganese at alkaline medium (COD removal of 69.4%) can be obtained in pH 10.2 and Mn2+ concentration of 1.71 g L-1. Moreover, COD removals above 60% can be obtained for pH values of 9.5 to 11 and Mn2+ concentrations of 0.6 g L-1.

Abstract The authors have synthesized water-dispersible NaYF4:Er3+/Yb3+ upconversion particles via a thermal decomposition route and optimized the green upconversion emission through a concentration variation of the Yb3+ sensitizer. The prepared particles were found to be ellipsoid in shape having an average particle dimension of 600 × 150 nm. It is observed that the sample with 18 mmol% Yb3+ ion concentration and 2 mmol% Er3+ ion gives optimum upconversion intensity in the green region under 980 nm excitation. Colloidal dispersibility of the sample in different solvents was checked and hexane was found to be the best medium for the prepared particles. The particle size of the sample was found to be suitable for the preparation of colloidal ink and security writing on a plain sheet of paper. This was demonstrated successfully using ink prepared in polyvinyl chloride gold medium. © 2018 Astro Ltd.

Abstract In this study, we examined the thickness of the electrical double layer (EDL) in ionic liquids using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. We focused on BF4- anion adsorption from the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) ionic liquid on the Au(111) surface. At both DFT and MD levels, we evaluated the capacitance-potential dependence for the Helmholtz model of the interface. Using MD simulations, we also explored a more realistic, multilayer EDL model accounting for the ion layering. Concurrent analysis of the DFT and MD results provides a ground for thinking whether the electrical double layer in ionic liquids is one- or multi-ionic-layer thick.

Abstract Mixing of ionic liquids provides new opportunities for their tuning, enabling the applications of ionic liquid mixtures to expand. At the same time, the genesis of the fundamental properties of ionic liquid mixtures is still poorly understood. In this study we carried out a molecular dynamics simulation of binary mixtures of 1-buthyl-3-methylimidazolium hexafluorophosphate, 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-buthyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate ([C(4)mim][PF6] + [C(4)mim][NTf2], [C(4)mim][PF6] + [C(4)mim][FAP], [C(4)mim][FAP] + [C(4)mim][NTf2]) in a wide concentration range at 303.15 K and complemented it with quantum mechanical calculations. Three pure ionic liquids underwent the same kind of analysis for comparison purposes. We found that the addition of the [FAP](-)-anion to a mixture enhances the segregation of non-polar domains and weakens the hydrogen-bond network. The H-bonds in the studied mixtures are rather weak, as follows from QTAIM analysis, with the rarest occurrence for the [FAP](-)-anion. The competition of two anions in the mixtures for the most acidic hydrogen of the 1-butyl-3-methylimidazolium cation is reported. In most of the cases, the smaller anion ([PF6](-) or [NTf2](-)) with stronger charge concentration displaces the bigger one ([NTf2](-) or [FAP](-)) from the preferred coordination site. The existing nano-segregation in some mixtures notably slows down ion diffusion. Our results show that the differences in anion size, shape and nature are the main reasons for nano-segregation and the non-ideal behavior of ionic liquid mixtures.

Abstract Copper (Cu) is an abundant metal in the environment coming from anthropogenic activities and natural sources that, in excess, easily becomes phytotoxic to most species, being its accumulation in plants considered an environmental threat. This study aimed to compare the physiological and molecular responses of Solanum lycopersicum and its wild counterpart Solanum cheesmaniae to Cu stress. In particular, we wanted to address the hypothesis that S. cheesmaniae is more adapted to Cu stress than S. lycopersicum, since the former is equipped with a more efficient antioxidant defense system than the latter. Biomarkers of oxidative status (lipid peroxidation, hydrogen peroxide (H2O2) and superoxide anion (O-2(center dot-)) levels) revealed a more pronounced imbalance in the redox homeostasis in shoots of S. lycopersicum than in S. cheesmaniae in response to Cu. Furthermore, the activity of key antioxidant enzymes clearly differed in both species in response to Cu. Catalase (CAT) activity increased in S. cheesmaniae shoots but decreased in the domestic species, as well as ascorbate peroxidase (APX). Both species preferentially accumulated Cu in the radicular system, although a great increase in the aerial parts of S. lycopersicum was measured, while in leaves of Cu-treated S. cheesmaniae, the levels of Cu were not changed. Overall, results validated the hypothesis that S. cheesmaniae is more tolerant to excess Cu than S. lycopersicum and the data provided will help the development of breeding strategies toward the improvement of the resistance/tolerance of cultivated tomato species to heavy metal stress.

Abstract Disruption of cell-cell communication or quorum sensing (QS) is considered a stimulating approach for reducing bacterial pathogenicity and resistance. Although several QS inhibitors (QSIs) have been discovered so far their clinical use remains distant. This problem can be circumvented by searching for QSI among drugs already approved for the treatment of different diseases. In this context, antibiotics have earned special attention. Whereas at high concentrations antibiotics exert a killing effect, at lower concentrations they may act as signaling molecules and as such can modulate gene expression. In this study, the antibiotic furvina was shown to be able to cause inhibition of the 3-oxo-C12-HSL-dependent QS system of Pseudomonas aeruginosa. Furvina interacts with the LasI/LasR system. The data were validated by modeling studies. Furvina can also reduce biofilm formation and decrease the production of QS-controlled virulence factors.

Abstract Overuse of pesticides has resulted in environmental problems, threating public health through accumulation in food chains. Phytoremediation is a powerful technique to clean up contaminated environments. However, it is necessary to unravel the metabolic mechanisms underlying phytoremediation in order to increase the efficiency of this process. Therefore, growth, physiological and biochemical responses in leaves and roots of Solanum nigrum L. exposed to the commonly used fungicide metalaxyl were investigated. This species shows characteristics that make it valuable as a potential tool for the remediation of organic pollutants. We found that once inside the plant, metalaxyl altered carbon metabolism, which resulted in a reduction of growth and lower biomass accumulation due to impairment of carbohydrate production (total soluble sugar, starch, rubisco) and increased photorespiration (glycolate oxidase, Gly/Ser ratio). A significant increase of antioxidant defenses (polyphenols, flavonoids, tocopherols, ascorbate, glutathione, superoxide dismutase, catalase, peroxidases, monodehydroascorbate-and dehydroascorbate reductase, gluthatione reductase) kept reactive oxygen species (ROS) levels under control (superoxide anion) leaving cell membranes undamaged. The results suggest that enhancing carbon assimilation and antioxidant capacity may be target parameters to improve this species' phytoremediation capacities. Highlights Metalaxyl inhibits growth by reducing photosynthesis and inducing photorespiration Elevated antioxidant defenses protect metalaxyl-treated plants from oxidative damage Ascorbate and glutathione are key antioxidants in metalaxyl tolerance.

Abstract Herein, the synthesis and crystal structure of 7-hydroxy-3-(2-methoxyphenyl)-2trifluoromethyl-4H-chromen-4-one, C17H11F3O4, are reported. This isoflavone is used as a starting material in the preparation an array of potent and competitive FPR antagonists. The pyran ring significantly deviates from planarity and the dihedral angle between the benzopyran mean plane and that of the exocyclic benzene ring is 88.18 (4)degrees.In the crystal, O-H center dot center dot center dot O hydrogen bonds connect the molecules into C(8) chains propagating in the [010] direction.

Abstract The strategy of combining electroactive polymers and inorganic nanomaterials has been widely explored in recent years in order to improve some of their properties, namely electrocatalysis and electrochromism. This report focuses on a new composite prepared through the electropolymerization of the transition metal complex [Ni(3-Mesalen)], designated as [1] in the presence of WO3 nanoparticles (NPs) and its electrochromic (EC) performance. The WO3 NPs were prepared using tungsten metal powder; their characterization indicated quasi-spherical morphology, high crystallinity and particle sizes in the range 30-40 nm. The nanocomposite WO3@poly[1] films displayed similar electrochemical responses to those of pristine poly[1] films in LiClO4/CH3CN, but higher electroactive surface coverages, an advantage of NPs incorporation in the nanocomposite. The presence of the WO3 NPs in the poly[1] matrix was assessed by X-ray photoelectron spectroscopy and scanning electronic microscopy. The nanocomposite presented similar electronic spectra to those of poly[1], indicating that the electronic structure of the pristine film is maintained in the nanocomposite, but exhibited lower e-values for bands associated with charge transfer transitions for high oxidised states, revealing an enhanced stability towards ligand over-oxidation. The WO3@ poly[1] nanocomposite showed more favourable EC properties in LiClO4/CH3CN than the pristine film. For typical coverages ( Gamma = 0.06-0.10 mu mol cm (2)) the composite showed lower switching times (tau = 1.3 - 3.6 s), higher optical contrast (Delta T approximate to 31%, an improvement of ca. 40%) and better colouration efficiencies (in the range eta = 104 - 115 cm(2)C (1), improvement of ca. 13 - 22%).