Publications

Abstract Thermodynamic properties of 3- and 4-phenoxyphenol have been determined by using a combination of calorimetric and effusion techniques as well as by high-level ab initio molecular orbital calculations. The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the condensed and gas states, Delta(f)H(m)degrees(cr or 1) and Delta(f)H(m)degrees(g), at T = 298.15 K, of 3- and 4-phenoxyphenol were derived from their energies of combustion in oxygen, measured by a static bomb calorimeter, and from the enthalpies of vaporization or sublimation derived respectively by Calvet microcalorimetry for the 3-phenoxyphenol and, by Knudsen effusion technique for the 4-phenoxyphenol. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. Furthermore, this composite approach was also used to obtain information about the gas-phase acidities, gas-phase basicities, proton and electron affinities, adiabatic ionization enthalpies, and, finally, O-H bond dissociation enthalpies. The good agreement between the G3MP2B3-derived values and the experimental gas-phase enthalpies of formation for the 3- and 4-phenoxyphenol gives confidence to the estimate concerning the 2-phenoxyphenol isomer, which was not experimentally studied, and to the estimates concerning the radical and the anion. Additionally, the experimental values of gas-phase enthalpies of formation were also compared with estimates based on the empirical scheme developed by Cox.

Abstract The description of the reassembling and testing of a twin heat conduction, high-precision, drop microcalorimeter for the measurement of heat capacities of small samples are presented. The apparatus, originally developed and used at the Thermochemistry Laboratory, Lund, Sweden, has now been reassembled and modernized, with changes being made as regarding temperature sensors, electronics and data acquisition system. The apparatus was thereafter thoroughly tested, using benzoic acid and hexafluorobenzene as test substances. The accuracy of the C(p,m)(c) (298.15 K) data obtained with this apparatus is comparable to that achieved by high-precision adiabatic calorimetry. Here we also present the results of heat capacity measurements on of some polyphenyls (1,2,3-triphenylbenzene, 1,3,5-triphenylbenzene, p-terphenyl, m-terphenyl, o-terphenyl, p-quaterphenyl) at T = 298.15 K, measured with the renewed high precision heat capacity drop calorimeter system. The high resolution and accuracy of the obtained heat capacity data enabled differentiation among the ortho-, meta-, and para-phenyl isomers.

Abstract Porous phosphate heterostructures (PPH), functionalized with different ratios of aminopropyl and mercaptopropyl groups, labelled as N(x=5,25,50)-PPH and S(x=5,25,50)-PPH, respectively, were tested as adsorbents for Ni(II) and Hg(II) found in industrial sewage from electroplating processes and button battery recycling. X-ray diffraction was used to study the structures. The specific surface area of the pristine material (PPH) was 620 m(2) g(-1), whereas the specific surface areas of the modified mercaptopropyl (S(5)-PPH) and aminopropyl (N(5)-PPH) were 472 and 223 m(2) g(-1), respectively. The adsorption data were fitted to a Langmuir isotherm model. The S(5)-PPH material was saturated by 120 mmol Hg(II) per 100 g of material, whereas for Ni(II) adsorption, N(25)-PPH material displayed the highest adsorption with a saturation value of 43.5 mmol per 100 g. These results suggest that functionalized PPH materials may be promising toxic metal scavengers and that they may provide an alternative environmental technology.

Abstract We herein report the reversible formation of a planar lamellar phase as an intermediate structure in a vesicle-micelle transition induced by temperature, for a salt-free catanionic surfactant-water system. Turbidity, small-angle neutron scattering, dynamic light scattering and microscopy data altogether demonstrate that the vesicles formed by hexadecyltrimethylammonium octylsulfonate (TA(16)So(8)) in water fuse at high temperature into planar lamellae before transforming into elongated micelles. On cooling the micelles first nucleate into lamellae, and only then vesicles appear through lamellae fission. This behavior is both intriguing and counter-intuitive, since a monotonous dependence of the spontaneous curvature of the surfactant film on temperature should be expected.

Abstract In this paper, we investigate the phase behavior and microstructure for a series of salt-free catanionic surfactants of the type Cm+Cn- with varied chain length mismatch (m not equal n), using light microscopy, DSC, turbidity, surface tension, SAXS and SANS. The compounds consist of alkyltrimethylammonium alkylsulfonates, denoted by TA(m)So(n). Depending on the asymmetry between both ions, three regimes can be identified: (i) weakly asymmetric; (ii) approximately symmetric; and (iii) highly asymmetric. For the TA(16)So(n) compounds, with n = 8 and 9 (weakly asymmetric), the surfactant forms a lamellar phase in water, however, with a striking miscibility gap. This miscibility gap is a consequence of the concentration dependent bilayer charge density. For n = 8, also a temperature-dependent vesicle-to-micelle transition at low surfactant concentration is observed. When the mismatch is low (n = 10) only a non-swelling lamellar phase is formed (approximately symmetric regime). For high mismatch, (n = 6 and 7) an extensive micellar phase is obtained - highly asymmetric regime. Conversely, for the TA(m)So(8) compounds, where m = 12 and 14, the unconventional lamellar miscibility gap and vesicle-micelle transition are again present. These findings are rationalized by considering the effect of film charge density-arising from the chain solubility difference-on the spontaneous curvature and balance of colloidal forces. The type of phase behavior reported here should be extensive to other families of salt-free catanionic amphiphiles, where an appropriate tuning of the solubility mismatch can allow the control of self-assembly.

Abstract In the present work a set of five Ni(II) complexes with general formula [Ni(L)(2)] and with HL = N-thenoylthiocarbamic-O-n-alkylylesters (n = 2-6) has been prepared and characterized in solution by UV-vis and NMR spectroscopies. Three of them were also characterized in the solid state by X-ray diffractometry. The energy rotation of the thiophene ring of ligand was evaluated theoretically. Liposomes of complexes were prepared in order to evaluate their ability to interact with the membrane. Furthermore, their biological activities were evaluated in a set of bacteria (gram+ and gram-) and yeasts. The X-ray structure determination confirms that bidentate ligand forms a tetra co-ordinated complex with an S2O2 co-ordination sphere around the nickel(II) ion in a cis configuration. The metal centre is coordinated in a square planar fashion. NMR spectra taken in solution show a diamagnetic signal compatible with a square-planar geometry around the metal centre. The values obtained for the liposome/water partition coefficients (K-p) show that [Ni(ttete)(2)] and [Ni(ttpre)(2)] have a similar membrane partition ability, whilst the [Ni(ttbue)(2)] derivative presents a significantly higher K-p, describing a stronger interaction within the membrane. For all the compounds, [Ni(ttpre)(2)] has a higher efficacy against Gram negative bacteria and yeasts nevertheless, the anti-yeast and anti-bacterial activity values of all tested compounds are lower than ones of the reference compounds.

Abstract The performance of multivariate curve resolution (MCR-ALS) to decompose sets of excitation emission matrices of fluorescence (EEM) of nanocomposite materials used as analytical sensors was assessed. The two fluorescent nanocomposite materials were: NH(2)-polyethylene glycol (PEG200) functionalized carbon dots, sensible to aqueous Hg(II) (CD); and, CdS quantum dots attached to the dendrimer DAB, sensible to the ionic strength of the aqueous medium (CdS-DAB). The structures of these sets of EEM, obtained as function of the Hg(II) concentration and ionic strength, are characterized by collinear properties (CD) and non-linear spectral variations (CdS-DAB). MCR-ALS was able to detect that the source of the collinearities is the presence of different size CD that show similar affinity towards Hg(II). Moreover, MCR-ALS was able to model the non-linear spectral variations of the CdS-DAB that are induced by varying ionic strength. The chemometric preprocessing of the fluorescent data sets using soft-modelling multivariate curve resolution like MCR-ALS is a critical step to transform these nanocomposites with interesting fluorescent proprieties into analytical useful nanosensors.

Abstract Among new potential solvents for lignocellulosic materials, ionic liquids (ILs) are attracting considerable attention. Hence, the knowledge of the thermophysical properties of such fluids is essential for the design of related industrial processes. Therefore, in this work, a set of thermophysical properties, namely, density, viscosity, and refractive index, as a function of temperature, and isobaric thermal expansivity and heat capacities at a constant temperature, were determined for eight ionic liquids with the 1-ethyl-3-methylimidazolium cation combined with the following anions: acetate, methylphosphonate, methanesulfonate, trifluoromethanesulfonate, dicyanamide, thiocyanate, tosylate, and dimethylphosphate. Imidazolium-based HA were chosen since these are the most studied ionic fluids in biomass dissolution approaches, while a large array of anions was investigated because it was already demonstrated that it is the IL anion that mainly governs the dissolution.

Abstract Electrospray ionization mass spectrometry with variable collision induced dissociation of the isolated [(cation)(2)anion](+) and/or [(anion)(2)cation] ions of imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ionic liquids (Its) combined with a large set of anions, such as chloride, tetrafluoroborate, hexafluorophosphate, trifluoromethane-sulfonate, and bis[(trifluoromethyl)sulfonyl]imide, was used to carry out a systematic and comprehensive study on the ionic liquids relative interaction energies. The results are interpreted in terms of main influences derived from the structural characteristics of both anion and cation. On the basis of quantum chemical calculations, the effect of the anion upon the dissociation energies of the ionic liquid pair, and isolated [(cation)(2)anion](+) and/or [(anion)(2)cation](-) aggregates, were estimated and are in good agreement with the experimental data. Both experimental and computational results indicate an energetic differentiation between the cation and the anion to the ionic pair. Moreover, it was found that the quantum chemical calculations can describe the trend obtained for the electrostatic cation anion attraction potential. The impact of the cation anion interaction strengths in the surface tension of ionic liquids is further discussed. The surface tensions dependence on the cation alkyl chain length, and on the anion nature, follows an analogous pattern to that of the relative cation anion interaction energies determined by mass spectrometry.