Publications

Abstract Educational institutions are not being effective, because they do not give individuals what they need to integrate into postmodern society, nor produce citizens that postmodern society needs. Shortcomings include the scientific literacy and cognitive domain levels attained, with an aggravating waning interest in science among pre-university students. We present an inquiry module, an inquiry dynamic, as an education resource for the study of perturbations of a chemical equilibrium state by pre-university or university students of basic chemistry, to contribute to the relevance and popularity of science, potentiation of science literacy and development of cognition. Here we describe an investigation with pre-university students.

Abstract Technology is getting closer to the classroom. Laptops, tablets, smartphones and mobile phones are devices that go hand in hand with the student's books and exercise books. The ereaders, which are gradually entering the Portuguese market, have some characteristics that may make them a useful tool for teachers and students. In some countries, the digitization of educational material is a reality. This idea reinforce the need of exploitation these technologies among Portuguese students. The purpose of this study was to determine what impact has the use of ereaders and ebooks on learning, more specifically in the interpretation of texts, vocabulary, pronunciation and the reading speed of 23 students in the advanced levels of Cambridge Advance Certificate (CAE) and Cambridge Proficiency Exam (CPE) at International House of Coimbra. To this end, a plan was drafted with four sessions, one for each of the four weeks of the intervention. A survey was also carried out, we observed the sessions and at the end of the intervention, interviews were conducted with six students and the teacher. Was concluded that - at the light of the theoretical framework in which this experiment was based - ereaders and ebooks can be an important factor in motivating students to read and a useful tool for the classroom, due to the similarity with the traditional book, the portability and the large capacity file storage, enabling the effortless transport of several books, dictionaries and other documents. Regarding the technology and according to the testimony of students and teacher, the ereaders still need many improvements, there being some scepticism when compared to tablets with multimedia capabilities for audio, video and web browsing similar to the computers. Paper is still the format that offers greatest comfort to students, especially when it comes to underlining and note-taking. However, in general, they all feel that the ebooks and digital format will eventually play a key role in schools.

Abstract Tryptophan doped carbon dots (Trp-CD) were microwave synthesized. The optimum conditions of synthesizing of the Trp-CD were established by response surface multivariate optimization methodologies and were the following: 2.5 g of glucose and 300 mg of tryptophan diluted in 15 mL of water exposed for 5 min to a microwave radiation of 700 W. Trp-CD have an average size of 20 nm, were fluorescent with a quantum yield of 12.4% and the presence of peroxynitrite anion (ONOO ) provokes quenching of the fluorescence. The evaluated analytical methodology for ONOO detection shows a linear response range from 5 to 25 mu M with a limit of detection of 1.5 mu M and quantification of 4.9 mu M. The capability of the ONOO quantification was evaluated in standard solutions and in fortified serum samples.

Abstract A systematic molecular dynamics study using large simulation boxes has been performed in order to extend the analysis of the mesoscopic segregation behavior observed in ionic liquids of the 1,3-dialkyl-imidazolium bis(trifluoromethylsulfonyl)imide homologous series, [C(n)C(m)im][Ntf(2)] (2 <= n <= 10, 2 <= m <= n). The analyses include the discussion of the structure factors, S(q), in the low-q range (1.6 <= q/nm(-1) <= 20); the confirmation of the periodicity of the polar network of the ionic liquid and its relation to the so-called intermediate peaks; and the characterization of the polar network and the nonpolar regions that are formed along the series using aggregate analyses by means of five different statistical tools. The analyses confirmed that the percolation of the nonpolar regions into a continuous domain occurs when the total number of carbon atoms in the alkyl chains exceeds six but that this is not a sufficient condition for the emergence of a distinct and intense prepeak. The existence of such a peak also requires that the longer alkyl chain contains more than a critical alkyl length (CAL) of five carbon atoms.

Abstract The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor-liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methanesulfonate, and 1-butyl-3-methylimidazolium acetate, which allows the evaluation of the influence of the IL anion through the phase behavior. Isobaric VLE data were measured at 0.05, 0.07, and 0.1 MPa for IL mole fractions ranging between 0 and 0.7. The observed increase in the boiling temperatures of the mixtures is related with the strength of the interaction between the IL anion and water. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was further used to describe the obtained experimental data. The ILs were treated as molecular associating species with two association sites per IL. The model parameters for the pure fluids and the binary interaction parameter k(ij) between water and ILs were determined by a simultaneous fitting to pure-IL densities, water activity coefficients at 298.15 K and VLE data at 0.1 MPa. Pure-IL densities, water activity coefficients, and VLE data were well described by PC-SAFT in broad temperature, pressure, and composition ranges. The PC-SAFT parameters were applied to predict the water activity coefficients at infinite dilution in ILs, and a satisfactory prediction of experimental data was observed.

Abstract Gemini surfactants have been successfully used as components of gene delivery systems. In the present work, a family of gemini surfactants, represented by the general structure [CmH2m+1(CH3)(2)N+(CH2)(s)N (+)(CH3)(2)CmH2m+1]2Br , or simply m-s-m, was used to prepare cationic gene carriers, aiming at their application in transfection studies. An extensive characterization of the gemini surfactant-based complexes, produced with and without the helper lipids cholesterol and DOPE, was carried out in order to correlate their physico-chemical properties with transfection efficiency. The most efficient complexes were those containing helper lipids, which, combining amphiphiles with propensity to form structures with different intrinsic curvatures, displayed a morphologically labile architecture, putatively implicated in the efficient DNA release upon complex interaction with membranes. While complexes lacking helper lipids were translocated directly across the lipid bilayer, complexes containing helper lipids were taken up by cells also by macropinocytosis. This study contributes to shed light on the relationship between important physico-chemical properties of surfactant-based DNA vectors and their efficiency to promote gene transfer, which may represent a step forward to the rational design of gene delivery systems.

Abstract A combined experimental and computational study was developed with the aim of evaluate and understand the structural, energetic and reactivity properties of phenoxazine and phenothiazine. Experimentally, differential scanning calorimetry, static and rotating bomb combustion calorimetries, Knudsen effusion and Calvet microcalorimetry were employed to determine, respectively, the standard (p degrees = 0.1 MPa) molar enthalpies of fusion, Delta H-1(cr)m degrees, at the temperature of fusion, the standard molar enthalpies of formation, in the crystalline phase, Delta H-f(m)degrees(cr), at T = 298.15 K, the temperature-vapor pressures dependences, and the standard molar enthalpies of sublimation, Delta H-g(cr)m degrees, at T = 298.15 K. These data allowed the derivation the experimental standard molar enthalpies of formation, in the gaseous phase, Delta H-f(m)degrees(g), of phenoxazine, (100.8 +/- 4.3) kJ.mol (1), and of phenothiazine, (273.5 +/- 4.7) kJ.mol (1). Computationally, the composite G3(MP2)//B3LYP approach was used to optimize the structures of these two compounds and to estimate their Delta H-f(m)degrees(g) values, which are found to be in very good agreement with the experimental ones. Calculations were also performed for additional analyses of their natural bond orbitals (NBO) and to obtain other gas-phase thermodynamic properties, namely N-H bond dissociation enthalpies, gas-phase acidities and basicities and proton affinities.

Abstract The standard (p(degrees) = 0.1 MPa) molar enthalpy of formation, in the crystalline phase, of N-acetyl-L-cysteine, NAC, at T = 298.15 K, was derived from the standard molar energy of combustion in oxygen, measured by static bomb combustion calorimetry. A value of -(737.8 +/- 1.9) kJ . mol (1) was obtained. For this compound, the standard molar enthalpy of sublimation, at T = 298.15 K, could not be determined due to the decomposition of the compound during the corresponding experiments. A theoretical study at the G3 and G4 levels has been carried out, and a value of -(610.7 +/- 4.0) kJ . mol (1) is recommend for the enthalpy of formation in the gas phase. Using this theoretical value and the experimental enthalpy of formation in the crystalline phase, it is possible to estimate a value of (127.1 +/- 4.4) kJ . mol (1) for the enthalpy of sublimation of this compound.

Abstract Thermodynamic properties of ortho, meta and para methoxybenzamides were determined using the Knudsen effusion method and calorimetric experiments as well as computational approaches. The vapour pressure of the crystalline phase of the three isomers was measured and values of the standard (p(o) = 0.1 MPa) molar enthalpy, Gibbs energy and entropy of sublimation, at T = 298.15 K, were derived. Static bomb combustion calorimetry was used to measure the standard molar enthalpies of combustion from which the standard molar enthalpies of formation in the crystalline state, at T = 298.15 K, were derived. Together with the standard molar enthalpies of sublimation, these results yielded the standard molar enthalpies of formation in gaseous phase of the three isomers. The standard Gibbs energies of formation in crystalline and gaseous phases were also derived and used to differentiate the thermodynamic stability of the three isomers. Moreover, differential scanning calorimetry analysis enabled determination of the temperature and molar enthalpies of fusion of the studied compounds. Gas-phase enthalpies of formation of the three compounds were estimated computationally at the G3 and G4 levels of theory and compared with the experimental results.