Publications

Abstract Gemini surfactants and bile acid salts are interesting amphiphiles owing to their unconventional and versatile molecular structure, and consequent unusual aggregation properties. In this work, we investigated the phase behavior of binary surfactant/water systems for the cationic bis-quat gemini surfactants 12-2-12 (short spacer) and 12-6-12 (intermediate spacer) and subsequently catanionic mixtures of each gemini surfactant and the bile salt sodium taurodeoxycholate, STDC The phase diagrams and phase structure were unraveled by polarized light microscopy, differential scanning calorimetry, deuterium NMR and small angle X-ray scattering. The 12-2-12 and 12-6-12 gemini form a micellar-lamellar-cubic and micellar-hexagonal-cubic phase sequence, respectively, denoting the strong influence of the spacer length on the self-assembly properties. Both the catanionic 12-212/STDC/water and 12-6-12/STDC/water systems display a rich mesomorphic behavior. One of the most striking features is that the STDC micelles are able to incorporate enormous amounts of gemini surfactant, forming an extremely wide solution region of mixed micellar structures. By contrast, the gemini micelles can only solubilize limited amounts of STDC. The liquid crystalline phases from the binary systems incorporate sizeable amounts of the counterpart surfactant, forming mixed catanionic aggregates at high concentration. Interestingly, the dilute region of both systems is dominated by liquid-liquid phase separation implying the formation of aqueous twophase micellar systems. The observed features are qualitatively rationalized in terms of packing and electrostatic effects between the surfactants at play.

Abstract In formal education, evaluation is often an intrinsic part of learning. However, in non-formal contexts, such as science centers and museums, evaluation methods are usually invasive and conflicting with visitors' agendas. The I SEA project - a science communication project - intends to develop an immersive virtual reality experience (VRE - I SEA), combining science communication and its evaluation in the same experience, becomes a meaningful procedure for both visitors and institutions. The VRE - I SEA will be hosted at two Portuguese science centers (Planetarium and Expolab). Fieldwork on these centers was developed with the following goals: characterizing each center (i.e., mission, public, models of science communication), perceiving expectations and conditions for integrating the VRE - I SEA, acknowledging experience with virtual reality (VR), and learning their vision about communicating deep seas ecosystems contents. An interview script was developed to cover these themes. Two researchers visited both centers, interviewing a total of 10 intervenients (5 percent), among stakeholders, staff members, and visitors. Data were analyzed with NVivo and cross-compared to participant observation, field notes, and audiovisual records. Results point out different visions concerning the integration of the VRE - I SEA. In the Planetarium, a science center focused on space - astronomy contents, in Porto, most participants identified common characteristics in space and deep seas ecosystems exploration and between the immersiveness of the Planetarium's sessions and the technology to be used in the VRE - I SEA. In Expolab, an Azorean science and technology center, the location was one of the main themes referred by the interviewed when discussing deep-sea ecosystems. In addition, VR is familiar to this center, as Expolab provides VR applications to several science subjects. As for science communication, the analysis of the interviews and the activities available at the time of the visits show a prevalence of a deficit and a contextual model. In fact, personnel from both centers highlight the public's search for contact with the experts and the development of the public's scientific literacy as key points in their mission. Inferring from the viewpoints of the interviewees, what distinguishes science centers from formal education is exactly the absence of systematic evaluation. In addition, science evaluation is sometimes confounded as feedback, which neither of the centers seems to have implemented in a systematic manner. However, there are several attempts for public dialogue (through interactions at the end of science sessions) and obtaining of informal feedback. In sum, the centers' flexibility in integrating and justifying a new theme of deep-sea ecosystems is remarkable, however, considering that one of the I SEA project's purpose is to incorporate a method for science communication evaluation in non-formal contexts, these results lead us to challenge the current communication models in both centers. The I SEA project leads us to rethink the purpose of science communication evaluation, through the development of non-invasive methods, with benefits for both science centers and visitors. Also, the integration of science communication evaluation into the science communication channels may present an essential component towards a more dialogical communication model for science centers, replicable in other non-formal contexts such as museums.

Abstract The standard molar enthalpies of formation in the gaseous state, at T= 298.15 K, of the 2-cyclopentenone and 3-methyl-2-cyclopentenone were derived from their standard molar energies of combustion and from their standard molar enthalpies of vaporization, obtained from static-bomb combustion calorimetry measurements and high-temperature Calvet microcalorimetry, respectively. The enthalpies of hydrogenation of the two cyclopentenones were derived from their gas-phase enthalpies of formation and the gas-phase enthalpies of formation of the corresponding cycloalkanones. The gas-phase standard molar enthalpy of formation of the compounds studied were also obtained using high level ab initio calculations and are in very good agreement with the experimental ones. In addition, thermochemical parameters associated to 2-cyclopentenone and 3-methyl-2-cyclopentenone transformations were investigated using the G3(MP2)//B3LYP level of theory. The conversions of both compounds to longer chain alkanes were found to be thermodynamically favourable. (C) 2019 Elsevier Ltd.

Abstract This work is a contribution to the thermochemical characterization of bicyclic hydrocarbons, reporting the study of six indane derivatives: 4-aminoindane, 5-aminoindane, 5-methoxyindane, 1-indanol, 2-indanol, and 5-indanol. The combustion calorimetry technique was used to measure the massic energy of combustion of each compound in the condensed state, which has been used to derive the corresponding standard (p degrees = 0.1 MPa) molar enthalpy of formation, at 298.15 K. The standard molar enthalpies of sublimation or vaporization of the compounds were determined by high-temperature Calvet microcalorimetry. For each indane derivative, the results obtained for those two properties, allowed to derive the respective value of standard molar enthalpy of formation, in the gaseous phase. Additionally, a theoretical study at the G3(MP2)//B3LYP level has been carried out, and the calculated enthalpies of formation have been compared with the experimental values. The values of the enthalpy of formation, in the gaseous phase, were analysed in terms of correlations between the structural (different substituents in the indane core) and energetics characteristics.

Abstract Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.

Abstract In the present work, the gas-phase standard molar enthalpy of formation of 2-(1H-indol-3-yl)ethanol was derived, at T = 29B.15 K, from the enthalpy of combustion for the crystalline compound, measured by static-bomb calorimetry, and its enthalpy of sublimation obtained from Calvet microcalorimetry measurements. The standard molar enthalpies of formation of this compound and for (1H-indol-2-yl)methanol, (1H-indol-3-yl)methanol and 2-(1H-indol-2-yl)ethanol were calculated using the composite G3 method. The experimental value of the gasphase enthalpy of formation of 2-(1H-indol-3-yl)ethanol is -(48.5 +/- 3.3) kJ mol(-1), being in excellent agreement with the G3 value, thus giving confidence to the estimates. The results were analysed in terms of the enthalpic methylene increments and compared with other related systems.

Abstract Calorimetric experiments performed for ethyl 2-aminobenzoate and ethyl 3-aminobenzoate allowed the determination of their standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T= 298.15 K. The techniques used were static bomb combustion calorimetry and high temperature Calvet microcalorimetry, which enabled the determination of the standard molar enthalpies of formation in the liquid phase, and the standard molar enthalpies of vaporization, at T= 298.15 K, of the above aminobenzoates. In addition, computational calculations, through the G4 composite method, were performed to estimate the enthalpies of formation in the gas phase of the title compounds. Boltzmann weighted averages were performed over sets of stable conformers of each compound, using Gibbs energy to compute population weights. The ethyl 2-aminobenzoate presents an intramolecular hydrogen bond, which was confirmed through topological analyses of the electron density. Furthermore, the energetic effect caused from exchanging the position of the amino substituent was evaluated, and was also compared with similar compounds. (C) 2019 Published by Elsevier Ltd.

Abstract A series of piperic acid esters and amides were synthesized using a two-step strategy. Mass spectrometry and unidimensional (H-1 NMR, C-13 NMR, DEPT) and bidimensional (COSY, HSQC, HMBC) NMR methodologies were used to study the molecular structure of the final compounds, resulting in the assignment of all detected signals. Preliminary biological data of piperine and the derivatives thereof showed that piperic acid 2 and amides 3 and 4 did not display significant inhibitory activity at 10 tiM against both hMAO-A and hMAO-B. In contrast, the esters 5 and 6 displayed relevant hMAO inhibitory activities, with IC50 values for hMAO-B lower than piperine and within the nanomolar range (compound 1: IC50 = 1.05 ttM; compound 6: IC50 =169 nM; compound 5: IC50 =156 nM). Moreover, X-ray crystallographic analyses showed relevant differences between amides 3 and 4 and esters 5 and 6 constituting a valuable information to understand the ligand-target interactions. Additional studies are warranted for a systematic lead optimization process that can lead in the future to a more potent and selective hMAO-B inhibitor based on piperine scaffold.

Abstract Despite a growing number of research reports on neat room temperature ionic liquids (RTILs) and their mixtures with molecular solvents in recent years, understanding and rationalising of such systems is still a challenge. In this work, we performed a classical molecular dynamics simulation study of the pure components - 1-ethyl-3-methylimidazolium thiocyanate (C2C1 imSCN), methanol, and ethanol - and their binary mixtures at room temperature. Thermodynamic (density and heats of vaporization), transport (viscosity and self-diffusion coefficients) and structural (in terms of radial, angular and spatial distributions) properties were analysed. It was found, that with the decrease of RTIL content, the ions self-diffusion coefficients notably increase, reaching higher values in the C2C1 imSCN-MeOH system. Density and viscosity follow the opposite trend, reaching their minimum at lower RTIL mole fraction. Negative deviations of excess molar volume from ideality in the studied mixtures with minima at similar to 0.2-03 mole fraction of RTIL suggest the strongest ion-molecular interactions at this mixture composition. A careful analysis at the molecular level revealed that introducing of alcohols to both systems weakens the inter-ionic H-bonding network, particularly, at low RTIL content. The cation-cation arrangement was found to lose its characteristic above/below orientation in neat RTIL and become disordered at low RTIL content. As to the tail length of the selected alcohols, this was found to have an insignificant effect on the structural properties of the addressed systems.