Publications

Abstract The sublimation vapor pressures of three metallic (group 6) hexacarbonyls, Cr(CO)(6), Mo(CO)(6), and W(CO)(6), were measured using the Knudsen mass-loss effusion method. The standard (p (o) = 0.1 MPa) molar enthalpies, entropies, Gibbs energies, and heat capacity difference between the gas and solid state, at T = 298.15 K, were derived from the experimental results combined with selected literature ones covering a wide range of temperature. The temperatures and molar enthalpies of fusion of those compounds were measured using differential scanning calorimetry. The thermodynamic stability of the hexacarbonyls was evaluated taking into account the standard Gibbs energies of formation in the crystalline and gaseous phases. Gas-phase absolute entropies, heat capacities, and enthalpies of formation of the three compounds studied as well as the bond distances M-C and C-O were calculated.

Abstract This study aimed at assessing the learning effects of different ways of integrating digital educational resources in chemistry education. The alternative hypothesis is that digital educational resources contribute more effectively for students’ learning than pen-and-paper consolidation worksheets. A sample of 61 students participated in a pretest-posttest quasi-experimental design with four conditions (control, and three digital-based approaches: Outside the classroom individual approach, inside the classroom individual approach, inside the classroom group approach). Three digital educational resources were developed to address three chemistry themes (particle motion, gas pressure, and electric current through a solution). Results revealed that the inside the classroom individual digital-based approach and the outside the classroom individual digital-based approach were more effective in helping students to perform better, thus partially supporting the alternative hypothesis. The study contributed for the progress of the state of the art by drawing our attention to the plethora of phenomena around the use of computer-based technologies in education, in particular, highlighting the need to consider carefully the resources and pedagogical strategies underpinning one-to-one computing. © Springer Nature Switzerland AG 2019.

Abstract Surface modification of ultra-small nanostructured lipid carriers (usNLC) via introduction of a positive charge is hypothesized to prompt site-specific drug delivery for glioblastoma multiforme (GBM) treatment. A more effective interaction with negatively charged lipid bilayers, including the blood-brain barrier (BBB), will facilitate the nanoparticle access to the brain. For this purpose, usNLC with a particle size of 43.82 +/- 0.03 nm and a polydispersity index of 0.224 were developed following a Quality by Design approach. Monomeric and gemini surfactants, either with conventional headgroups or serine-based ones, were tested for the surface modification, and the respective safety and efficacy to target GBM evaluated. A comprehensive in silico-in vitro approach is also provided based on molecular dynamics simulations and cytotoxicity studies. Overall, monomeric serine-derived surfactants displayed the best performance, considering altogether particle size, zeta potential, cytotoxic profile and cell uptake. Although conventional surfactants were able to produce usNLC with suitable physicochemical properties and cell uptake, their use is discouraged due to their high cytotoxicity. This study suggests that monomeric serine-derived surfactants are promising agents for developing nanosystems aiming at brain drug delivery.

Abstract Although there is a current well stablished role for infographics in science communication, not a lot of attention has been given to audiences' previous representations regarding topics depicted in infographics, or how these affect the effectiveness of communication. This paper presents preliminary results of a research which aims to clarify the role of social representations on participants' levels of effortful thinking and attitude formation when these are processing persuasive science communication messages via digital infographics, with a focus on marine litter. Participants of the research are undergraduate college students from Arts. Our research falls into three main steps. First, accordingly with the theory of social representations, participants will be investigated about how they are representing the theme of marine litter. Secondly, a redesign of a multimedia infographic about marine litter will take place, to include participants' social representations on the topic. An already published online digital infographic about marine litter developed by a Portuguese newspaper team, will be used as a basis for the redesign process. In a third step, participants will be randomly assigned to one out of two conditions of infographic processing - in the first condition, the infographic used will be the one developed by the newspaper team; in the second condition, the redesigned infographic, which attends to participants' social representations, will be used. Levels of elaboration or effortful thinking of both situations will be measured and compared to best understand if attending to participants' social representations while designing infographics for communicating scientific topics improved the persuasion levels in participants. Data was collected through a questionnaire with three distinct parts; a free association assessment of marine litter and infographics related social representations and a marine litter related knowledge assessment; two attitudinal scales related first with the marine litter topic, and, secondly, with infographics; and, finally, an assessment of participants' sociodemographic information. Results regarding the first step of the research are presented in this article. The social representations of 190 participants regarding "marine litter" and "infographics" brought terms like "pollution", "death" and "plastics"; but this representation didn't include more specific terms like "microplastics" or "litter ingestion". Comparably, the representation of "infographics" seems not to be evenly present in our participants, as 57% of participants affirmed not to know what an infographic was. Nevertheless, in the cases where participants knew what an it was, the representation revolved around terms like "imagetics", "information" and "graphics", which although consistent with the denotative meaning of an infographic, does not tell us much about its connotative social meaning. Expected further results are an increase on participants' elaboration levels when they process the infographic message that will redesigned to attend to their social representations on marine litter, when compared to the situation in which such message was not redesigned. This study is significant for the area of science communication, as it will help to clarify the role of social representations in the construction of scientific messages for non-specialist audiences.

Abstract Considering the European guidelines about the education's change through information and communications technologies and the gap between researchers and teachers, the goal of this research was to identify and reflect on the conditions of genesis and sustainable development of an affinity space for science education using multimedia: mSciences [mCiencias]. The research felt into three different empirical studies. In the first study, a syncretic notion based on social learning systems, such as communities of practice and affinity spaces, was adopted to lead an action-research process on a previous existent online platform - that was developed for making available the research that had been carried out in Portugal, between 2010 and 2015 and targeted for all who might be interested in multimedia in science teaching. Through this platform we aimed to implement strategies to attract and to retain the public and therefore, progressively, create a community of peers. In the second study, based on the theory of planned behaviour, we assessed 60 science teachers about their beliefs and their intention of participation (registration, sharing or comment on projects, practices or resources) in the affinity space mSciences. In the third study, we conducted a thematic analysis of qualitative data gathered through an online questionnaire sent to nine participants that interacted in different degrees with the mSciences platform. Results led us to introduce several changes in the previous platform to include the features associated with affinity spaces. The intention towards the participation in the mSciences platform of the science teachers revealed a high degree of perceived behavioural control on the detected positive intention of participation (70% of the participants). By using a syncretic notion between communities of practice and affinity spaces, it was possible to start devising bridges between researchers and science teachers that hopefully might enable future improvements of practice through links with research. Identifying the main underlying beliefs of teacher's adherence to affinity spaces allowed the development of future lines of action to challenge negative beliefs. For example, it seems to be important to design persuasive communication actions to present the participation on the affinity space as a non-time-consuming activity, that does not compete or interfere with other professional or personal activities, but instead an activity that can be seen as a way for sharing ideas, practices and resources among science teachers, aiming the improvement of their professional development. Acting on the subjective evaluation of a belief, mainly on increasing the subjective evaluation of control beliefs, might increase the intention to participate but also the actual participation. The current results can be taken into consideration when designing new national or international platforms, suggesting a conceptual turn from affinity spaces into affinity communities. Such affinity communities might reduce the distance between researchers and teachers, thus enabling future transmission of learning innovations from research to educational practice, allowing practitioners to integrate research findings into their practices but also to make researchers aware of what is important to practitioners.

Abstract This paper reports the standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of acridone and N-methylacridone as (50.0 +/- 5.0) kJ . mol(1) and (60.6 +/- 4.3) kJ . mol(1), respectively. These data were obtained from experimental thermodynamic parameters, namely the standard molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, derived from the standard molar enthalpies of combustion measured by static-bomb combustion calorimetry, and the standard molar enthalpies of sublimation, at T = 298.15 K, determined by Calvet microcalorimetry or the Knudsen effusion techniques. Additionally, the gas-phase enthalpies of formation were estimated by G3(MP2)//B3LYP calculations, using several hypothetical gas-phase reactions, and were compared with the corresponding ones determined experimentally. The gas-phase keto-enol tautomerization chemical equilibrium of acridone M 9-acridinol was analysed using the Boltzmann's distribution, being confirmed that the equilibrium favours the formation of the keto form. The bond dissociation enthalpies (N-H) and (C-H) and the gas-phase acidities were also determined. The electrostatic potential surfaces and the frontier molecular orbitals were determined for both compounds, allowing us to infer about their reactivity properties. Other properties studied include the HOMO-LUMO energy gap and the ionization potential. (C) 2017 Elsevier Ltd.

Abstract Theoretical and experimental studies on the energetic, structural and some other relevant physicochemical properties of the antioxidant tyrosol (1), hydroxytyrosol (1OH) molecules and the corresponding radicals 1(rad)(center dot) and 1O(rad)(center dot) are reported in this work. The experimental values of the gas -phase enthalpy of formation, Delta H-f(m)0(g), in kJ.mol(-1), of 1 (-302.4 +/- 3.4) and 1OH (-486.3 +/- 4.1) have been determined. Quantum chemical calculations, at DFT (M05-2X) and composite ab initio G3 and G4 levels of theory, provided results that served to (i) confirm the excellent consistency of the experimental measurements performed, (ii) establish that the stabilizing effect of H -bond of hydroxyethyl chain and aromatic ring (OH center dot center dot center dot pi interaction) is smaller in radicals than in parent molecules, (iii) deduce-combining experimental data in isodesmic reactions-Delta H-f(m)0(g) of radicals 1(rad)(center dot) (-152.3 +/- 4.4 kJ.mol(-1)) and 1O(rad)(center dot) (-370.6 +/- 3.8 kJ.mol(-1)), (iv) estimate a reliable O-H bond dissociation enthalpy, BDE of 1 (368.1 +/- 5.6 kJ.mol(-1)) and of 1OH (333.7 +/- 5.6 kJ.mol(-1)), and (v) corroborate-using "BDE criteria"-than 1OH is a more effective antioxidant than 1.

Abstract The wealth of site-selective structural information on CO2 speciation, obtained by spectroscopic techniques, is often hampered by the lack of easy-to-control synthetic routes. Herein, an alternative experimental protocol that relies on the high sensitivity of C-13 chemical shift anisotropy (CSA) tensors to proton transfer, is presented to unambiguously distinguish between ionic/charged and neutral CO2 species, formed upon adsorption of (CO2)-C-13 in amine-modified porous materials. Control of the surface amine spacing was achieved through the use of amine protecting groups during functionalisation prior to CO2 adsorption. This approach enabled the formation of either isolated or paired carbamate/carbamic acid species, providing a first experimental NMR proof towards the identification of both aggregation states. Computer modelling of surface CO2-amine adducts assisted the solid-state NMR assignments and validated various hydrogen-bond arrangements occurring upon formation of isolated/aggregated carbamic acid and alkylammonium carbamate ion species. This work extends the understanding of chemisorbed CO2 structures formed at pore surfaces and reveals structural insight about the protonation source responsible for the proton-transfer mechanism in such aggregates.

Abstract Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, but the process is not well understood. In this work, aqueous SWNT dispersions were produced by sonicating pristine SWNT powder in the presence of an amphiphilic triblock copolymer (Pluronic F127) as dispersant. Upon centrifugation, one obtains a supernatant with suspended individual tubes and thin bundles and a precipitate with large bundles (and impurities). In the supernatant, that constitutes the final dispersion, we determined the dispersed SWNT concentration by thermogravi-metric analysis (TGA) and UV-vis spectroscopy, and the dispersant concentration by NMR The fraction of dispersant adsorbed at the SWNT surface was obtained by H-1 diffusion NMR Sigmoidal dispersion curves recording the concentration of dispersed SWNTs as a function of supernatant dispersant concentration were obtained at different SWNT loadings and sonication times. As SWNT bundles are debundled into smaller and smaller ones, the essential role of the dispersant is to sufficiently quickly cover the freshly exposed surfaces created by shear forces induced during sonication. Primarily kinetic reasons are behind the need for dispersant concentrations required to reach a substantial SWNT concentration. Centrifugation sets the size threshold below which SWNT particles are retained in the dispersion and consequently determines the SWNT concentration as a function of sonication time.