Publications

Abstract In this work, energetic and structural studies concerning vanillyl alcohol, based both on experimental and computational studies, were developed. The massic energy of combustion and the vapour pressures at different temperatures were measured by static bomb combustion calorimetry and Knudsen mass-loss effusion techniques, respectively. The computational studies were performed using the G3(MP2)//B3LYP method. The combination of experimental and computational data enabled the determination of the enthalpies, entropies and Gibbs energies of sublimation and formation of this compound both in the crystal and gas phase. The intramolecular hydrogen bond energy present in vanillyl alcohol was evaluated, together with the O-H homolytic bond dissociation enthalpy. The new data are very useful for process design and development in the biorefinery. (C) 2016 Elsevier Ltd.

Abstract The main purposes of the research were to know how multimedia was used to teach science and also what methods were chosen to evaluate the pedagogical designs in the Portuguese Education between 2010-2014. A systematic review of literature was conducted. The corpus of analysis consisted of Master dissertations, PhD thesis and conference papers that were retrieved from the online repositories or proceedings. The criteria to include or exclude a given document were the following: (i) the document should report actual cases of pedagogical intervention(s) based on multimedia to teach science (i. e., Biology, Natural Sciences, Physics, Geology, Mathematics and Chemistry); (ii) the interventions should be aimed at the k5-k12 levels and should necessarily include students; (iii) the Master dissertations and PhD thesis should be available at the institutional online repositories and the articles should have been published in the proceedings of the two most important Conferences on Information and Communication Technologies in Portugal. The corpus consisted of 75 works (49% Mathematics; 15% - Physics; 14% - Natural Sciences; 11% - Chemistry; 7% - Biology; 4% - Geology). A content analysis was run. Interventions were coded according to the TPACK framework and the methodological designs were coded as experimental, quasi-experimental or non-experimental. Results showed that a wide range of multimedia was used, including multimedia specifically designed to teach sciences (e.g., simulations) and non-specific multimedia (e.g., Excel). The level of interactivity and openness of the multimedia was also variable (e.g., low interactivity - videos and animations; high interactivity - games and simulations; closed environments - calculator; open environments - wikis) and the affordances of the multimedia were often not fully used. Most pedagogical designs were based on co-constructivist perspectives (43%) or dialogic perspectives (34%), while transmissive perspectives (16%) and constructivist perspectives (7%) were less used. Most research was nonexperimental (case-studies), based on small samples, using non-validated questionnaires and field notes. Mixed methods or qualitative methods were most frequently selected to gather and analyse data. The study is very significant in that it allowed us to map the trends on multimedia research in the particular case of science teaching. These trends revealed an imbalance between non-experimental, exploratory research and alternatives that increase internal validity (such as quasi-experimental or experimental designs) or that allow to explore meaning and pedagogical appropriation of technology associated with the use of multimedia to teach sciences on the long run. It also showed that it is necessary to pay more attention to emergent practices (including mobile technologies and participatory designs). At the same time, this research provides important information also for science teachers that want to improve their performance using best-practices. Current research includes monitoring an online site that gives access to the raw data of the study and allows users to suggest and upload new documents according to an open and participatory science framework.

Abstract The purpose of the research is to identify the most common social representations of chemistry, green chemistry, robotics and sustainability among teenagers as they were engaging in a project that links robotics and green chemistry. Subjects were students from a school in the north of Portugal enrolled in year 9 (n = 163, 73 males and 86 females, 4 missing values, mean age around 15 years-old). Data was collected through a questionnaire that consisted of four open-ended, free association questions. Participants were asked to express their ideas and thoughts on each one of the four mentioned stimuli and asked to draw a robot. Written responses and drawings of robots were submitted to a content analysis. Preliminary results showed that the ten most frequent words associated with chemistry explain around 49% of the semantic field (average of 4.5 words per participant) and largely consist of conceptual elements, e.g., atoms (38), protons (22) and ions (22), experiments (114), laboratory (62) and explosions (19). The ten most frequent words associated with green chemistry explain around 42% of the semantic field of the representation. Participants - which never have learnt about green chemistry at school curriculum - filled their representations (2.8 words per participant) with elements derived from environment (e.g., nature, environment, trees,...). Only 92 participants defined sustainability, many of them associating the concept with earth's natural resources and future. The ten most frequent words associated with robotics (4.1 words per participant) explain around 53% of the semantic field which consists of robots (129), technology (50), electricity (39), metal (33), energy (20), circuits (18) and computers (17): electronics rather than informatics contribute for the representation. Most of the drawings of robots were anthropomorphic resembling more C-3PO than R2-D2 from Star Wars movies. Human elements, such as eyes, mouth and hands are largely present while movement is assured by means of feet or wheels. The significance of the study is that there is a decalage between science and technology developments and teenager audience understanding. From the point of view of the theory of social representations, this gap is not only expected but also understandable. Popular culture although still inspire the representation of chemistry is not as relevant as it would be if participants have not attended physics and chemistry classes for three years. On the other hand, since green chemistry and robotics are not included in the ordinary curriculum until year 9, the concepts are at loose and their meaning must be grounded elsewhere. Despite the impressive and rapid changes that characterize the technology research, its market and advertising, old metaphors and symbols still contribute to build the representations of teenagers about robotics while green chemistry - a relatively new approach - has its poor semantic field rooted in chemistry and environment. School, thus, must act as a medium to help students to build a coherent worldview that is capable of copying with contemporary challenges, strongly affected by science and technology namely regarding sustainability. An ongoing project is designed to introduce green chemistry experiments that involve slow reactions via a programmable robotic arm in the school laboratory to conduct. The planned activities include monitoring experiences by students at home by means of a live webcam.

Abstract In a recent study on oxygen-containing heterocycles, two of the current authors suggested the gas phase enthalpy of formation of 2,5-dihydrofuran in lieu of an experimentally determined quantity. The current study provides new analysis with well-precedented assumptions and literature measurements to result in the value (-63 +/- 4) kJ . mol (1). For the isomeric 2,3-dihydrofuran the value of (-77 +/- 3) kJ . mol (1) is suggested in satisfactory accord with the combustion calorimetric combustion result of (-72.2 +/- 0.4) kJ . mol (1).

Abstract The use of gemini surfactants in gene delivery has been driven by the structural versatility of these compounds, which can be attained by a combination of different spacers, tails, and headgroups. Great efforts have been focused on the inclusion of natural motifs, such as sugars, lipids, and amino acids, to improve their biocompatibility. In this chapter, structural characteristics of gemini surfactants are correlated with their biological impact on cells, in terms of adverse effects produced and capacity to deliver and promote expression of nucleic acids. In the latter process (transfection), emphasis will be given to morphological changes of surfactant-nucleic acid complexes. These are induced by interaction with membranes or triggered by alterations of pH and reducing conditions within the cells, which can play a role in complex dissociation and nucleic acid release. Examples from the literature will illustrate the ability of those complexes to circumvent biological barriers associated with the different steps leading to gene expression, with emphasis on membrane translocation and endosomal escape.

Abstract Carbon quantum dots (CQDs) coated with poly(amidoamine) (PAMAM-NH2) dendrimer are prepared from folic acid and phosphoric acid under a hydrothermal procedure. The obtained nanoparticles are successfully used as fluorescent sensor for Pt(IV) (in the form of chloroplatinate ion). CQDs possess many attractive features including uniform dispersion with average size about 13 nm for unmodified particles and, 30 nm when they are coated with PAMAM-NH2 dendrimer. The synthesized nanoparticles have been characterized by elemental analysis, attenuated total reflectance (ATR), X-ray photoelectron (XPS) and Raman spectroscopies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and steady-state and life-time fluorescence. CQDs are used as fluorescent sensor of Pt(IV) ion in aqueous media showing linear quenching effect of their fluorescence. The results obtained demonstrated a limit of detection of 657 nM with an accuracy of the method of 0.13% (as RSD, n = 10) and sensitivity of 78 nM. Moreover, with the presence of other interference species, good results are obtained when applied in real samples from platinum nanoparticles synthesis. The dissolved platinum ions can be quantified in the range 6-96 mu M with an accuracy of 2.5%.

Abstract A highly hydrophilic planar membrane fabricated with regenerated cellulose (RC-4 membrane), a biocompatible polymer, was modified by inclusion of water-soluble silicon quantum dot nanoparticles (SiQDs). Both bare SiQDs and SiQDs coated with a PAMAM-OH dendrimer were employed in order to obtain luminescent and thermally stable membrane systems (RC-4/SiQDs and RC-4/SiQDs-PAMAM-OH membranes). Original and SiQDs-modified membranes were characterized by fluorescence spectroscopy (steady and confocal), derivative thermogravimetric analysis and impedance spectroscopy measurements. According to these results, both SiQDs-regenerated cellulose composite membranes present luminescent character as well as higher thermal resistance and conductivity than the original sample, although the dendrimer coverage of the SiQDs might partially shield such effects. Moreover, the permanence of SiQDs nanoparticles in the structure of the cellulosic support in aqueous environments and their effect on diffusive transport were determined by water uptake as well as by membrane potential measurements at different concentrations of a model electrolyte (KCl). These results demonstrate the possible use of these stable nano-engineered membranes, which are based on SiQDs nanoparticles, in electrochemical devices under flow conditions.

Abstract In this work, we investigate the nature of the O-O and O-N interactions in protonated 1,2-dioxirane-3-one derivatives and protonated 1,2-oxaziridine-3-one derivatives, respectively. The quantum theory of atoms in molecules and the natural bond orbital (NBO) method in conjunction with the localized molecular orbital energy decomposition analysis (LMOEDA) have been used. LMOEDA and NBO analyses reveal that the O-O and O-N interactions exhibit characteristics of dative covalent bonds. In addition, the L(r) = -ac(2) rho(r) function reveals that the O-O and O-N interactions can be categorized as strong hole-lump interactions.

Abstract Introduction: Piperine is a simple and pungent alkaloid found in the seeds of black pepper (Piper nigrum). Following its isolation and full characterization, the biological properties of piperine have been extensively studied, and piperine-like derivatives have shown an interesting range of pharmacological activities. In this context, significant advances have been made in the discovery of new chemical entities based on the piperine scaffold endowed with therapeutic potential. Areas covered: The aim of this review is to provide a thorough inquiry on the therapeutic potential of piperine and related derivatives. It provides an overview of recent developments in patented processes and applications thereof between 2000 and 2015. Expert opinion: Cumulative evidence shows that piperine is currently paving its way to become a privileged scaffold for the development of bioactive compounds with therapeutic application in multiple human diseases. In particular, piperine derivatives were shown to modulate the activity of several targets related to neurological disorders, including epilepsy, Parkinson's disease, depression and pain related disorders. Moreover, the efflux pump inhibitory ability of piperine and its analogues tackles important drug resistance mechanisms and may improve the clinical efficacy of antibiotic and anticancer drugs. Although the use of piperine as a scaffold for bioactive compounds is still in its early stages, the continuous exploration of this structure may lead to remarkable advances in drug discovery programs.

Abstract Steady-state and time-resolved fluorescence techniques and theoretical calculations were employed to study the photoprotolytic properties of a newly synthesized photoacid 3-hydroxypyridine-dipicolinium cyanine (HPPC) dye. This dye is similar to quinone cyanine 9, which we have previously studied and is the strongest photoacid currently synthesized. In this compound, we found that several proton transfer phenomena occur after excitation. We found that the excited-state proton transfer (ESPT) rate in water is ultrafast with k(pT) approximate to 1.5 x 10(12) s(-1). In methanol and ethanol the rate is slower by about 5 and 6 times, respectively. The fluorescence spectrum of HPPC in water consists of three bands with maxima at 520, 600, and 665 nm, whereas in monols and other protic solvents the fluorescence spectrum consists only of two emission bands at 530 and similar to 700 nm. We assign the emission bands of HPPC at 520 nm to the protonated form and the 700 nm band in monols and 665 nm in water to the deprotonated form. The 600 nm band that is the most intense band in the fluorescence spectrum of HPPC in water we assign to the tautomeric form in which the proton is attached to the pyridine's nitrogen atom. On the basis of density functional calculations, we suggest that in water the proton transfer process to the pyridine's nitrogen atom occurs in a stepwise manner via a two water molecule bridge.