Publications

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 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.

Abstract Due to the generalization of electronically supported activities, we anticipate that, in the near future, the letter "e" in "e-learning," indicating the use of electronic media and information and communication technologies in education, will be dropped and that "e-learning" will be referred to as simply "learning." This paper presents an attempt at understanding the causes of the name shift and at predicting its consequences. We offer a constructive reflection on how e-learning has been looked upon and on what we foresee will happen in the future, drawing briefly on several areas of knowledge and on the experience of the authors as educators at university, teacher training and high school levels. Our effort has also resulted in greater awareness of the importance of social tools and of the relevance of the human factor in the learning process.

Abstract This paper reports an experimental and theoretical study on the structural and energetic characterization of the 2-mercaptoimidazole (2-MI) in the solid and in the gaseous phases. The single crystal X-ray diffraction determinations on the anhydrous and hemihydrate 2-MI forms were carried out at T = (296 +/- 2) K and T = (150 +/- 2) K, respectively, and suggest that in both forms the 2-MI molecule is closer to the thione conformation, albeit some single bond character is possible. The energy of combustion of the title compound was measured by rotating-bomb combustion calorimetry, being used to derive the corresponding enthalpy of formation in the crystalline-phase. The enthalpy of sublimation of 2-MI, at T = 298.15 K, was obtained from high temperature Calvet microcalorimetry measurements. These two parameters yielded the gas-phase enthalpy of formation, allowing the inherent energetic analysis of the molecule. This result was discussed together with the corresponding predictions for 2-MI and its tautomer, 1,3-dihydro-2H-imidazole-2-thione, by the G3 method. The dehydration reaction of 2-MI center dot 0.5H(2)O(cr) was also investigated and the corresponding enthalpy of dehydration was determined by Calvet microcalorimetry.

Abstract We present herein the synthesis, and the structural and spectroscopic analysis of a non-planar tripod-shaped p-(N,N′-dimethylamino)benzyliden-1,3-indandione (DMABI) chromophore. This novel molecule is composed of a Si core with three incorporated arms, each of them contains a 1,3-indandione derivative with an electron donating (-NMe2) group, thus providing fluorescence capabilities. We prepared a DMABI arm by coupling a p-(N,N′-dimethylamino)benzaldehyde (DMAB) tripod substituted molecule with 1,3-indandione via aldol condensation. The structures of DMAB-tripods were confirmed by spectroscopic data and studied by quantum chemical calculations. Fluorescence spectroscopy was used for optical characterization. Quantum yields and the corresponding lifetimes reveal typical characteristics of conjugated derivatives. Finally, we monitored the enhancement in fluorescence intensity of compound 1 in the presence of 4-chloro-2,6-dinitroaniline (4CDNA) in the range between 0 and 20 mg L-1. We justify this enhancement by calculated energies and the distribution of the HOMO and the LUMO for DMABI-tripod and 4CDNA. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016.