Publications

Abstract The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.

Abstract An experimental and theoretical study of solution and solvation of mono-and divalent alkali metal cations in the protic ionic liquid (IL) ethylammonium nitrate (EAN) is reported. High precision solution-reaction calorimetry was used to obtain the heat of solvation, which was used for the analysis of the thermodynamics. A close relation between the structure of the salts in the crystalline phase and its enthalpy of solvation in the IL is reported. A detailed picture of the molecular environments in the solvation shells around the metal cations is provided by means of molecular dynamics simulations. The analysis of the energetics and structure of solvation confirms the well-known water-like solvation properties of EAN, with the solvation shell around the metal cations in both media being very similar. On the other hand, the results show that it is energetically more favourable to solvate smaller cations with higher valence. Indeed, the simulations show that the long-range electrostatic interactions are the main contribution to solvation interaction, with the electric field at the surface of the alkali metal cations as the basic magnitude controlling it.

Abstract While surfactants and polymers have been independently investigated as agents to separate, disperse and stabilize carbon nanotubes (CNTs) in water, mixed polymer/surfactant (P/S) systems have been far less studied for those ends. In this work, we investigated the ability of various types of P/S mixtures to effectively separate multiwalled carbon nanotubes (MWNTs) in water, using rigorously controlled processing conditions. Two types of mixtures were explored: i) nonionic polymer (PVP, polyvinylpyrrolidone) and ionic surfactant (sodium dodecylbenzene sulfonate, SDBS, or cetyltrimethylammonium bromide, CTAB); and ii) ionic polymer (poly(diallyl dimethyl ammonium chloride), PDDA, and sodium polyacrylate, PAS) and nonionic surfactant (TX-100). Detailed, high precision dispersibility curves (concentration of dispersed nanotubes vs. total P/S concentration, at fixed S concentration) are presented for four P/S mixtures (PVP/SDBS, PVP/CTAB, PDDA/TX-100 and PAS/TX-100) and their respective individual components. Quantitative metrics extracted from the dispersibility curves allow for reliable comparisons between the systems. In all P/S mixtures, beneficial (synergistic) effects in nanotube dispersibility are observed compared to the individual components, with the exception of the PDDA/TX-100 one for which a detrimental (antagonistic) effect occurs. Morphological characterization of the as-obtained dispersions by scanning electron microscopy (SEM) shows a significant degree of nanotube separation by the P/S systems. Surface tension and zeta potential measurements provide further information on the interactions at play between the MWNTs and the P/S mixtures, allowing to conceive plausible mechanisms for the synergistic effects observed. P/S association may not only offer conditions for an enhanced dispersibility of CNTs but also expand the types of noncovalent, reversible functionalization required in many applications, such as the development of nanocomposite particles, films and coatings.

Abstract The development of functional materials with uniquely advanced properties lies at the core of nanoscience and nanotechnology. From the myriad possible combinations of organic and/or inorganic blocks, hybrids combining metal nanoclusters and carbon nanomaterials have emerged as highly attractive colloidal materials for imaging, sensing (optical and electrochemical) and catalysis, among other applications. While the metal nanoclusters provide extraordinary luminescent and electronic properties, the carbon nanomaterials (of zero, one or two dimensions) convey versatility, as well as unique interfacial, electronic, thermal, optical, and mechanical properties, which altogether can be put to use for the desired application. Herein, we present an overview of the field, for experts and non-experts, encompassing the basic properties of the building blocks, a systematic view of the chemical preparation routes and physicochemical properties of the hybrids, and a critical analysis of their ongoing and emerging applications. Challenges and opportunities, including directions towards green chemistry approaches, are also discussed.

Abstract Inspired by previous disclosure of room-temperature ionic liquids derived from primaquine and cinnamic acids, which displayed slightly enhanced blood-stage activity compared to the parent drug, we have now combined this emblematic antimalarial with natural fatty acids. This affords surface-active ionic liquids whose liver-stage antiplasmodial activity is either retained or slightly enhanced, while revealing blood-stage antiplasmodial activity at least one order of magnitude higher than that of the parent compound. These findings open new perspectives towards the cost-effective recycling of classical drugs that are either shelved or in decline, and which is not limited to antimalarial agents.

Abstract Transition metal dichalcogenides (TMDs), like other two-dimensional layered materials beyond graphene, have gained enormous interest in recent years owing to their distinct electronic and optical properties, and potential applicability in areas such as sensing, nanoelectronics and catalysis. Surfactant -assisted exfoliation is commonly used to prepare aqueous dispersions of TMD nanosheets, but a clear picture of the TMD and surfactant features that influence the dispersion process is still lacking. In this work, we present a systematic study of the dispersibility of MoS2, WS2 and MoSe2 in aqueous medium using a cationic (cetyltrimethylammonium bromide, CTAB) and an anionic (sodium cholate, SC) dispersant, in a wide concentration range (seven orders of magnitude) and resorting to a carefully controlled sonication-centrifugation procedure. We present detailed, high precision dispersibility curves (concentration of dis-persed TMD versus concentration of surfactant used), together with zeta potential and pH measurements, allowing insight on the influence of the type of metal and chalcogen, surfactant charge and surfactant concentration, on the effectiveness of the exfoliation and stabilization. The metal (Mo vs. W) influences the dispersibility at low surfactant concentrations, while the chalcogen (S vs. Se) plays a more significant role as the surfactant concentration is increased, alongside the surfactant charge. Structural characterization by scanning electron microscopy (SEM), Raman spectroscopy and atomic force microscopy (AFM) shows that the methodology applied yields well-exfoliated nanosheets with controlled mean lateral dimension (asymptotic to 100 nm) and thickness (<= 5 layers). Finally, the type of ionic surfactant (cationic vs. anionic) and its concentration play a pivotal role in the profile of the dispersibility curves, leading us to propose two types of master curves with distinct regions of phase behavior.

Abstract Chemical recycling can be used to separate fibers that are constituents of different types of fabrics. This type of process can be considered one of the most effective forms of recycling, given that a large part of fabrics is made up of fiber mixtures. As part of an innovative circular strategy, the main goal of this work was to study the conditions for extracting cellulose from mixed textile wastes by acid hydrolysis and further transform it into cellulose derivatives, thus contributing to reduce such wastes and expanding the possible sources of cellulose. Our work covers a wide range of textile wastes and addresses the main technical challenges of this recycling methodology. The percentage of recovered cellulose powder varies between 65 and 88%. To evaluate the feasibility of using the extracted cellulose as raw material to produce cellulose derivatives, two strategies were applied: etherification to obtain sodium carboxymethylcellulose (with degree of substituion between 0.27 and 0.61) and esterification, to obtain cellulose acetate (with degree of substituion of 2.59). The cellulose derivatives obtained are very useful as additives in the textile industry, and hence the concept and practice of a circular economy are promoted.

Abstract This paper focuses on developing and assessing a non-obtrusive and transformative method, based on virtual reality, to evaluate science communication projects in science centres. The method was tested using deep-sea cutting-edge scientific content. We applied a mixed design, with 72 adult participants randomly assigned to experimental conditions (with/without exhibition exposure). Results showed that the exhibition promoted a better understanding of science. The non-obtrusive measures on awareness and engagement were positively related with questions posed via questionnaire and interview. The study adds theoretical and empirical support to the design and implementation of non-obtrusive and transformative evaluation experiences in science exhibitions in science centres and museums.

Abstract This paper examines the relationship between science and religion in the education system of Roman-Catholic Portuguese society. In particular, we explored perceptions of the relationship between science and religion for religious education teachers. We surveyed 198 Portuguese religious education teachers about how they view science and religion. The questionnaires' results revealed a number of similarities: religious education teachers are highly involved in religious practices and exposed to science; they perceived a compatibility between science and religion; and they have an openness to dialogue between both. They do not adhere to anti-scientific perspectives, but they simultaneously try to limit what can be explained by science. Thus, an interpretative view of dialogue and/or integration seems to best explain the perceptions of religious education teachers of the relationship between science and religion. These findings allow a space of discussion, enabling teachers to possibly foster the science-religion dialogue in their contexts of pedagogical activity.