João M M Araújo

New University of Lisbon, Lisboa, Lisbon, Portugal

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Publications (33)167.95 Total impact

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    ABSTRACT: In this work, novel and non-toxic fluorinated ionic liquids (FILs) totally miscible in water that could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry and surface tension measurements in order to study various thermodynamic and surface properties which demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures.
    Langmuir 01/2015; 31(4). · 4.38 Impact Factor
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    RSC Advances 06/2014; 4. · 3.71 Impact Factor
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    ABSTRACT: The subject of ionicity has been extensively discussed in the last decade, due to the importance of understanding the thermodynamic and thermophysical behaviour of ionic liquids. In our previous work, we established that ionic liquids' ionicity could be improved by the dissolution of simple inorganic salts in their milieu. In this work, a comparison between the thermophysical properties of two binary systems of ionic liquid + inorganic salt is presented. The effect of the ammonium thiocyanate salt on the ionicity of two similar ionic liquids, 1-ethyl-3-methylimidazolium ethylsulfonate and ethylsulfate, is investigated in terms of the related thermophysical properties, such as density, viscosity and ionic conductivity in the temperature range 298.15-323.15 K. In addition, spectroscopic (NMR and Raman) and molecular dynamic studies were conducted in order to better understand the interactions that occur at a molecular level. The obtained results reveal that although the two anions of the ionic liquid exhibit similar chemical structures, the presence of one additional oxygen in the ethylsulfate anion has a major impact on the thermophysical properties of the studied systems.
    Physical Chemistry Chemical Physics 09/2013; · 4.20 Impact Factor
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    ABSTRACT: In order to evaluate the feasibility of partially replace perfluorocarbons (PFCs) with fluorinated ionic liquids (FILs) in PFCs-in-water emulsions, usually used for biomedical purposes, herein the (liquid + liquid) phase equilibria of FILs containing fluorinated chains longer than four carbons with PFCs were carried out in a wide range of temperatures. With this goal in mind, two PFCs (perfluorooctane and perfluorodecalin) were selected and the (liquid + liquid) equilibria of the binary mixtures of these PFCs and FILs were studied at atmospheric pressure in a temperature range from T (293.15 to 343.15) K. For these studies, FILs containing ammonium, pyridinium and imidazolium cations and different anions with fluorocarbon alkyl chains between 4 and 8 were included. Additionally, Non-Random Two Liquid (NRTL) thermodynamic model was successfully applied to correlate the behaviour of the PFCs + FILs binary mixtures. Moreover, thermodynamic functions that describe the solvation process were calculated from the experimental data.
    The Journal of Chemical Thermodynamics 09/2013; 64:71–79. · 2.42 Impact Factor
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    ABSTRACT: In order to overcome the problems associated with low water solubility, and consequently low bioavailability of active pharmaceutical ingredients (APIs), herein we explore a modular ionic liquid synthetic strategy for improved APIs. Ionic liquids containing L-ampicillin as active pharmaceutical ingredient anion were prepared using the methodology developed in our previous work, using organic cations selected from substituted ammonium, phosphonium, pyridinium and methylimidazolium salts, with the intent of enhancing the solubility and bioavailability of L-ampicillin forms. In order to evaluate important properties of the synthesized API-ILs, the water solubility at 25°C and 37°C (body temperature) as well as octanol-water partition coefficients (Kow's) and HDPC micelles partition at 25°C were measured. Critical micelle concentrations (CMC's) in water at 25°C and 37°C of the pharmaceutical ionic liquids bearing cations with surfactant properties were also determined from ionic conductivity measurements.
    International Journal of Pharmaceutics 08/2013; · 3.99 Impact Factor
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    ABSTRACT: The dissolution of uracil - a pyrimidine nucleic-acid base - in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]) has been investigated by methods of 1H and 13C NMR spectroscopy, 1H-1H NOESY NMR spectroscopy, and quantum chemical calculations. The uracil-[C2mim][CH3COO] interactions that define the dissolution mechanism comprise the hydrogen bonds between the oxygen atoms of the acetate anion and the hydrogen atoms of the N1-H and N3-H groups of uracil, and also the hydrogen bonds between the most acidic aromatic hydrogen atom (H2) of the imidazolium cation and the oxygen atoms of the carbonyl groups of uracil. The bifunctional solvation nature of the ionic liquid can be inferred from the presence of interactions between both ions of the ionic liquid and the uracil molecule. The location of such interaction sites was revealed using NMR data (1H and 13C chemical shifts both in the IL and in the uracil molecule), complemented by DFT calculations. NOESY experiments provided additional evidence concerning the cation-uracil interactions.
    The Journal of Physical Chemistry B 03/2013; · 3.38 Impact Factor
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    ABSTRACT: Ionic liquids have become a green media for engineering applications due to exceptional physicochemical properties, such as their practically nonvolatile nature, null flammability, low melting point, high ionic conductivity, and thermal and electrochemical stability. This work aimed to select the best fluorinated ionic liquids for the following applications: recovery/recycling of perfluorocarbon contaminants such as greenhouse perfluorocarbons gases and perfluoroalkyl acids of industrial effluents that are persistent, bioaccumulative, and toxic, and the partial or total replacement of inert perfluorocarbons in oxygen therapeutic emulsions by enhancing the emulsion stability and increasing the solubility of respiratory gas. With this dual goal in mind, thermodynamic and thermophysical properties of fluorinated ionic liquids (FILs) and their toxicity and biocompatibility are discussed so that the feasibility of the proposed applications can be evaluated. Herein, FILs are defined as ionic liquids with fluorinated chain lengths equal or greater than four carbon atoms. This paper provides a critical review of the experimental data for fluorinated ionic liquids available in the literature, and subsequently, with the aim of expanding knowledge of FILs, eight new fluorinated ionic liquids were selected for characterization. The attained results will clearly impact applications using polyfluorinated compounds.
    ACS Sustainable Chemistry & Engineering. 02/2013; 1(4):427–439.
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    ABSTRACT: The use of ionic liquids as a media for dissolving DNA holds great promise for the development of new base materials in electrochemistry. This paper reports the systematic study of the effect of two nucleic acid bases, uracil and adenine, on the ionicity of 1-alkyl-3-methylimidazolium acetates achieved by monitoring several thermodynamic and transport properties. Density, dynamic viscosity, speed of sound, refractive index and ionic conductivity of 1-ethyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium acetate were studied as a function of temperature at atmospheric pressure. The thermal expansion coefficients and molar volumes of these ionic liquids were calculated from the experimental density values. The various properties of the binary mixtures 1-ethyl-3-methylimidazolium acetate with uracil or adenine, namely, their ionic conductivity, density and viscosity in the temperature range 298 K–343 K were determined as a function of the nucleobase content. Walden plots were determined and used to clarify the role of the nucleobases in the ionic liquids ionicity.
    The Journal of Chemical Thermodynamics 02/2013; 57:1–8. · 2.42 Impact Factor
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    ABSTRACT: Ionic-liquid-based aqueous biphasic systems (ABS) have been the focus of a significant amount of research in the last decade. However, only (moderately) toxic and poorly biodegradable ionic liquids have been explored hitherto. Focusing on the development of more benign and sustainable approaches, a novel class of ABS using cholinium-based ionic liquids is proposed. For the first time, it is shown that a large assortment of cholinium-based ionic liquids is capable of undergoing liquid–liquid demixing in the presence of aqueous solutions with strong salting-out species. In order to assess the applicability of these systems for separation purposes, the partitioning of two antibiotics and/or their hydrochloride forms was also investigated. Cholinium-based ABS are shown to be improved routes for the extraction of pharmaceuticals, achieving complete extractions in a single-step by way of the proper tailoring of the phase forming components and their concentrations in the aqueous media.
    RSC Advances 01/2013; 3(6):1835-1843. · 3.71 Impact Factor
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  • International Journal of Pharmaceutics 01/2013; · 3.79 Impact Factor
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    ABSTRACT: Pereiro, A. B. Araujo, J. M. M. Oliveira, F. S. Esperanca, J. M. S. S. Canongia Lopes, J. N. Marrucho, I. M. Rebelo, L. P. N.
    The Journal of Chemical Thermodynamics 12/2012; 55:29-36. · 2.42 Impact Factor
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    ABSTRACT: During the past decade, ionic-liquid-based Aqueous Biphasic Systems (ABS) have been the focus of a significant amount of research. Based on a compilation and analysis of the data hitherto reported, this critical review provides a judicious assessment of the available literature on the subject. We evaluate the quality of the data and establish the main drawbacks found in the literature. We discuss the main issues which govern the phase behaviour of ionic-liquid-based ABS, and we highlight future challenges to the field. In particular, the effect of the ionic liquid structure and the various types of salting-out agents (inorganic or organic salts, amino acids and carbohydrates) on the phase equilibria of ABS is discussed, as well as the influence of secondary parameters such as temperature and pH. More recent approaches using ionic liquids as additives or as replacements for common salts in polymer-based ABS are also presented and discussed to emphasize the expanding number of aqueous two-phase systems that can actually be obtained. Finally, we address two of the main applications of ionic liquid-based ABS: extraction of biomolecules and other added-value compounds, and their use as alternative approaches for removing and recovering ionic liquids from aqueous media.
    Chemical Society Reviews 10/2012; 41:4966-4995. · 30.43 Impact Factor
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    ABSTRACT: During the past decade, ionic-liquid-based Aqueous Biphasic Systems (ABS) have been the focus of a significant amount of research. Based on a compilation and analysis of the data hitherto reported, this critical review provides a judicious assessment of the available literature on the subject. We evaluate the quality of the data and establish the main drawbacks found in the literature. We discuss the main issues which govern the phase behaviour of ionic-liquid-based ABS, and we highlight future challenges to the field. In particular, the effect of the ionic liquid structure and the various types of salting-out agents (inorganic or organic salts, amino acids and carbohydrates) on the phase equilibria of ABS is discussed, as well as the influence of secondary parameters such as temperature and pH. More recent approaches using ionic liquids as additives or as replacements for common salts in polymer-based ABS are also presented and discussed to emphasize the expanding number of aqueous two-phase systems that can actually be obtained. Finally, we address two of the main applications of ionic liquid-based ABS: extraction of biomolecules and other added-value compounds, and their use as alternative approaches for removing and recovering ionic liquids from aqueous media.
    Chemical Society Reviews 06/2012; 41(14):4966-95. · 30.43 Impact Factor
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    ABSTRACT: Novel ionic liquids containing ampicillin as an active pharmaceutical ingredient anion were prepared with good yields by using a new, efficient synthetic procedure based on the neutralization of a moderately basic ammonia solution of ampicillin with different organic cation hydroxides. The relevant physical and thermal properties of these novel ionic liquids based on ampicillin were also evaluated.
    Medicinal Chemistry Communication 04/2012; 3(4):494-497. · 2.63 Impact Factor
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    ABSTRACT: This work explores the possibility of increasing the ionicity of ionic liquids via the solubilization of inorganic salts in their midst. The resulting purely ionic media-distinct ionic liquid plus inorganic salt mixtures-are liquid in an extensive concentration range and can be aptly denominated High Ionicity Ionic Liquids (HIILs).
    Chemical Communications 03/2012; 48(30):3656-8. · 6.38 Impact Factor
  • The Journal of Chemical Thermodynamics 03/2012; · 2.42 Impact Factor
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    ABSTRACT: Organic acids constitute a key group among the building-block chemicals since they are extremely useful as starting materials for the chemical industry. However, the extraction processes of these acids from dilute waste water and fermentation broths normally use organic solvents which imply additional environmental hazards. In this work we have tested the efficiency of hydrophobic ionic liquids, namely phosphonium-based, to extract three short-chain organic acids (l-lactic, l-malic, and succinic acids) from dilute aqueous solutions, as model systems for the use of ionic liquids to extract bioproducts from fermentation broths. The effect of the anion’s nature and the concentration of the acid in the aqueous solution on the partition coefficients was evaluated. Two different approaches to recover the organic acid from the ionic liquid, viz. reduced pressure distillation and pH variation were assessed. The results gathered in this work proved that phosphonium-based ILs can be better extractants than the organic solvents traditionally used. In addition, the predictive capacity of the COSMO-RS for the ternary systems water + organic acid + ionic liquid was evaluated.
    Separation and Purification Technology 02/2012; 85(10):137-146. · 3.07 Impact Factor
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    ABSTRACT: NMR studies of uracil, thymine, and adenine dissolved in 1-ethyl-3-methyl-imidazolium acetate ([C(2)mim][CH(3)COO]) and 1-butyl-3-methyl-imidazolium acetate ([C(4)mim][CH(3)COO]) show that hydrogen bonds (HB) dictate the dissolution mechanism and that both cations and anions participate in the solvation process. For that, the 1,3-dialkylimidazolium acetate ionic liquids (ILs) were considered to be bifunctional solvation ionic liquids. In the solvation of uracil and thymine, the [CH(3)COO](-) anion favors the formation of hydrogen bonds with the hydrogen atoms of the N1-H and N3-H groups of the nucleobases, while the aromatic protons in the bulky cations ([C(2)mim](+) and [C(4)mim](+)), especially the most acidic H2, interact with the oxygen atoms of the carbonyl groups. In the adenine solvation, while the [CH(3)COO](-) anion favors the formation of hydrogen bonds with the hydrogen atoms of the amino and N9-H groups of adenine, the aromatic protons in the bulky cations ([C(2)mim](+) and [C(4)mim](+)), especially the most acidic H2, prefer to interact with the unprotonated nitrogen atoms (N1, N3, and N7) of adenine. It is clearly demonstrated that hydrogen bonding is the major driving force in the dissolution of nucleobases in 1,3-dialkylimidazolium acetate ILs. Our results show that the ionic liquid must be a good hydrogen bond acceptor and a moderate hydrogen bond donor to dissolve nucleic acid bases. To strengthen the evidence of the proposed mechanism, NMR studies in the absence of deuterated cosolvents have been used, because the use of deuterated solvents could seriously hinder the dissolving capability of the IL for nucleobases.
    The Journal of Physical Chemistry B 08/2011; 115(36):10739-49. · 3.38 Impact Factor