Joao A. P. Coutinho

Publications (372) View all

• Article: Attachment/detachment of Saccharomyces cerevisiae on plasma deposited organosilicon thin films

  M. Lehocký, P. F. F. Amaral, M. A. Z. Coelho, P. Sťahel, A. M. Barros-Timmons, J. A. P. Coutinho
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  ABSTRACT: Bio-interactive and bio-inert materials prepared by plasma deposition of organosilicon thin films on polycarbonate substrates were studied and described in this communication. The atmospheric pressure surface barrier discharge was applied. Nitrogen with small admixture of hexamethyldisiloxane (HMDSO) was used as plasma discharge gas. The zeta potential measurement followed by cell adhesion to polystyrene was used to find optimal values of stability of the cell suspension and cell adhesion to the tested surfaces. The samples of plasma deposited layers were characterized by contact angle measurement.
  Czechoslovak Journal of Physics 04/2012; 56:B1256-B1262. · 0.42 Impact Factor
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  Available from: Joao A. P. Coutinho

  Article: Viscosity and Liquid Density of Asymmetric n -Alkane Mixtures: Measurement and Modeling

  A. J. Queimada, I. M. Marrucho, J. A. P. Coutinho, E. H. Stenby
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  ABSTRACT: Viscosity and liquid density measurements were performed, at atmospheric pressure, in pure and mixed n-decane, n-eicosane, n-docosane, and n-tetracosane from 293.15 K (or above the melting point) up to 343.15 K. The viscosity was determined with a rolling ball viscometer and liquid densities with a vibrating U-tube densimeter. Pure component results agreed, on average, with literature values within 0.2% for liquid density and 3% for viscosity. The measured data were used to evaluate the performance of two models for their predictions: the friction theory coupled with the Peng–Robinson equation of state and a corresponding states model recently proposed for surface tension, viscosity, vapor pressure, and liquid densities of the series of n-alkanes. Advantages and shortcoming of these models are discussed.
  International Journal of Thermophysics 04/2012; 26(1):47-61. · 0.95 Impact Factor
• Article: Carbon dioxide in 1-butyl-3-methylimidazolium acetate. I. Unusual solubility investigated by Raman spectroscopy and DFT calculations.

  M Isabel Cabaço, M Besnard, Y Danten, J A P Coutinho
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  ABSTRACT: The unusual solubility of carbon dioxide in 1-butyl-3-methylimidazolium acetate (Bmim Ac) has been studied by Raman spectroscopy and DFT calculations. It is shown that the solubility results from the existence of two distinct solvation regimes. In the first one (CO(2) mole fraction ≤ 0.35), the usual Fermi dyad is not observed, a fact never reported before for binary mixtures with organic liquids or ionic liquids (IL). Strong experimental evidence complemented by effective DFT modeling shows that this regime is dominated by a chemical reaction leading to the carboxylation of the imidazolium ring accompanied by acetic acid formation. The reactive scheme proposed involves two concerted mechanisms, which are a proton exchange process between the imidazolium cation and the acetate anion and the carboxylation process itself initiated from the formation of "transient" CO(2)-1-butyl-3-methylimidazole 2-ylidene carbene species. In that sense, CO(2) triggers the carboxylation reaction. Moreover, this dynamic picture circumvents consideration of a long-lived carbene formation in dense phase. The second regime is characterized by the detection of the CO(2) Fermi dyad showing that the carboxylation reaction has been strongly moderated. This finding has been interpreted as due to the interaction of the acetic acid molecules with the COO group of acetate anions involved in monodentate forms with the cation. The observation of the Fermi doublet allows us to infer that CO(2) essentially preserves its linear geometry and that the nature and strength of the interactions with its environment should be comparable to those existing in organic liquids and other IL as well. These results have been supported by DFT calculations showing that the CO(2) molecule interacts with energetically equivalent coexisting structures and that its geometry departs only slightly from the linearity. Finally, we find that the CO(2) solvation in Bmim Ac and 1-butyl-3-methylimidazolium trifluoroacetate (Bmim TFA) cannot be straightforwardly compared neither in the first regime due to the existence of a chemical reaction nor in the second regime because CO(2) interacts with a variety of environments not only consisting of ions pairs like in Bmim TFA but also with carboxylate and acetic acid molecule.
  The Journal of Physical Chemistry A 02/2012; 116(6):1605-20. · 2.95 Impact Factor
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  Available from: Joao A. P. Coutinho

  Article: Solubility of CO2 in 1-butyl-3-methyl-imidazolium-trifluoro acetate ionic liquid studied by Raman spectroscopy and DFT investigations.

  M Isabel Cabaço, M Besnard, Y Danten, J A P Coutinho
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  ABSTRACT: The polarized and depolarized Raman spectra of 1-butyl-3-methyl-imidazolium-trifluoro acetate (Bmim TFA) ionic liquid and of the dense phase obtained after introduction of supercritical carbon dioxide (313K) under pressure (from 0.1 MPa up to 9 MPa) in the ionic liquid have been recorded. The spectrum of the pure ionic liquid has been assigned by comparison with the spectra of ionic liquids sharing the same cation and using literature data concerning the vibrational modes of the TFA anion. It was found that the spectra of the ionic liquid is almost unaffected by the CO(2) dilution. The only noticeable perturbation concerns a weak enhancement of the mode assigned here to the symmetric stretch vibration of the COO group of the TFA anion. The band shape analysis of the ν(CC) band in pure Bmim TFA shows that the carboxylate groups probe a variety of environments which are almost not affected by the dilution in carbon dioxide. The analysis of the Fermi dyad of carbon dioxide shows that this molecule is perturbed upon dilution in the ionic liquid. The spectra suggest the presence of carbon dioxide in two different environments. In the first one, carbon dioxide molecules interact with themselves, whereas in the second environment, this molecule interacts with the COO group of the TFA anion. This is supported by B3LYP-DFT calculations aimed at assessing the interaction between an ion pair dimer and a carbon dioxide molecule. It is shown that dissolved CO(2) molecules preferentially interact with the TFA anion through a weak charge transfer interaction taking place between the carbon atom of CO(2) (acting as a Lewis acid) and a oxygen atom of the COO group of TFA (as a Lewis base). The results show that Bmim TFA is able to accommodate a large amount of carbon dioxide without having its short-range local structure significantly perturbed. Most CO(2) is hosted in the voids existing among the ion pairs, while some also weakly interact with the anion. It is finally argued that the evolution of the local organization of the IL upon carbon dioxide dilution presents similarities with the microsegregation phenomena reported for IL upon increasing the alkyl chains lengths.
  The Journal of Physical Chemistry B 03/2011; 115(13):3538-50. · 3.70 Impact Factor
• Article: Evaluation of cation-anion interaction strength in ionic liquids

  A.M. Fernandes, M.A.A. Rocha, M.G. Freire, I.M. Marrucho, J.A.P. Coutinho, L.M.N.B.F. Santos
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  ABSTRACT: Cited By (since 1996): 1, Export Date: 10 November 2011, Source: Scopus
  Journal of Physical Chemistry B. 01/2011; 115:4033-4041.