Browsing by Author "Pires, Ana Clarissa dos Santos"

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    Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon : a thermodynamic study.
    (2017) Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hespanhol, Maria C.; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Gurgel, Leandro Vinícius Alves; Silva, Luis Henrique Mendes da
    Carbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye (ΓD) increased in the order ΓD (PR) < ΓD (AR) < ΓD (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed (ΓD,max) reached values of up to 2.00 μmol m−2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (ΔadsH) and entropy change (TΔadsSref) values were higher than −137.0 kJ mol−1 and −114.2 kJ mol−1, respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces.
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    Aggregation of sodium dodecylbenzene sulfonate : weak molecular interactions modulated by imidazolium cation of short alkyl chain length.
    (2020) Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Coelho, Yara Luiza; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Ionic liquids (ILs) can modify cooperative process in aqueous solutions to a large extent, including anionic surfactant aggregation. Here, the micellization of sodium dodecylbenzene sulfonate (SDBS) was evaluated in low concentrations of 1-alkyl-3-methylimidazolium chloride (CnmimCl, n = 0, 2, and 4) aqueous solutions through fluorescence spectroscopy, isothermal titration calorimetry, dynamic light scattering, and conductometry. The thermodynamic stability of SDBS aggregates strongly depended on the IL structure and concentration, following the order C4mim+ > C0mim+ ≈ C2mim+. At 1.0 mmol L−1 of the ILs, the increase of the hydrophobicity of the imidazolium cation decreased the enthalpic favorableness, changing from −3.75 ± 0.07 kJ mol−1, for C0mim+, to −2.69 ± 0.01 kJ mol−1, for C4mim+. On the other hand, the entropic feasibility showed an opposite trend, i.e., the higher hydrophobicity of C4mim+ overcame the kosmotropic effect of IL cations in the bulks. We suggested that the imidazolium cations interact with the SDBS monomers on the micellar surface, mainly through hydrophobic, π-π, and electrostatic interactions for C4mim+ and C2mim+, and through electrostatic interactions and hydrogen bonds for C0mim+.
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    Lactoferrin denaturation induced by anionic surfactants : the role of the ferric ion in the protein stabilization.
    (2018) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Patino Agudelo, Alvaro Javier; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Here, investigation was made of the interaction between lactoferrin (Lf) and the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium decyl sulfate (DSS), using isothermal titration calorimetry, Nano differential scanning calorimetry (NanoDSC), and fluorescence spectroscopy. The Lf-surfactant interaction was enthalpically favorable (the integral enthalpy change ranged from −5.99 kJ mol−1, for SDS at pH 3.0, to −0.61 kJ mol−1, for DSS at pH 12.0) and promoted denaturation of the protein. The Lf denaturation efficiency followed the order DSS < SDS < SDBS. The adsorption capacity of the protein with respect to surfactant strongly depended on pH and the surfactant structure, reaching a maximum value of 505 SDBS molecules per gram of Lf at pH 3.0. The different efficiencies of the surfactants in denaturing Lf were attributed to the balance of hydrophobic and electrostatic interactions, which also depended on pH and the surfactant structure, highlighting the SDBS-tryptophan residue specific interaction, where SDBS acted as a quencher of fluorescence. Interestingly, the NanoDSC and fluorescence measurements showed that the ferric ion bound to Lf increased its stability against denaturation induced by the surfactants. The results have important implications for understanding the influence of surfactants on structural changes in metalloproteins.
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    New insights into the partitioning of phenothiazine dyes in aqueous two-phase systems.
    (2020) Coelho, Yara Luiza; Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Castro, Alan Stampini Benhame de; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Aqueous two-phase systems (ATPSs) have proven to be efficient and environmentally safe methods for extracting chemical species. However, the driving forces behind the partition of solutes in these systems are still little understood. A complete thermodynamic partitioning of phenothiazine dyes was investigated in poly(ethylene oxide) (PEO) + salt + water ATPSs. Standard transfer parameters (Gibbs free energy change (ΔtrGo ), enthalpy change (ΔtrHo ) and entropy change (TΔtrSo )) were evaluated, and their dependence on the dye structure, electrolyte nature and tie line length (TLL). All phenothiazine dyes are concentrated predominantly in the polymer enriched phase, with ΔtrGo values ranging from −4.1 up to −13.4 kJ mol−1. Due to the dye-PEO attractive interactions that occur mainly via benzene condensed ring present in the structures of phenothiazine dyes, the partitioning of these dyes was enthalpically driven, with −11.4 ≥ ΔtrHo ≥ −52 kJ mol−1 and −4.93 ≥ TΔtrSo ≥ −38 kJ mol−1.
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    A simple and inexpensive thermal optic nanosensor formed by triblock copolymer and polydiacetylene mixture.
    (2018) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Ortega, Paulo Fernando Ribeiro; Silva, Luis Henrique Mendes da
    Polydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (Ttr) to as low as 24 °C. When using different TCs, the Ttr values can be ordered as L35 < F68< L64 < F127
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    Solvophobic effect of 1-alkyl-3-methylimidazolium chloride on the thermodynamic of complexation between β-cyclodextrin and dodecylpyridinium cation.
    (2019) Patino Agudelo, Alvaro Javier; Coelho, Yara Luiza; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Preferential solvation participate in various supramolecular self-assembly processes, whose thermodynamic properties can be modulated by the addition of ionic liquids (ILs). However, the effects of these liquids on the thermodynamics of the host-guest complexation process remain unexplored. In this study, the thermodynamic properties of the complexation between 1-dodecylpyridinium cations (C12Py+) and β-cyclodextrin (βCD) species in aqueous solutions with different concentrations of 1-alkyl-3-methylimidazolium halides (CnmimX) were investigated by isothermal titration calorimetry. In water, C12Py+ and βCD form a 1:1 inclusion complex, which is enthalpically ( −9.2 ± 0.1 kJ mol−1) and entropically ( 16.1 ± 0.2 kJ mol−1) favorable. However, in IL aqueous solutions, all the βCD―C12Py+ thermodynamic parameters of the complexation change and this IL effect is dependent on the carbon chain length of Cnmim+ cations. ILs with shorter alkyl chains (Cnmim+, n ≤ 4) decreases the system entropy, while ILs with longer alkyl chains (Cnmim+, n ≥ 6) reduce the enthalpy values. These effects are attributed to i) preferential solvation of surfactant tails by ILs; ii) ability of the ILs to modify the 3D water structure and iii) inclusion of IL molecules into the inner cavities of βCD.
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    Thermodynamic and kinetic analyses of curcumin and bovine serum albumin binding.
    (2018) Hudson, Eliara Acipreste; Paula, Hauster Maximiler Campos de; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hespanhol, Maria do Carmo; Silva, Luis Henrique Mendes da; Pires, Ana Clarissa dos Santos
    Bovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 105 L·mol−1 by fluorescence and microcalorimetric, and 103 and 104 L·mol−1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH○F = −8.67 kJ·mol−1), while microcalorimetry showed an entropic driven binding process (ΔH○cal = 29.11 kJ·mol−1). For the unfolded BSA/curcumin complex, it was found thatp ΔH○F = −16.12 kJ·mol−1 and ΔH○cal = −42.63 kJ·mol−1. BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding.
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    Thermodynamics of multi-walled carbon nanotube biofunctionalization using nisin : the effect of peptide structure.
    (2019) Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Almeida, Germanna Wilk Reis de; Soares, Nilda de Fatima Ferreira; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    A detailed adsorption thermodynamic study of two nisin variants (nisA and nisZ) on multi-walled carbon nanotubes (MWCNT) was conducted, and the antimicrobial properties of biofunctionalized MWCNT were evaluated. The MWCNT adsorption capacity for peptides () increased with pH increase, with greater values for nisZ ( up to 250 mg g−1) than for nisA ( up to 180 mg g−1) for all studied conditions. Zeta potential measurements (ζ) showed that the electrostatic repulsion between the MWCNT-peptide complexes determined the dispersion features that were stable at pH 2.0 and 3.0, with ζ reaching 45.0 mV at the lowest pH. Despite the similar ζ values for both peptides, slightly greater stabilization of MWCNT dispersions was exhibited in presence of nisZ at pH 3. At pH 4 and 5, peptide adsorption was not able to promote MWCNT dispersibility. Isothermal titration calorimetry revealed that the adsorption process was driven by enthalpy for both peptides, as the adsorption enthalpy changes () were less negative than −99.7 kJ mol−1. Despite the large dependence of on the pH and values, indicating the important role of electrostatic interactions on the adsorption process, a change in only one amino acid residue in the nisin structure promoted intense changes in the adsorption thermodynamic parameters. We have suggested that the more hydrophobic character of nisZ at the lower pH values caused this peptide to interact with the MWCNT surface through its two domains. Interesting, the antimicrobial properties of both peptides were not damaged, and the functionalized MWCNT showed antibacterial activity against the indicator micro-organism Lactococcus lactis in the agar diffusion and solution assays.