Browsing by Author "Machado, Giovanna"

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    Effect of TiO2 nanoparticles on polyaniline films electropolymerized at different pH.
    (2016) Leite Filho, Valfrido Furtado; Machado, Giovanna; Batista, Ronaldo Junio Campos; Soares, Jaqueline dos Santos; Oliveira, Alan Barros de; Vasconcelos, Cláudia Karina Barbosa de; Lino, Andre Alves; Manhabosco, Taíse Matte
    In this work hybrids of titanium nanoparticles and polyaniline are obtained by pulsed electrodeposition at different pH (1.5, 3.9 and 5.9) and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry, ultraviolet−visible, and Raman spectroscopies. We found that films deposited at pH 5.9 with nanoparticles incorporation are composed of emeraldine meanwhile films without nanoparticles are composed of pernigraniline. As a result, films deposited with nanoparticles incorporation present conductivity 6 times higher than that of films deposited without nanoparticles. Films deposited at pH 3.9 with or without nanoparticles incorporation are both made of pernigraniline. Even though films with nanoparticles incorporation still present higher conductivity. To explain such a result, we performed first-principles calculations on polyaniline/ TiO2 interface. The calculations predict a metallic polyaniline/TiO2 interface in spite of polyaniline and TiO2 being semiconductors. At pH 1.5, the presence of nanoparticles has negligible effect on films characteristics. We believe that at low pH (pH 1.5) H atoms tend to bind TiO2 surface resulting in positively charged nanoparticles, which are further screened by SO4 −2 anions. Such a screening layer prevents the physical contact between nanoparticles and polyaniline monomers diminishing the effects of nanoparticle presence.
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    Eletropolimerização e caracterização de polianilina com incorporação de nanopartículas de TiO2 a diferentes pHs.
    (2015) Leite Filho, Valfrido Furtado; Manhabosco, Taíse Matte; Machado, Giovanna; Manhabosco, Taíse Matte; Soares, Jaqueline dos Santos; Mota, Vinícius Cândido
    Neste trabalho, filmes de polianilina (PANI) foram sintetizados pela técnica eletroquímica de polimerização potenciostática pulsada a diferentes pHs com e sem a incorporação de nanopartículas de dióxido de titânio (TiO2). Os filmes foram caracterizados pelas técnicas de espectroscopia ultravioleta-visível (UV-Vis), microscopia eletrônica de varredura (MEV), difração de raios X, espectroscopia Raman, além de voltametria cíclica. Um estudo teórico computacional também foi realizado para fins de fundamentação dos resultados experimentais. Os filmes produzidos a pHs mais ácidos com nanopartículas de TiO2 incorporadas não exibiram significativa melhora na resposta eletroquímica, porém, a pHs menos ácidos, uma elevação na densidade de corrente ficou evidente em curvas de voltametria cíclica e em espectros de UV-Vis.
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    Physical-chemical effects of nanoparticles on electropolymerized polyaniline.
    (2021) Carvalho Júnior, José Agenor; Barboza, Ana Paula Moreira; Machado, Giovanna; Neves, Bernardo Ruegger Almeida; Oliveira, Alan Barros de; Batista, Ronaldo Junio Campos; Araújo, Fernando Gabriel da Silva; Soares, Jaqueline dos Santos; Manhabosco, Taíse Matte
    The incorporation of nanoparticles on polymer films is possible to obtain materials with desired properties. In the present work, we address the physical-chemical influence of nanoparticles in polymer films by producing and characterizing polyaniline hybrids with SiO2 and Au nanoparticles and comparing them with films with TiO2 nanoparticles. The hybrid films were characterized by SEM, EDS, UV-Vis, AFM, Raman, and cyclic voltammetry. Unlike TiO2 nanoparticles, SiO2 and Au nanoparticles do not promote any noticeable change in polyaniline oxidation state in less acid environments (pH 5.9 and 6.15). However, in those environments, the presence of nanoparticles significantly increases the film's conductivity. At a pH of 1.5 and 3.9, all three kinds of nanoparticles are screened by ions from the solution diminishing their physical-chemical effects on polyaniline. Thus, our results suggest that, in general, nanoparticles don't have any physical-chemical effects on polyaniline films when deposited in acid enough environments but can change their physical and chemical properties when deposited in less acid environments.
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    Soapstone reinforced hydroxyapatite coatings for biomedical applications.
    (2020) Mota, Laureana Moreira; Nicomedes, Daniel Nilson; Barboza, Ana Paula Moreira; Ramos, Sérgio Luís Lima de Moraes; Vasconcelos, Rebecca Schirmer de Souza; Medrado, Nathanael Vieira; Alvarenga, Érika Lorena Fonseca Costa de; Machado, Giovanna; Juste, Karyne Ramos de Campos; Vasconcelos, Cláudia Karina Barbosa de; Righi, Ariete; Manhabosco, Sara Matte; Resende, Rodrigo Ribeiro; Batista, Ronaldo Junio Campos; Soares, Jaqueline dos Santos; Manhabosco, Taíse Matte
    Mechanical resistant bioactive materials are of high interest for biomedical applications. In this work, we address the improvement in mechanical properties of HA coatings by the addition of a cheap and widely available secondary phase material, the talc from soapstone. The composites hydroxyapatite/talc (HA/talc) were successfully obtained by pulsed electrodeposition and characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, corrosion and wear resistance and biocompatibility tests. We found that the addition of talc greatly improves the mechanical properties of coatings (i. e., wear track and friction coefficient in wear tests were significantly diminished) without diminishing corrosion resistance and biocompatibility. Alamar Blue® tests, alkaline phosphatase activity, and collagen production indicate that the biocomposites are biocompatible and talc itself induce bone maturation.
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    Structural, optical, and magnetic evaluation of Co-, Ni-, and Mn-modified multiferroic BiFeO3 ceramics.
    (2021) Sales, Joel Neto Bispo de; Silva, Rafael Tomaz da; Lara, Luciano Roni Silva; Ramos, Sérgio L. L. M.; Soares, Jaqueline dos Santos; Soares, Thiago André Salgueiro; Machado, Giovanna; Manhabosco, Sara Matte; Oliveira, Alan Barros de; Carvalho, Hugo Bonette de; Batista, Ronaldo Junio Campos; Stumpf, Humberto Osório; Manhabosco, Taíse Matte
    Co-, Ni-, and Mn-doped BiFeO3 (BFO) ceramics were synthesized herein through a solid-state reaction. All doped BFO samples exhibit visible-light response, and the Co- and Ni-doped BFO samples present enhanced ferro-magnetic order at room temperature. All doped samples show secondary phases in minor quantities. Optical spectra reveal two absorptions bands, indicating multiple electron transitions for BFO and its secondary phases. M − H hysteresis loops suggest enhanced ferromagnetism in the Co- and Ni-doped BFO samples because of magnetic spinel CFP and NFO phases, respectively, whereas changes in oxygen vacancies and Fe–O–Fe bond angle play minor roles in the ferromagnetic behavior.