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Oliveira A.M.B.M.,Federal University of Campina Grande | Coelho L.F.O.,Federal University of Campina Grande | Gomes S.S.S.,Federal University of Paraiba | Costa I.F.,Federal University of Paraiba | And 4 more authors.
Water, Air, and Soil Pollution | Year: 2013

Natural palygorskite was used as an adsorbent for the removal of copper, cobalt and nickel from an aqueous solution. All assays were performed under controlled conditions to establish the adsorption capacity of the solid. Initially, the clay was characterized by chemical analysis, XRD, infrared spectroscopy and thermogravimetry. Adsorption experiments for the ions in aqueous solution were carried out by a batch method through which the reaction time, initial concentration of cations, temperature and pH of the aqueous solution were systematically varied. First-order, pseudo-second-order and intraparticle diffusion models were used to describe the kinetic data. The results show that the processes were fitted well by the pseudo-second-order model. Moreover, the equilibrium solid-cation systems followed the Langmuir isotherm model. The results indicate that raw palygorskite could be employed as a low-cost material for the removal of heavy metals from aqueous solution. © 2013 Springer Science+Business Media Dordrecht. Source

Bittencourt C.R.,Federal University of Piaui | De Oliveira Farias E.A.,Federal University of Piaui | Bezerra K.C.,Federal University of Piaui | Veras L.M.C.,Federal University of Piaui | And 9 more authors.
Materials Science and Engineering C | Year: 2016

This report details the development of thin films containing an antimicrobial peptide, specifically, dermaseptin 01 (GLWSTIKQKGKEAAIAAA-KAAGQAALGAL-NH2, [DRS 01]), and a natural polysaccharide, for a novel application in detecting the presence of Leishmania cells and maintaining anti-leishmanial activity. The peptide DRS 01 was immobilized in conjunction with natural cashew gum (CG) onto an indium tin oxide (ITO) substrate using the Layer-by-Layer (LbL) deposition technique. The LbL film ITO/CG/DRS 01, containing DRS 01 as the outer layer, was capable of detecting the presence of Leishmania cells and acting as an anti-leishmanial system. Detection was performed using cyclic voltammetry (CV) in phosphate buffer (pH 7.2) in the presence of promastigote cells (0-107 cells/mL). The results showed a linear and inversely proportional relation between the concentration of Leishmania infantum protozoan cells and the measured current values obtained for the films, which was attributed to the effect of peptide-induced lysis of the cell membrane, and resulted in freed residues that were adsorbed on the electrode surface. With this, the paper shows a method using thin films with this new material to demonstrate the anti-leishmanial activity in vitro models of carpet-like mechanisms. © 2015 Elsevier B.V. All rights reserved. Source

Nunes Pauli G.E.,Federal University of Santa Catarina | Araruna F.B.,Federal University of Piaui | Eiras C.,Federal University of Piaui | Eiras C.,Laboratorio Interdisciplinar Of Materiais Avancados | And 7 more authors.
Materials Science and Engineering C | Year: 2014

This paper reports the study and characterization of a new platform for practical applications, where the use of phaeophytin-b (phaeo-b), a compound derived from chlorophyll, was characterized and investigated for sensing purposes. Modified electrodes with nanostructured phaeo-b films were fabricated via the layer-by-layer (LbL) technique, where phaeo-b was assembled with cashew gum, a polysaccharide, or with poly(allylamine) hydrochloride (PAH). The multilayer formation was investigated with UV-Vis spectroscopy by monitoring the absorption band associated to phaeo-b at approximately 410 nm, where distinct molecular interactions between the materials were verified. The morphology of the films was analyzed by atomic force microscopy (AFM). The electrochemical properties through redox behavior of phaeo-b were studied with cyclic voltammetry. The produced films were applied as sensors for hydrogen peroxide (H2O2) detection. In terms of sensing, the cashew/phaeo-b film exhibited the most promising result, with a fast response and broad linear range upon the addition of H2O2. This approach provides a simple and inexpensive method for development of a nonenzymatic electrochemical sensor for H2O2. © 2014 Elsevier B.V. All rights reserved. Source

Sousa R.B.,Laboratorio Interdisciplinar Of Materiais Avancados | Nascimento V.A.,Laboratorio Interdisciplinar Of Materiais Avancados | Matos J.M.E.,Laboratorio Interdisciplinar Of Materiais Avancados | Lima C.L.,Federal University of Piaui | And 2 more authors.
Ceramica | Year: 2015

Barium tungstate (BaWO4) is an important ceramic material belonging to the family of scheelites, which is applied as photoluminescent material, as scintillator, light-emitting diodes (LEDs), solid-state lasers, among other, being a host matrix for lanthanide ions, due to its chemical and mechanical stability. This research aims to synthetize, characterize structurally and evaluate photoluminescent properties of barium tungstate powders and Ho3+-doped barium tungstate. Powders of Ba1-xHo2x/3WO4 (x= 0, 0.01 and 0.02) were obtained by coprecipitation and characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-Transformed Infrared spectroscopy (FTIR), UV-Vis spectroscopy, scanning electron microscopy (SEM) and photoluminescent spectroscopy. XRD and Raman spectroscopy analyses revealed crystalline ordering for these materials. Their morphology was characterized by the presence of octahedral grains with heterogeneous distribution of grain size. A broad band centered at 475 nm was identified for BaWO4 at 350,7 nm excitation in emission spectrum. The addiction of holmium ions into the BaWO4 matrix promoted a significant reduction of the optical gap and characteristic transitions (f-f transitions) of ions Ho3+ were identified. Source

Farias E.A.O.,Nucleo de Pesquisa em Biodiversidade e Biotecnologia | Dionisio N.A.,Nucleo de Pesquisa em Biodiversidade e Biotecnologia | Quelemes P.V.,Nucleo de Pesquisa em Biodiversidade e Biotecnologia | Leal S.H.,Federal University of ABC | And 6 more authors.
Materials Science and Engineering C | Year: 2014

Composites prepared from polyaniline (PANI) and the ceramic technology of titanium dioxide (TiO2) have been proposed, however, the interaction of these materials with greater control of molecular arrangement becomes attractive in order to achieve properties not previously described or yet the optimization of those already reported. Therefore, in this study, thin hybrid films made of polyaniline (PANI), a conductive polymer, and the technological ceramic, titanium dioxide (TiO2), were prepared by the layer-by-layer (LbL) self-assembly technique. The films were characterized by cyclic voltammetry (CV), UV-VIS spectroscopy and atomic force microscopy (AFM). Aiming to improve the dispersion of the ceramic in the polymer matrix, the commercial surfactant, cetyl trimethylammonium bromide (CTAB), was used in the formation of the films. The best condition of deposition was found showing synergic interactions between the conjugated materials. The antibacterial activity of the PANI(TiO2)/CTAB films was studied and the obtained results suggest their use as antimicrobial coatings. © 2013 Elsevier B.V. All rights reserved. Source

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