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Lima A.S.,University of Sao Paulo | Salles M.O.,University of Sao Paulo | Ferreira T.L.,Institute Ciencias Ambientais | Paixao T.R.L.C.,University of Sao Paulo | Bertotti M.,University of Sao Paulo
Electrochimica Acta | Year: 2012

The cathodic reduction of nitrate at copper electrodes was investigated by using scanning electrochemical microscopy (SECM) in the stripping-mode SECM (SM-SECM). This electrochemical process is facilitated at surfaces activated by a potential protocol involving anodic dissolution and subsequent reduction of copper cations, which causes an increase in the surface area. In the presence of chloride, a much more significant current enhancement was noticed, and a mechanism based on the formation of CuCl was proposed to explain the increased rate of nitrate reduction at this experimental condition. © 2012 Elsevier Ltd.

Costa L.T.,Federal University of Alfenas | Siqueira L.J.A.,Institute Ciencias Ambientais | Nicolau B.G.,University of Sao Paulo | Ribeiro M.C.C.,University of Sao Paulo
Vibrational Spectroscopy | Year: 2010

Raman spectra of polymer electrolytes based on poly(ethylene glycol) dimethyl ether (PEGdME) with LiClO 4, PEGdME/LiClO 4, and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, PEGdME/[bmim]PF 6, are compared. Raman spectroscopy suggests stronger interactions in PEGdME/LiClO 4 than PEGdME/[bmim]PF 6, thus corroborating previous results obtained by molecular dynamics simulations. Quantum Chemistry methods have been used to calculate vibrational frequencies and the equilibrium structure of segments of the polymer chain around the cation. A consistent picture has been obtained from Raman spectroscopy, density functional theory (DFT) calculations, and molecular dynamics simulations for these polymer electrolytes. © 2010 Elsevier B.V. All rights reserved.

Da Silva J.S.,Institute Ciencias Ambientais | Junqueira H.C.,University of Sao Paulo | Ferreira T.L.,Institute Ciencias Ambientais
Electrochimica Acta | Year: 2014

Microelectrode voltammetry was employed to gain information on the n-octanol/water partition ratio of phenothiazine dyes. The data were obtained as a function of pH and dye concentration in aqueous solutions. All the dyes present hydrophobic behavior at pH above 7.0. The analysis of the results shows not only the formation of neutral species in alkaline solution but the association of cationic form of these dyes with OH-play important roles in the partitioning of molecules from aqueous solution to n-octanol. © 2014 Elsevier Ltd. All rights reserved.

Santos R.T.D.,University of Sao Paulo | Longo L.S.,Institute Ciencias Ambientais | Alves S.,Institute Ciencias Ambientais
Molecular Crystals and Liquid Crystals | Year: 2014

In this work, we described the nonlinear optical properties from thermal origin of lamellar liquid crystals by Z-scan technique in different regions of the phase diagram. The results showed that nonlinear refractive index of LLC depends on the solvent layer space. We also studied the influence of the addition of magnetic nanoparticles in nonlinear optical properties of the system. © 2014 Copyright © Taylor & Francis Group, LLC.

Perez C.,Institute Ciencias Ambientais | Simoes F.R.,Unifesp Campus Baixada Santista | Codognoto L.,Institute Ciencias Ambientais
Journal of Solid State Electrochemistry | Year: 2015

In this work, a simple method for electroanalytical determination of 17α-ethinylestradiol (EE2) hormone in natural waters was developed using a boron-doped diamond electrode (BDD). The analyses were performed using square wave voltammetry and the parameters were optimized. The results showed a well-defined irreversible oxidation peak (BR buffer 0.1 mol L−1, pH 8.0) at +0.65 V (vs. Ag/AgCl). The voltammetric results showed also that the oxidation process is controlled by adsorption of species and indicated that there are two electrons involved. The obtained analytical curves for 17α-ethinylestradiol presented good linearity in the concentration range 9.9 × 10−7 to 5.2 × 10−6 mol L−1 in utlrapure water and 7.9 × 10−7 to 5.2 × 10−6 mol L−1 in natural water samples (supply dam). Detection limits (DL) obtained were between 2.4 × 10−7 and 7.5 × 10−7 mol L−1 and quantification limits (QL) between 7.9 × 10−7 and 2.5 × 10−6 mol L−1. The recovery experiments showed values between 86 and 114 % for spiked samples thus indicating the applicability of the electroanalytical methodology to quantify 17α-ethinylestradiol directly in natural water of supply Dam (Billings Dam in Diadema-SP. Brazil), without any preconcentration or derivatization. © 2015 Springer-Verlag Berlin Heidelberg

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