Filho VFL, Machado G, Batista RJC, Soares JS, de Oliveira AB, de Vasconcelos C, Lino AA, Manhabosco TM.
Effect of TiO2 Nanoparticles on Polyaniline Films Electropolymerized at Different pH. JOURNAL OF PHYSICAL CHEMISTRY C. 2016;120:14977-14983.
AbstractIn this work hybrids of titanium manopartides 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 nanopartide presence.
de Vasconcelos CKB, Batista RJC, da Regis MGR, Manhabosco TM, de Oliveira AB.
A simple model for solute-solvent separation through nanopores based on core-softened potentials. PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS. 2016;453:184-193.
AbstractWe propose an effective model for solute separation from fluids through reverse osmosis based on core-softened potentials. Such potentials have been used to investigate anomalous fluids in several situations under a great variety of approaches. Due to their simplicity, computational simulations become faster and mathematical treatments are possible. Our model aims to mimic water desalination through nano-membranes through reverse osmosis, for which we have found reasonable qualitative results when confronted against all-atoms simulations found in the literature. The purpose of this work is not to replace any fully atomistic simulation at this stage, but instead to pave the first steps towards coarse-grained models for water desalination processes. This may help to approach problems in larger scales, in size and time, and perhaps make analytical theories more viable. (C) 2016 Elsevier B.V. All rights reserved.
de Oliveira AB, Chacham H, Soares JS, Manhabosco TM, de Resende HFV, Batista RJC.
Vibrational G peak splitting in laterally functionalized single wall carbon nanotubes: Theory and molecular dynamics simulations. CARBON. 2016;96:616-621.
AbstractWe present a theoretical study of the vibrational spectrum, in the G band region, of laterally hydrogenated single wall carbon nanotubes through molecular dynamics simulations. We find that bilateral hydrogenation which can be induced by hydrogenation under lateral strain causes permanent oval deformations on the nanotubes and induces the splitting of vibrational states in the G-band region. We propose that such splitting can be used as a Raman fingerprint for detecting nanotubes that have been permanently modified due to bilateral hydrogenation. In particular, our results may help to clarify the recent findings of Araujo and collaborators [Nano Lett. 12, 4110 (2012)1 which have found permanent modifications in the Raman G peaks of locally compressed carbon nanotubes. We have also developed an analytical model for the proposed phenomenon that reproduces the splitting observed in the simulations. (C) 2015 Elsevier Ltd. All rights reserved.