Time filter

Source Type

Paulino A.T.,University of Campinas | Guilherme M.R.,University of Campinas | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Tambourgi E.B.,University of Campinas
Macromolecular Chemistry and Physics

By means of a conventional cross-linking/co-polymerization reaction of modified gum arabic (M-GA), acrylamide (AAm), and potassium acrylate (KAAc) in the presence of magnetite (Fe3O4) nanoparticles, a magnetic field-sensitive M-GA-based hydrogel (smart hydrogel) was synthesized to investigate its potential as a magnetic biomaterial and as a intelligent hydrogel. Characterizations through FT-IR, NMR, XRD, Mössbauer, SEM, and EDX inferred that the smart hydrogel was efficiently formed. Theoretically, the smart hydrogel obtained in this work may effectively be applied as biomaterial either on remote controlled release or tissue engineering or even in other areas of science and technology. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

This work reported the characterization of hydrogels constituted by methylcellulose (MC) entrapped in polyacrylamide (PAAm) network prepared by cross-linking polymerization (gelling process). Spectroscopic and morphologic properties were investigated using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Effects of AAm, MC contents, ionic charge of salt counter-ions (NaCl, KCl, NH4Cl, CaCl2, MnCl2, MgCl2, and AlCl3), and fertilizers [(NH4)2SO4 and KH2PO4] on kinetic and hydrophilic (swelling degree) properties were investigated in detail. By decreasing the MC content or by increasing acrylamide content, there was a pronounced decrease in water uptake by the hydrogels. The increase in counter-ion X-Cl salt and the presence of fertilizer on the external swelling medium also provoked a decrease in water uptake. The water uptake mechanism of PAAm-MC hydrogels swollen in water followed the Fickian diffusion, while the mechanisms of hydrogels swollen in salt or fertilizer aqueous media followed the anomalous transport process. With their fast and high water absorption, the porous, three-dimensional matrices containing PAAm and MC are promising for agriculture as carrier vehicles. Source

Oliveira J.E.,Federal University of Sao Carlos | Grassi V.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Scagion V.P.,Federal University of Sao Carlos | Mattoso L.H.C.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | And 2 more authors.
IEEE Sensors Journal

A disposable low cost and simple flow-cell electronic tongue for water analysis is described. A sensor array is used that is comprised of six interdigitated microelectrodes coated with nanofiber films of poly(lactic acid)/mutliwalled carbon nanotube (MWCNT) composites. Fiber films are deposited directly on the interdigitated electrodes surface by solution blow spinning. Fiber film thickness is varied by using different deposition times (1, 3, and 15 min). Analysis of scanning electron microscopy and transmission electron microscopy micrographs indicates that average fiber diameters are 400 nm for neat poly lactic acid (PLA) and 200 nm for the PLA/MWCNT composite. The MWCNT is poorly dispersed in the PLA fiber matrix and formed aggregates interspersed throughout the fiber length. There are also MWCNTs exposed or partially exposed at the fiber surface. Fiber films containing MWCNT (1%) give the highest dc conductivity values and the most linear I-V profiles at room temperature. Sensor arrays with thin fiber film coatings (1 min deposition time) provide the best result for discriminating potable water samples using principal component analysis (PCA). The flow-cell electronic tongue coupled with PCA is used to discriminate potable water samples from non-potable water contaminated with metals or traces of pesticides. © 2001-2012 IEEE. Source

Takeda H.H.,Federal University of Sao Carlos | Takeda H.H.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Takeda H.H.,Federal University of Rondonia | Janegitz B.C.,Federal University of Sao Carlos | And 4 more authors.
Sensors and Actuators, B: Chemical

A glassy carbon electrode (GCE) modified with functionalized multiwalled carbon nanotubes within a poly(allylamine hydrochloride) film (CNTs-PAH) to determine ciprofibrate using differential pulse voltammetry (DPV) is proposed. The CNTs/PAH film was previously valued and characterized with the zeta potential technique and scanning electronic microscopy (SEM). The DP voltammograms presented a ciprofibrate oxidation peak potential at 0.98 V in a 0.1 mol L -1 phosphate buffer solution (pH 7.0). The analytical curve was linear in the ciprofibrate concentration range from 1.33 × 10 -5 to 1.32 × 10 -4 mol L -1, with a detection limit of 8.34 × 10 -6 mol L -1. Precise and accurate results are in agreement with those obtained by the chromatographic method at a 95% confidence level. © 2011 Elsevier B.V. All rights reserved. Source

Oliveira J.E.,Federal University of Sao Carlos | Oliveira J.E.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Moraes E.A.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | Marconcini J.M.,Laboratorio Nacional Of Nanotecnologia Para O Agronegocio | And 4 more authors.
Journal of Applied Polymer Science

The properties of mixtures of poly(lactic acid) (PLA) and poly(ethylene oxide) (PEO) were studied in polymer solutions by dilute solution viscometry, and in-solution blow-spun nanofibers were studied by microscopy (scanning electron and transmission electron microscopy) and thermal and spectral analysis. Three mixtures of PLA and PEO (3:1, 1:1, and 1:3) were solution-blended in chloroform. Dilute solvent viscometry indicated that the 3:1 mixture of PLA and PEO had a higher miscibility coefficient value than the other mixtures. The neat polymers and mixtures were solution-blow-spun into nanofibers. The fiber diameters were smallest in the neat polymers. Transmission electron micrographs revealed a core/sheath structure for the sample mixtures. X-ray analysis indicated that the crystallinity was positively correlated with the PEO content. Fibers from the mixtures had contact angle measurements similar to those of the neat PEO. Fourier transform infrared and Raman spectroscopy of the mixtures indicated interactions between ester and ether groups, which were attributed to dipole-dipole interactions between the ester groups of PLA and the ether groups of PEO. Copyright © 2013 Wiley Periodicals, Inc. Source

Discover hidden collaborations