Leonardo G. Paterno

University of Brasília, Brasília, Federal District, Brazil

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Publications (46)82.13 Total impact

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    ABSTRACT: Conjugated polymers are organic materials endowed with a π-electron conjugation along the polymer backbone that present appealing electrical and optical properties for technological applications. By using conjugated polymeric materials in the nanoscale, such properties can be further enhanced. In addition, the use of nanostructured materials makes possible miniaturize devices at the micro/nano scale. The applications of conjugated nanostructured polymers include sensors, actuators, flexible displays, discrete electronic devices, and smart fabric, to name a few. In particular, the use of conjugated polymers in chemical and biological sensors is made feasible owning to their sensitivity to the physicochemical conditions of its surrounding environment, such as chemical composition, pH, dielectric constant, humidity or even temperature. Subtle changes in these conditions bring about variations on the electrical (resistivity and capacitance), optical (absorptivity, luminescence, etc.), and mechanical properties of the conjugated polymer, which can be precisely measured by different experimental methods and ultimately associated with a specific analyte and its concentration. The present review article highlights the main features of conjugated polymers that make them suitable for chemical sensors. An especial emphasis is given to nanostructured sensors systems, which present high sensitivity and selectivity, and find application in beverage and food quality control, pharmaceutical industries, medical diagnosis, environmental monitoring, and homeland security, and other applications as discussed throughout this review.
    Journal of Nanoscience and Nanotechnology 09/2014; 14(9). DOI:10.1166/jnn.2014.9362 · 1.34 Impact Factor
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    ABSTRACT: Iron oxide nanostructured (ION) electrodes were assembled layer-by-layer onto ITO-coated glass substrates and their structure, morphology, and electrochemical properties were investigated, the latter aiming at the development of a chemical sensor for Cu2+. The electrodes were built by immersing the substrate alternately into an aqueous colloidal suspension of positively charged magnetite nanoparticles (np-Fe3O4, 8 nm) and an aqueous solution of anionic sodium sulfonated polystyrene (PSS). The adsorbed amount of both materials was monitored ex-situ by UV-vis spectroscopy and it was found to increase linearly with the number of deposition cycles. The resulting films feature a densely-packed structure of magnetite nanoparticles, as suggested by AFM and Raman spectroscopy, respectively. Cyclic voltammograms of electrodes immersed in acetate buffer (pH 4.6) displayed three electrochemical events that were tentatively ascribed to the reduction of Fe(III) oxy-hydroxide to magnetite, reduction of maghemite to magnetite, and finally oxidation of magnetite to maghemite. The effect of np-Fe3O4/PSS bilayers on the ION electrode performance was to increase the anodic and cathodic currents produced during electrochemical oxidation-reduction of the Fe(CN)3−/4− redox couple. With more bilayers, the ION electrode provided higher anodic/cathodic currents. Moreover, the redox couple exhibited a quasi-reversible behavior at the ION electrode as already observed with other working electrode systems. Fitting of voltammetry data provided the apparent electron transfer constants, which were found to be higher in ION electrodes for both redox couples (Fe(CN)3−/4− and Cu2+/0). By means of differential pulsed anodic stripping voltammetry, the ION electrodes were found to respond linearly to the presence of Cu2+ in aqueous samples in the range between 1.0 and 8.0×10−6 mol·L−1 and displayed a limit of detection of 0.3×10−8 mol·L−1. The sensitivity was ∼0.6 μA/μmol·L−1. In standard addition and recovery experiments performed with tap water the recovery was about 102%–119%. In similar experiments conducted with ground and instant coffee samples the recovery was 92.5% and 103%, respectively. Furthermore, the ION electrodes were almost insensitive to the presence of common interfering ions, such as Zn2+, Mn2+, Ni2+, and Fe3+, even at concentrations ten times higher than that of Cu2+.
    Journal of Nanoscience and Nanotechnology 09/2014; 14(9). DOI:10.1166/jnn.2014.9379 · 1.34 Impact Factor
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    ABSTRACT: Bionanocomposite films have been prepared by casting an aqueous suspension of acetylated starch (ST) and poly(vinyl alcohol) (PVA) loaded with graphene oxide (GO). A photochemical and reagentless method has been successfully performed to convert the GO phase into reduced graphene oxide (RGO). The nanocomposites have displayed improved thermal and electrical properties when the amount of the GO phase is increased and properly converted to RGO. The molecular-level interactions between components are mainly hydrogen-bonding type according to attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and Raman spectroscopies, as well as thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) has confirmed the effective mixing between the GO and the ST-PVA matrix. The thermal diffusivity and electrical resistivity of ST-GO nanocomposites have increased one order and decreased two orders of magnitude, respectively, after the photochemical treatment. These findings have confirmed the effectiveness of the proposed approach to produce starch-based nanocomposites with improved thermal and electrical properties.
    06/2014; 106(1):305-11. DOI:10.1016/j.carbpol.2014.02.008
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    ABSTRACT: Graphene oxide (GO) multilayers were produced by the layer-by-layer technique after successive immersions of quartz slides into aqueous suspensions of cationic poly(diallyldimethyl ammonium chloride) (PDAC) and anionic GO. The adsorbed amount of GO within the multilayers measured ex situ by UV-vis spectroscopy was found to increase linearly with the number of PDAC-GO bilayers. UV-vis and Raman spectra confirmed the conversion of GO to its reduced form, namely reduced graphene oxide (RGO), when the multilayers were subjected to hot hydrazine. According to AFM images, multilayers are flat with GO sheets forming edge structures. Additionally, impedance spectroscopy provided information regarding the multilayer growth mechanism, which starts with isolated GO sheets that bridge each other after deposition of five PDAC-GO bilayers. As a proof of principle, it was demonstrated that a sensor array composed by reduced multilayers deposited onto interdigitated microelectrodes and interrogated by impedance spectroscopy is capable of discriminating vapours of volatile solvents, including toluene, gasoline, ethanol, chloroform, and acetone, as well as chemicals in aqueous solutions, such as hydrochloric acid, sodium chloride, ammonium hydroxide, and sucrose. This capability was made possible only because the LbL assembly permitted one to tune the sensors' sensitivity with the number of PDAC-GO bilayers. The results presented herein suggest that the reduced PDAC-GO multilayers are promising elements for non-specific chemical sensors.
    RSC Advances 01/2014; 4(34):17917. DOI:10.1039/c4ra01469c · 3.84 Impact Factor
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    ABSTRACT: Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan δ) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces.
    Physical Chemistry Chemical Physics 10/2013; 15(45). DOI:10.1039/c3cp53602e · 4.20 Impact Factor
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    ABSTRACT: Ultra-thin (thicknesses of 50–90 nm) nanocomposite films of cobalt ferrite nanoparticles (np-CoFe 2 O 4 , 18 nm in diameter) and polyelectrolytes (doped polyaniline-PANI, poly-3,4-ethylenedioxy thiophene: polystyrene sul-fonic acid–PEDOT:PSS, and sulfonated lignin-SL) are assembled layer-by-layer onto interdigitated microelec-trodes aiming at to create novel nanostructured sensoactive materials for liquid media chemical sensors. The nanocomposites display a distinctive globular morphology with nanoparticles densely-packed while surrounded by polyelectrolytes. Due to the presence of np-CoFe 2 O 4 the nanocomposites display low electrical conductivity according to impedance data. On the other hand, this apparent shortcoming turns such nanocomposites much more sensitive to the presence of ions in solution than films made exclusively of conducting polyelectrolytes. For example, the electrical resistance of np-CoFe 2 O 4 /PEDOT:PSS and PANI/SL/np-CoFe 2 O 4 /SL architectures has a 10-fold decrease when they are immersed in 20 mmol. L −1 NaCl solution. Impedance spectra fitted with the response of an equivalent circuit model suggest that the interface created between nanoparticles and poly-electrolytes plays a major role on the nanocomposites electrical/dielectrical behavior. Since charge transport is sensitive to nanoparticle-polyelectrolyte interfaces as well as to the physicochemical conditions of the environ-ment, the np-CoFe 2 O 4 -based nanocomposites can be used as sensing elements in chemical sensors operated under ac regime and room temperature.
    09/2013; 2(3):175-183. DOI:10.1166/jon.2013.1053
  • Leonardo G. Paterno · Maria A. G. Soler
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    ABSTRACT: The layer-by-layer (LbL) technique is a wet chemical method for the assembly of ultrathin films, with thicknesses up to 100 nm. This method is based on the successive transfer of molecular layers to a solid substrate that is dipped into cationic and anionic solutions in an alternating fashion. The adsorption is mainly driven by electrostatic interactions so that many molecular and nanomaterial systems can be engineered under this method. Moreover, it is inexpensive, can be easily performed, and does not demand sophisticated equipment or clean rooms. The most explored use of the LbL technique is to build up molecular devices for chemical sensing and energy conversion. Both applications require ultrathin films where specific elements must be organized with high control of thickness and spatial distribution, preferably in the nanolength and mesolength scales. In chemical sensors, the LbL technique is employed to assemble specific sensoactive materials such as conjugated polymers, enzymes, and immunological elements onto appropriated electrodes. Molecular recognition events are thus transduced by the assembled sensoactive layer. In energy-conversion devices, the LbL technique can be employed to fabricate different device’s parts including electrodes, active layers, and auxiliary layers. In both applications, the devices’ performance can be fully modulated and improved by simply varying film thickness and molecular architecture. The present review article highlights the main features of the LbL technique and provides a brief description of different (bio)chemical sensors, solar cells, and organic light-emitting diodes enabled by the LbL approach.
    JOM: the journal of the Minerals, Metals & Materials Society 06/2013; 65(6). DOI:10.1007/s11837-013-0608-1 · 1.76 Impact Factor
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    ABSTRACT: ______________________________________________________________________________________________________ Resumo: Os polímeros condutores são polímeros contendo ligações conjugadas em suas cadeias que se tornam condutores através de processos de dopagem. A grande gama de polímeros e a possibilidade do controle de suas propriedades em escala molecular têm tornado tais materiais extremamente atrativos em inúmeras aplicações. Aqui revisaremos os princípios básicos do funcionamento dos sensores e como os polímeros condutores podem ser usados para aumentar e melhorar a sua detecção e/ou seletividade. Na terceira e última etapa cobriremos o uso de polímeros condutores em biossensores. Palavras-chave: Sensores; polímeros condutores; nanotecnologia; aplicações. ___________________________________________________________________________________________________ Abstract: Conducting polymers are polymers containing conjugated bonds in their backbones that can become conductive through several doping processes. A wide range of polymers and the possibility of controlling their properties at the molecular scale have made such materials extremely attractive in numerous applications. Here we review the basic principles of sensors and how conductive polymers can be used to enhance sensor detection limit and/or selectivity. In the third and final part, we will review the use of conducting polymers in biosensors.
  • Maria A. G. Soler · Leonardo G. Paterno · Paulo C. Morais
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    ABSTRACT: Nanostructured magnetic materials are nowadays focus of intensive scientific and industrial research pushed by expectations from fields as diverse as microelectronics, medicine and health care. One of the challenges faced by these materials before getting into many of these applications is the development of methodologies capable of processing them in the form of thin films. Nonetheless, the layer-by-layer technique (LbL) emerges as a powerful yet very simple way of producing ultra-thin films of magnetic nanoparticles while addressing at the same time rigorous control of film morphology and end properties. The LbL approach takes advantage on electrostatic interactions established between charged colloidal nanoparticles and polyelectrolytes to engineer mono and multilayered films onto several types of solid substrates. Moreover, the LbL technique is benefited by the intensive research conducted in colloidal chemistry which is capable of producing magnetic nanoparticles with high control of chemical composition, crystalinity, shape, and size. Superparamagnetic iron oxide particles (SPIO) represented by magnetite, maghemite and cobalt ferrite are suitable candidates for the LbL assembly. In combination with a myriad of polyelectrolytes, SPIO-based LbL films display very interesting properties that can be fully modulated during film assembly. This review article describes in detail the LbL assembly of SPIO materials including analytical techniques employed during film formation, structure and morphology characterizations. Many examples of SPIO-based LbL films are described herein. The review also emphasizes possible ways of tailoring via LbL the magnetic properties of the resulting films. Moreover, a deeper understanding of magnetic properties of these films is attempted by a combination of experimental and simulation studies described at the end of the text.
    12/2012; 1(2):101-119. DOI:10.1166/jon.2012.1015
  • Guilherme S. Braga · Leonardo G. Paterno · Fernando J. Fonseca
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    ABSTRACT: 2-Methylisoborneol (MIB) and geosmin (GSM) are sub products from algae decomposition and, depending on their concentration, can be toxic; otherwise, they give unpleasant taste and odor to water. For water treatment companies it is important to constantly monitor their presence in the distributed water and avoid further costumer complaints. Lower-cost and easy-to-read instrumentation would be very promising in this regard. In this study, we evaluate the potentiality of an electronic tongue (ET) system based on non-specific polymeric sensors and impedance measurements in monitoring MIB and GSM in water samples. Principal component analysis (PCA) applied to the generated data matrix indicated that this ET was capable to perform with remarkable reproducibility the discrimination of these two contaminants in either distilled or tap water, in concentrations as low as 25 ng L−1. Nonetheless, this analysis methodology was rather qualitative and laborious, and the outputs it provided were greatly subjective. Also, data analysis based on PCA severely restricts automation of the measuring system or its use by non-specialized operators. To circumvent these drawbacks, a fuzzy controller was designed to quantitatively perform sample classification while providing outputs in simpler data charts. For instance, the ET along with the referred fuzzy controller performed with a 100% hit rate the quantification of MIB and GSM samples in distilled and tap water. The hit rate could be read directly from the plot. The lower cost of these polymeric sensors allied to the especial features of the fuzzy controller (easiness on programming and numerical outputs) provided initial requirements for developing an automated ET system to monitor odorant species in water production and distribution.
    Sensors and Actuators B Chemical 08/2012; s 171–172:181–189. DOI:10.1016/j.snb.2012.02.092 · 4.29 Impact Factor
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    ABSTRACT: In this study we report an experimental approach capable of tuning dipolar interactions in hybrid magnetic nanofilms produced via layer-by-layer assembly of positively-charged maghemite nanoparticles and sodium sulfonated polystyrene onto glass and silicon substrates. Morphological and magnetic properties of the as prepared nanofilms were determined by Raman spectroscopy, atomic force microscopy, conventional and SQUID magnetometry. Maghemite nanoparticles form densely packed layers with voids between particles being filled by polymeric material as observed in atomic force microscopy images. Magnetic hysteresis loops and zero-field-cooled/field-cooled magnetization curves reveal a superparamagnetic behavior at room temperature. The energy barrier for the magnetic moment reversal of the nanofilms has been determined from the frequency dependent ac susceptibility and is related to the gamma-Fe2O3 nanoparticles concentration used in the colloidal dispersion throughout film fabrication. Variations on the interparticle distances have a direct effect on the interparticle dipolar interactions. A less concentrated colloid gives rise to large separated nanoparticles inside the nanofilm with a consequent reduction on the energy barrier for the magnetic moment reversal. The fabrication process exploring the control of the nanoparticle concentration can thus be used to tune the magnetic dipolar interactions in the nanofilms.
    Journal of Nanoscience and Nanotechnology 08/2012; 12(8):6672-8. DOI:10.1166/jnn.2012.4554 · 1.34 Impact Factor
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    ABSTRACT: The internal morphology and magnetic properties of layer-by-layer assembled nanofilms of polyaniline (PANI) and maghemite (gamma-Fe2O3-7.5-nm diameter) were probed with cross-sectional transmission electron microscopy (TEM) and magnetization measurements (magnetic hysteresis loops, magnetization using zero-field cooled/field-cooled protocols, and ac magnetic susceptibility). Additionally, simulations of the as-produced samples were performed to assess both the nanofilm's morphology and the corresponding magnetic signatures using the cell dynamic system (CDS) approach and Monte Carlo (MC) through the standard Metropolis algorithm, respectively. Fine control of the film thickness and average maghemite particle-particle within this magnetic structure was accomplished by varying the number of bilayers (PANI/gamma-Fe2O3) deposited onto silicon substrates or through changing the concentration of the maghemite particles suspended within the colloidal dispersion sample used for film fabrication. PANI/gamma-Fe2O3 nanofilms comprising 5, 10, 25 and 50 deposited bilayers displayed, respectively, blocking temperatures (T-B) of 30, 35, 39 and 40 K and effective energy barriers (Delta E/k(B)) of 1.0 x 10(3), 2.3 x 10(3), 2.8 x 10(3) and 2.9 x 10(3) K. Simulation of magnetic nanofilms using the CDS model provided the internal morphology to carry on MC simulation of the magnetic properties of the system taking into account the particle-particle dipolar interaction. The simulated (using CDS) surface-surface particle distance of 0.5, 2.5 and 4.5 nm was obtained for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm, respectively. The simulated (using MC) T-B values were 33.0, 30.2 and 29.5 K for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm, respectively. We found the experimental (TEM and magnetic measurements) and the simulated data (CDS and MC) in very good agreement, falling within the same range and displaying the same systematic trend. Our findings open up new perspectives for fabrication of magnetic nanofilms with pre-established (simulated) morphology and magnetic properties.
    Journal of Nanoparticle Research 03/2012; 14(3-3). DOI:10.1007/s11051-011-0653-z · 2.28 Impact Factor
  • Adalberto L. Garçom · Fernando J. Fonseca · Leonardo G. Paterno
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    ABSTRACT: Polymeric sensors with improved resistance to organic solvents were produced via the layer-by-layer thin film deposition followed by chemical cross-linking. According to UV-vis spectroscopy, the mass loss of polyaniline/poly(vinyl alcohol) and polyaniline/novolac-type resin based films deposited onto glass slides was less than 20% when they were submitted to successive immersions (up to 3,000 immersion cycles) into commercially available ethanol and gasoline fuel samples. Polyallylamine hydrochloride/nickel tetrasulfonated phthalocyanine films presented similar stability. The electrical responses assessed by impedance spectroscopy of films deposited onto Au-interdigitated microelectrodes were relatively unaffected after continuous or cyclic immersions into both fuels. After these studies, an array including these polymeric sensors was employed to detect adulteration in ethanol and gasoline samples. After principal component analysis, it was possible to conclude that the proposed sensor array is capable to discriminate with remarkable reproducibility ethanol samples containing different amounts of water or else gasoline samples containing different amounts of ethanol. In both examples, more than 90% of data variance was retained in the first principal component. For each type of sample, ethanol and gasoline, it was found a linear correlation between one of the principal components and the sample's composition. These findings allow one to conclude that these films present great potential for the development of reliable and low-cost sensors for fuel analysis in liquid phase.
    Sensor Letters 03/2012; 10(3):866-873. DOI:10.1166/sl.2012.2586 · 0.56 Impact Factor
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    ABSTRACT: The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film thickness increasing from about 20 to 120 nm while shifting from 3 to 10 CoFe(2)O(4)/PSS bilayers, using the 8.9 × 10(-6) (moles of cobalt ferrite per litre) suspension.
    Physical Chemistry Chemical Physics 12/2011; 13(48):21233-42. DOI:10.1039/c1cp22693b · 4.20 Impact Factor
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    ABSTRACT: A multisensor system combining electronic tongue (ET) and nose (EN) was here developed to improve fuel quality control. Several impedance microelectrode sensors, with different geometries and sensoactive materials, were used separately and simultaneously in both liquid and vapor samples. The combined system significantly improved the substance discrimination compared to isolated ET and EN.
    09/2011; DOI:10.1063/1.3626349
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    ABSTRACT: This paper introduces a new approach for simulating magnetic properties of nanocomposites comprising magnetic particles embedded in a non-magnetic matrix, taking into account the 3D structure of the system in which particles' positions correctly mimic real samples. The proposed approach develops a multistage simulation procedure in which the size and distribution of particles within the hosting matrix is firstly attained by means of the Cell Dynamic System (CDS) model. The 3D structure provided by the CDS step is further employed in a Monte Carlo (MC) simulation of zero-field-cooled/field-cooled (ZFC/FC) and magnetic hysteresis loops ($M \times H$ curves) for the system. Simulations are aimed to draw a realistic picture of the as-produced ultra-thin films comprising maghemite nanoparticles dispersed in polyaniline. Comparison (ZFC/FC and $M \times H$ curves) between experiments and simulations regarding the maximum of the ZFC curve ($T_{\scriptsize MAX}$), remanence ($M_R/M_s$) and coercivity ($H_C$) revealed the great accuracy of the multistage approach proposed here while providing information about the system's morphology and magnetic properties. For a typical sample the value we found experimentally for $T_{\scriptsize MAX}$ (54 K) was very close to the value provided by the simulation (53 K). For the parameters depending on the nanoparticle clustering the experimental values were consistently lower ($M_R/M_s$ = 0.32 and $H_C$ = 210 Oe) than the values we found in the simulation ($M_R/M_s$ = 0.53 and $H_C$ = 274 Oe). Indeed, the approach introduced here is very promising for the design of real magnetic nanocomposite samples with optimized features.
    Journal of Magnetism and Magnetic Materials 08/2011; 347. DOI:10.1016/j.jmmm.2013.07.054 · 2.00 Impact Factor
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    ABSTRACT: Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe2O4 nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material.
    Journal of Magnetism and Magnetic Materials 05/2011; 323:1372-1377. DOI:10.1016/j.jmmm.2010.11.049 · 2.00 Impact Factor
  • Guilherme S. Braga · Leonardo G. Paterno · Fernando J. Fonseca
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    ABSTRACT: An electronic tongue (ET) system consisting of conducting polymer sensors was employed to detect geosmin (GSM) in distilled water. GSM is a tainting compound and known to cause undesirable tastes and odors in water and aquaculture farming. Diluted solutions of GSM were prepared in distilled water at different concentrations. The electrical response (capacitance) of the sensors was analyzed using principal analysis component (PCA). The data obtained were separated into different clusters indicating a good sensibility of the ET system to this compound in distilled water. The ET showed signal saturation for concentrations higher than 300ng.L -1 . So far, the detection limit of our system is 25ng.L -1 . Nevertheless, close grouping
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    ABSTRACT: A molecularly imprinted polymer (MIP) impedance-based sensor was employed to detect theophylline in distilled water. To evaluate its sensibility, impedance measurements were carried out in a diluted solution of theophylline (1mM) and distilled water using MIP and NIP (reference non-imprinted polymer) sensors. MIP showed higher sensitivity to theophylline than the NIP. This feature shows their suitability for developing an electronic tongue system for determination of methylxanthines.

Publication Stats

370 Citations
82.13 Total Impact Points

Institutions

  • 2010–2014
    • University of Brasília
      • • Institute of Chemistry
      • • Institute of Physics
      Brasília, Federal District, Brazil
  • 2008–2010
    • University of São Paulo
      San Paulo, São Paulo, Brazil
  • 2001–2002
    • Universidade Federal de São Carlos
      • Departamento de Engenharia de Materiais (DEMa)
      São Carlos, Estado de Sao Paulo, Brazil