P.S.P. Herrmann

Universidade Federal de São Carlos, São Carlos do Pinhal, São Paulo, Brazil

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Publications (37)47.04 Total impact

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    ABSTRACT: Nanometric TiO 2 powders were obtained from low tem-perature calcination of a TiO 2 resin prepared using the Pechini's method. Firing the TiO 2 resin at 500 o C/2h a powder with anatase phase was obtained, otherwise firing the TiO 2 resin at 700 o C/2h a powder with rutile phase was achieved as measured by X-ray diffraction (XRD). The anatase powder presented average particle size of 60 nm observed by Scanning Electronic Microscopy (SEM-FEG) micrographs and average crystallite size of 13 nm calcu-lated from the XRD, while the rutile powder presented av-erage crystallite size of 34 nm. Nanocrystalline TiO 2 films with good homogeneity and optical quality were obtained with 80 nm and 320 nm in thickness by Electron Beam Physical Vapour Deposition (EB-PVD) in vacuum on amorphous quartz substrates submitted at 350 o C during the evaporation. The 80 nm-thick film presented average particle size of 140 nm and roughness (R a) of 1.08 nm and the 320 nm-thick film showed average particle size of 350 nm and roughness (R a) of 2.14 nm measured by Atomic Force Microscopy (AFM). In these conditions of deposi-tion the films presented only anatase phase observed by XRD and MicroRaman spectroscopy.
    Full-text · Article · Jun 2015
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    C Steffens · F L Leite · A Manzoli · R D Sandoval · O Fatibello · P S P Herrmann

    Full-text · Dataset · Jun 2014
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    C Steffens · F.L. Leite · A Manzoli · R.D. Sandoval · O Fatibello · P.S.P. Herrmann
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    ABSTRACT: In the present work, PANI (polyaniline) emeraldine salt (doped) and base (dedoped) were used as the sensitive layer of a silicon microcantilever, and the mechanical response (deflection) of the bimaterial (coated microcantilever) was investigated under the influence of humidity. PANI in the emeraldine base oxidation state was obtained by interfacial synthesis and was deposited on the microcantilever surface by spin-coating (dedoped). Next, the conducting polymer was doped with 1 M HCl (hydrochloric acid). A four-quadrant AFM head with an integrated laser and a position-sensitive detector (AFM Veeco Dimension V) was used to measure the optical deflection of the coated microcantilever. The deflection of the coated (doped and undoped PANI) and uncoated microcantilever was measured under different humidities (in triplicate) at room pressure and temperature in a closed chamber to evaluate the sensor's sensitivity. The relative humidity (RH) in the chamber was varied from 20% to 70% using dry nitrogen as a carrier gas, which was passed through a bubbler containing water to generate humidity. The results showed that microcantilevers coated with sensitive layers of doped and undoped PANI films were sensitive (12,717 ± 6% and 6,939 ± 8%, respectively) and provided good repeatability (98.6 ± 0.015% and 99 ± 0.01%, respectively) after several cycles of exposure to RH. The microcantilever sensor without a PANI coating (uncoated) was not sensitive to humidity. The strong effect of doping on the sensitivity of the sensor was attributed to an increased adsorption of water molecules dissociated at imine nitrogen centers, which improves the performance of the coated microcantilever sensor. Moreover, microcantilever sensors coated with a sensitive layer provided good results in several cycles of exposure to RH (%). SCANNING 9999:1-6, 2013. © Wiley Periodicals, Inc.
    Full-text · Article · May 2014 · Scanning
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    C Steffens · F L Leite · A Manzoli · R D Sandoval · O Fatibello · P S P Herrmann
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    ABSTRACT: This paper describes a silicon cantilever sensor coated with a conducting polymer layer. The mechanical response (deflection) of the bimaterial (the coated microcantilever) was investi-gated under the influence of several volatile compounds—methanol, ethanol, acetone, propanol, dichloroethane, toluene and benzene. The variations in the deflection of the coated and uncoated microcantilevers when exposed to volatile organic compounds were evaluated, and the results indicated that the highest sensitivity was obtained with the coated microcantilever and methanol. The uncoated microcantilever was not sensitive to the volatile organic compounds. An increase in the concentration of the volatile organic compound resulted in higher deflections of the microcan-tilever sensor. The sensor responses were reversible, sensible, rapid and proportional to the volatile concentration.
    Full-text · Article · Mar 2014 · Journal of Nanoscience and Nanotechnology
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    Full-text · Article · Feb 2014 · Journal of Materials Science
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    ABSTRACT: a b s t r a c t Bio-inspired materials designed for mimicking nature has gained attention in the last years, owing to their appealing properties, such as adhesive and self-cleaning properties. However, studies reporting bio-inspired sensors able to detect minimal amounts of pheromones are still scarce. Here we report on the functionalization of AFM cantilever with polyaniline (PANI), which was used as a sensor to detect pheromone 2-heptanone. This hormone is very significant for honey bees, which release it as a repellent scent marking to avoid enemies and other bees. The functionalization of the sensor was achieved by depositing a thin film of PANI in the emeraldine state on the cantilever through spin-coating. Infrared spectroscopy showed that the 2-heptanone was adsorbed by PANI film deposited on cantilever surface. The linear response of the coated cantilever sensor regarding 2-heptanone concentration for distinct tem-peratures was evaluated, as well as its mechanical behavior, hysteresis and storage time. The approach proposed here to functionalize AFM cantilever with PANI film to detect 2-heptanone showed a poten-tial methodology for designing sensors able to detect minimal amounts of pheromones and natural compounds.
    Full-text · Article · Jan 2014 · Sensors and Actuators B Chemical
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    C Steffens · A Manzoli · F.L. Leite · O Fatibello · P.S.P. Herrmann
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    ABSTRACT: a b s t r a c t A microcantilever sensor is presented. Functionalization of the cantilever with a polyaniline (PANI) sen-sitive layer and its use as a humidity sensor were investigated. Polyaniline was produced by interfacial synthesis and the sensitive layer was deposited on the microcantilever surface by the spin-coating method. The microcantilever deflection at various levels of relative humidity (RH) was read by means of the optical lever of an atomic force microscope (AFM Veeco Dimension V). A range of RH from 20% to 70% was introduced into the AFM chamber by mixing streams of dry and wet nitrogen. The sensitivity and reversibility of the sensors were assessed at various RH and temperatures (10, 20 and 30 °C). A large deflection was observed in the coated microcantilever sensors, with faster response time at 10 °C and bet-ter sensitivity and reversibility at 30 °C. These results demonstrate that the spin-coated microcantilever can be used as a sensor to detect relative humidity at various different temperatures. Ó 2013 Elsevier B.V. All rights reserved.
    Full-text · Article · Jan 2014 · Microelectronic Engineering
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    C Steffens · A Manzoli · F L Leite · O Fatibello · P S P Herrmann
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    ABSTRACT: a b s t r a c t A microcantilever sensor is presented. Functionalization of the cantilever with a polyaniline (PANI) sen-sitive layer and its use as a humidity sensor were investigated. Polyaniline was produced by interfacial synthesis and the sensitive layer was deposited on the microcantilever surface by the spin-coating method. The microcantilever deflection at various levels of relative humidity (RH) was read by means of the optical lever of an atomic force microscope (AFM Veeco Dimension V). A range of RH from 20% to 70% was introduced into the AFM chamber by mixing streams of dry and wet nitrogen. The sensitivity and reversibility of the sensors were assessed at various RH and temperatures (10, 20 and 30 °C). A large deflection was observed in the coated microcantilever sensors, with faster response time at 10 °C and bet-ter sensitivity and reversibility at 30 °C. These results demonstrate that the spin-coated microcantilever can be used as a sensor to detect relative humidity at various different temperatures. Ó 2013 Elsevier B.V. All rights reserved.
    Full-text · Dataset · Nov 2013
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    Clarice Steffens · Fabio L Leite · Carolina C Bueno · Alexandra Manzoli · Paulo Sergio De Paula Herrmann
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    ABSTRACT: This review article discusses and documents the basic concepts and principles of nano/biosensors. More specifically, we comment on the use of Chemical Force Microscopy (CFM) to study various aspects of architectural and chemical design details of specific molecules and polymers and its influence on the control of chemical interactions between the Atomic Force Microscopy (AFM) tip and the sample. This technique is based on the fabrication of nanomechanical cantilever sensors (NCS) and microcantilever-based biosensors (MC-B), which can provide, depending on the application, rapid, sensitive, simple and low-cost in situ detection. Besides, it can provide high repeatability and reproducibility. Here, we review the applications of CFM through some application examples which should function as methodological questions to understand and transform this tool into a reliable source of data. This section is followed by a description of the theoretical principle and usage of the functionalized NCS and MC-B technique in several fields, such as agriculture, biotechnology and immunoassay. Finally, we hope this review will help the reader to appreciate how important the tools CFM, NCS and MC-B are for characterization and understanding of systems on the atomic scale
    Full-text · Dataset · Dec 2012
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    Clarice Steffens · Fabio L Leite · Carolina C Bueno · Alexandra Manzoli · Paulo Sergio De Paula Herrmann
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    ABSTRACT: This review article discusses and documents the basic concepts and principles of nano/biosensors. More specifically, we comment on the use of Chemical Force Microscopy (CFM) to study various aspects of architectural and chemical design details of specific molecules and polymers and its influence on the control of chemical interactions between the Atomic Force Microscopy (AFM) tip and the sample. This technique is based on the fabrication of nanomechanical cantilever sensors (NCS) and microcantilever-based biosensors (MC-B), which can provide, depending on the application, rapid, sensitive, simple and low-cost in situ detection. Besides, it can provide high repeatability and reproducibility. Here, we review the applications of CFM through some application examples which should function as methodological questions to understand and transform this tool into a reliable source of data. This section is followed by a description of the theoretical principle and usage of the functionalized NCS and MC-B technique in several fields, such as agriculture, biotechnology and immunoassay. Finally, we hope this review will help the reader to appreciate how important the tools CFM, NCS and MC-B are for characterization and understanding of systems on the atomic scale.
    Full-text · Article · Dec 2012 · Sensors
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    ABSTRACT: A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness.
    Full-text · Article · Dec 2011 · Sensors
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    ABSTRACT: The control of materials properties and processes at the molecular level inherent in nanotechnology has been exploited in many areas of science and technology, including agriculture where nanotech methods are used in release of herbicides and monitoring of food quality and environmental impact. Atomic force microscopy (AFM) and related techniques are among the most employed nanotech methods, particularly with the possibility of direct measurements of intermolecular interactions. This chapter presents a brief review of the applications of AFM in agriculture that may be categorized into four main topics, namely thin films, research on nanomaterials and nanostructures, biological systems and natural fibers, and soils science. Examples of recent applications will be provided to give the reader a sense of the power of the technique and potential contributions to agriculture.
    Full-text · Chapter · Dec 2009
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    ABSTRACT: Low-cost sensors were developed in two steps: (i) using a negative template to print graphite electrodes on vellum paper and (ii) coating with conductive polymers. Thin films of polyaniline (PANI) in the emeraldine oxidation state were investigated as active layers, after being synthesized by two routes: (a) polyaniline doped with dodecylbenzenesulfonic acid (DBSA) deposited by supercritical fluid (SC CO2) and (b) PANI doped with hydrochloric acid (HCl) by the in situ polymerization method. The electrical response (mV) was measured with dedicated circuitry, both in static laboratory air and with a flow of dry nitrogen gas (N2) at room pressure and temperature in a closed chamber, to assess the sensors for their sensitivity and reversibility. The phase morphology (microfiber structure) was characterized by FE-SEM. Results showed a difference in behavior between the sensors obtained by SC CO2 coating with PANI and by in situ polymerization. The voltage in the SC CO2 sensor decreased when it was exposed to the flow of dry nitrogen, whereas the opposite effect was observed in the other sensor.
    No preview · Article · Nov 2009 · Synthetic Metals
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    ABSTRACT: The existence of conducting islands in polyani-line films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Mi-croscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH = 3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force mi-croscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting is-lands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we in-ferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism.
    Full-text · Article · Nov 2008 · Applied Physics A
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    ABSTRACT: The study of intermolecular interactions at interfaces is essential for a number of applications, in addition to the understanding of mechanisms involved in sensing and biosensing with liquid samples. There are, however, only a few methods to probe such interfacial phenomena, one of which is the atomic force spectroscopy (AFS) where the force between an atomic force microscope tip and the sample surface is measured. In this study, we used AFS to estimate adhesion forces for a nanostructured film of poly(o-ethoxyaniline) (POEA) doped with various acids, in measurements performed in air. The adhesion force was lower for POEA doped with inorganic acids, such as HCl and H(2)SO(4), than with organic acids, because the counterions were screened by the ethoxy groups. Significantly, the morphology of POEA both in the film and in solution depends on the doping acid. Using small-angle X-ray scattering (SAXS) we observed that POEA dissolved in a mixture of dimethyl acetamide exhibits a more extended coil-like conformation, with smaller radius of gyration, than for POEA in water, as in the latter POEA solubility is lower. In AFS measurements in a liquid cell, the force curves for a POEA layer displayed an attractive region for pH>or=5 due to van der Waals interactions, with no contribution from a double-layer since POEA was dedoped. In contrast, for pH<or=3, POEA was doped and the repulsive double-layer force dominated. With AFS one is therefore able to correlate molecular-level interactions with doping and morphology of semiconducting polymers.
    Full-text · Article · Jul 2008 · Micron
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    F. L. LEITE · E.C. ZIEMATH · P. S. P. HERRMANN

    Full-text · Article · Mar 2008 · Scanning
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    F. L. LEITE · M.MIR · A. M.ROSSI · E. L.MOREIRA · Y. P. MASCARENHAS · P. S. P. HERRMANN

    Full-text · Article · Mar 2008 · Scanning
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    ABSTRACT: Understanding the adsorption mechanisms in nanostructured polymer films has become crucial for their use in technological applications, since film properties vary considerably with the experimental conditions utilized for film fabrication. In this paper, we employ small-angle X-ray scattering (SAXS) to investigate solutions of polyanilines and correlate the chain conformations with morphological features of the nanostructured films obtained with atomic force microscopy (AFM). It is shown that aggregates formed already in solution affect the film morphology; in particular, at early stages of adsorption film morphology appears entirely governed by the chain conformation in solution and adsorption of aggregates. We also use SAXS data for modeling poly(o-ethoxyaniline) (POEA) particle shape through an ab initio procedure based on simulated annealing using the dummy atom model (DAM), which is then compared to the morphological features of POEA films fabricated with distinct pHs and doping acids. Interestingly, when the derivative POEA is doped with p-toluene sulfonic acid (TSA), the resulting films exhibit a fibrillar morphology-seen with atomic force microscopy and transmission electron microscopy-that is consistent with the cylindrical shape inferred from the SAXS data. This is in contrast with the globular morphology observed for POEA films doped with other acids.
    Full-text · Article · Jan 2008 · Journal of Colloid and Interface Science
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    ABSTRACT: Atomic force spectroscopy (AFS) was used to measure interaction forces between the tip and nanostructured layers of poly(o-ethoxyaniline) (POEA) in pure water and CuSO4 solutions. When the tip approach and retraction were carried out at low speeds, POEA chains could be physisorbed onto the Si3N4 tip via nonspecific interactions. We conjecture that while detaching, POEA chains were stretched and the estimated chain lengths were consistent with the expected values from the measured POEA molecular weight. The effects from POEA doping could be investigated directly by performing AFS measurements in a liquid cell, with the POEA film exposed to liquids of distinct pH values. For pH [greater-than-or-equal] 6.0, the force curves normally displayed an attractive region for POEA, but at lower pH valuesthe repulsive double-layer forces dominated. Measurements in the liquid cell could be further exploited to investigate how the film morphology and the force curve are affected when impurities are deliberately introduced in the liquid. The shape of the force curves and the film morphology depended on the concentration of heavy metal in the liquid cell. AFS may therefore be used to study the interaction between film and analyte, with important implications for the understanding of mechanisms governing the sensing ability of taste sensors.
    Full-text · Article · Aug 2007 · Microscopy and Microanalysis
  • L. H. C. Mattoso · P. S. P. Herrmann

    No preview · Article · Jan 2007 · Polímeros

Publication Stats

355 Citations
47.04 Total Impact Points

Institutions

  • 2014
    • Universidade Federal de São Carlos
      • Department of Chemistry
      São Carlos do Pinhal, São Paulo, Brazil
  • 1997-2012
    • Brazilian Agricultural Research Corporation (EMBRAPA)
      Brasília, Federal, Brazil
  • 2003-2008
    • CEP America
      Emeryville, California, United States