Fabrication and characterization of chemical sensors made from nanostructured films of poly(o-ethoxyaniline) prepared with different doping acids

Chemical sensors made from nanostructured films of poly(o-ethoxyaniline) POEA and poly(sodium 4-styrene sulfonate) PSS are produced and used to detect and distinguish 4 chemicals in solution at 20 mM, including sucrose, NaCl, HCl, and caffeine. These substances are used in order to mimic the 4 basic tastes recognized by humans, namely sweet, salty, sour, and bitter, respectively. The sensors are produced by the deposition of POEA/PSS films at the top of interdigitated microelectrodes via the layer-by-layer technique, using POEA solutions containing different dopant acids. Besides the different characteristics of the POEA/PSS films investigated by UV-Vis and Raman spectroscopies, and by atomic force microscopy.. it is observed that their electrical response to the different chemicals in liquid media is very fast, in the order of seconds, systematical, reproducible, and extremely dependent on the type of acid used for film fabrication. The responses of the as-prepared sensors are reproducible and repetitive after many cycles of operation. Furthermore, the use of an "electronic tongue" composed by an array of these sensors and principal component analysis as pattern recognition tool allows one to reasonably distinguish test solutions according to their chemical composition. (c) 2007 Published by Elsevier B.V.

Optical chemical sensors using polythiophene derivatives as active layer for detection of volatile organic compounds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reduced graphene oxide multilayers for gas and liquid phases chemical sensing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

An Electrochemical Sensor Based on Nanostructured Hollandite-type Manganese Oxide for Detection of Potassium Ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detection of volatile organic compounds using a polythiophene derivative

Conjugated polymers have been subject of great interest in the recent literature from both fundamental point of view and applied science perspective. Among the several types of conjugated polymers used in recent investigations, polythiophene and its derivatives have attracted considerable attention over the past 20 years due to their high mobility and other remarkable solid-state properties. They have potential applications in many fields, such as microelectronic devices, catalysts, organic field-effect transistors, chemical sensors, and biosensors. They have been studied as gas and volatile organic compounds (VOCs) sensors using different principles or transduction techniques, such as optical absorption, conductivity, and capacitance measurements. In this work, we report on the fabrication of gas sensors based on a conducting polymer on an interdigitated gold electrode. We use as active layer of the sensor a polythiophene derivative: poly (3-hexylthiophene) (P3HT) and analyzed its conductivity as response for exposure to dynamic flow of saturated vapors of six VOCs [n-hexane, toluene, chloroform, dichloromethane, methanol, and tetrahydrofuran (THE)]. Different responses were obtained upon exposure to all VOCs, THF gave the higher response while methanol the lower response. The influence of moisture on the measurements was also evaluated. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Sintering of tin oxide using zinc oxide as a densification aid

The physicochemical electronic characteristics of SnO2 render it useful in many technical applications, including ceramic varistors, stable electrodes used in electric glass-melting furnaces and electrometallurgy of aluminum, transparent windows and chemical sensors. The use of ZnO as a sintering aid was explored in this study to obtain SnO2 as a dense ceramic. Compacts were obtained by mechanical mixing of oxides, isostatic pressing at 210 MPa and sintering in situ inside a dilatometer at heating rates of 10degreesC/min. The grain size and microstructure were investigated by scanning and transmission electron microscopy (SEM/TEM). The phases and chemical composition were analyzed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that ZnO acts as a densification aid for SnO2, improving its grain growth with additions of up to 2 mol%. ZnO forms a solid solution with SnO2 UP to 1 mol%, above which SnZnO3 precipitates in the grain boundary, potentially inhibiting shrinkage and grain growth. (C) 2004 Kluwer Academic Publishers

Optically anisotropic and photoconducting Langmuir-Blodgett films of neat poly(3-hexylthiophene)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The role of hierarchical morphologies in the superior gas sensing performance of CuO-based chemiresistors

The development of gas sensors with innovative designs and advanced functional materials has attracted considerable scientific interest given their potential for addressing important technological challenges. This work presents new insight towards the development of high-performance p-type semiconductor gas sensors. Gas sensor test devices, based on copper (II) oxide (CuO) with innovative and unique designs (urchin-like, fiber-like, and nanorods), are prepared by a microwave-assisted synthesis method. The crystalline composition, surface area, porosity, and morphological characteristics are studied by X-ray powder diffraction, nitrogen adsorption isotherms, field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Gas sensor measurements, performed simultaneously on multiple samples, show that morphology can have a substantial influence on gas sensor performance. An assembly of urchin-like structures is found to be most effective for hydrogen detection in the range of parts-per-million at 200 °C with 300-fold larger response than the previously best reported values for semiconducting CuO hydrogen gas sensors. These results show that morphology plays an important role in the gas sensing performance of CuO and can be effectively applied in the further development of gas sensors based on p-type semiconductors. High-performance gas sensors based on CuO hierarchical morphologies with in situ gas sensor comparison are reported. Urchin-like morphologies with high hydrogen sensitivity and selectivity that show chemical and thermal stability and low temperature operation are analyzed. The role of morphological influences in p-type gas sensor materials is discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Giant Chemo-Resistance of SnO disk-like structures

Single crystalline SnO micro-disks, synthesized by a carbothermal reduction process, exhibited a nearly 1000-fold increase in resistance upon exposure to 100 ppm of NO2 without addition of catalysts or dopants nor the existence of nano-sized dimensions. Moreover, the SnO displayed a greater than 100-fold selectivity to NO2 over potential interferents including CO, H2 and CH4. The high sensor signal and exceptional selectivity for this novel sensor material are attributed to the existence of a high density of active lone pair electrons on the exposed (0 0 1) planes of the single crystalline SnO disks. This, thereby, identifies new means, not utilizing nano-dimensions, to achieve high gas sensitivity. © 2013 Elsevier B.V. All rights reserved.

Estudo de filmes poliméricos de complexos a base de tiofeno8Schiff na construção de sensores eletroquímicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Construção de filmes ultra finos de Bismarck Brown R por eletropolimerização e sua aplicação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modulação das propriedade ópticas de semicondutores pela incorporação de íons terras raras

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação de nanofio via deposição eletroquímica utilizando modelo de membrana porosa

From the last decade of the twentieth century, the rapid growth of nanotechnology has resulted in the discovery of a number of forms of nanoparticles and nanoclusters. We can cite as an example: nanotubes, nanowires, nanobelts, and nanoconesnanoclusters which have a wide range of applications, particularly as catalysts magnetic material nanodevices, chemical sensors, degradation of toxic chemicals, or even as possible carriers for the isotope medical applications.. The first step is the production and characterization of nanowires multithreaded using different types of metals (nickel, silver, gold) and polymers (pyrrole), which are prepared by electrochemical deposition process. Will be held by the characterization of the same images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Aplicação eletroanalítica de complexos oxo-manganês biomimetizadores de centros ativos enzimáticos na determinação de espécies de interesse analítico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)