Use of hemoglobin as alternative to peroxidases in cholesterol amperometric biosensors

Sophisticated molecular architectures can be produced with the layer-by-layer (LbL) method, which may combine distinct materials on the same film. In this study, we take advantage of this capability to produce cholesterol amperometric biosensors from LbL films containing hemoglobin (Hb) and cholesterol oxidase in addition to the polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(ethylene imine) (PEI). Following an optimization procedure, we found that an LbL film deposited onto ITO substrates, with the architecture ITO(PEI/Hb)5(PEI/COx)10, yielded a sensitivity of 93.4 μA μmol L-1 cm-2 for cholesterol incorporated into phospholipid liposomes, comparable to state-of-the-art biosensors. Hb acted as efficient electron mediator and did not suffer interference from phospholipids. Significantly, cholesterol could also be detected in real samples from chicken egg yolk, with no effects from potential interferents, including phospholipids. Taken together these results demonstrate the possible fabrication of low cost, easy-to-use cholesterol amperometric biosensors, whose sensitivity can be enhanced by further optimizing the molecular architectures of the LbL films. © 2012 Elsevier B.V.

Quantification of water in ethanol using a photothermal transparent transducer

Ethanol with added water may be found during the process of assessing its physical and chemical properties. This addition can damage automotive vehicle engines and also may contribute to tax evasion. The present contribution describes a method based on a photothermal transparent transducer to determine the water content in ethanol. A chamber with a window of lithium tantalate coated with a thin layer of indium tin oxide was used, and a 1450-nm laser diode was employed as the excitation source. The results indicated a nearly linear response of the apparatus, as a function of the water content in water/ethanol solutions ranging from 0 to 100 (vol.%). The results for the dependency of the photothermal signal on the laser power and chopping frequency suggested that reliable results can be obtained using laser power and chopping rates above 100 mW and 10 Hz, respectively. The results reported here may be useful in the development of an alternative method that can provide real-time data on the water concentration in ethanol in a rapid, portable and unambiguous way, and that can be easily used in laboratory analyses or in gas stations. © 2013 Elsevier B.V.

Dielectric behavior of epoxy/BaTiO3 composites using nanostructured ceramic fibers obtained by electrospinning

Composite materials made of epoxy resin and barium titanate (BT) electrospun nanostructured fibers were prepared. BT fibers were synthesized from a sol based on barium acetate, titanium isopropoxide, and poly(vinyl pyrrolidone). The fibers were heat-treated at different temperatures and characterized by X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy. Mats of BT fibers heat-treated at 800 C were embedded in epoxy resin into suitable molds. The composites were characterized by SEM, and dielectric measurements were performed by means of dielectric spectroscopy. The dielectric permittivity and dielectric modulus of epoxy resin/BT-fiber composites were measured for two types of samples: with the electrodes parallel and perpendicular to the BT fiber layers. Interestingly, composite samples with electrodes perpendicular to the fiber layers and a BT content as low as 2 vol % led to dielectric permittivities three times higher than that of pure epoxy resin. © 2013 American Chemical Society.

Development of an electrochemical sensor based on nanostructured hausmannite-type manganese oxide for detection of sodium ions

The preparation and electrochemical characterization of hausmannite-type manganese oxide to use as a sensing material for sodium ion is described. This paper reports a new via synthetic to obtain of the hausmannite-type manganese oxide and its application in the construction of modified electrode as a voltammetric sensor. The electrochemical activity of hausmannite-type manganese oxide is controlled by intercalation/deintercalation of the sodium ions within the oxide lattice. The detection is based on the measurement of anodic current generated by oxidation of MnIII-MnIV at electrode surface. The best electrochemical response was obtained for a sensor composition of 20% (w/w) hausmannite oxide in the paste, a TRIS buffer solution of pH 6.0-7.0 and a scan rate of 50 mV s-1. A sensitive linear voltammetric response for sodium ions was obtained in the concentration range of 2.01 × 10 -5-2.09 × 10-4 mol L-1 with a slope of 355 μA L mmol-1 and a detection limit of 7.50 × 10 -6 mol L-1 using cyclic voltammetry. The use of hausmannite has significantly improved the selectivity of the sensor compared to the birnessite-type manganese oxide modified electrode. Under the working conditions, the proposed method was successfully applied to determination of sodium ions in urine samples. © 2013 Elsevier B.V.

Programação, conexão e avaliação de psicrômetro aspirado de termopar de baixo custo em micrologger para estudos agrometeorológicos

As the psychrometric method is considered standard for the measurement of relative humidity, many studies have used aspirated thermocouple psychrometers connected to microloggers but, however, they do not detail how the aspiration of the air stream is done. However, one of the major difficulties of aspirated thermocouple psychrometers is to program and to connect it in micrologger, because specific programming and connection are requires, and still some skills in getting accurate measurements. This work aimed to provide the programming and the connection of the aspirated thermocouple psychrometer type T for the CR10X microloggers and CR23X of Campbell Scientific, evaluating the quality of measurements of temperature and air relative humidity in relation the a sensor Vaisala HMP50. The non-continuous measurements were made in the period 2006/09/04 to 2007/07/11 at Jaboticabal, SP. The air temperature measurements were similar between the Vaisala sensors and aspirated thermocouple psychrometer, but the relative humidity measurements were significantly different. The measurements obtained by the aspirated thermocouple psychrometer connected to CR10X micrologger were the most accurate. Using the programming and connection of a micro-fan to suck in the dry and moist bulbs of aspirated thermocouple psychrometer in microloggers models CR10X and CR23X, it is possible to obtain measurements of air temperature with good precision and accuracy, and measurements of air relative humidity with good precision, but accuracy is not always attainable due to the difficulties inherent to the physical processes that occur in the wet bulb, the skill in the use and maintenance of this equipment and the reservoir protection against radiative effects.

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.

Concepção, desenvolvimento e aplicação do banco de imagens georreferenciadas no contexto do mapeamento terrestre móvel

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

Sensoriamento remoto e geoestatística na caracterização espaço-temporal de plantas aquáticas

Pós-graduação em Ciências Cartográficas - FCT

Laboratório remoto de qualidade da energia elétrica em ambiente virtual

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estimação do diâmetro e rugosidade em um processo de furação utilizando multi sensores e redes neurais artificiais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

MATIW 1451 - monitoramento e acionamento de transdutores inteligentes através da Web (Padrão IEEE 1451)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fabricação e caracterização morfológica de filmes layer-by-layer de DODAB/FTALOCIANINA de níquel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Diretrizes para análise e desenvolvimento de identidade visual: contribuições para o design ergonômico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação do desempenho hidro-energético de sistemas fotovoltaicos utilizados no bombeamento de água

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Síntese de hidroxiapatia porosa com nanopartículas magnéticas de óxido de ferro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)