Adsorption and detection of DNA dendrimers at carbon electrodes

Dendritic nucleic acids are highly branched and ordered molecular structures, possessing numerous single-stranded oligonucleotide arms, which hold great promise for enhancing the sensitivity of DNA biosensors. This article evaluates the interfacial behavior and redox activity of nucleic acid dendrimers at carbon paste electrodes, in comparison to DNA. Factors influencing the adsorption behavior, including the adsorption potential and time, solution conditions, or dendrimer concentration, are explored. The strong adsorption at the anodically pretreated carbon surface is exploited for an effective preconcentration step prior to the chronopotentiometric measurement of the surface species. Coupled with the numerous guanine oxidation sites, such stripping protocol offers remarkably low detection limits (e.g., 3 pM or 2.4 femtomole of the I-layer dendrimer following a 15 min accumulation). The new observations bear important implications upon future biosensing applications of nucleic dendrimers.

Synthesis and Characterization of Ordered Intermetallic Nanostructured PtSn/C and PtSb/C and Evaluation as Electrodes for Alcohol Oxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hydrogen oxidation on ordered intermetallic electrodes covered with CO

This describes an experimental evaluation of the electrocatalytic activity of the hydrogen oxidation reaction on electrodes of platinum and the ordered intermetallic phases PtSb and PtSn, on which CO has previously been deposited. The experiments were carried out in perchloric acid solution and the analysis based on steady-state polarization curves and Tafel plots derived from chronoamperometric data. Both intermetallics, PtSb and PtSn, performed better than Pt towards the HOR, when their surface was deliberately covered with CO. It is suggested that the intermetallic surfaces have a lower affinity for CO molecules, causing a lower CO coverage on these surfaces, and/or a weaker surface-CO interaction, compared to Pt under the same conditions. (C) 2007 Elsevier B.V. All rights reserved.

Ferroelectric and piezoelectric properties of bismuth layered thin films grown on (100) Pt electrodes

The effect of film orientation on piezoelectric and ferroelectric properties of bismuth layered compounds deposited on platinum coated silicon substrates was investigated. Piezo-force microscopy was used to probe the local piezoelectric properties of Bi(4)Ti(3)O(12), CaBi(4)Ti(4)O(15) and SrBi(4)Ti(4)O(15) films. Our measurements on individual grains clearly reveal that the local piezoelectric properties are determined by the polarization state of the grain. A piezoelectric coefficient of 65 pm/V was attained after poling in a grain with a polar axis very close to the normal direction. The piezoelectric coefficient and the remanent polarization were larger for a-b axes oriented than for c-axis-oriented films. (c) 2007 Elsevier B.V All rights reserved.

Leakage current behavior of Bi3.25La0.75Ti3O12 ferroelectric thin films deposited on different bottom electrodes

Bi3.25La0.75Ti3O12 (BLT) thin films were grown on LaNiO3 (LNO), RuO2 (RuO2) and La0.5Sr0.5CoO3 (LSCO) bottom electrodes by using the polymeric precursor method and microwave furnace. The bottom electrode is found to be an important parameter which affects the crystallization, morphology and leakage current behaviors. The XRD results clearly show that film deposited on LSCO electrode favours the growth of (117) oriented grains whereas in films deposited on LNO and RuO2 the growth of (001) oriented grains dominated. The film deposited on LSCO has a plate-like grain structure, and its leakage current behavior is in agreement with the prediction of the space-charge-limited conduction model. on the other hand, the films deposited on RuO2 and LNO electrodes present a rounded grain shape with some porosity, and its high field conduction is well explained by the Schottky and Poole-Frenkel emission models. The remanent polarization (P-r) and the drive voltage (V-c) were in the range of 11-23 mu C cm(-2) and 0.86-1.56 V, respectively, and are better than the values found in the literature. (c) 2007 Published by Elsevier B.V.

Setting the preheating and steady-state operation of electronic ballasts, considering electrodes of hot-cathode fluorescent lamps

This paper presents a new methodology for the adjustment of the preheating process and steady-state operation of electronic ballasts intended for hot-cathode fluorescent lamps. The classical series-resonant parallel-loaded half-bridge inverter is the power stage analyzed in this paper. In addition, the preheating process is based on the imposition of a constant rms current through the electrodes, in order to provide a proper value of the R-h/R-c ratio before the lamp start. According to the proposed methodology, it is possible to set suitable operating points for, the electronic ballast, considering optimal conditions for the lamps electrodes. Therefore, the proposed methodology for setting the preheating and steady-state operation is a complete platform to the design of electronic ballasts for hot-cathode fluorescent lamps.

Treatment of simulated wastewater containing n-phenyl-n-isopropyl-p-phenylenediamine using electrolysis system with Ti/TiRuO2 electrodes

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

Photocatalytic Degradation of Phenol by Thermal Titanium Dioxide Thin Layer Electrodes

Electrochemical processes in industrial effluents have been studied as a means to obtain higher efficiency in wastewater treatment. Heterogeneous photocatalysis appears as a low-cost alternative through the use of lower wattage lamps and thermal TiO2 films. Photocatalysis became a clean process for water treatment due to hydroxyl radicals generated on semiconductor surface. Such radicals are able to degrade several organic compounds. This study used different electrodes and analytical methods for degradation of phenol molecules to reduce treatment costs, improve efficiency, and identify compounds formed during the decomposition of phenolic molecules. Thermal growth of TiO2 film was observed on the titanium electrode in rutile form. Application of an electrical potential on the Ti/TiO2 working electrode increases efficiency in reducing concentration of phenol after photocatalytic treatment. Still, high energy radiation (UVC) showed best degradation rates in photolytic process. Different compounds formed during the degradation of phenol were also identified in the UVC-PE treatment.

Optimization of the use of carbon paste electrodes (CPE) for electrochemical study of the chalcopyrite

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

Platinum-coated nanostructured oxides for active catalytic electrodes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Electrochemical and spectroscopic characterization of screen-printed gold-based electrodes modified with self-assembled monolayers and Tc85 protein

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

Effect of niobium dopant on fatigue characteristics of BiFeO3 thin films grown on Pt electrodes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Oxidation of Hydroxylamine on Gold Electrodes in Mildly Acidic Aqueous Electrolytes: Electrochemical and In Situ Differential Reflectance Studies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

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

Toxicity assessment and degradation of disperse azo dyes by photoelectrocatalytic oxidation on Ti/TiO2 nanotubular array electrodes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)