Biomimetic sensor based on 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H- porphyrin iron (III) chloride and MWCNT for selective detection of 2,4-D

Exploitation of the electronic properties of carbon nanotubes for the development of voltammetric and amperometric sensors to monitor analytes of environmental relevance has increased in recent years. This work reports the development of a biomimetic sensor based on a carbon paste modified with 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron (III) chloride (a biomimetic catalyst of the P450 enzyme) and multi-wall carbon nanotubes (MWCNT), for the sensitive and selective detection of the herbicide 2,4- dichlorophenoxyacetic acid (2,4-D). The sensor was evaluated using cyclic voltammetry and amperometry, for electrochemical characterization and quantification purposes, respectively. Amperometric analyses were carried out at -100 mV vs. Ag/AgCl(KClsat), using a 0.1 mol L-1 phosphate buffer solution at pH 6.0 as the support electrolyte. Under these optimized analytical conditions, the sensor showed a linear response between 9.9 × 10-6 and 1.4 × 10-4 mol L-1, a sensitivity of 1.8 × 104 (±429) μA L mol -1, and limits of detection and quantification of 2.1 × 10 -6 and 6.8 × 10-6 mol L-1, respectively. The incorporation of functionalized MWCNT in the carbon paste resulted in a 10-fold increase in the response, compared to that of the biomimetic sensor without MWCNT. In addition, the low applied potential (-100 mV) used to obtain high sensitivity also contributed to the excellent selectivity of the proposed sensor. The viability of the application of this sensor for analysis of soil samples was confirmed by satisfactory recovery values, with a mean of 96% and RSD of 2.1% (n = 3). © 2013 Elsevier B.V.

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.

A new hybrid polyhedral cubic silsesquioxane chemically modified with 4-amino-5-(4-pyridyl)-4H-1,2,4-triazole-3-thiol (APTT) and copper hexacyanoferrate(III) for voltammetric determination of nitrite

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

Electrochemical behavior of ruthenium-hexacyanoferrate modified glassy carbon electrode and catalytic activity towards ethanol electrooxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical Properties of Oxo-Manganese Complex Biomimicking Enzyme Active Sites and Its Electrocatalytic Application for Dopamine Determination

This work describes the characterization of the [Mn2 IV,IVO2(terpy)2(H2O)2]4+ complex in aqueous solution by UV-vis spectrophotometry, cyclic voltammetry, and linear sweep voltammetry with a rotating disk electrode. The pH effect, potential scan rate, effect of perfluorosulfonate polymer, and anion of supporting electrode on the electrochemical behavior of the modified electrode for better performance were investigated. The potential peak of the modified electrode was linearly dependent upon the ratio [ionic charge]/[ionic radius]. The modified electrode exerted an electrocatalytic effect on dopamine oxidation in aqueous solution with a decrease in the overpotential compared with the unmodified glassy carbon electrode. This way, the modified electrode showed an enzymatic biomimicking behavior. Tafel plot analyses were used to elucidate the kinetics and mechanism of dopamine oxidation. © 2013 Springer Science+Business Media New York.

A cubic silsesquioxane modified with purpald®: Preparation, characterization and a voltammetric application for determination of sulfite

A novel composite formed by interaction of a octa(3-chloropropyl)octasilsesquioxane modified with Purpald®, and its subsequent reaction with silver and hexacyanoferrate (III) (AgHSP), was synthesized and initially characterized by Fourier transform infrared spectra (FTIR) and cyclic voltammetry. The cyclic voltammogram of the modified graphite paste electrode with AgHSP, showed one redox couple with formal potential Eθ'=0.64V (vs Ag/AgCl, KNO3, 1.0 mol L-1; v = 20 mV s-1), attributed to the Fe2+(CN)6/ Fe3+(CN)6 process. The redox couple presents an electrocatalytic response for determination of sulfite. The modified electrode showed a linear response from 7.0×10-5 to 1.0×10-3 mol L-1 with the corresponding equation Y(μA) = 18.05 + 29.983×103 [sulfite], and a correlation coefficient of r=0.999. The method showed a detection limit of 0.115×10-4 mol L-1 with a relative standard deviation of ± 4% (n = 3) and amperometric sensitivity of 29.983×10-3A mol L-1. The modified electrode showed a excellent stability and good reproducibility during experiments. © 2013 by ESG.

The relation between structural features and electrochemical activity of MnO2 nanoparticles synthesized from a polyol-made Mn 3O4 precursor

A simple hybrid synthesis processing method was developed to synthesize γ-MnO2 nanocrystalline particles. The polyol method was modified by the addition of nitric acid in order to allow the synthesizing of single-phase Mn3O4 in a large scale. In the sequence, the acid digestion technique was used to transform Mn3O4 into γ-MnO2. Structural and morphological characterization was carried out by X-ray diffractometry, Infrared and Raman spectroscopy, thermogravimetric analysis, nitrogen adsorption isotherm, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The synthesized material exhibits a specific capacitance of 125.1 F g-1 at a mass loading of 0.98 mg cm-2. The relation between structural features and electrochemical activity is discussed by comparing the synthesized material with commercial electrolytic manganese dioxide. © 2013 Springer-Verlag Berlin Heidelberg.

A novel LTCC electrochemical cell construction and characterization: A detection compartment for portable devices

In this work we described for the first time the construction of a 25 μL electrochemical cell from low temperature co-fired ceramic (LTCC) material and carbon screen-printed electrode applicable in portable devices. Firstly, a carbon screen-printed electrode was prepared and characterized by cyclic voltammetry and scanning electron microscopy. Afterwards carbon polymeric film and metal pastes were dropped into the LTCC cell cavities in order to determine the device electrodes, and this arrangement was also electrochemically characterized. The great advantage of this promising device is the simple construction method and its widespread applicability in reusable portable devices. © 2013 The Royal Society of Chemistry.

Electrochemical sensor for ranitidine determination based on carbon paste electrode modified with oxovanadium (IV) salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicyllideneiminato)oxovanadium (IV) complex ([VO(salen)]) as well as its application for ranitidine determination are described. The electrochemical behavior of the modified electrode for the electroreduction of ranitidine was investigated using cyclic voltammetry, and analytical curves were obtained for ranitidine using linear sweep voltammetry (LSV) under optimized conditions. The best voltammetric response was obtained for an electrode composition of 20% (m/m) [VO(salen)] in the paste, 0.10 mol L- 1 of KCl solution (pH 5.5 adjusted with HCl) as supporting electrolyte and scan rate of 25 mV s- 1. A sensitive linear voltammetric response for ranitidine was obtained in the concentration range from 9.9 × 10- 5 to 1.0 × 10- 3 mol L- 1, with a detection limit of 6.6 × 10- 5 mol L- 1 using linear sweep voltammetry. These results demonstrated the viability of this modified electrode as a sensor for determination, quality control and routine analysis of ranitidine in pharmaceutical formulations. © 2013 Published by Elsevier B.V.

Fast assembly of non-thiolated DNA on gold surface at lower pH

In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the electrode at neutral pH overnight. Here we report fast adsorption of non-thiolated DNA oligomers on gold electrodes at acidic pH (i.e., pH ~3.0). The peak-to-peak potential difference and the redox peak currents in typical cyclic voltammetry of [Fe(CN)6]3- are investigated to monitor the attachment. Compared with incubation at neutral pH, the lower pH can significantly promote the adsorption processes, enabling efficient adsorption even in 30min. The adsorption rate is DNA concentration-dependent, while the ionic strength shows no influence. Moreover, the adsorption is base-discriminative, with a preferred order of A>C≫G, T, which is attributed to the protonation of A and C at low pH and their higher binding affinity to gold surface. The immobilized DNA is functional and can hybridize with its complementary DNA but not a random DNA. This work is promising to provide a useful time-saving strategy for DNA assembly on gold electrodes, allowing fast fabrication of DNA-based biosensors and devices. © 2013 Elsevier Inc.

Estudo da eletrocatálise da reação de oxidação de etanol sobre fases intermetálicas ordenadas Pt-M (M = Mn,Mo, Pb, Sb e Sn)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo da eletrocatálise da reação de oxidação do glicerol sobre as fases intermetálicas ordenadas PtSn e AuSn

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Utilização de uma língua eletrônica para classificação de amostras de açúcar em uma usina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Potencialidades eletroanalíticas de complexos binucleares de nitroprussiato de metais de transição suportado em 3-aminopropil sílica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades analíticas e eletroanalíticas de um silsesquioxano nanoestruturado organofuncionalizado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)