Construction and application of an electrochemical sensor for paracetamol determination based on iron tetrapyridinoporphyrazine as a biomimetic catalyst of P450 enzyme

This work describes the construction and application of a biomimetic sensor for paracetamol determination in different samples. The sensor was prepared by modifying a glassy carbon electrode surface with a Nafion (R) membrane doped with FeTPyPz. The best performance of the sensor in 0.1 mol L-1 acetate buffer was at pH 3.6. Under these conditions, an oxidation potential of paracetamol was observed at 445 mV vs. Ag vertical bar AgCl. The sensor presented a linear response range between 4.0 and 420 mu mol L-1, a sensitivity of 46.015 mA L mol(-1) cm(-2), quantification and detection limits of 4.0 mu mol L-1 and 1.2 mu mol L-1, respectively. A detailed investigation about its electrochemical behavior and selectivity was carried out. The results suggested that FeTPyPz presents catalytic properties similar to P450 enzyme for paracetamol oxidation. Finally, the sensor was applied for paracetamol determination in commercial drugs and for the monitoring of its degradation in an electrochemical batch reactor effluent.

Application of a Biomimetic Sensor Based on Iron Phthalocyanine Chloride: 4-Methylbenzylidene-Camphor Detection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical sensor highly selective for estradiol valerate determination based on a modified carbon paste with iron tetrapyridinoporphyrazine

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sensor for hydrogen peroxide based on Prussian Blue modified electrode: Improvement of the operational stability

Improvement of the operational stability of amperometric sensors based on Prussian Blue (PB) modified glassy carbon electrodes is presented. The long term performance of the sensors was evaluated by injection of hydrogen peroxide (5 μM in potassium buffer) solutions in a flow-injection system during a period of 5-10 h. The following parameters were investigated and correlated with the performance of the sensor: the times for electrodeposition and electrochemical activation, temperature, storage time, pH, composition of the buffer solution and of volume sample injected. These analytical characteristics of the modified electrode can be emphasized: initial sensitivity of 0.3 A cm-2 M-1, detection limit of ca. 0.5 μM, precise results (r.s.d.< 1.5%) and possibility to carry out around 50 samples (50 μL) per hour.

Self-optimization of dense wireless sensor networks based on simulated annealing

Wireless sensor network (WSN) Is a technology that can be used to monitor and actuate on environments in a non-intrusive way. The main difference from WSN and traditional sensor networks is the low dependability of WSN nodes. In this way, WSN solutions are based on a huge number of cheap tiny nodes that can present faults in hardware, software and wireless communication. The deployment of hundreds of nodes can overcome the low dependability of individual nodes, however this strategy introduces a lot of challenges regarding network management, real-time requirements and self-optimization. In this paper we present a simulated annealing approach that self-optimize large scale WSN. Simulation results indicate that our approach can achieve self-optimization characteristics in a dynamic WSN. © 2012 IEEE.

Sensor for diuron quantitation based on the P450 biomimetic catalyst nickel(II) 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine

A biomimetic sensor based on a carbon paste electrode modified with the nickel(II) 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine complex was developed as a reliable alternative technique for the sensitive and selective analysis of the herbicide diuron in environmental media. The sensor was evaluated using cyclic voltammetry and amperometric techniques. The best amperometric responses were obtained at 750 mV vs. Ag/AgCl (KClsat), using 0.1 mol L-1 phosphate buffer solution at pH 8.0. Under these conditions, the sensor showed a linear response for diuron concentrations between 9.9 × 10-6 and 1.5 × 10-4 mol L -1, a sensitivity of 22817 (±261) μA L mol-1, and detection and quantification limits of 6.14 × 10-6 and 2 × 10-5 mol L-1, respectively. The presence of the nickel complex in the carbon paste improved selectivity, stability, and sensitivity (which increased 700%), compared to unmodified paste. The applicability of the sensor was demonstrated using enriched environmental samples (river water and soil). © 2012 Elsevier B.V. All rights reserved.

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.

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.

A novel ozone gas sensor based on one-dimensional (1D) alpha-Ag2WO4 nanostructures

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

An Electrochemical Sensor for Reducing Sugars Based on a Glassy Carbon Electrode Modified with Electropolymerized Molecularly Imprinted Poly-o-phenylenediamine Film

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

An Informatics Technical Note on Interaction of DNA - Graphene Chemical Sensor System as Reaction-Diffusion Wave-Based Computing System in Ionised Gaseous environments and their Applications Using Theoretical Studies and Scientific Computation Overview

The physics of plasmas encompasses basic problems from the universe and has assured us of promises in diverse applications to be implemented in a wider range of scientific and engineering domains, linked to most of the evolved and evolving fundamental problems. Substantial part of this domain could be described by R–D mechanisms involving two or more species (reaction–diffusion mechanisms). These could further account for the simultaneous non-linear effects of heating, diffusion and other related losses. We mention here that in laboratory scale experiments, a suitable combination of these processes is of vital importance and very much decisive to investigate and compute the net behaviour of plasmas under consideration. Plasmas are being used in the revolution of information processing, so we considered in this technical note a simple framework to discuss and pave the way for better formalisms and Informatics, dealing with diverse domains of science and technologies. The challenging and fascinating aspects of plasma physics is that it requires a great deal of insight in formulating the relevant design problems, which in turn require ingenuity and flexibility in choosing a particular set of mathematical (and/or experimental) tools to implement them.

A new biomimetic sensor based on molecularly imprinted polymers for highly sensitive and selective determination of hexazinone herbicide

A new selective sensor based on molecularly imprinted polymers (MIPs) was developed for the determination of hexazinone (HXZ) in environmental samples. MIPs were synthesized using a non-covalent approach, and selection of the monomers employed in the polymerization reaction was carried out by molecular modeling. Three functional monomers with high (2-vinylpyridine (MP17)) and intermediate (methacrylic acid (MP12) and acrylamide (MP5)) energies of binding to the template (HXZ) were selected for preparation of the MIPs, in order to conduct comparative studies and validate the theoretical data. For sensor construction, carbon pastes were modified with each MIP or NIP (non-imprinted polymer), and HXZ determination was performed using differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV). All parameters affecting the sensor response were optimized. In HCl at pH 2.5, the sensor prepared with MP17 (5% w/w in the paste) showed a dynamic linear range between 1.9 × 10−11 and 1.1 × 10−10 mol L−1, and a detection limit of 2.6 × 10−12 mol L−1, under the following conditions: accumulation time of 200 s at a potential of −0.5V, scan rate of 50 mVs−1, pulse amplitude of 60 mV, and pulse width of 50 ms. The sensor was selective in the presence of other similar compounds, and was successfully applied to the analysis of HXZ in river water samples.

Surface coverage in wireless sensor networks based on delaunay tetrahedralization

In this work is presented a new method for sensor deployment on 3D surfaces. The method was structured on different steps. The first one aimed discretizes the relief of interest with Delaunay algorithm. The tetrahedra and relative values (spatial coordinates of each vertex and faces) were input to construction of 3D Voronoi diagram. Each circumcenter was calculated as a candidate position for a sensor node: the corresponding circular coverage area was calculated based on a radius r. The r value can be adjusted to simulate different kinds of sensors. The Dijkstra algorithm and a selection method were applied to eliminate candidate positions with overlapped coverage areas or beyond of surface of interest. Performance evaluations measures were defined using coverage area and communication as criteria. The results were relevant, once the mean coverage rate achieved on three different surfaces were among 91% and 100%.

Sensitive luminescent paper-based sensor for the determination of gaseous hydrogen sulfide

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