Nanotechnology is the understanding and control f matter at dimensions of roughly 1 - 100 nm. At the nanoscale, the properties like electrical conductivity and mechanical strength are not the same as the materials with particles in dimensions much more than 100 nm. The electronic structure changes dramatically too. Between nanomaterials, there is recently a great number of works that investing as the synthesis as the properties of the magnetic nanoparticles. The interest in these materials is due to its magnetic applications. Some of more representative magnetic materials are the metallic oxides, as some ferrites. However, the ferrites are often obtained as mixture of some oxides, which implies that the magnetic properties are not always well defined and reproducible. Thus, the researches has been turned to use of the magnetic metals, between which the cobalt. The cobalt is investigated because its high magnetic susceptility. However, this transition metal is easily oxidate in air and is toxic to human organism. For this reason, it has looked for to effect synthesis involving core - shell structures, which no to allow the oxidation of the cobalt and prevent against its toxicity. Between the shells that come being obtained it is of silica and of gold. In addition, in if treating to catalysis in a general way, the price of the cobalt and its magnetic properties are adjusted for the attainment core - shell catalysts, Cocore@Ptshell, (Co@Pt). So, the aim of this article is to present and to do an analysis of the more representative synthetic route used until the present moment to obtain the core - shell structures: Co@SiO2, Co@Au and Co@Pt.

The development of methodologies to detect and quantify azo dyes in treated water is required because some of these dyes exhibit genotoxic activity, even at low concentrations. Here, the construction and characterization of an impedimetric immunosensor for determination of the textile azo dye Disperse Red 1 (DR1) by means of a label-free assay is reported. Anti-DR1 antibodies (Ab anti-DR1) were successfully coupled to glassy carbon electrode (GCE) surface by bonding using electrochemically generated activated carboxylic groups. The concentration of DR1 was measured by the increase in charge transfer resistance (RCT) when the immune reaction occurred, using Fe(CN)6 3−/4− as a probe. Electrochemical characterizations of the sensor by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed, and infra-red spectra were obtained to complement the electrochemical results showing immobilization of the antibodies. Under optimal conditions, the change in RCT presented a linear relationship with DR1 concentration in the range from 8.40 to 100 nM, and the sensor provided low limit of detection (LOD = 2.52 nM) and quantification (LOQ = 8.40 nM). No significant interference from other azo dyes was observed. The performance of the immunosensor was evaluated using tap water spiked with 20.0 nM DR1 and a satisfactory recovery of 98.5% was found. The proposed immunosensor is simple, relatively inexpensive, and shows good sensitivity for this application.

Precise surface area is needed for accurate characterization of self-assembled monolayers (SAMs) on metallic surfaces. The aim of this manuscript was to emphasize that miscalculation of surface area is the major source of errors in SAM electrochemical characterization. Limitations are discussed and recommendations given for beginners in analyses of SAM functionalized electrodes. The electrochemical measurements and examples were based on bare gold electrode immobilized with dodecanethiol. The degree of compression of the monolayer properties of formation and reproducibility of the electrochemical response depends on roughness factor, with values closer to the unit being better.

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.