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A novel electrochemical methodology for the growth of arrays of Ni and Co nanowires (NWs) with linear and non-linear varying micro-height gradient profiles (μHGPs), has been developed. The growth mechanism of these microstructures consists of a three-dimensional growth originating from the allowed electrical contact between the electrolyte and the edges of the cathode at the bottom side of porous alumina membranes. It has been shown that the morphology of these microstructures strongly depends on electrodeposition parameters like the cation material and concentration and the reduction potential. At constant reduction potentials, linear Ni μHGPs with trapezoid-like geometry are obtained, whereas deviations from this simple morphology are observed for Co μHGPs. In this regime, the μHGPs average inclination angle decreases for more negative reduction potential values, leading as a result to more laterally extended microstructures. Besides, more complex morphologies have been obtained by varying the reduction potential using a simple power function of time. Using this strategy allows us to accelerate or decelerate the reduction potential in order to change the μHGPs morphology, so to obtain convex- or concave-like profiles. This methodology is a novel and reliable strategy to synthesize μHGPs into porous alumina membranes with controlled and well-defined morphologies. Furthermore, the synthesized low dimensional asymmetrically loaded nanowired substrates with μHGPs are interesting for their application in micro-antennas for localized electromagnetic radiation, magnetic stray field gradients in microfluidic systems, non-reciprocal microwave absorption, and super-capacitive devices for which a very large surface area and controlled morphology are key requirements.

First-order reversal curve diagrams, or FORC diagrams, have been studied to determine if the widths of their distributions along the interaction and coercivity axes can be related to the mean-field magnetization dependent interaction field (MDIF). Arrays of nanowires with diameters ranging from 18 up to 100 nm and packing fractions varying from 0.4 to 12% have been analyzed. The mean-field MDIF has been measured using the remanence curves and used as a measuring scale on the FORC diagrams. Based on these measurements, the full width of the interaction field distribution and the full width at half maximum (FWHM) of the FORC distribution profile along the interaction field direction are shown to be proportional to the MDIF, and the relation between them is found. Moreover, by interpreting the full width of the coercive field distribution in terms of the dipolar induced shearing, a simple relation is found between the width of this distribution and the MDIF. Furthermore, we show that the width of the FORC distribution along the coercive field axis is equal to the width of the switching field distribution obtained by the derivation of the DC remanence curve. This was further verified with the switching field distribution determined using in-field magnetic force microscopy (MFM) for very low density nanowires. The results are further supported by the good agreement found between the experiments and the values calculated using the mean-field model, which provides analytical expressions for both FORC distributions.

El daño por Fusarium oxysporum en las plantas de tomate es de gran importancia económica en todo el mundo debido a las importantes pérdidas que genera en el cultivo. Los avances en nanotecnología proporcionan alternativas que pueden aplicarse en el control de patógenos. Las nanopartículas de plata (AgNP) estabilizadas con quito­sano (Cs) tienen actualmente un uso generalizado para el control de patógenos de plantas. El objetivo de la presente investigación fue determinar el efecto de la aplicación de AgNP-Cs sobre la tolerancia de plántulas de tomate y control de la marchitez vascular, provocada por el fitopatógeno. Los resultados mostraron que la aplicación de las NPs no mostró efectos negativos en el desarrollo vegetativo normal de las plántulas de tomate (hasta 2000 ppm). Las nanoestructuras fueron significativamente efectivas para inhibir el crecimien­to del micelio hasta en más del 70%, además el tratamiento fue eficaz para reducir la gravedad de la enfermedad en plántulas inoculadas con Fusarium oxysporum después de 14 días post-inoculación.

A self-supported nickel nanowire array coated with Ni(OH)2 (Ni(OH)2@SNWA) with enhanced electrochemical performance was successfully fabricated by template-directed electrodeposition and oxidation treatment. Porous polycarbonate membrane was used as the template for the preparation of self-supported nickel nanowire array with a small wire diameter and high wire density. The Ni(OH)2 on the surface formed through oxidation treatment is in close contact with the inside nickel wire. Due to its self-supported and integrated core–shell structure, the Ni(OH)2@SNWA has excellent ionic and electrical conductivities, and shows enhanced electrochemical performance at high current densities.

Nanoporous Ni with rational pore structure decorated with Ni(OH)2 nanosheets (Ni(OH)2@NPN) was fabricated by a cost-effective process of template-directed electrodeposition combined with surface conversion. Nitrocellulose (NC) template controls the pore structure of NPN with interconnected pore channels and diameters of a few hundred nanometers, which provides short pathways for rapid electrolyte diffusion, and offers enough space for the growth of Ni(OH)2 nanosheets. The direct conversion of Ni(OH)2 nanosheets from the surface metallic Ni of NPN ensures a low contact resistance at the interface and high utilization of Ni(OH)2. Benefiting from the structural features, Ni(OH)2@NPN shows significantly improved electrochemical performance.

Alloys of Sm-Fe-Ti were synthesized by mechanical milling for 5 h; the hysteresis loop for nanocrystalline Sm-Fe-Ti alloys showed bistable behavior, which is partly repressed because of the presence of an effective field. The magnetic properties of remanence for nanocrystalline Sm-Fe-Ti alloys were measured to study the interactions between nanograins. Henkel et al. confirmed the structural disorder of the nanocrystalline Sm-Fe-Ti alloys obtained after 5 h of mechanical milling, while for nanocrystalline Sm-Fe-Ti alloys, obtained by mechanical milling for 5 h and annealing, the predominant effects were due to the mean field. Mossbauer spectroscopy was used to study magnetic interactions in the nanocrystalline Sm-Fe-Ti alloys.

A fully analytical model to describe the magnetostatic properties of these 2D nanocylinder arrays (tubes and wires) is presented. The model allows calculating the components of the effective demagnetizing field as a function of the cylinder height, inner and outer diameters, and the center-to-center distance. From these components, it is possible to calculate the shape anisotropy of the cylinder, the dipolar interaction between them, and the total magnetostatic energy. The model allows performing calculations very simply, using a simple spreadsheet or open-access software such as Geogebra. This allows analyzing the effect of each geometrical parameter in the different contributions to the magnetostatic energy. Amongst the most interesting findings is that the model describes naturally the magnetization easy-axis reorientation transition induced by the dipolar interaction, for which a general phase diagram has been calculated for both tubes and wires. For the case of nanowires, our results show a very good agreement with previously published results. While for nanotubes, the model predicts that the magnetization easy-axis reorientation transition is frustrated as the tube wall thickness decreases and reaches a critical value even when the distance between tubes is reduced to its lowest possible value.

We present the structural, morphological and photocatalytic properties of stretchable composites made with carbon nanotubes (CNTs), silicon rubber and Ni@TiO

In this work, melamine sponges were functionalized, to obtain hydrophobic and magnetic materials capable to absorb oil and hydrocarbons, by the addition of stearic acid (SA) and ferrofluid (FF) in a simple way. Physicochemical and structural properties of melamine sponges with stearic (M-SA) and stearic acid with ferrofluid (M-SA+FF) were evaluated. Scanning electron microscopy shows that the sponges have porous structure, which make them highly absorbent. Water contact angles (WCA), demonstrated that both (M-SA and M-SA+FF) sponges are hydrophobic, and that the SA concentration influences in WCA. The absorption capacity for hydrocarbons (toluene and diesel) and motor oil, was higher with M-SA than M-SA+FF sponges; both materials have good recyclability, and the separation of motor oil from water was done successfully in a continuous mode. The advantage of the M-SA+FF sponge is that it can be easily manipulated with an applied magnetic field. This work propose low cost and easy large scale manufacturing hydrophobic materials to separate oil from water.

Flowerlike Al-doped Ni(OH)2 with different mole ratios of Ni2+/Al3+ were synthesized using hydrothermal method in ethanol solution. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Brunauer-Emmetto-Teller (BET) plot of nitrogen adsorption/desorption isotherms were used to characterize the structure changes of the synthesized samples, and electrochemical measurements were used to study the effect of Al on the electrochemical performance of flowerlike Al-doped Ni(OH)2. The results showed that flowerlike Al-doped Ni(OH)2 has a mixed phase of pure Ni(OH)2 and NiAl layered double hydroxide. Aluminum improves the 3-dimensional flowerlike structure, significantly increases the specific surface area and enhances the electrochemical performance of reversibility, rate capability and cyclic stability of Al-doped Ni(OH)2, but also seriously reduces the specific capacitance. This work suggested that aluminum content is an important factor that needs to be considered when flowerlike Al-doped Ni(OH)2 is used as electrode material for supercapacitor applications.

A method is presented that allows quantifying the average value of the interaction field in arrays of magnetic nanowires from the field difference between the isothermal remanence (IRM) and the DC demagnetizing (DCD) remanence curves when the normalized magnetization is equal to one third. Arrays of magnetic nanowires of different diameters and packing fractions are used to experimentally test the method. The results have been compared with those obtained using the method based on the difference between the remanence coercivity fields and with a mean-field expression for the interaction field, providing a very good agreement and thus validating the method. Additionally, it is shown that both the position (m0) and the shift along the magnetization axis of the intersection between the remanence curves with respect to the value of one third (δm = m0 − 1/3) provide qualitative information about the interaction field. The former indicates the type of interaction depending if the intersection is above (m0 > 1/3) or below (m0

The fabrication of electrically conductive natural-Jute fibers using a commercially available conductive paint that can be easily sprayed on the fibers is proposed. The results show that this paint forms a continuous coating, leading to electrically conductive fibers. These fibers are not stiff so they can be bent without significant loss of their conductivity. These fibers are easy to make, non-expensive, and are interesting for flexible conductors, or elements to make responsive or smart tissues/textiles, as threads for electromagnetic shielding covers.

This work reports the electrochemical characterization of flexible carbon nanotube (CNT) based asymmetric supercapacitors (SCs) made with ≈90% of biodegradable components. BaFe12O19, (BaFeO) nanoparticles (NPs) with sizes of 100–300 nm were introduced in the biodegradable SCs in order to enhance their electrochemical performance. These nanoparticles presented a hexagonal structure according to the analysis by X-ray diffraction. The electrochemical tests revealed that the capacitance and energy density of the SCs increased from 274.2 to 861.6 F g−1 and from 54.8 to 172.3 Wh kg−1 after decorating their anodes with BaFeO NPs. Surprisingly, a stable output voltage of 1.3 V was observed for the device containing BaFeO NPs during 10 h, suggesting a battery-like behavior not previously seen in flexible SCs fabricated with biodegradable components. The analysis of the SC electrodes by optical absorbance and XPS demonstrated the presence of oxygen vacancy defects, Ba1/Ba2 sites and Fe2+/Fe3+/Fe4+ ions, which acted as redox centers for the charge storage in the devices. The results obtained in this work demonstrate that making eco-friendly SCs is possible while maintaining a high electrochemical performance. Thus, our results are promising for the development of new biodegradable supercapacitors with similar capacities to these for batteries.

Nanofibrous mats of poly e-caprolactone (PCL) were fabricated by electrospinning. The nanofiber structures were investigated and characterized by scanning electron microscope, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, static water-contact-angle analysis and mechanical properties. The results showed that the nanofibrous PCL is an ideal biopolymer for cell adhesion, owing to its biocompatibility, biodegradability, structural stability and mechanical properties. Differential scanning calorimetry results showed that the fibrous structure of PCL does not alter its crystallinity. Studies of the mechanical properties, wettability and degradability showed that the structure of the electrospun PCL improved the tensile modulus, tensile strength, wettability and biodegradability of the nanotemplates. To evaluate the nanofibrous structure of PCL on cell adhesion, osteoblasts cells were seeded on these templates. The results showed that both adhesion and proliferation of the cells is viable on these electrospun PCL membranes. Thus electrospinning is a relatively inexpensive and scalable manufacturing technique for submicron to nanometer diameter fibers, which can be of interest in the commodity industry.

The microstructural evolution of Duplex Stainless Steel 2205 was investigated during Gas Tungsten Arc Welding with three types of protective atmosphere: (a) Ultra-high purity Ar, (b) 98% Ar-2% N 2 mixture, and (c) 95% Ar-5% N 2 mixture. The microstructural evolution was also characterized for three different heat inputs: low, medium, and high (0.5, 1.5, and 2.5 J mm −1 . In terms of the effect of fatigue resistance and corrosion leading, the best performance was seen at values of 0.5 and 2.5 J mm −1 , respectively. The decrease of the (Austenite) phase in Ar welding was associated with low performance in terms of resistance to fatigue and corrosion. On the other hand, the N 2 content had a slight effect on the fatigue strength, tension, and impact resistance. A ductile fracture, which is desirable in this type of testing, was consistently observed. Protection with 2% and 5% N 2 atmospheres and the control of heat input in the plasma process enabled a 45-fold lowering of the corrosion rate, increasing the life of the welded joint.

Magnetic microcomposites were fabricated by emulsification of a mixture of polydimethylsiloxane (PDMS) and nickel microparticles. The composites were obtained in a temperature-controlled water-surfactant media with and without the influence of an external magnetic field. The presence of a moderate external magnetic field of 80 G (8 mT) during the polymerization stage leads to the arrangement of nickel microparticles into chains that form the magnetic core of the synthesized composites. The method allows controlling the shape of the composite particles by applying a magnetic field and varying the stirring speed. Three shapes of composite particles, namely spherical, teardrops, and ellipsoidal, were obtained and magnetically characterized. Room temperature hysteresis loops and dM/dH versus H curves in the second-to-third quadrants show that spherical particles are isotropic while non-spherical particles show an induced uniaxial magnetic anisotropy which depends on the shape of the resulting composite particles.

Using arrays of bistable magnetic nanowires, we show that their microwave absorption properties can be reversibly configured using low magnetic field cycling by virtue of the double ferromagnetic resonance absorption spectra. These characteristics lead to a single bifunction microwave filter that can be configured to work as a bandstop or a bandpass filter, making these materials very attractive for compact multifunction planar microwave devices. The bifunction microwave properties of these systems are successfully predicted using a mean field model for their magnetic configuration-dependent effective permeability.

HGMS is effective in separating or filtering fine and weakly magnetic particles and widely applied in mineral processing, water treatment, cell and protein purification. The magnetic matrix is a crucial device used in magnetic separator to generate high magnetic field gradient and provide surface sites for capturing magnetic particles. The material, geometry, size and arrangement of the matrix elements can significantly affect the gradient and distribution of the magnetic field, and the separating or filtrating performance. In this paper, the researches and developments of magnetic matrices used in HGMS are reviewed. Keywords: Magnetic matrix, HGMS, Review

Pectin films were prepared by addition of different quantities of Rosin in order to test the effects of this natural hydrophobic polymer in increasing the water resistance of Pectin films. Scanning Electron Microscopy, infrared spectroscopy, as well as thermogravimetric analysis suggest that Rosin disperses into the Pectin film forming small isolated drops, which allows it to exist as a separate phase. Water solubility tests clearly show an improvement of the water resistance in the Rosin containing films with respect to the pure Pectin films. These results provide evidence of the practical use of these films as all natural biodegradable vehicles for controlled substance delivery in aqueous environments.

Herein henequen fibers have been functionalized by coating with a mixture containing stearic acid and ferrofluid. The surface coating was done using a one step immersion method giving as a result fibers with a surface layer having a magnetic response. Scanning electron microscopy shows that henequen has a regular porous structure, which makes it compatible with ferrofluid and allows setting a layer of magnetic nanoparticles and stearic acid on the surface of the fiber. The X-ray and infrared analyses as well as the hysteresis loops are consistent with separated phases of ferrofluid and stearic acid. The main advantage of these magnetic fibers is that it can be easily manipulated with an applied magnetic field.

This work reports the electrochemical properties of stretchable supercapacitors fabricated with carbon nanotubes (CNTs) sheets as electrodes. According to the SEM images of the electrodes, the CNTs look like interconnected wires oriented in one direction. The electrochemical analysis indicated that the devices subjected from 0 to 150% strain decreased their capacitance from 712.2 to 88.4 F/g. Interestingly, the device stretched 525 times at 50% strain had a capacitance of 1328.3 F/g, which is one of the highest capacitance values reported so far for stretchable supercapacitors. The cycling voltammetry curves of the stretched devices showed redox peaks, suggesting that these devices store charge by Faradaic reactions. The presence of redox centers (carboxylic groups and oxygen vacancies) was confirmed by Fourier transform infrared spectroscopy, optical absorbance measurements, and X-ray photoelectron spectroscopy measurements. The galvanostatic charge/discharge curves showed the presence of two components: capacitive (discharge with exponential decay) and battery-type (stable output voltage). This output voltage was controlled with the strain %, since values of 1.05 V, 0.72 V, and 0.32 V were obtained for 0, 50, and 100% strain, respectively. The high capacitance and stable voltage demonstrated by the devices suggest that they could be used as energy sources in wearable/portable applications.

Amorphous Ni(OH)2 closely coating on interconnected nickel nanowire arrays (Ni(OH)2@INWA) with rational architectures were prepared. The INWA with small wire diameter and high wire density acts both as miniature conductive scaffold and highly conductive core providing large surface area to load amorphous Ni(OH)2 and ensuring high ionic/electronic conductivities. The amorphous Ni(OH)2 nanosheets in-situ converted from the metallic surface of INWA are in seamless contact with the metallic core forming a close core-shell structure. Because of the material and architecture advantages, the amorphous Ni(OH)2@INWA presents enhanced electrochemical performance of ultrahigh specific capacitances of 3400 F g−1 at a specific current of 5 A g1, remarkable rate capability (3000 F g−1 at 100 A g−1). The asymmetric supercapacitor of Ni(OH)2@INWA//reduced graphene oxide delivers a high specific energy of 53 Wh kg1 at a specific power of 395 W kg−1, and a specific energy of 31 Wh kg−1 can be maintained at a specific power of 4973 W kg−1. It also shows a long-term stability with 91 % retention of the initial capacitance after 10000 cycles at a specific current of 2 A g−1.

This work reports the electrochemical properties of flexible supercapacitors whose anodes were fabricated with carbon nanotubes (CNTs), silver nanowires (Ag NWs), and Nickel hydroxide nanowires (Ni(OH)2 NWs). The SEM analysis of the anodes demonstrated that the CNTs are oriented in a preferential direction, which favors the transport of charge carriers. Also, the Ag NWs, and Ni(OH)2 NWs have formed on the anodes a porous nanostructured network which look like a bird-nest, thus providing a high surface area for the charge storage. According to the optical transmittance spectra, the anodes made with the three components: CNTs, Ag NWs and Ni(OH)2 NWs presented an average transmittance of 46% in the visible region. The SC devices with anodes made with single CNT, CNT/Ag NWs, CNT/Ni(OH)2 NWs, and CNT/Ag NWs/Ni(OH)2 NWs were named CN, CN–Ag, CN–Ni, and CN–Ag/Ni, respectively. All these devices were semi-transparent and their cyclic voltammetry curves showed the presence of redox peaks, which suggest that these devices stored charge by redox reactions. In addition, the galvanostatic charge/discharge profiles of the SCs demonstrate that they can release energy for at least 10 h. The best SC device (CN–Ag/Ni) had a capacitance and energy density values of 88.6 F/g and 177.3 Wh/Kg, respectively. XPS, FTIR, and absorbance measurements were also carried out and confirmed the presence of oxygen vacancy defects, nickel hydroxides, silver oxides, and metallic silver in the anodes of the SCs. The presence of all these compounds was important because they acted as redox centers which all contribute simultaneously to the charge storage. Hence, the results presented here reveal that a flexible SC could be a feasible option as an energy source for portable devices.

The effects of the deposition potential on the structural and magnetic properties of Ni nanowires with a diameter of 40 nm and lengths varying from 16 up to 56 μm have been studied. The results show that very long NWs exhibit a large enhancement of their uniaxial magnetic anisotropy. This anisotropy reaches values as high as 1.6 × 10 6 erg/cm3 that is comparable with the value due to the magnetostatic anisotropy contribution ( ≈ 5 × 10 6 erg/cm3) and as shown from the results this large anisotropy is practically insensitive to the deposition potential. Moreover, as shown on shorter NWs, this enhancement of the anisotropy is not observed and interestingly the potential does induce structural changes that relate to their magnetic properties. The enhanced anisotropy observed in long NWs is a robust effect as it is independent of the potential, making this property attractive for applications where high uniaxial anisotropies are required.

In this study the pressure distribution homogeneity on the catalytic surface is found to provide a simple and reliable fuel flow parameter that can be used to optimize the bipolar plate geometry and the PEM fuel cell performance. Finite element commercial ANSYS software was used to determine the fuel velocity, pressure and mass distribution on eight different bipolar plate geometries. These geometries were also fabricated and characterized experimentally in order to establish a correlation between the power densities with the fuel flow parameters obtained from the simulations. The results show that a highly uniform pressure distribution of the fuel in the bipolar plate is necessary to obtain higher power densities. Inversely, non-homogeneous pressure distributions lead to lower power densities. Additionally, the measured power density increases when the geometry dependent effective catalytic surface area increases. These results are interesting since they provide an optimization methodology for PEM fuel cells that simplifies and reduces computing requirements, experimentation and manufacturing time.

3-D alloyed and multilayered interconnected nanofiber networks have been fabricated by electrodeposition techniques, allowing a controlled composition and 3-D structural topology. These features have been found crucial to tailor their magnetic and magneto-transport properties. Their interplay along with the use of a simple analytical model based on the particular interconnected topology of the networks has allowed to accurately determine the anisotropic magnetoresistance (AMR) ratio. The as-obtained AMR ratio for interconnected nanofiber networks is consistent with an average that results from all the nanowires orientations in the membrane. The careful choice of magnetic and non-magnetic layer thicknesses has been decisive for the fabrication of Co/Cu multilayered interconnected nanofiber networks with giant magnetoresistive response as high as 19%. Interconnected nanofiber networks with controlled material composition and specific structural features are very attractive for the development of mechanically stable superstructures suitable for potential technological device applications.

The diatom silicified cell wall (frustule) contains pore arrays at the micro- to nanometer scale that display efficient luminescence within the visible spectrum. Morphometric analysis of the size and arrangement of pores was conducted to observe whether any correlation exists with the photoluminescence (PL) of two diatom species of different ages. UV-excited PL displays four clearly defined peaks within the blue-region spectrum, on top of the broad PL characteristic of synthetic porous silicon dioxide, recorded for reference and where discrete lines are absent. A set of shifted emission lines was observed when diatom cultures reached adulthood. These discrete line shifts correlate with structural changes observed in adult frustules: reduction in pore diameter; appearance of pores within pores, 10 nm in size; an increase in the gap distance between stria; and the deposition of several girdle bands with a concomitant increase in the diatom waist length, as well as the appearance of pores on such bands. Destruction of the pores results in the disappearance of all discrete emission lines. The PL shifts are correlated with a substantial increment of Si–OH groups adsorbed on the frustule surface, as revealed by Fourier transform infrared spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.

A large enhancement of the magnetic anisotropy of Ni nanowires (NWs) embedded in anodic aluminium oxide porous membranes is obtained as a result of an induced magnetoelastic (ME) anisotropy contribution. This unusual large anisotropy enhancement depends on the diameter of the NWs and exceeds the magnetostatic (MS) contribution. As a consequence, it leads to effective magnetic anisotropy energies as large as 1.4 × 10(6) erg cm(-3), which are of the same order of magnitude and comparable to the MS energies of harder magnetic materials like Co NWs. Specifically, from ferromagnetic resonance experiments, the magnetic anisotropy of the NWs has been observed to increase as its diameter is decreased, leading to values that are about four times larger than the corresponding value when only the MS anisotropy is present. Our results are consistent with the recently proposed growth mechanism of Ni NWs that proceeds via a poly-crystalline stage at the bottom followed by a single-crystalline stage with texture [110] parallel to the axis of the NWs. A strong correlation between reducing the diameter of the NWs with the decrease of the length of the poly-crystalline segment and the enhancement of the effective magnetic anisotropy has been shown. Magnetization curves obtained from alternating gradient magnetometry experiments show that the average ME anisotropy results from the competition between the magnetic anisotropies of both crystalline segments of the NWs. Understanding the influence of size and confinement effects on the magnetic properties of nanocomposites is of prime interest for the development of novel and agile devices.

A simple and nonexpensive adapted dip-coating technique is presented and used to fabricate arrays of magnetic nanowires with a linear varying height profile. This approach allows controlling the wire height from tenths of nanometers up to several micrometers. Furthermore, the main parameters of this height gradient can be controlled, such as the maximum wire height and the lateral span of the wire array, which can be predicted with excellent accuracy using a proposed analytical model. Moreover, we show that by sequential electrodeposition with dip-coating, arrays of these height varying wires can be grown. This technique represents a novel method to fill porous templates with controlled spatial growth, leading to the fabrication of novel structures and providing control over structural features on the nanoscale level. In particular, the use of these asymmetrically loaded magnetic nanowired substrates to obtain improved microwave nonreciprocal behavior is shown for a microwave phase shifter.

We report on the direct evaporation of a conductive aluminum film onto the surface of a partially cured polydimethyl-siloxane elastomer, in order to produce conductive flexible films without the need of an anchoring layer to promote adhesion between the conductive layer and the elastomer. These layers show good adhesion as shown by the Scotch tape peeling test and their surface presents non-ordered but regular wrinkles due to the buckling surface. Electrical resistance measurements done using a four-probe configuration show an ohmic linear response. Measurements of the electrical resistance versus sample elongation show that these maintain their conductivity up to deformations of 30–40%. Finally, a simple working circuit is presented to validate the sample fabrication procedure.

Arrays of electrodeposited Co0.96Cu0.04/Cu nanowires into porous polycarbonate membranes have been characterized by ferromagnetic resonance measurements in order to study the effect of the dipolar interactions on the effective anisotropy field as a function of the magnetic and non magnetic layer thickness. It is found that breaking the infinite cylinder geometry reduces their shape anisotropy field, which can be modified to a large extent from 6.5 kOe for non layered nanowires down to nearly zero for layered nanowires with the thinnest magnetic layers. An analytical model is proposed to describe the magnetostatic interactions between magnetic layers and their effect on the total anisotropy field which shows a good agreement with the experiment.

The effects of the solution pH and deposition potential on the structural and magnetic properties in arrays of electrodeposited CoCu nanowires with low Cu content have been studied combining ferromagnetic resonance, magnetometry and electron transmission microscopy. It is shown that, depending on the synthesis parameters, the average crystallographic structure can be controlled, giving rise to sensible changes in the effective crystal anisotropy field which varies from -4.05 to +2.75 kOe. It is also shown that in CoCu/Cu multilayered nanowires, the preferential structure of the CoCu-magnetic layer can also be controlled by both pH and deposition potential, opening an interesting route for designing multilayered CoCu/Cu nanowires with controlled and alternated crystal anisotropy.

This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also discussed.

The magnetic properties of arrays of electrodeposited Co nanowires have been studied by ferromagnetic resonance as a function of the electrolytic bath acidity and the plating current intensity. It is observed that by adjusting the pH or the plating current it is possible to find appropriate electrolyte-deposition conditions which lead to the deposition of Co nanowires with a c-axis orientation either parallel or perpendicular to the wires. At relatively high plating currents, systems containing a dominant fraction of grains having the c-axis oriented perpendicular to the wires are favoured. Such wires show a significant decrease of the effective anisotropy due to the competition between the magnetocrystalline and the shape anisotropy that can be as low as 4.3 kOe. In contrast, at low plating currents the c-axis is aligned parallel to the wires and an effective anisotropy field, that can be as high as 12 kOe, is observed.

The effects of the electrolytic bath acidity, or pH, on the magnetic properties in arrays of electrodeposited Co nanowires and their correlation with the crystalline properties have been studied using ferromagnetic resonance. The results show that, depending on the value of the pH of the electrolyte, appreciable changes in the effective anisotropy can be induced. These changes are attributed to modifications in the microstructure of the Co nanowires. In particular, quantification of the effective anisotropy field shows that the microstructure of the deposited Co wires can be set to contain a dominant fraction of the Co-hcp phase with the c-axis oriented perpendicular to the wires, for pH values of 3.8-4.0, or parallel to the wires, for pH values >or=6.0. This results in a competitive or additive magnetocrystalline contribution to the total anisotropy field. Furthermore, at a pH value of 2.0, no contribution from the magnetocrystalline anisotropy is present, indicating a lack of texture in the Co microstructure. As a result, the effective anisotropy can be controlled over a field range of 5 kOe.

Interconnected or crossed magnetic nanowire networks have been fabricated by electrodeposition into a polycarbonate template with crossed cylindrical nanopores oriented ±30° with respect to the surface normal. Tailor-made nanoporous polymer membranes have been designed by performing a double energetic heavy ion irradiation with fixed incidence angles. The Ni and Ni/NiFe nanowire networks have been characterized by magnetometry as well as ferromagnetic resonance and compared with parallel nanowire arrays of the same diameter and density. The most interesting feature of these nanostructured materials is a significant reduction of the magnetic anisotropy when the external field is applied perpendicular and parallel to the plane of the sample. This effect is attributed to the relative orientation of the nanowire axes with the applied field. Moreover, the microwave transmission spectra of these nanowire networks display an asymmetric linewidth broadening, which may be interesting for the development of low-pass filters. Nanoporous templates made of well-defined nanochannel network constitute an interesting approach to fabricate materials with controlled anisotropy and microwave absorption properties that can be easily modified by adjusting the relative orientation of the nanochannels, pore sizes and material composition along the length of the nanowire.

"El tomate es una de las principales hortalizas que se produce y exporta en México. Debido a su fisiología y alto contenido de agua es altamente perecedero y susceptible a podredumbres causadas por fitopatógenos como Alternaria alternata, el cual produce pérdidas postcosecha. Las enfermedades son detectadas una vez que los síntomas son visibles en el fruto y ya es demasiado tarde para controlarlas, por lo que surge el interés de contar con métodos alternativos para la detección temprana del patógeno antes del desarrollo de la enfermedad. Se ha reportado que tanto los frutos como los microorganismos, así como durante el proceso de infección, éstos emiten metabolitos volátiles (MV) los cuales pueden ser utilizados como indicadores de la enfermedad o de la presencia del patógeno. En este trabajo se evaluaron cambios en el perfil de MV en tomates sanos e infectados por Alternaria alternata con el fin de evaluar la posibilidad de utilizarlos para la detección temprana de la infección, así como también metabolitos volátiles liberados por el hongo. Se inocularon frutos de tomate con esporas de A. alternata y tomates no inoculados fueron utilizados como testigo. Los frutos se mantuvieron a 15 y 20°C por 48 horas. Se tomó una muestra del espacio de cabeza mediante la técnica de cromatografía de gases y microextracción en fase sólida (CG-MEFS), a las 0, 3, 6, 9, 12, 24, y 48 horas post-inoculación. Adicionalmente se determinaron los MV emitidos por A. alternata Los metabolitos volátiles se analizaron mediante un cromatógrafo de gases utilizando estándares comerciales y un detector de masas cuadrupolo para su identificación."

Nucleoside-functionalized multi-walled carbon nanotubes (N-MWCNTs) were synthesized and characterized. A self-organization process using hydrogen bonding interactions was then used for the fabrication of self-assembled N-MWCNTs films free of stabilizing agents, polymers, or surfactants. Membranes were produced by using a simple water-dispersion-based vacuum-filtration method. Hydrogen-bond recognition was confirmed by analysis with IR spectroscopy and TEM images. Restoration of the electronic conduction properties in the N-MWCNTs membranes was performed by removing the organic portion by thermal treatment under an argon atmosphere to give d-N-MWCNTs. Electrical conductivity and thermal gravimetric analysis (TGA) measurements confirmed the efficiency of the annealing process. Finally, oxidative biodegradation of the films N-MWCNTs and d-N-MWCNTs was performed by using horseradish peroxidase (HRP) and low concentrations of H2O2. Our results confirm that functional groups play an important role in the biodegradation of CNT by HRP: N-MWCNTs films were completely biodegraded, whereas for d-N-MWCNTs films no degradation was observed, showing that the pristine CNT undergoes minimal enzyme-catalyzed oxidation This novel methodology offers a straightforward supramolecular strategy for the construction of conductive and biodegradable carbon nanotube films. Conductive and biodegradable films: A self-organization process using hydrogen-bond interactions (see scheme, MWCNT=multiwalled carbon nanotube) is used for the fabrication of conductive and biodegradable carbon nanotube films totally free of stabilizing agents, polymers, or surfactants.

Arrays of cobalt nanowires of diameter 23-70 nm were grown by electrodeposition. Their magnetic properties are probed using ferromagnetic resonance. Depending on the solution pH and deposition rate, the orientation of the dense planes of the hexagonal structure can be controlled so that its c-axis is oriented either parallel or perpendicular to the wires axis. In particular, the effects of the pH and deposition current on the structural and magnetic properties are considered and it is shown that the wire diameter plays an important role in the final preferred structure by inducing local changes of the pH within the pores.

The diatom silicified cell wall (frustule) contains pore arrays at the micro- to nanometer scale that display efficient luminescence within the visible spectrum. Morphometric analysis of the size and arrangement of pores was conducted to observe whether any correlation exists with the photoluminescence (PL) of two diatom species of different ages. UV-excited PL displays four clearly defined peaks within the blue-region spectrum, on top of the broad PL characteristic of synthetic porous silicon dioxide, recorded for reference and where discrete lines are absent. A set of shifted emission lines was observed when diatom cultures reached adulthood. These discrete line shifts correlate with structural changes observed in adult frustules: reduction in pore diameter; appearance of pores within pores, 10 nm in size; an increase in the gap distance between stria; and the deposition of several girdle bands with a concomitant increase in the diatom waist length, as well as the appearance of pores on such bands. Destruction of the pores results in the disappearance of all discrete emission lines. The PL shifts are correlated with a substantial increment of Si-OH groups adsorbed on the frustule surface, as revealed by Fourier transform infrared spectroscopy.

In the present work, we report on the in situ magnetic force microscopy (MFM) study of the magnetization reversal in two-dimensional arrays of ferromagnetic Ni80Fe20 and Co55Fe45 nanowires(NW) with different diameters (40, 50, 70 and 100 nm) deposited inside low porosity (P, 6 pages, 4 figures, To appear in Journal of Applied Physics

A mean field model is presented for the configuration dependent effective demagnetizing and anisotropy fields in assemblies of exchange decoupled magnetic particles of arbitrary shape which are expressed in terms of the demagnetizing factors of the particles and the volumetric shape containing the assembly. Perpendicularly magnetized 2D assemblies have been considered, for which it is shown that the demagnetizing field is lower than the continuous thin film. As an example of these 2D systems, arrays of bistable cylindrical nanowires have been characterized by remanence curves as well as ferromagnetic resonance, which have served to show the correspondence of these measurements with the model and also to validate the mean field approach. Linear chains of cylinders and spheres have been analyzed leading to simple expressions to describe the easy axis rotation induced by the interaction field in chains of low aspect ratio cylindrical particles, and the dipolar magnetic anisotropy observed in the linear chain of spheres. These examples serve to underline the dependence on the dipolar interaction field and effective demagnetizing factor on the contributions that arise from the shape of the outer volume., Comment: 21 pages, 4 figures, 1 table

The influence of the packing fraction on thermally induced magnetoelastic effects has been studied in Ni nanowires embedded in polycarbonate, poly(vinylidene difluoride), and alumina nanoporous membranes of different porosities for temperatures between 77 K and 345 K. For nanowires embedded in polymer membranes, the contrasting shift in the ferromagnetic resonance frequency when the temperature is either above or below ambient temperature is consistent with the occurrence of uniaxial magnetoelastic anisotropy effects due to the large thermal expansion coefficient mismatch between the metal nanowires and the membrane. A model which considers the influence of the nanowires packing fraction and the membrane material on the magnetoelastic effects, arising from the matrix-assisted deformation process, is proposed. The model is able to successfully explain the experimentally observed effects for the Ni nanowire arrays embedded in the different porous membranes and their variation with the packing fraction. The possibility to modulate the magnetic anisotropy of such nanocomposites by an appropriate choice of membrane material, packing fraction, and sample temperature is of considerable importance to achieve magnetically tunable devices.