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In this study, we investigate the magnetic properties of interconnected permalloy nanowire networks using micromagnetic simulations. The effects of interconnectivity on the hysteresis curves, coercivity, and remanence of the nanowire networks are analyzed. Our results reveal intriguing characteristics of the hysteresis curves, including nonmonotonic behaviors of coercivity as a function of the position of horizontal nanowires relative to vertical nanowires. By introducing horizontal nanowires at specific positions, the coercivity of the nanowire networks can be enhanced without altering the material composition. The normalized remanence remains relatively constant regardless of the position of the horizontal wires, although it is lower in the interconnected nanowire arrays compared to nonconnected arrays. These findings provide valuable insights into the design and optimization of nanowire networks for applications requiring tailored magnetic properties. [ABSTRACT FROM AUTHOR]

In this paper, our objective was to investigate the static and dynamic magnetic properties of Fe3O4 nanotubes that are 1000 nm long, by varying the external radius and the thickness of the tube wall. We performed a detailed numerical analysis by simulating hysteresis curves with an external magnetic field applied parallel to the axis of the tubes (along the z-axis). Our findings indicate that nanotubes with an external radius of 30 nm exhibit non-monotonic behavior in their coercivity due to a change in the magnetization reversal mechanism, which was not observed in nanotubes with external radii of 80 nm. Additionally, we explored the dynamic susceptibility of these nanotubes and found that the position and number of resonance peaks can be controlled by manipulating the nanotube geometry. Overall, our study provides valuable insights into the behavior of Fe3O4 nanotubes, which can aid in the design and improvement in pseudo-one-dimensional technological devices. [ABSTRACT FROM AUTHOR]

Ferromagnetic films down to thicknesses of tens of nanometers and composed by polycrystalline Fe and Fe2O3 nanopillars are grown in large areas by glancing angle deposition with magnetron sputtering (MS-GLAD). The morphological features of these films strongly depend on the growth conditions. Vertical or tilted nanopillars have been fabricated depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively. The magnetic properties of these nanopillars films, such as hysteresis loops squareness, adjustable switching fields, magnetic anisotropy and coercivity, can be tuned with the specific morphology. In particular, the growth performed through a collimator mask mounted onto a not rotating azimuthally substrate produces almost isolated well-defined tilted nanopillars that exhibit a magnetic hardening. The first-order reversal curves diagrams and micromagnetic simulations revealed that a growth-induced uniaxial anisotropy, associated with an anisotropic surface morphology produced by the glancing angle deposition in the direction perpendicular to the atomic flux, plays an important role in the observed magnetic signatures. These results demonstrate the potential of the MS-GLAD method to fabricate nanostructured films in large area with tailored structural and magnetic properties for technological applications. [ABSTRACT FROM AUTHOR]

The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 μg/mL concentration. [ABSTRACT FROM AUTHOR]

An antimicrobial polymeric bilayer structure based on the application of an acrylic coating containing hollow zinc oxide nanotubes over a polymeric substrate was developed in this work. Firstly, zinc oxide nanotubes (ZnONT) were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers followed by polymer removal through calcination with the purpose of obtaining antimicrobial nanostructures with a high specific area. Parameters of electrospinning, ALD, and calcination processes were set in order to obtain successfully hollow zinc oxide nanotubes. Morphological studies through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) microscopies confirmed the morphological structure of ZnONT with an average diameter of 180 nm and thickness of approximately 60 nm. Thermal and X-ray diffraction (XRD) analyses provided evidence that calcination completely removed the polymer, resulting in a crystalline hexagonal wurtzite structure. Subsequently, ZnONT were incorporated into a polymeric coating over a polyethylene extruded film at two concentrations: 0.5 and 1 wt. % with respect to the polymer weight. An antimicrobial analysis of developed antimicrobial materials was performed following JIS Z2801 against Staphylococcus aureus and Escherichia coli. When compared to active materials containing commercial ZnO nanoparticles, materials containing ZnONT presented higher microbial inhibition principally against Gram-negative bacteria, whose reduction was total for films containing 1 wt. % ZnONT. Antiviral studies were also performed, but these materials did not present significant viral reduction. [ABSTRACT FROM AUTHOR]