Interfacing conjugated polymers with magnetic nanowires

Universal Method to Transfer Membrane-Templated Nano-Objects to Aqueous Solutions

A wide range of nano-objects are synthesized by combining template synthesis, using polycarbonate membrane as template, with different material deposition methods. The resulting nanostructures varied from robust inorganic gold nanowires grown by electrodeposition to rigid polypyrrole nanotubes synthesized by chemical polymerization and softer nanotubes made of different combinations of synthetic and natural polyelectrolytes fabricated by layer-by-layer (LbL) assembly. The morphology of these various nano-objects is characterized prior to and after their immersion in water, revealing that the rigidity degree of LbL nanotubes strongly decreases after being in contact with water, leading to highly swollen and flexible nanotubes in aqueous solution that tend to stick to any surface and are very difficult to collect and disperse quantitatively in aqueous solution. Different processes to collect these nano-objects and disperse them in aqueous medium for further analysis and application were then studied. Among them, a method based on simple filtration of nanotubes in the presence of a powdered dextran adjuvant leads to the quantitative collection and dispersion in water of all types of tested cylindrical nano-objects. This universal method to efficiently collect membrane templated nano-objects paves the way to further characterization of a large variety of nanotubes in aqueous solution and to their potential use as cargo nanocarriers or as nanoreactors.

Multisegmented FeCo/Cu nanowires: electrosynthesis, characterization, and magnetic control of biomolecule desorption

In this paper, we report on the synthesis of FeCo/Cu multisegmented nanowires by means of pulse electrodeposition in nanoporous anodic aluminum oxide arrays supported on silicon chips. By adjustment of the electrodeposition conditions, such as the pulse scheme and the electrolyte, alternating segments of Cu and ferromagnetic FeCo alloy can be fabricated. The segments can be built with a wide range of lengths (15-150 nm) and exhibit a close-to-pure composition (Cu or FeCo alloy) as suggested by energy-dispersive X-ray mapping results. The morphology and the crystallographic structure of different nanowire configurations have been assessed thoroughly, concluding that Fe, Co, and Cu form solid solution. Magnetic characterization using vibrating sample magnetometry and magnetic force microscopy reveals that by introduction of nonmagnetic Cu segments within the nanowire architecture, the magnetic easy axis can be modified and the reduced remanence can be tuned to the desired values. The experimental results are in agreement with the provided simulations. Furthermore, the influence of nanowire magnetic architecture on the magnetically triggered protein desorption is evaluated for three types of nanowires: Cu, FeCo, and multisegmented FeCo15nm/Cu15nm. The application of an external magnetic field can be used to enhance the release of proteins on demand. For fully magnetic FeCo nanowires the applied oscillating field increased protein release by 83%, whereas this was found to be 45% for multisegmented FeCo15nm/Cu15nm nanowires. Our work suggests that a combination of arrays of nanowires with different magnetic configurations could be used to generate complex substance concentration gradients or control delivery of multiple drugs and macromolecules.

Preparation and electromagnetic properties of core/shell polystyrene@polypyrrole@nickel composite microspheres

Through a novel method, we successfully synthesized electromagnetic (EM) functional polystyrene@polypyrrole@nickel (PS@PPy@Ni) composite microspheres. The PS@PPy spheres with well-defined core/shell structure have been synthesized via an in situ chemical oxidative copolymerization of pyrrole (Py) and N-2-carboxyethylpyrrole (PyCOOH) templated by PS microspheres. The reaction was carried out under heterophase conditions using the mixture of ethanol and water as the continuous phase. Tailored by the carboxyl groups on the surface of microspheres, magnetic nickel layer has been steady deposited onto the P(Py-PyCOOH) layer of the microspheres through an activation-electroless plating technology. The fine PS@P(Py-PyCOOH)@Ni core/shell structures could be obtained with the PyCOOH content up to 50 wt % in the P(Py-PyCOOH) layer. Moreover, the as-prepared PS@P(Py-PyCOOH)@Ni composites are ferromagnetic materials and behave as a good electromagnetic (EM) absorption material due to the coating of Ni layer around the PS@P(Py-PyCOOH) spheres. The PS@P(Py-PyCOOH)@Ni composite spheres show the remarkable EM wave absorption property with the maximum reflection loss (around -20.06 dB) at 10.69 GHz. The EM wave absorption can retained lower than -10 dB within a broad frequency range from 9.16 to 13.75 GHz.