ABSTRACT
In this paper a study on the ion transmission ratio of a nanoporous alumina sample is presented. The sample was investigated by scanning transmission ion microscopy (STIM) with different beam sizes. The hexagonally close-packed Al(2)O(3) nanocapillary array, realized as a suspended membrane of 15 microm thickness, had pore diameters of approximately 215 nm and spacing of approximately 450 nm. When the proton beam size was limited to a single domain, a peak transmission ratio of 19% was observed as is expected from the geometry (approximately 19-20%). This result points out an almost perfectly parallel alignment of the capillaries within one domain. However, for larger beam scanning areas (sampling multiple domains) the transmission ratio was reduced to 5%. The STIM analysis over an area larger than the typical domain size revealed an overall capillary angular spread of approximately 2 degrees.
ABSTRACT
We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires obtained by electrodeposition of the metal within the nanopores of an alumina template supported on a silicon wafer. Carboxymethylpullulan (CMP) and chitosan (CHI) multilayers were grown on brushes of Ni nanowires; subsequent grafting of an enzyme was performed by conjugating free amine side groups of chitosan with carboxylic groups of the enzyme. The nanowires are finally released by a gentle ultrasonic treatment. Transmission electron microscopy, electron energy-dispersive loss spectroscopy, and x-ray photoelectron spectroscopy indicate the formation of an homogeneous coating onto the nickel nanowires when one, two, or three CMP/CHI bilayers are deposited. This easy and efficient route to the biochemical functionalization of magnetic nanowires could find widespread use for the preparation of a broad range of nanowires with tailored surface properties.
Subject(s)
Biopolymers/chemistry , Coated Materials, Biocompatible/chemistry , Magnetics , Nanowires/chemistry , Nickel/chemistry , Carbohydrate Conformation , Carbohydrate Sequence , Chitosan/chemistry , Glucans/chemistry , Materials Testing , Molecular Sequence Data , Particle Size , Surface Properties , UltrasonicsABSTRACT
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.
Subject(s)
Crystallization/methods , Electric Wiring , Electrochemistry/methods , Magnetics/instrumentation , Metals/chemistry , Nanotechnology/methods , Nanotubes/chemistry , Crystallization/trends , Electric Conductivity , Electrochemistry/instrumentation , Nanotechnology/instrumentation , Nanotechnology/trends , Nanotubes/analysisABSTRACT
Applying a constant voltage to superconducting nanowires we find that its I-V characteristic exhibits an unusual S behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: j(c2) at which the pure superconducting state becomes unstable and j(c1)
