AVS2011 Session MI-ThP: Magnetic Interfaces and Nanostructures Poster Session

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. This work is funded by the DOE Office of Science, Office of Basic Energy Science, Division of Materials Sciences and Engineering. The Advanced Photon Source (APS) is supported by the Director, Office of Science, Office of Basic Energy Sciences.

The nano dimensions of materials are comparable to the size of the target analyte biomolecule, higher catalytic reaction, better affinity binding or more efficient molecule-capturing may occur, leading to high sensitivity. And it is possible to use nanoparticle tags for designing electrical bioaffinity assays with remarkable sensitivity and multiplexing ability. So far, efforts have always been made to design novel nanomaterials useful in solving emerging bioanalytical problems such as rapidness, anti-interfering ability, specificity, stability and sensitivity. Synergies of nanocomposite materials, generally retaining the functional properties of each component and possibly yield synergistic effects via cooperative interactions, have exploited a new area to miniaturize and optimize nano-scale sensors and electronics. The synergistic interesting new features include but not limited to increased surface area, enhanced electrocatalytic activities, improved biocompatibility, promoted electron transfer and better invulnerability against intermediate species. A lot of efforts have been made to fabricate nanocomposite materials of metals/metal oxides nanostructures and carbon materials, using a number of techniques, including sputtering, sol–gel, hydrothermal, microwave and electrodeposition from different precursor solutions containing complex agents. Among these, electrodeposition is the easiest, most controllable, environment-friendly and robust technique for synthesis of metal/ metal oxides NPs, in which, the size, density, composition and even the shape of NPs could be well-controlled by electrodeposition potential, time, concentration and composition of metal precursor solutions.

Herein, we report a general two-step approach of electrodeposition useful in facile, controllable and 'green' electrochemical synthesis of metal oxide NPs onto carbon supports, using carbon nanotubes (CNTs) as an example. First, metal nanostructures were electrochemically deposited onto carbon supports at a constant potential with the density, size, shape and elctrocatalytic activities of the produced nanostructures well-controlled by the time and deposition potential applied as well as the concentration of the precursor solution. Then the as-deposited metallic nanostructures were oxidized into metal oxide nanostructures by repetitive potential cycling with extent of oxidation and generation of metal oxides controlled by the number of potential circles.The as-synthesized metal oxides-CNTs composites were characterized and applied as a glucose sensor for illustration of their electrocatalytic properties.

In a search for new multiferroic materials where the direction of magnetization can be switched by an applied electric field, we have looked for materials in which polarization and magnetization are strongly coupled. Recent theory calculations predicted that the family of compounds MTiO ₃ (M = Mn, Fe, Ni), in a certain polymorphic structure (acentric R3c), are promising candidates where a polar lattice distortion can induce weak ferromagnetism. Guided by these insights, a rhombohedral phase of Ni TiO₃ has been prepared in epitaxial thin film form, whose structure is very close to that predicted to be a multiferroic. The synthesis of such new epitaxial films, their full structural characterization along with our first-principles DFT calculations to predict the desired NiTiO₃ structure and its stability are reported .