Oct 2, 2009
Magnetic cores allow polymeric nanotubes to be manipulated
Nanostructuring is a useful way to improve and control the electrical and optical properties of semiconducting conjugated polymers. Applications for these polymeric one-dimensional nano-objects include OLEDs and organic photovoltaics, as well as sensors and bio-systems. One stumbling block is the material's weak mechanical strength, which can present problems when it comes to manipulating the structures or device integration. To address this issue, researchers at the Institute of Materials in Nantes, France, have developed a template-based method for growing coaxial nanowires with magnetic cores of nickel and an outer skin of photoactive PPV polymer.
"We have shown recently that poly(p-phenylene vinylene) (PPV) nanowires and nanotubes exhibit original photoluminescent properties in comparison to thin films," said Jean-Luc Duvail, head of the project. "Here, the challenge was to manipulate them as building-blocks."
"The chemical template method used for synthesis can be scaled up, and the magnetic response of these coaxial wires provides a route for physically manipulating them," commented Jean-Marc Lorcy, the PhD student who developed the synthesis route.
As initiated by Florian Massuyeau, another member of the team, the tubes are produced by wet filling of nanoporous membranes with the PPV polymer, which coats the inside of the pores.
Rigid wires or flexible tubes
Electrodeposition is used to fill the core of the pores with nickel before the membrane is dissolved to reveal the co-axial nanowires. By controlling the length of Ni filling, the team can produce either rigid filled wires, or flexible polymer tubes with magnetic Ni-filled heads.
There are a number of benefits to the group’s approach. The polymer shell prevents the metallic nanowire from oxidation and corrosion, while the nickel segment strengthens the PPV nanotube. This allows the nanostructures to be manipulated using very small magnetic fields in comparison with the ones required for manipulating superparamagnetic nanoparticles.
In these prototypes, part of the photoluminescence is quenched, due to the proximity of the metal. The next challenge is to optimize the design so that the composite benefits fully from the properties of each constituent.
The researchers presented their work in Nanotechnology.
About the author
Jean-Luc Duvail is an assistant professor at the Institut des Matériaux de Nantes Jean Rouxel (CNRS, University of Nantes), France. He is head of the PMN group and his research is focused on conjugated polymer and/or magnetic metal based hybrid 1D nanostructures.