JAPAN NANONET BULLETIN - 45th Issue - May 26, 2005

Fabrication of DNA-metal hybridized nano wires by selective electroless plating

Recently double-stranded DNA molecules have attracted attention as new functional materials, such as a building block for suprastructures. We have studied novel nano fabrication methods by using single DNA molecules immobilized on a substrate as a template. It is known that a DNA molecule, which is a kind of anionic polyelectrolyte, can be bound to a cationic lipid monolayer to form a polyionic complex through electrostatic interactions. When the cationic lipid was spread onto an aqueous DNA solution, the polyion complex monolayer consisting of the cationic lipid and DNA was formed, and DNA can be transferred to a solid substrate using a vertical lifting method. We have found that transferring with a slow lifting speed gives stretched single DNA molecules immobilized on a glass substrate. We have investigated the fabrication of metal nanowires by electroless plating of stretched single DNA molecules immobilized on substrates as a template. AFM and SEM measurements after the metallization procedure showed that thin lines (ca. 20 nm height and ca. 50 nm width) were fabricated on the substrate. Fine silver particles were deposited along the stretched DNA molecules selectively. We are attempting to measure electronic conductivity of the metal nano wire using conducting AFM.

Fig. 1 Large Image
Schematic illustration of the LB deposition of a DNA-cationic amphiphile polyion complex monolayer formed at the air-water interface.

Fig. 2 Large Image
(Left) Fluorescence image of a DNA-cationic amphiphile polyion complex monolayer transferred onto a glass substrate (Fluorescence-labeled DNA was used); (Right) AFM image of silver metal wires deposited on stretched single DNA molecules.

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