Raytheon Company (Tucson, AZ), in U.S. Patent Application 20100012021, reveals a new method for growing and cloning precursor chiral nanotubes with a specified chirality via epitaxial growth.
This is accomplished, according to inventors William R. Owens and Eric A. Gifford, by first specifying the design of the desired nanotube including the material selected from carbon, nitrogen, boron, titanium, silicon, germanium, aluminum and gallium and combinations thereof, chirality and typically the diameter. Given the specifications of the nanotube, a substrate of crystal material having sheet lattice properties complementary to the lattice properties of the selected material is provided. A cylindrical surface of the specified diameter (1 to 100 nm) is formed as either a void in the substrate or as crystal material projecting from the substrate. The cylindrical surface is formed at an orientation with respect to the axes of the crystal substrate corresponding to the specified chirality.
A monocrystalline film of the selected material is epitaxially grown on the cylindrical surface that takes on the sheet lattice properties and orientation of the crystal substrate to form the specified precursor chiral nanotube in or on the crystal substrate. The precursor chiral nanotube may have its own utility or may be used to clone itself. The precursor is cloned by attaching a catalyst to the precursor and dissolving atoms of the specified material into the catalyst, which clone both the sheet lattice properties and orientation of the precursor.
Typically, the cloned chiral nanotubes will be harvested by separating them from the substrate allowing the precursor to be reused. Alternately, the cloned nanotube and precursor nanotube embedded in the substrate may have utility as a unit. In addition to growing SWNT or MWNTs with a specified chirality, this approach can be used to grow concentric cylinders of a specified geometry and cylinders in which a first portion is embedded in the crystal along the length of the nanotube. The approach also provides a mechanism for the introduction of other materials into the nanotube.
