Scientific and technological interest in one-dimensional nanomaterials, in particular carbon nanotubes, is a result of their fascinating properties and their ability to serve as templates for directed assembly.
For applications in nanoelectronics it is necessary to create ordered arrays of nanotubes for large-scale integrated circuits, and to produce controllable patterns on individual nanotubes so that multiple transistors can be fabricated on them.
A group of scientists from Drexel Nanotechnology Institute, [Li et al., doi: 10.1038/NNANO.2009.91] have shown crystalline block copolymers can be placed with accuracy along a carbon nanotube, leading to amphiphilic alternating patterns with a periodicity of approximately 12 nm. End functionalization of the block copolymers is also possible and allows gold nanoparticles to be periodically attached to the nanotubes. Li and his colleagues have successfully shown that this approach provides a relatively simple method for the periodic patterning of one dimensional nanomaterials.
The functionalization of carbon nanotubes is of great interest from both a scientific and technological viewpoints. Periodically functionalized carbon nanotubes can directly lead to the creation of controlled two- or three-dimensional carbon nanotube suprastructures, which is an essential step towards building future carbon nanotube-based nano devices. Regarding the patterning on the carbon nanotube surface, all the reported periodic patterns to date have suffered from limitations such as the locality of the pattern or poor periodicity. Here, Li et al report the use of low-molecular-weight polyethyleneb- poly(ethylene oxide) (PE-b-PEO) block copolymer to obtain uniform, periodic patterns on carbon nanotubes. This unique hybrid structure holds promise for a variety of nanoelectronic and biomedical applications.
Li et al propose a growth mechanism for the formation of the alternating stripes on SWNTs. uniformly patterned hybrid structure represents a unique nanoscale complex architecture that has not been achieved previously. Because PE is hydrophobic and PEO is hydrophilic, this system features a hybrid structure on individual carbon nanotubes that has alternating amphiphilicity with an approximate 12 nm period. The domain size can be controlled by changing the block copolymer molecular weight.
Li et al also synthesized thiol-terminated PE-b-PEO following the same procedure, SWNTs were periodically attached by the block copolymer with thiol groups present in the PEO stripes.
Gold nanoparticles were patterned periodically along the SWNTs, with a period the same as that of the block copolymer/SWNT hybrid. The number of gold nanoparticles on each PEO stripe can be tuned by controlling the lateral dimension of the block copolymer stripes on the carbon nanotube surface. This periodic gold nanoparticle/SWNT hybrid is of great interest in various areas of nanoelectronics and single-electron devices.