HOUSTON -- (Feb. 23, 2011) -- A lab at Rice University has stepped forward with an efficient method to disperse nanotubes in a way that preserves their unique properties -- and adds more.
The new technique allows inorganic metal complexes with different functionalities to remain in close contact with single-walled carbon nanotubes while keeping them separated in a solution.
That separation is critical to manufacturers who want to spin fiber from nanotubes, or mix them into composite materials for strength or to take advantage of their electrical properties. For starters, the ability to functionalize the nanotubes at the same time may advance imaging sensors, catalysis and solar-activated hydrogen fuel cells.
Better yet, a batch of nanotubes can apparently stay dispersed in water for weeks on end.
Keeping carbon nanotubes from clumping in aqueous solutions and combining them with molecules that add novel abilities have been flies in the ointment for scientists exploring the use of these highly versatile materials.
They've tried attaching organic molecules to the nanotubes' surfaces to add functionality as well as solubility. But while these techniques can separate nanotubes from one another, they take a toll on the nanotubes' electronic, thermal and mechanical properties.
Angel Marti, a Rice assistant professor of chemistry and bioengineering and a Norman Hackerman-Welch Young Investigator, and his students reported this month in the Royal Society of Chemistry journal Chemical Communications that ruthenium polypyridyl complexes are highly effective at dispersing nanotubes in water efficiently and for long periods. Ruthenium is a rare metallic element.
One key is having just the right molecule for the job. Marti and his team created ruthenium complexes by combining the element with ligands, stable molecules that bind to metal ions. The resulting molecular complex is part hydrophobic (the
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