Researchers at the U.S. Energy Department's Lawrence Livermore National Laboratory said they have identified a signature for water inside single-walled carbon nanotubes, or SWCNTs -- the first time researchers have been able to obtain such a "snapshot" inside the nanotubes, which offer the potential to act as a unique nanofiltration system.

LLNL scientists Jason Holt and Julie Herberg, with the University of North Carolina's Yue Wu and colleagues, said they used a technique called nuclear magnetic resonance, or NMR, to get a glimpse of the water confined inside one-nanometer diameter SWCNTs.

The nanotubes are hollow and more than 50,000 times thinner than a human hair. The confined water exhibited very different properties from that of bulk water, allowing it to be distinguished in the NMR spectrum.

"There have been many predictions about how water behaves within carbon nanotubes," said Holt, the project's principal investigator. "With experiments like these, we can directly probe that water and determine how close those predictions were."

The research appears in the journal Nanoletters.