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Nanotubes perform for the cameras

点击量:   时间:2019-03-02 10:20:04

By Helen Knight All it takes is an optical microscope and a video camera to film carbon nanotubes being jostled by water molecules, researchers have found. The discovery could provide biologists with a relatively cheap and simple way to study how nanotubes interact with living cells and DNA. Doctoral student Rajat Duggal of the Carbon Nanotechnology Laboratory at Rice University in Texas, US, came up with the idea while studying DNA fragments under an optical microscope. He realised the technique could be applied to carbon nanotubes. Matteo Pasquali, also at Rice University, told New Scientist: “The diameter of DNA molecules and nanotubes is similar, so if you can see one in this way then you should be able to see the other.” Nanotubes tend to clump together, so to film them individually, Pasquali and Duggal first put clumps of the tubes into a mixture of water and a surfactant called sodium dodecyl sulphate (SPS). They bombarded the clumps with ultrasound waves to break them apart, allowing the SDS to surround and encase each tube. The researchers then added a red fluorescent dye, which attached itself to the SDS coating and glowed under an optical microscope, making the nanotubes clearly visible. Without the SDS molecules, the nanotubes are 3000 to 5000 nanometres long and about 1 nanometre in diameter, and 7 nanometres in diameter with the SDS. Watch a video of the moving nanotubes here (4.5MB wmv). When the researchers filmed the nanotubes and analysed the video frame by frame, they were able to witness some of the longer nanotubes bending harmonically like guitar strings under the bombardment of surrounding water molecules. They report their findings in a paper to be published in the journal Physical Review Letters in July. Researchers currently use electron microscopes to study nanotubes, which offer higher magnification. But the tubes have to be held stationary in a vacuum, so the technique does not allow scientists to study how they move in a liquid. Nanotubes can be studied in water but only if it is frozen. “And it’s important to understand the dynamics of the nanotubes as well as their structure,” says Pasquali. Peter Harris at the Centre for Advanced Microscopy at the University of Reading, UK, says the technique could be useful in several areas of nanotube research. “This technique gives us a new way of probing their behaviour in liquids, which could be important in preparing nanotube-containing composite materials, and in understanding how nanotubes interact with other molecules,” he says. Pasquali and his team are now using the technique to study the effects of different forces on carbon nanotubes,