Sandia researchers construct carbon nanotube device that can detect colors of t...( LIVERMORE Calif. Researchers at San...)

LIVERMORE, Calif. Researchers at Sandia National Laboratories have created the first carbon nanotube device that can detect the entire visible spectrum of light, a feat that could soon allow scientists to probe single molecule transformations, study how those molecules respond to light, observe how the molecules change shapes, and understand other fundamental interactions between molecules and nanotubes.

Carbon nanotubes are long thin cylinders composed entirely of carbon atoms. While their diameters are in the nanometer range (1-10), they can be very long, up to centimeters in length.

The carbon-carbon bond is very strong, making carbon nanotubes very robust and resistant to any kind of deformation. To construct a nanoscale color detector, Sandia researchers took inspiration from the human eye, and in a sense, improved on the model.

When light strikes the retina, it initiates a cascade of chemical and electrical impulses that ultimately trigger nerve impulses. In the nanoscale color detector, light strikes a chromophore and causes a conformational change in the molecule, which in turn causes a threshold shift on a transistor made from a single-walled carbon nanotube.

"In our eyes the neuron is in front of the retinal molecule, so the light has to transmit through the neuron to hit the molecule," says Sandia researcher Xinjian Zhou. "We placed the nanotube transistor behind the moleculea more efficient design."

Zhou and his Sandia colleagues Franois Lonard, Andy Vance, Karen Krafcik, Tom Zifer, and Bryan Wong created the device. The team recently published a paper, "Color Detection Using Chromophore-Nanotube Hybrid Devices," in the journal Nano Letters.

The idea of carbon nanotubes being light sensitive has been around for a long time, but earlier efforts using an individual nanotube were only able to detect light in narrow wavelength ranges at laser intensities. The Sandia team found that thei
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