Nanotubes behave as optical antennae

Dec 21, 2010 By Anne Ju
An artistic rendering of carbon nanotubes scattering light. Credit: Shivank Garg

(PhysOrg.com) -- Just as walkie-talkies transmit and receive radio waves, carbon nanotubes can transmit and receive light at the nanoscale, Cornell researchers have discovered.

Carbon nanotubes, cylindrical rolled-up sheets of , might one day make ideal optical scattering wires -- tiny, mostly invisible with the ability to control, absorb and emit certain colors of light at the nanoscale, according to research led by Jiwoong Park, Cornell assistant professor of chemistry and chemical biology. The study, which includes co-author Garnet Chan, also in chemistry, is published online Dec. 19 in the journal Nature Nanotechnology. The paper's first author is Daniel Y. Joh, a former student in Park's lab.

The researchers used the Rayleigh scattering of light -- the same phenomenon that creates the blue sky -- from carbon nanotubes grown in the lab. They found that while the propagation of light scattering is mostly classical and macroscopic, the color and intensity of the scattered radiation is determined by intrinsic . In other words, the nanotubes' simple carbon-carbon bonded molecular structure determined how they scattered light, independent of their shape, which differs from the properties of today's metallic optical structures.

"Even if you chop it down to a small scale, nothing will change, because the scattering is fundamentally molecular," Park explained.

They found that the nanotubes' light transmission behaved as a scaled-down version of radio-frequency antennae found in walkie-talkies, except that they interact with light instead of . The principles that govern the interactions between light and the are the same as between the radio antenna and the , they found.

To perform their experiments, the researchers used a methodology developed in their lab that completely eliminates the problematic background signal, by coating the surface of a substrate with a refractive index-matching medium to make the substrate "disappear" optically, not physically. This technique, which allowed them to see the different light spectra produced by the nanotubes, is detailed in another study published in Nano Letters.

The technique also allows quick, easy characterization of a large number of nanotubes, which could lead to ways of growing more uniform batches of nanotubes.

The paper's principal authors are former student Daniel Y. Joh; graduate student Lihong Herman; and Jesse Kinder, a postdoctoral research associate in Chan's lab.

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User comments : 7

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Bog_Mire
3.5 / 5 (2) Dec 21, 2010
just love the word. NANOTUBE. nnnnnnnnnnaaaaaaaaaaaaannnnnnnnnnnnnnoooooooooooottttttttttttttuuuuuuuuuuuuuubbbbbbbbbbbe.
Quantum_Conundrum
1 / 5 (1) Dec 21, 2010
Potential optical transistor?

Optical "radio" or "port" for a nano-computer or nano-robot?

Quantum_Conundrum
1 / 5 (1) Dec 21, 2010
Based on the molecular structure indicated here, this particular type of carbon nano-tube looks to be about 10 to 12nm in diameter. This would give it a circumfernce of about 31nm to 37nm.

No imagine a chip where you have a forest of nano-tubes standing on end. The nano-tubes are coated in silicon, and then electronic and optical transistors are printed onto the surface in 3d. By the time you count the layer of silicon, the diamer would be 12-15nm, and circumference 40nm to 50nm.

So if the nano-tube is like 100nm long, then you would be able to eventually fit several of 16nm transistors on this tube's surface, and perhaps 128 of 4nm transistors could fit on this surface (must leave room for nano-wires).

Then if you had an entire forest of such tubes....You could fit roughly 8 to 10 times as many transistors on a forest of 100nm length nanotubes standing on end on a surface, as you could place directly on the surface itself.
jscroft
1 / 5 (1) Dec 22, 2010
If I'm understanding this result correctly, it opens the door to the construction of optical phased arrays. That's cool!
Quantum_Conundrum
1 / 5 (1) Dec 22, 2010
If I'm understanding this result correctly, it opens the door to the construction of optical phased arrays. That's cool!


Yes, 3-d optical phased arrays which work something like phased array radars should be possible.

This would make ideal synthetic eyes, capable of both detecting color in the terrapixel resolution, maybe even Petapixel and beyond, AND calculating distance absolutely, the same way existing radar does.

You could make reactive contact lenses capable of both improving your vision, and actually displaying the distance to an object in a "HUD" style.
Quantum_Conundrum
1 / 5 (1) Dec 22, 2010
This would make the creation of 3-d models for video games and archetecture a snap.

You could have 3 cameras of this type, 1 along each axis. You then place models or model objects posing near the center, with no dinky reference dots glued to their skin, etc, the way was done for most blue screen movies like Star Wars.

This would allow truly "Holographic" imaging to instantly produce a 3-d model of any actor or prop, which could be used as a 3-d model in 3-d video games or simulators.

the actor would simply wear the character's outfit and props (sword, shield, clothes, armor, guns, grenades, etc, for an RPG or RTS,) and then go through the motions of actually using them, making several "takes" just like they are making a movie. Thenthe game developer or movie developer just keeps the best "takes" for each sequence and puts them into the game or movie.

It should literally be "as good as star trek quality" at least in terms of optics and telemetry.
Decimatus
not rated yet Jan 04, 2011
This could change the nature of radio and satellite based communication immeasurably.

You could get laser/fiber speed data transmission from Satellites and other line of sight communications platforms that would blow microwave/radio out of the water in the data rate category.

I suppose the biggest problem would be weather, as optical would attenuate and scatter much faster than microwave would.

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