Light Bends Matter, Surprising Scientists

LiveScience ^ | 24 March 2010 | Clara Moskowitz

[neverdem]

After 72 hours of exposure to ambient light, strands of nanoparticles twisted and bunched together. Credit: Nicholas Kotov

Light can twist matter, according to a new study that observed ribbons of nanoparticles twisting in response to light.

Scientists knew matter can cause light to bend – prisms and glasses prove this easily enough. But the reverse phenomenon was not shown to occur until recently.

The researchers assembled strings of nanoparticles, which are tiny clumps of matter on the scale of nanometers (one nanometer is one billionth of a meter). In a darkened lab, the scientists linked nanoparticles together into ribbons. At first the nano ribbons were flat, but when a light was shone on them, they curled up into spirals.

The discovery was so novel, the researchers were skeptical of their own results at first.

"I didn't believe it at the beginning," Kotov said. "To be honest, it took us three and a half years to really figure out how photons of light can lead to such a remarkable change in rigid structures a thousand times bigger than molecules."

The surface of the nanoparticles in this experiment were made of cadmium sulfide. To begin with, they had a slightly negative electromagnetic charge. But when photons, or particles of light, hit the nanoparticles, their energy excited electrons on the nanoparticles, causing chemical reactions that made them even more negatively charged. Since two negative charges repel each other, the nanoparticles began to repel more strongly.

"What's happening is a layer of nanoparticles starts repulsing from the others, so it creates mechanical stress, and in order to release this stress the ribbon twists itself," Kotov told LiveScience...

[neverdem]

Light-Controlled Self-Assembly of Semiconductor Nanoparticles into Twisted Ribbons

The collective properties of nanoparticles manifest in their ability to self-organize into complex microscale structures. Slow oxidation of tellurium ions in cadmium telluride (CdTe) nanoparticles results in the assembly of 1- to 4-micrometer-long flat ribbons made of several layers of individual cadmium sulfide (CdS)/CdTe nanocrystals. Twisting of the ribbons with an equal distribution of left and right helices was induced by illumination with visible light. The pitch lengths (250 to 1500 nanometers) varied with illumination dose, and the twisting was associated with the relief of mechanical shear stress in assembled ribbons caused by photooxidation of CdS. Unusual shapes of multiparticle assemblies, such as ellipsoidal clouds, dog-bone agglomerates, and ribbon bunches, were observed as intermediate stages. Computer simulations revealed that the balance between attraction and electrostatic repulsion determines the resulting geometry and dimensionality of the nanoparticle assemblies.

[Voter62vb]

Ohhh. So all that crazy talk about miracles from the Light of the World is...

never mind.

Science and religion are very very seperate. Mya bad.

[GeronL]

interesting

[a fool in paradise]

Is it true that dark is heavier than light and that’s why it sinks to the bottom of the ocean?

[a fool in paradise]

[yefragetuwrabrumuy]

This was poorly written. They might as well have said that “light can affect matter”. Big deal. In this case, light can cause an electrochemical change in matter. Been doing it in plants for a long time.

[RobRoy]

I see matter as nothing more than, metaphorically speaking, coagulated energy. I also think that an excellent analogy to our “real world” would be “The Matrix”. What we perceive as the “real world” is almost entirely empty space.

That is significant.

[668 - Neighbor of the Beast]

Learned this at age 5 when I left an old 45rpm on the window sill.

[RobRoy]

I forgot how fun science is! :)

[Vermont Lt]

Light is a bunch of photons zipping through space at, well, the speed of light. Even though their mass is miniscule, the fact that they beat the hell out of something after a while should really not be a surprise.

Or am I missing something?

[a fool in paradise]

You should have kept with it. It could have been the start of a very promising career.

[happinesswithoutpeace]

/

[D-fendr]

Sounds to me like this is an electromagnetic/chemical effect - not the corollary of space bending light.

[stuckinloozeeana]

what happened to nanoparticles not exposed to ambient light?

[Beagle8U]

I know that cold dark water is more dense.

I learned that fact years ago while ice fishing. When the sun goes down and the temp drops, it takes much longer for your line to sink back to the bottom.

The difference is enough that you will instantly notice it when the sun goes down.

[DManA]

Light causes plants to move too. Phototropism. Maybe the ambient light heated the strands differentially.

[Hot Tabasco]

After 72 hours of exposure to ambient light, strands of nanoparticles twisted and bunched together.

[DallasDeb]

God created science.

[Voter62vb]

QED!!

[MrB]

Ah, so you’ve heard the theory of the heaviness of dark, have you?

Those things on the ceiling that make you squint when you look at them? Some people call them “lights” or “light bulbs”, but in reality, they are “dark suckers”. The sun, like all stars, is just one huge dark sucker.

Now, sometimes they get full of dark, and have to be replaced. And that dark that you see under the table? Well, that’s because the dark can’t be sucked into the dark sucker because the table’s in the way.