Skip to comments.Light Bends Matter, Surprising Scientists
Posted on 03/25/2010 10:57:48 AM PDT by 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...
(Excerpt) Read more at livescience.com ...
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.
Ohhh. So all that crazy talk about miracles from the Light of the World is...
Science and religion are very very seperate. Mya bad.
Is it true that dark is heavier than light and that’s why it sinks to the bottom of the ocean?
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.
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.
Learned this at age 5 when I left an old 45rpm on the window sill.
I forgot how fun science is! :)
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?
Sounds to me like this is an electromagnetic/chemical effect - not the corollary of space bending light.
what happened to nanoparticles not exposed to ambient light?
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.
Light causes plants to move too. Phototropism. Maybe the ambient light heated the strands differentially.
God created science.
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.
Of course it is.
Notice that those things we call "light bulbs" turn dark or black when they've collected all the dark they can hold? Some get so full of dark matter they won't let any light in, so they look silvery and reflect your image (light) back at you! ;^)
Not sure why this seems to be a big deal; we've used different frequencies to cause physical actions on the atomic/molecular level for decades.
One of my favorite quotes of all time: “Those who say science and religion are incompatible are missing the point of both.”
I comprehensively verified that theory through extensive experimentation with a magnifying glass and some unlucky ants as a young lad.
If I'm remembering correctly back in the mid to late 60's photocell operated relays were fabricated from cadmium sulfide as the photo sensitive element used to control the relay operation. I seem to recall selenium also have photo sensitive properties. Selenium was mainly used in "solid state" rectifiers to produce DC from AC input without resorting to vacuum tubes or mercury filled "ignitrons". This technology was in use before WWII and most contemporary EE have never even heard of it.
FReepmail me if you want on or off my health and science ping list.
No, photons carry both energy and mass. This particular effects seems to be due to the energy they contain. But their momemtum can have large scale effects as well.
For example, if you had a really powerfull laser on a spaceship, it could be used to propel the ship. Shine it in one directoin and you accellerate in the other direction. Not very quickly unless it's really honking big laser, but move you will. Of course such a laser could be used as a weapon as well. Or for signaling over very very long distances.
The momentum of a photon, like it's energy, is only dependent on it's wavelength. (or color if it happens to fall in the visible spectrum).
So the other direction, lasers can now blast an incoming missile by heat and energy input ..... 8<)
Thanks for the ping.
Heat is energy. But, IIRC, some of the damage mechanism for short pulse lasers is due to momentum transfer. Short of like pounding on the missile with a ball peen hammer, only much harder.
But other lasers, such as the one on the ABL 747, do there thing by energy deposition.
Right on. Science is man's halting effort to read God's handwriting directly. We've translated a few letters of the alphabet.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.