How do photoswitches work?
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| Number of Parts | 163 | |
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| License | CC Attribution - NoDerivatives 4.0 International: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.5446/50359 (DOI) | |
| Publisher | 05jdrrw50 (ROR) | |
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00:00
Computer animation
00:08
MoleculeOrganische ChemieMaterials scienceFunctional groupChemical property
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Materials scienceRecreational drug useRelease agentStimulus (physiology)AspirinMeeting/Interview
00:41
Controller (control theory)Chemical propertyMoleculeThermoformingMeeting/Interview
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MoleculeLeft-wing politicsThermoformingColourantBlue cheeseHuman body temperatureMeat analogueEssenz <Lebensmittel>PharmacySeleniteSea levelDiagram
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MoleculeMaterials scienceEngineering drawing
Transcript: English(auto-generated)
00:08
Welcome, my name is Stefan Hecht. I'm leading the laboratory of organic chemistry and functional materials here at Humboldt University in Berlin. My group's research is aiming to use molecules as smart switches in order to control the properties of
00:23
materials and devices with light. Think of possible applications. They could be as smart transistors that can be programmed with light or they could be in remote controlled catalysts or even drug release agents. So now you may ask why light? Light is an external stimulus that can be applied with superior spatiotemporal resolution.
00:46
In other words, we have exact control over where and when the molecular action takes place. Now, of course, the molecules come into play. So we need molecules that can be interfaced with light. Molecules that absorb light and can be converted between two different forms that have drastically different properties.
01:05
So now this may sound complicated, but it's actually not. There's a very simple principle underneath and let's have a closer look at it. First, we need a molecule that can exist in two forms. The chemists calls them isomers, but I use stickman here as an analogy to keep it simple.
01:23
One of the two guys, the guy on the right, has to invest a bit more energy holding both arms up. In fact, thinking about energy is the key here. In hands, we typically discuss energy minima and maxima, such as the mountain in the middle separating both valleys.
01:40
At normal temperature, the energy of the guy on the left is not sufficient to climb over the mountain and this is where light comes into play. We now can shine light, for example, blue light on the left guy and he is propelled as if he would use an elevator to an upper level. This is the so-called excited state and molecules can only enter it when absorbing a photon,
02:03
so accepting the smallest quantity of the light's energy. As molecules, and in fact humans too, typically want to relax, the guy wants to get rid of the excess energy. So he leaves the excited state by first falling into a valley that leads directly onto the mountain, separating the two valleys in the ground state.
02:22
From this point, the outlet of the so-called photochemical funnel, he falls further on the right side. As a result, the light energy was used to make him lift his arm and become the guy on the right. Now the guy on the right cannot climb the mountain pass either, at least at normal temperatures.
02:42
However, as he is less stable, so contains more energy, as pointed out earlier, light of lower energy, for example green light, is sufficient to kick him up again on the excited state and then he falls through the funnel back again on the left hand side. In essence, we have two different guys, actually I should better say molecules now,
03:04
that can be transformed into each other using light of different color, so energy. Hence, we can address each of the two different molecules individually and therefore we have our molecular switch. That was easy. Now the next thing is that both switching forms have different characteristics that we can use.
03:24
Let's get back to the analogy to the guys one more time. While the guy on the left has both of his hands very far apart, the guy on the right has them both close together and therefore he is able to use them together in concert, so to speak. In other words, while the guy on the left is taking it easy, he is in the so-called resting or off state,
03:45
the guy on the right is on and can do things such as playing the piano. Using the appropriate colored light, we are able to switch between the two guys and hence have the music been played or not. This, in a nutshell, is the concept of remote controlling molecular or any action by light.
04:27
Although we'd love to play the piano we just heard it, we are actually scientists, so we work in a lab. Together in a team we're designing and synthesizing new molecules and then we try to implement them into new materials and devices together
04:40
with physicists, engineers and material scientists. Working together is a lot of fun and hence we hope that our new molecules will have a bright future.