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Nanocar Race 2017: 4. Driving the Nanocar – Manipulation of single molecules

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Nanocar Race 2017: 4. Driving the Nanocar – Manipulation of single molecules
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4
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163
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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.
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How can you move a single molecule? We could use our tip like a finger and push the nanocar. Actually this would also be possible at the nanoscale! In this case the tip needs to touch the molecule. But pushing the nanocar in this way is forbidden at the Nanocar Race. Only electric power is allowed! As we have shown before there is a tunneling current between tip and sample. We can use this current to inject electric power into the nanocar. The molecule has different energy levels. Without any influence the molecule is in the ground state. If you change the voltage between the tip and the molecule, you can inject electrons in the excited state of the molecule. So it has a higher energy. By filling more and more electrons in the molecule which is done by ramping the bias voltage we also excite states where the molecule does vibrations or rotations. And then it moves. We can control the direction of the movement by the position where we place the tip. The molecule always follows our tip when we inject electrons. So we know exactly where the molecule goes. But then we have to scan again to see the molecule. Because we know where the molecule went after excitation, we can choose a small scan range around this area to get a quick image. The time for a scan is quite long in comparison to the electron injection. By choosing a small scan range at the right position we reduce the time we need to finish the race track at the Nanocar Race.
Keywords
Tidal raceTiermodellIntergranular corrosionMachinabilityScreening (medicine)Computer animationChemical experiment
Surface scienceMoleculeChemical experimentMeeting/Interview
Computer animation
Meeting/Interview
Tidal raceChemical experiment
WalkingMeeting/Interview
Meeting/Interview
Forkhead-GenMoleculeProcess (computing)
Meeting/Interview
Surface scienceMoleculeProcess (computing)
MoleculeWaterfallElectronCHARGE syndromeCrown etherBattery (electricity)Motion (physics)Resonance (chemistry)Diagram
Meeting/Interview
Quantum chemistryDeath by burningTidal raceComputer animation
Tidal raceMeeting/Interview
Tidal raceMeeting/Interview
Transcript: English(auto-generated)
In the last video we saw at a model how the STM, a very sensitive microscope, works. But all of that just takes place in this machine? Yeah, everything that you have seen at the model happens in this machine here. Okay, but you already told me that you cannot just look in here to see an image. How do you get the image? For this we have to look at our computer screen. There you can see some images. Let's do that.
Alright. So what do you see there? So here on the left side you see single nanocars on the surface. But that's quite a few of them, right? Exactly. Each right triangular here is one single nanocar. And how do you move such a single molecule? Do you just take the nanocar and push it like this?
This would be forbidden in the race but actually we could do it. You could do that? Yeah, this would be possible. But what we do is that we place the tip here and then we apply a bias voltage and our nanocar will follow the position of the tip. Okay.
And I also have some tips here that you can see some of them. So they are here in this box. Okay. So please have a look. Oh, but they are really tiny. I almost see nothing right here. Yeah, it's almost impossible to see it. So that's why we use some microscopes again to see such a tip.
Okay. But how does the car know where the tip is? This happens by a physical process. So the molecule when it is on the surface is in the ground state and by sweeping the bias voltage we can change the energy. The voltage increases and also the energy increases and if the voltage is
in resonance with the excited state of the molecule we can inject an electron. So the molecule has more energy than before. So it's like a charged battery and this energy is released in a motion of the molecule. So that's how the molecule can move.
Okay. Here on this image I also see some grey lines. What's that? Yeah, actually that is our racetrack. So the grey lines are the rails of our racetrack. I can show you the video here and you see the nanocar moving. Ah, but there you left the racetrack, right? Yeah, exactly. We have left the racetrack so this is forbidden in a nanocar race.
Okay. And if that happens to you in the race, what do you do then? Then we have to go back on the racetrack and then we can continue. Ah, okay. So now we learned about how to move a small object like a nanocar. But what does the racing track even look like and what material is it made of? You'll find about that in the next video that you will find, as always, linked below. I'll see you there and have a good time. Bye bye.