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  • So this is a transmission electron microscope image.

  • It's formed by having beams of electrons actually transmitted through a sample, and you build up an image from those beams of electrons.

  • What it is, actually is one of these single nanoparticle from this solution of nano particles on The reason I'm showing it to you is because a couple of years ago we had a master class for high school students on the students actually made these nano particles on DDE.

  • Well, both they and me got very, very excited when we could see the nanoparticles they made with quite simple chemistry.

  • And you can see those right down to the single nanoparticle limit will take a little droplet of this solution.

  • We put it onto a grid on dhe.

  • We let that we let the solvent evaporates, and then we put the sample into the microscope.

  • On dhe, we can see a CZ.

  • You can see the individual particle.

  • It's a gold nanoparticle.

  • It's a single gold nanoparticles, tiny, tiny chunk of gold.

  • In this case containing about 125,000 atoms on dhe, we can see they are faces on this which sometimes call it a chunk or nano particle, but it's actually better described in this case is a nano crystal in seriously, these ridges these edges on those arise because when you form these particles, they grew up to a certain size and they have certain certain fierce is what I'm showing you.

  • You here is it's not quite the same crystal structure, but it doesn't really matter.

  • As gold has on, you have different fear says, and those verses will have different reactivity is because of you.

  • If we look at different atoms on these, fierce is sometimes they're bonded to tree atoms below.

  • Sometimes, in other cases, the bonded to two atoms below on that leaves what are called dangling bones sticking out on north.

  • Dangling bonds affect the reactivity affected.

  • The crystal grows on dhe.

  • Some faces will grow.

  • Some crystal faces will grow faster than others.

  • On dhe, we end up with these.

  • You can see these facets on there.

  • So this is these are facets and when you grow crystals, you grow older.

  • You can go crystals at very large structures.

  • Of course, if you look at diamond, you can see the facets in the diamond, but this is at an unimaginably small level.

  • This is 15 nanometers across on the other.

  • 125,000 atoms.

  • Yes, when you worked as an atom is incredibly small.

  • A gold atom diameter of a gold atom is roughly a little bit less than three Angstrom.

  • Sultry 10th of an animator.

  • So you were talking about roughly 125,000?

  • All I've done there, I must admit, before you get your calculator site and all the experts Philip the Commons Shit.

  • Go on.

  • How did he manage to work that out?

  • He's out by a factor of 2%.

  • What I've done is I've just taken the volume of an atom.

  • I've taken the volume of the Nano particle.

  • If I the one by the other guy, Very rough estimate for the number of atoms.

  • Maybe I should point out at this point, I guess one of the interesting culture changes when people come that we experience when people come from school, from high school, from second disco to university.

  • To do a physics degree is that we don't care.

  • In the vast majority of cases, we don't really care if we've got an answer to 19 decimal places way make a lot of approximation.

  • So, for example, you know, if we're talking about gold nanoparticles were on, we want to work at the number of atoms and knows I would make a lot of approximations and I'll give you a guesstimate.

  • And it's the interesting because it seems to me that many of you are many first year students undergraduates on dhe.

  • People who aren't signed us find that quite strange, for science is always portrayed as this very, very exact.

  • We really want to do the values to find down to the end Desperate place, and that's not really have physicists work.

  • So the common joke is that you know, a cow to a physicist is basically just a large sphere.

  • Sometimes you consider the tales.

  • Sometimes you don't, but that's that's really really it.

  • So about 125,000 atoms I've been doing some back it literally back at worst, my envelope purposely, yeah, literally back of the envelope calculations.

  • So we do a lot of this.

  • We do a lot of mucking around in back of in envelopes, backs of envelopes.

  • I didn't age because it was the closest thing to a hand.

  • And then when you work out in terms of the volume of this, compared to this, you get 10 to the 18 which is one quintillion off these into this volume really continually tells me stop talking.

  • In terms of 10 to the 18 intent of the 19 intended, the bloody blood means nothing, and it absolutely doesn't mean anything.

  • But it turns out that if you wanted to have 10 to the 18 of these, how much volume with article, well again, back of the envelope calculation, it would.

  • You'd require a 20 meter deep pile off multi zone, which spread out over an area the size of Ireland and for the doors of you on the other side of the big pond.

  • Ireland was about the same area as the state of Indiana, as well as sort of seeing the fiercest.

  • These lines are lattice planes on.

  • They arise from the Waveland off the electrons that were using to make this image.

  • It starts that they defrocked from the crystal planes on those diffraction just the same way as if you take a c.

  • D.

  • Uh, you might have a CD queens of the Stone Age, the colors that you get so so that the remember color that comes from the fraction that comes because the say's off the off.

  • The features on the disk that used to be called the information are roughly the same size as the wavelength of light.

  • Now what you basically have here is an atomic scale, DVD or atomic scale CD, and now, instead of bouncing light, offered your bouncing electron waves on.

  • In this case, the electron with rave land is roughly is comparable to the spacing of the cleanse, and you end up seeing that the fraction from those plans in the in the image.

  • No, I have not seen that has the same papers, but I've never seen it in real life before that where it's really need to see.

So this is a transmission electron microscope image.

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B1 中級

金のナノ粒子-60のシンボル (Gold Nanoparticle - Sixty Symbols)

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    林宜悉 に公開 2021 年 01 月 14 日
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