So, like in a metal, the reason why it can conduct electricity very well is that there basically is a continuum of states between like filled and unfilled states. Um and so you're all the like electrons, you know, at that like highest energy in the material, there's like always an empty state that they can move to. So that's why you can flow electrons through a wire made up of metal.
SPEAKER_06Oh. So the conduction through a wire is is because in the in the coordination, maybe that's the wrong word, of of all the different atoms you get it's easier for electrons to flow between states. Because the states are more con there's just more there's more states. I mean it's still quantized, but it's but there's m so many more states that they can be in when they're in the full material.
SPEAKER_01Exactly. Yeah, yeah, yeah. Exactly.
SPEAKER_06And so then so then the this electronic shell electron in this atom can very easily drop to fill this like slightly lower energy state in the in the in the atom next door. And then another one can jump and it just makes it so they can just flow. But it's not but it's but it's the but it's what what makes it so they can flow is is they actually have to change energy levels to flow between Yeah, that's a great question.
SPEAKER_00So they basically don't have to change energy levels.
SPEAKER_06Um hi.
SPEAKER_00Hi, good to meet you.
SPEAKER_01Uh so how do you know Leah?
SPEAKER_06Uh we just met uh like around Stanford. Like we just met and like ended up getting coffee and chatting and it was really nice.
unknownCool.
SPEAKER_06We just became friends.
SPEAKER_00Cool, cool.
SPEAKER_06Yeah, I love it. We like I we started it's kind of the thing that is the podcast, right, where um we just were talking and I asked her what she did, and she you know started to give me the elevator speech, you know, the sort of like, I know you don't really understand, so I'll sort of like explain it in a simplistic way. And then I was like, okay, now tell me how it actually works, right? Because I do understand. Um and we ended up getting into it for like 45 minutes, uh, and it's great. Um, because what she's doing is amazing. Uh cool.
SPEAKER_00Yeah. I actually haven't gotten the pitch from her, so maybe I should reach out to her and try to get it.
SPEAKER_06Yeah. Yeah, yeah. I mean, you don't know her research, it's incredible what she's doing.
SPEAKER_00So I Leah is like, she we were classmates in undergrad. Um, so I'm I am I would say I'm like peripherally aware of what she's been up to because she's been up to some pretty cool things over the years. But I haven't heard her like uh, you know, the pitch for her her independent career or seen her like seminars or anything of that. So that would be exciting. Yeah, I would love to hear that.
SPEAKER_06Yeah, it's cool. I'm super curious. So, okay, Lilia she?
SPEAKER_01She uh is okay, yeah. Yeah, that's good.
SPEAKER_06Assistant professor of chemistry at Princeton.
SPEAKER_00Yes. Nice. So I think I probably have the same, maybe the same title as Leah, but just yeah. We're in a pretty similar spot.
SPEAKER_06Yeah, yeah. Um, but you do material science.
SPEAKER_00Yeah.
SPEAKER_06What is it?
SPEAKER_00So I actually have a dual appointment in chemistry, and there's this Princeton Materials Institute here.
SPEAKER_06So I'm super curious. Like, what uh what are you working on?
SPEAKER_00We're making materials um and trying to study their properties. Uh so that's probably, yeah, I don't know. So I but before this call, I was thinking, like, oh man, I should probably work on my elevator pitch because I I feel like I I haven't gotten it down yet. But um yeah, because materials are all around us, right? Um there's like a lot of known, well-known materials that um we probably take for granted in our day-to-day lives. But then there are uh, you know, there's always room for improvement in known materials. Um and then I think there's like new materials might form the basis for completely new technologies, right? Like sometimes they say the technologies of the future. Um, maybe are gonna be based on things that we haven't even made yet, with properties that we can only imagine. So um that's kind of where we come in.
SPEAKER_06Yeah. So what I'm I'm so curious, what like what materials are you working on right now?
SPEAKER_00So we are primarily interested in inorganic materials. I would say things that fall under the category of inorganic material. So that means things that have some metals in them. Um and a lot of times the metals are what gives the materials some properties that we're interested in. So um, and then I guess another bucket. So yeah, so maybe my answer to this would depends on who I'm talking to, like what kinds of materials are we working on. Um so in some sense, I would say another bucket that uh we are interested in is quantum materials. So that can probably be defined as materials um with physical properties that really depend on quantum mechanics to exist. So they involve some kind of um complicated interactions uh among the electrons from the atoms. So basically there's some kind of way that these atoms are arranged that allows their electrons to interact um and kind of delocalize, talk to each other um to give some emergent property.
SPEAKER_04Oh boy.
SPEAKER_00But I feel like, yeah, so this is why I say I need to work on my elevator pitch.
SPEAKER_06No, this is great. So okay, so we've got so we've got doping. We've got doping with metals.
SPEAKER_00So it's not necessarily doping, right? Like some of these materials, so a lot of the materials just have metals. Like we're interested in things like um transition metal dichalcogenides. So this is transition metal Dicalcogenides. So what is a di like so this is like a a class of materials.
SPEAKER_06Um I think you spell the word or like di what's the word dialogue.
SPEAKER_00Dicalcogenides. Um is there a chat here? Or I can text it to you.
SPEAKER_06No, no, no, you gotta say it because it's a record, it's a podcast.
SPEAKER_00Right, right, right. But if you want to like have the spelling, so you can say it.
SPEAKER_06Okay. Yeah, if you I can yeah, sure.
SPEAKER_00There is a chat, right?
SPEAKER_06Yeah, yeah, and then I'll say it. Yeah, yeah.
SPEAKER_00But anyway, I mean, uh, I don't know if we should be saying this word, but this is what I said transition metal dye calcogenize.
SPEAKER_06A lot of them D-I-C-H-A-L-C-O-G-E-L-I.
SPEAKER_00So, basically this word cal calcogen. So, calcogen is that calcogen is um the name for the row of the periodic table that starts with oxygen. So it goes oxygen, sulfur, selenium, tellurium. But oxygen is pretty different from the others in most chemical contexts. Um, so I'm not familiar with this name.
SPEAKER_06I mean, I'm familiar with like the al you know, the like the alkalides and the and the halogens. I've never heard calcogens.
SPEAKER_00So it's basically like the halogen. Just one row over from the halogens.
SPEAKER_06Yeah, yeah. Okay.
SPEAKER_00Actually, I don't know. I guess it's probably Greek or something. Um, the etymology. I should probably know that, but I don't know.
SPEAKER_06It probably is. Like they're always Greek, right? Um so die, so just like two, right? So so it's just so it's like ox like O2 or S2.
SPEAKER_00Right, right, right. So like the prototypical example of this class of materials is um a material called uh molybdenum disulfide or MOS2.
SPEAKER_06Yeah, which I actually just talked a lot about with um uh oh no, her name is escaping me.
SPEAKER_00Uh is it someone at Stanford?
SPEAKER_06Yeah.
SPEAKER_00Is it Feng Liu?
SPEAKER_06Yes.
SPEAKER_00Yeah, yeah, yeah.
SPEAKER_06Yeah, I just I just we I we didn't look at that.
SPEAKER_00She's really cool.
SPEAKER_06Yeah, she's at like a whole thing in all the in specific and like the the mult the multiple layers at the two-dimensional, like essentially two-dimensional, like molybdenum disulfides, and then how you can like so that their conformation is slightly different, which makes this sort of like honeycomb shape, and then how you can adjust the uh the physical properties and the electrical properties and the and the and the light absorption and transmission properties um and shift through the electron structure inside each one of the little sections. Exactly temporarily. Yeah.
SPEAKER_00So there's like a lot of really cool layered materials that you can do those kinds of manipulations to. Um, and some of those layered materials fall in this family of transition metal di-chalcogenides. Um but I guess the reason why you can peel them apart, um, you know, into 2D layers so that you can do things like study the single sheet properties, and then you can take two sheets, stack them on each other in a different arrangement, right? Have this twist angle. Um, the reason why, in a chemical sense, you can do that is basically because you have the transition metal, like each layer of this material is kind of like a sandwich. So you have the transition metal in the middle, and then it's sandwiched on both sides by these calcogen atoms. So that's something that's like sulfur or selenium or tellurium.
SPEAKER_06Um and then And we talk all about that about how about how the the the chemical um like equation of what's the like you know the MOS2, but actually it's you get like it's really like three, you know, molybdenum atoms and then six sulfur atoms, right? And they sort of like and then they sort of can right but it becomes this like each molybdenum atom like sort of connects to like six different sulfur atoms, but then multiple molybdenum atoms connect to like the other, you know, the other ones also. So it becomes this um diffuse um sharing of electrons, which feels a lot like a metal. Exactly. Like it feels like straight, it feels like a metal. Uh the way that people just like flow.
SPEAKER_00That's like um I think this whole category of materials can be thought of as I think it's not wrong to call them quantum materials. So basically, like I was saying earlier, um, there's some kind of bonding between, you know, the atoms that make up these materials that allows the electrons to delocalize, right, to some extent, to greater or lesser extents across different parts of the structure. Um and then that really can give rise to these interesting properties. So optical properties, electronic properties. Um, and then when you change these structural elements or these compositional elements, then you can also tune the properties. Um and I'm really interested in how to change the chemistry to control the properties. Um, not so much by changing the composition of the layers themselves, but I'm interested in putting new um species, new components between the layers to basically change how much the layers are talking to each other. So it's kind of related to what Fong is doing with twisting. Um, I think some of my ideas are very inspired by what that community has done. Basically, they've shown that by changing this twist angle between two layers of materials, you can so you get this like Ware super lattice. You introduce this new length scale. So this like new periodicity. Yeah. So you have this new pattern, right? You have like the pattern, the repeating pattern that's formed by your atoms themselves.
SPEAKER_02Yeah.
SPEAKER_00And then when you have this twist angle, it's kind of like, I don't know if you've ever looked at like a window screen.
SPEAKER_06So we actually like she had she had two um flat uh just pieces of plastic with we and we like and we look, we're able to hold it up and be like put it together and like twist it a little bit. And you can see how it the honey shifts as you twist them.
SPEAKER_00Right.
SPEAKER_06Yeah.
SPEAKER_00Right. So basically, um the pattern that you can see uh has like a very profound effect on the behavior of the electrons. Yeah. Um and so the way that one way you can think about that is you can describe, you know, the moray superlattice by a length scale, which here would just mean like um how long does it take before you get to the same like repeating unit again?
SPEAKER_04Okay.
SPEAKER_00Right. If you change the angle, then basically like the size of that pattern will change.
SPEAKER_06So this becomes like nanometers? This becomes Right, exactly.
SPEAKER_00Yeah. So normally in this material on its own, when you're just looking at the atomic scale structure, that's on the length scale of angstroms. Yeah. Right. So that's a tenth of a nanometer. But then with this twisting, you can get patterns on like 10 times or more bigger. You can get nanometer scale or even tens of nanometers just by changing the angle between them. Um and then that basically changes like the length scale that the electrons feel as well.
SPEAKER_06That the electrons feel. Oh, I love it.
SPEAKER_00Yeah. So that is like kind of a way to change like, you know, the quantum mechanical properties of the electrons. Um, because they now have like, you know, it's kind of like the electron is wandering in a forest, then maybe there's like a log cabin, right? Every, you know, it's gonna be pretty different if you're wandering in the forest and there's a log cabin every 10 steps versus every 100 steps versus every like 900 miles. Yeah.
SPEAKER_06There's something about the lattice that prevents electron travel outside its specific um it's specific like little hexagon.
SPEAKER_00Yeah. So like that's basically what's happening in these more like super lattices. You create this.
SPEAKER_06So the bigger the hexagon, the more electrons can interact in this one space because they don't, for some reason they which is wild because it's it's based on the two layers and the and the electrons. How do the electrons like in one layer it makes sense that the elect like like a metal, right? Like the electrons just are free-flowing.
SPEAKER_00But then then how is it that the that the two layers interact such that they prevent electron movement beyond the places where I think that basically is like getting to the thing that I'm really interested in in manipulating um in these materials. So that's like a super deep question. It's like how are the electrons behaving in each layer? And how are they behaving across the layers? So it's like basically, right, you have these like like it sounds like um this great example that Fong has this demo with like two sheets of plastic. Like it's very intuitive to us that um the the sheet of plastic or like a sheet of paper or any like two-dimensional kind of any sheet, right, that we interact with in our daily lives, like it has two dimensions that are similar and then one dimension, like the thickness is very different.
SPEAKER_04Yeah.
SPEAKER_00So it's like the same thing, right? For these electrons. Like in these 2D materials, like within the sheet, um, in the 2D plane, they behave one way, but then um if they have to go from layer to layer, it's very different.
SPEAKER_06Oh, get into it. Get into it. Yeah.
SPEAKER_00So the reason why you can I guess that's kind of, yeah, that's a really good question. Like what you asked, which was something like how do the electrons know, right? That their environment is changing when you change this like long large pattern that they live in.
SPEAKER_06Yeah, like what is it about the interaction between the two layers that somehow prevents a free flow of electrons?
SPEAKER_00Yeah. So it really has to do with the layer. Yeah, yeah, yeah. So when you twist these layers, right, you end up creating these different um stacking uh patterns of the two layers. Like when you look at it visually, right, some areas look darker, other areas look lighter.
SPEAKER_04Yep.
SPEAKER_00And that basically is a product of whether um like the vertices of your pattern are on top of each other. Oh no. Or if they're like um staggered, right?
SPEAKER_06Why did my internet just go down?
SPEAKER_00I think we might be experiencing a technical difficulty.
SPEAKER_06Oh, wait a second. Okay, for some reason my internet is saying, Oh no, now it's back. For some reason my internet just went down. It said that was so weird, but then like came back. Okay.
SPEAKER_00Okay, yeah, I think that just happened, like, I think we're we're back now.
SPEAKER_06Yeah, we're back.
SPEAKER_00Yeah, so so um okay, so we're sorry, I feel like I'm giving you like the most terrible description.
SPEAKER_06No, this is great.
SPEAKER_00This is like it doesn't actually. I haven't given I haven't given you enough context to actually understand.
SPEAKER_06No, no, no, no. This is what this podcast is about, is right, is right like um no like the right, the name of the podcast, right? Like no reason to get excited, right? Because this is so exciting. Um and it's it's that there's this gap between what we're able to explain using pop culture language, right? And then the the like where I'm at, which is which is like I've taken collegiate level science courses, right? So like I know what aromaticity is, right? Like I know what, right? Like we can talk about electron spin, right? And I will know, like, I know what you're talking about, right? Um, like when you say quantum and how they're communicating all this stuff, like I know, like I know we're talking about electron spin, right? Um at least I think that's what we're talking about. Um but then there's this there's this layer beyond where you once you've done like more and more and more classes and like gotten really into how it works and really spent a lot of time with it, you end up at this like higher understanding, this more complicated understanding, but then there's a gap of communication of like how do you actually like explain that? Right? This is tough. Like that's what this is all about, is like, okay, let's do it. Like, I want to know. I'm so excited. And I don't expect you to be able to do it like it's not something that we regularly do.
SPEAKER_00Yeah.
SPEAKER_06Um, we're fundamentally we're communicating between the layers. We're learning how to communicate.
SPEAKER_00There's so many puns, yeah. This is like an area that's very rich for for puns. Um it has made me realize that I think when I if I do try to communicate um science, you know, to any audience, I am very used to relying on visual aids. Yeah. Like, you know, usually there's a PowerPoint or there's some kind of like, I'll prepare some, you know, demonstration material, right? Like like this example that that you were talking about with Fang, she had some like plastic sheets, right? She had the picture and then the picture is worth a thousand words.
SPEAKER_03Right.
SPEAKER_00I think there's so many things in science, it's so much easier to get the point across with a picture or with a model. And then if you're just using your words, um I feel like if I sat down and really thought about it, like if I were to write it out, um I might be able to come up with something. Do it right now. But like off the cuff is not something I'm used to doing.
SPEAKER_05Yeah, we'll figure, yeah, that's that's good. Like, okay, right? Let's, yeah, it's the best way. We're like we're discovering together. It's good science, right? We're like, we're discover we're discovering, right?
SPEAKER_00But I think that's super interesting that there is this um gap. And I think the the more time I spend in science, the more I feel like um a lot of the people I look up to, and I think a lot of people generally who you can say without question, these are like very successful uh scientists. Um they are super good at communicating the science to different audiences. Um whether it's like in the field or kind of also beyond the field, right? Because that's how you get people, that's how you get new ideas into your field, that's how you get interest in whatever. You're working on. That's how you get funding. That's how you get funding. Yeah. So I think that's like super important.
SPEAKER_06Um I mean, if this goes, if this podcast, like, like my like eventually where this could be good, where this could go is um like guests can have like a funding link, right? And if people like what they're working on, they could just be like a go fund me. Where it's like, just let's just send your send a bunch of money to your lab, right? And people can contribute five bucks, ten bucks, like that's worth it. Let's right. And who knows, like maybe it becomes a meaningful source of funding, right?
SPEAKER_00Oh man, that would be really interesting. Yeah, that would only be quite disruptive. Yeah.
SPEAKER_04That would be what?
SPEAKER_00That would be disruptive. Yeah. I mean, in in the sense of, you know, that would be new. Yeah, yeah, we would just it would disrupt the standard.
SPEAKER_06But I mean, NIH is not like, right? Like it's we need more, like we need more. And all we and like and crowdfunding is way, I just had this really great one with a political scientist. Um and it was like one of the things we talked about was um funding of campaigns and how um people who can rely on people who can figure out a way to connect to a large part of the population and and get many small donations can raise incredible amounts of money. Right? It all goes back to the March of Dimes. They're like that's the first one that I know about, which is which is for cancer research, right? The March of Dimes comes from the original word building cancer research. Um and the idea was you don't have very much money, but you have a dime. And so they like did this huge push all across the country of like the March of Dimes that's gonna that's gonna fund pediatric cancer research. So I think that was like the 30s or the 40s, I'm not sure. Um but yeah, that's like so okay, so let's do it. So let's get let's like let's help people like like let's get people excited about how amazing which it was. So okay. Um so we've got these layers. So we've got two layers of of a molybdenum of a molybdenum disulfide or any other, you know, transition metal di capogen. Uh and we twist our angles so that certain sections are like in closer contact or something.
SPEAKER_00Kind of, yeah. There's just gonna be different um different area like the fact that you can see the pattern means that uh well it's density.
SPEAKER_06Arrangement is different in different when you do it with two little pieces of plastic, like what you're seeing where where it's darker is it's just density. Right? It's density of of plastic in a specific shape that is blocking more light. Right? Yeah. Is that the same thing where it's somehow it's just like it's the density in this particular edge of this hexagon that makes it?
SPEAKER_00It's kind of like it becomes the density of the electrons in those regions is different. Yeah, yeah. So it's a little bit more complicated than just like what you see with your eyes, but I think it's like a pretty direct analogy.
SPEAKER_06I mean, is it right? So, like what is what makes it complicated?
SPEAKER_00What about what is it about the density of the electrons in those Oh, because it's like not necessarily the same place where it looks darker, right, when you overlap it. So it has to do with like the actual like energies of the electrons. So like you have to, it's not a one-to-one with what you see, but in terms of the analogy, there's gonna be some areas where there's a lot of things. Oh no, let's get into it.
SPEAKER_06Let's get into it. What is it actually, what is it actually about the electrons that creates those boundaries?
SPEAKER_00Um I mean, so basically, if you have any atom, right, there's gonna be certain states that your electrons live in. So that's basically if we go back to basic quantum mechanics.
SPEAKER_06Just basic orbital, like states of spin or states of like orbital energy.
SPEAKER_00Yeah, orbitals.
SPEAKER_06Okay.
SPEAKER_00Yeah. So if you go to quantum mechanics, that basically, you know, um for like a hydrogen atom, right? Yeah. That tells us that there is certain allowed states.
SPEAKER_06It's actually where we get the word quantum, right?
SPEAKER_00Right.
SPEAKER_06That there's like specific, it's like an an electron can't have a continuous amount of energy. It can either have this much energy or like then there's a gap, and then there's this like next level of energy that it can have. There's a gap, and then there's this next level of energy that can, which is where we get, you know, when then when it's when it bounces, like how we know that is they bounce back and we see emission spectra that are very precise, right? So it's like clear that there are gaps where like, how come it can only do yellow light and green light? How come it can't also do like light in between, right? That doesn't make sense. If it was continuous, it would, right? And this is where we get the idea of orbitals, right? That's where we come up with the construct of orbitals is the quanta, is like the the like the that there is like quanta, that there are like specific amounts that they that they can have, and the and in the spaces between they can't hold that, right? So okay, so that's where we're right.
SPEAKER_00So the orbitals are basically where the electrons can live. Right.
SPEAKER_06Um and that's sort of a physical space, but we don't really know. Like we draw them in class. Like we draw here's an S orbital circle, here's a P orbital.
SPEAKER_00Yeah, it's like a physical space.
SPEAKER_06You know, the two teardrops, right?
SPEAKER_00It's a physical space. I mean, what you draw is like, you know, it's an approximation. So it's not really like a well-defined solid thing with edges, right? It's like kind of a cloud.
SPEAKER_06It's a probability cloud.
SPEAKER_00Right. Yeah, exactly. Um I'm with you.
SPEAKER_06I'm right here with you. Like, I'm with you. Let's do it.
SPEAKER_00Okay. So so we have orbitals, we have states where the electron is allowed to live, right? And then the electron, those states have certain energies associated with them.
SPEAKER_06Yeah, it's a physical space, but it also maps to it's like a physical probability. It's a probability cloud of like where can it actually be in space. But it also that is also like an energy state.
SPEAKER_03Mm-hmm.
SPEAKER_06Yeah. Like higher energy can leads to a different shape of space that it will most likely be in.
SPEAKER_01Right. Yeah.
SPEAKER_06And those are undisentangled, like you can't disentangle those things, right? You can't like have a higher energy electron be hanging out in an S orbital, right? The higher energy is the P orbital.
SPEAKER_00Yeah. I think so. I guess it depends, right? Like with a lot of things, it it depends. But yeah, the I think that the energies of orbitals are well defined. And yes, they are intimately connected with um their identity.
SPEAKER_06Oh man, we're about to get into like with quantum mechanics. It's like, can you like increase the can you give an electron p orbital energy, but have it be in the in in the physical space of an s orbital?
SPEAKER_00Um I mean, you can do things like you can change the atom, right? So if you want, so so for chemists, if we want to form a bond, let's say, between an s orbital and a p orbital, then we probably, you know, one way to get a strong bond is you want good energy overlap. Um, so you might want to choose an atom that has an s orbital that's, you know, the same energy as the p orbital of another atom. And then that means they can like communicate well with each other, at least in terms of energy. But another ingredient in terms of that overlap, like how well they can bond with each other, is um what we call spatial overlap. So that's like, are the orbitals, you know, large enough so that when you put these atoms next to each other, are they going to actually physically overlap with each other such that like the wave function of the electron can mix efficiently between these two atoms.
SPEAKER_06Which is why it's gonna make a difference if it's molybdenum dioxide versus molybdenum disulfide, because the the size of the oxygen nucleus versus the size of the sulfur nucleus is gonna change the I did so so the amount of energy in an S orbital, in an electron in an S orbital, if it's around a hydrogen atom, right? Versus if it's around um, I don't know, tungsten. I mean anything, right? Like just something bigger, right? A sodium atom or like anything bigger. Um the actual energy of that electron in the s orbital is different. S orbitals aren't all can a consistent amount of energy.
SPEAKER_00Yeah, so that depends on which s orbital it is, right? So like hydrogen just has okay, it has one like in the ground state, right? For a hydrogen atom, you have one electron and then one s orbital.
SPEAKER_04Yeah.
SPEAKER_00Um and then you can like have these excited states, right?
SPEAKER_06If we want to make nuclear bombs, right? Like we can make, we can add protons, we can add, I guess that's adding protons. Um if you want to make like heavy water, like tritium or or right, something like that.
SPEAKER_00Yeah, so so tritium and deuterium are actually what we call isotopes.
SPEAKER_04Yeah, yeah.
SPEAKER_00So it has the same number of electrons, but it has one more neutron. Like deuterium has has oh man.
SPEAKER_06Deuterium is deuterium is is a is a neutron, is one neutron, right? And tritium is two neutrons.
SPEAKER_01Yeah, yeah, yeah, yeah.
SPEAKER_06Um okay, but if you got so if you've got like a sodium, but there's more than one s orbital? I thought there was only one s orbital that could have two electrons.
SPEAKER_00But then you also have a two s orbital, a three s orbital, a four s orbital, right? So you have these four principal quantum numbers. Um, right. So there's n, which is the shell, and then there's l, which tells you what type of orbital it is, and then there's m sub l, which tells you basically like which orbital it is. And then I'm that's the spin. M sub s. M sub s is the spin.
SPEAKER_06Yeah. So you get like one s. So you get like, so you have like the one s orbital and you can put two electrons in it, and one's gonna be plus one half and the other one's minus one half.
SPEAKER_01Yeah, exactly.
SPEAKER_06Okay. So like oxygen has got six electrons, uh eight electrons. Six. Eight. No, eight. So, so but there's still but like I thought it was still only like two electrons in the s orbital, and that was it, and the others are all in p orbit p orbitals, or am I doing that wrong?
SPEAKER_00So for uh in the valence shell, there's only two electrons in the two s orbital, and then there's four electrons in p orbitals. But then you still have this one s orbital. But we just generally we that's what we call like a core electrons.
SPEAKER_06Oh, that's right. So as you go down the levels of the periodic table, like there's you have the hydrogen and and helium, which only have the one s orbital. And then you get into what sodium and lithium, and you get the two s orbital, but then you also start to fill up p orbitals. And then there's like you're gonna get down another layer. Now there's a 3s orbital, which is now outside, it's like it's outside the one, the like not just the 1s and the 2s orbitals, but also the full p orbitals. Is it like actually physically outside?
SPEAKER_00It's not a physically outside. There's like a lot of overlap in terms of what we call the radial extension.
SPEAKER_02Yeah.
SPEAKER_00Um, but I think it's not wrong to think about outside. Like the periodic table is kind of like you have uh nesting dolls, right? It's like as you go, as you increase the the atomic number, it kind of has the previous uh atom inside of it, right? Yeah. Um I think it's not wrong to think of it that way. Yeah.
SPEAKER_06And so if you want an s orbital to interact with a p orbital in two different atoms, it might be that this has a two p like a uh a two p orbital and this has a three s orbital, and those two have equivalent energies?
SPEAKER_00They could, yeah. Like depending on what atoms they are.
SPEAKER_06Aaron Powell Depending on yeah, oh depending on what.
SPEAKER_00Yeah. So like the reason why different elements have different properties is basically all because their orbitals have different energies. And then the frontier orbitals, which are mostly responsible for the properties of the all the variance. Different configurations and different energies. Yeah.
SPEAKER_06Okay. So now let's tie it back to materials. So, okay. What are what's uh like what's material you're working on right now that you like that's like really got you? That's like whoa.
SPEAKER_00So like a lot of the materials that I'm interested in are like pretty similar to things like molybdenum disulfide, but just um maybe they have like one more electron, right? So that or one less electron. So tantalum disulfide has one uh fewer electron than molybdenum disulfide.
SPEAKER_05What you see?
SPEAKER_00The properties tantalum is next to molybdenum on the periodic table. Or sorry, it's like it's diagonal from molybdenum.
SPEAKER_06I wait, but this is like tantalum.
SPEAKER_00Yeah. So tantalum.
SPEAKER_06So tantalum? Why is that like this is like not a name I'm familiar with? I would I am surprised to like hear the name of an element and like not recognize it.
SPEAKER_00So there's a row, right? It goes vanadium is at the top of that row. No, vanadium. I know vanadium. Niobium is below vanadium, and then tantalum is below niobium.
SPEAKER_05Okay.
SPEAKER_00And then if you go one over, then you get uh chromium.
SPEAKER_06Which is just which is one below molybdenum.
SPEAKER_00Uh one above, yeah. So you get chromium molybdenum.
SPEAKER_06So chromium is smaller than molybdenum or bigger? Chromium is smaller. Chromium is smaller than molybdenum. And tantalum is then smaller than niobium?
SPEAKER_00Ah, so it gets a little tricky. So the second and third row gets a little bit tricky. Like the actual sizes are very similar in a lot of materials in a lot of molecules, like in in practice. But the atomic number is higher.
SPEAKER_06Okay. So like we're very much in transition metals. Like that's what like is this like actinides or lanthanides or still.
SPEAKER_00No, this is the D block. So these are all transition metals. You can make really interesting materials with the F block, with actinides and lanthanides. Um but most of what I'm looking at right now is with transition metals. So we're looking at D blockons.
SPEAKER_06Why do you like why do you like tansinum disulfide?
SPEAKER_00Uh well, the one reason why it's different from molybdenum disulfide is that it's a metal. So so when we talk about materials, when we talk about electronic properties of materials, um there's, I would say like three big buckets that we can categorize materials into. Um, and those would be insulators, semiconductors, and metals. So maybe when you hear metal, you would think oh, something like copper or gold or steel, right? Like those are, you know, elemental metals for steel is definitely not an element. Steel is not an elemental metal, but it's like, you know, a structural metal.
SPEAKER_06Steel's a mixture of iron and tin, right? I think it's iron and tin.
SPEAKER_00It can be a mixture of a lot of different things. Okay. So steel is not an element, but that's like something, you know, when we talk about metal in our everyday lives, right? That's the same thing.
SPEAKER_06Yeah, and you think about the properties, it's like strong, but and but like not as flexible, right?
SPEAKER_00Um, steel, like right. But when we think about um metals in the normal sense, there's a lot of overlap with what we mean by metals in the electronic sense, which is that they can conduct electricity very well. Um and in terms of the so this is where I was going with like trying to discuss the energy levels. So when you have an atom, you have these like discrete, well-defined energy levels. But in materials, at least in you know, crystalline materials, which is what I'm interested in mostly, um, you have a lot of atoms, right? Like a material is you know on the order of 10 to the 23, something like that, number of atoms. Avogadro depends on, right? Um, it's a lot of atoms. Um what happens when you have so many atoms is that you get these delocalized energy states, right? So our electrons are not just confined to these, you know, single quanti states that belong to a single atom, but now the energy states um live on many, many, many atoms. Um, and that's basically formed by this like continuous network of bonding.
SPEAKER_06And so you can end up existing between quanta.
SPEAKER_00So the energy states are still they're still quantized in that like there's only certain states that an electron can exist in. It's not just all like smeared.
SPEAKER_06It hasn't become continuous.
SPEAKER_00Um, it hasn't become uh so it can be um much more continuous in energy.
SPEAKER_06Yeah.
SPEAKER_00Yeah.
SPEAKER_06Yeah, you get a lot more please, yeah. Sorry.
SPEAKER_00So like in a metal, the reason why it can conduct electricity very well is that there basically is a continuum of states um between like filled and unfilled states. Um and so you're all the like electrons, you know, at that like highest energy in the material, there's like always an empty state that they can move to. So that's why you can flow electrons through a wire made up of metal.
SPEAKER_06Oh so the conduction through a wire is is because in the in the coordination, maybe that's the wrong word, of of all the different atoms you get it it's easier for electrons to flow between states. Because the states are more con there's just more there's more states. I mean still quantized, but it's but there's m so many more states that they can be in when they're in the full material.
SPEAKER_01Exactly. Yeah, yeah, yeah. Exactly.
SPEAKER_06And so then so then the this electron right, like this shell electron in this atom can very easily drop to fill this like slightly lower energy state in the in the in the atom next door. And then another one can jump and it just makes it so they can just flow. But it's not but it's but it's the but it's what what makes it so that they can flow is is they actually have to change energy levels to flow between Yeah, it's a great question.
SPEAKER_00So they basically don't have to change energy levels. Um like there's another state that is like essentially at the same energy that you can just like go into.
SPEAKER_06Whoa, and that's how they actually move.
SPEAKER_00Yeah.
SPEAKER_06Yeah. I thought of it as like I think of it like aromaticity.
SPEAKER_00Where it's like it is kind of like that. It's not wrong.
SPEAKER_06But when I think of that, I think of it as I think of it as that they're not actually moving, but like that the cloud the overlap of the p orbitals in the aromat in the aromatic ring like are all at the same energy, so they can just flow. It's like there's something they all just kind of like exist in there together freely flowing. Right. But if I didn't think of it as they're like actually changing between states to flow between them, it's just easier to do that because the states are closer.
SPEAKER_00Yeah, I think maybe it's a question of like the whether you're when we think about like conducting current, right? We're putting electrons in and taking electrons out, right? So there's it's like not a static picture, it's like a more dynamic process. Yeah. Right. So if you have this like delocalization, um then you can easily, you know, take electrons out of one end and put electrons on the other end.
SPEAKER_06But also there's but also now you get into quantum mechanics where the actual speed of the electrons flowing through a wire isn't all that fast. But somehow the somehow the communication down the wire that that's happening happens almost at the speed of light, right? It's it's almost instantaneous. Right? Electricity flow, it's like, but the actual, but it's not like pushing dominoes and right, like great, we can push dominoes, but like you still don't get the last domino doesn't fall until all the other dominoes have like, you know, like we're gonna push one, it's gonna push the next one, it's gonna push the next one, right? And they don't, the electrons in the wire don't actually move all that fast, but somehow the electron all the way at the end of the wire almost instantaneously knows that the electron at the front of the wire is being pushed. Even though the push hasn't passed like, which is crazy. Right?
SPEAKER_01Yeah.
SPEAKER_06Is that like is that kind of what you're what you're look like? I want to go back to like what really interests you about this.
SPEAKER_00Like you're like the stuff that's really interesting is Yeah, I would say like at the most fundamental level, it's the chemistry of materials, which is um how do you change the atoms that materials are made of to change these properties, right? Like, how do you change the flow of electrons through a material by changing like what Orbitals you have that are participating in these like networks of bonding, um, you know, changing their energies, changing their symmetries. Um, okay, wait, I have an idea.
SPEAKER_06I have an idea. Okay. Without trying to say it to me in a way that I will understand. Right? Like, don't do that. Like, say it, say it the way it makes sense to you, and then and then I will ask if I don't understand. Right? Um what's the thing where you're like, oh my god, like the electrons are doing this. When you like got into like, what's the thing about like these materials with all like where you started to see like there's this thing happening that defies your comprehension, right? That like expand, it's like oh my god, that's possible. Right? I mean, is that what happened? Like you like looked at these materials, you like had this awareness of like chemistry and and and you know, electron physics and all this stuff, and and then you were like, oh my god, they're doing this. What yeah. But don't try to say it in a way that I can understand, right?
SPEAKER_00Like, don't I actually don't know, I don't know if I ever had that like moment exactly. But I think what is really cool, like why I think I like what I do, is it feels a little bit like playing with Legos, um, where you have all these elements in the periodic table, right? And you can kind of to some extent mix, you can mix and match, you know, the elements that are making up your material. Um, and then they will assemble themselves in a different way. And then they will have different properties, right? And those properties can be tied back to how those different elements are bonding with each other or how they're interacting with each other.
SPEAKER_06Um what's a property, what's a property that blows your mind?
SPEAKER_00Um, I think there's a lot of properties. Like that's why like things that fall under this category of quantum materials, the properties are things like superconductivity, maybe, or something called a charge density wave, which is kind of like the electrons will localize in certain areas of your material. Um and then sometimes that can lead to like this additional distortion of the structure. Um so basically just a lot of properties, or like I'm also super interested in magnetism. So that has to do with how the spins of the electrons can communicate with each other across, you know, this like long-range um like material, right?
SPEAKER_06How do you know that's happening? How do you know that they're able to do that?
SPEAKER_00So there's certain experimental appropriate that we can use to measure the magnetism of materials. So we can basically directly measure the magnetic moment as a function of the temperature and as a function of the applied field. Um, and then there's certain just like well-established signatures, like changes in the moment um that can tell us like if there's magnetic order or not.
SPEAKER_04How do you measure that?
SPEAKER_00Uh so the way that we usually do it is there's um we basically have a cryostat, so it's something that can take us down to low temperatures because often magnetic order is stable at low temperatures.
SPEAKER_06Aaron Powell We're talking like one Kelvin.
SPEAKER_00Yeah, on the order of like two Kelvin to room temperature. That's like a pretty typical range that we look at.
unknownOkay.
SPEAKER_06Um and you want to go cold because it because they can't the magnetic moment can't shift as much in the cold. It doesn't have the like with less energy, it's just more still.
SPEAKER_00Yeah, exactly. So things generally tend to be more ordered at low temperatures than at high temperatures, um, because you have this like KBT term, right? You have this thermal energy.
SPEAKER_04You have this what?
SPEAKER_00Thermal energy. Or I mean sometimes people don't like that term. So KBT, uh right. So KB, like K sub B, this is Boltzmann's constant. And then T is the temperature. So like a lot of processes. Um there is some term that's like, you know, E to the minus KBT. So basically that that's just to say that like a lot of processes depend on the temperature.
SPEAKER_06What is Boltzmann's constant? Where does that come from? Oh, but I mean no, look, I mean, I know the Planck length.
SPEAKER_00I know like I'm not gonna be able to give you a good explanation.
SPEAKER_06No?
SPEAKER_00This is not gonna be a satisfying explanation. I mean, Boltzmann's constant I would say is just like a constant that scales temperature to energy. That's like a very simple way of Yeah, yeah.
SPEAKER_06I mean, those things all come out of the math, right? It's just like we did experiments and we figured out that these numbers always relate to each other in this proportion. And so that's yeah, exactly.
SPEAKER_01Right, right, right, right.
SPEAKER_06Right. Um you get it really cold. And then how do you measure the magnetic moment of like a specific one?
SPEAKER_00Um so uh the way that okay, so so we have um okay, we have a cryostat, and then we generally we like put the sample um on like a stick. The stick is vibrating, and then um it's like moving the sample through uh just like a a coil. Like it's a solenoid. Yeah, like like a solenoid. Yeah, yeah. And then it's just measuring like the induced current in that coil. And the induced current corresponds to the magnetic moment.
SPEAKER_06Okay. So like the the like the stronger the induced current, the stronger the magnetic moment?
SPEAKER_00Yeah, like that's how the instrument is measuring the moment, the the magnetic moment.
SPEAKER_06Is the magnetic moment quantized?
SPEAKER_00Oh, it is for an atom, yeah.
SPEAKER_06Um like it is um Well, you say for an atom, but isn't it specific electrons that have magnetic moment?
SPEAKER_00Right, right, right. Like in an actual material, the the the moment that you measure is usually not quantized.
SPEAKER_06Um, because it's the sum of all the electrons.
SPEAKER_00Exactly, yeah.
SPEAKER_06Yeah, so you so it's more continuous.
SPEAKER_00Right, right.
unknownOkay.
SPEAKER_00But so then how can you But it comes from like the number of unpaired spins, right? So like on that level it is quantized, yeah.
SPEAKER_06Uh the number of unpaired spins, that's what makes that's what makes something magnetic.
SPEAKER_00Is that yeah, you have some spins that are not paired up. So then if all those spins are aligned in the same direction, then um that's what we call ferromagnetism. So uh like a fridge magnet, it it's very complicated. It's actually uh basically like enough of the spins in a fridge magnet are aligned in the same direction that it has like a net um persistent like net moment.
SPEAKER_06Yeah. Oh wait, okay. So we're starting to get somewhere that is so fundamental, which is the overlap of magnetic fields and electric fields, right? How one induces the other.
SPEAKER_00So that's how we measure the moment. I think that is like a very uh rich area. I would say that I'm more interested in the chemistry behind the materials than like developing, you know, instrumentation to actually do the measurements.
SPEAKER_06Well, so then let's go there. So, like, so like I keep I keep asking, and you know what, you like, right? Uh uh I want you to give me something specific, right? Something like you like the chemistry of the materials, right? And I know it's hard because it's like, but there's so many cool things about the materials, right? Um But what's one specific thing that's really cool about these materials that you really, really like?
SPEAKER_00Yeah, yeah, yeah. So what I am interested in doing, like I would say what I'm super the question I'm super interested in exploring, um, you know, at least right now in my career with my lab, is whether we can incorporate molecules into these layered materials as a way to tune their properties in a way that gives us more control than just choosing, you know, these elements from the periodic table. So, like what I've always really loved about materials chemistry is it feels kind of like playing with Legos, right? You have all these different elements to choose from. You can combine them in different ways and get different properties. Um, but you still have this like finite number of, you know, possible like in the periodic table. But with molecular chemistry, there's pretty much like an infinite amount of tunability that you could theoretically have. Um, like organic chemists have developed all these amazing ways to make, you know, different molecules with different properties, different shapes, different sizes, different polarities, different types of interactions that they like to have with other molecules. Like there's just so many different things that we can control. Um, and so I'm really interested in how you can put molecules into these materials that are otherwise made of like inorganic elements, right? Like, you know, different things from the periodic table. Um, and how we can kind of combine these two fields that are traditionally kind of separate, molecular materials and um solid state, inorganic, solid-state materials, um, and trying to see if there is like some synergy um at the overlap between these two fields.
SPEAKER_06This is cool. This is cool. Uh let's go to like what's a specific molecule that you've added.
SPEAKER_00Yeah. So um I don't know if it's that easy to say like what the specific molecules are.
SPEAKER_06No, there's gonna be many, right? There's I like it's like it's I know there isn't like one and that it's like, it's like, but it's like the we're we're it's like instead of being like, what are your 10, what's your favorite movie? Like, right, like there's 10 favorite movies, right? We can't pick one favorite movie, but like an easier way to do that is like just what's one of the things that's on your list of 10.
SPEAKER_00Yeah. So like one um one thing I'm really interested in is using molecules that have strong interactions with each other, like among each other, um, and putting those into materials and then seeing if those like intermolecular interactions can basically give rise to new properties, new structures. Um, so like one example um could be this molecule called tetrathiofulvaline, um which is a pretty well-known building block for like organic metals, organic conductors, organic electronics. Um, and this molecule really likes to form stacks. So likes to form like 1D stacking. Um anyway, like keep keep going. Can there be some kind of like stacking um among these molecules between the sheets of these other, you know, these like layered materials that can kind of impart some new symmetry and new structure um to these layered materials that then changes the properties of those layers?
SPEAKER_06Do you and like have you found something that does?
SPEAKER_00Uh no. So like that's the problem because we're so like early on, right? So I've been here for just a bit over a year. Um so the first year we really, I mean, my students have been so amazing. Like they've made materials, they've grown crystals, they've set up the lab, um, they're doing all sorts of measurements. Um, I think we're at a point now where you know we can start to kind of try to collect data to answer some of these questions. Um, I think that's like one of the challenges of being, you know, a young faculty. Um, at least like for me, I feel like I'm delving into a pretty like relatively newer area compared to what I was working on before as a graduate student and as a postdoc. So there's a lot of, you know, there's this a lot that you have to do to get research areas off the ground. Um so yeah, I would say a lot of these things are like things we're super excited about. Um I don't have any like new really meaningful results to share right now. But that's something, yeah.
SPEAKER_06Like, you know, it's material you're closest to testing.
SPEAKER_00So we've done some, yeah. So like there's a lot of properties that we're potentially interested in, right? So so one is you know, things that have to do with like conduction of electrons. Um, and so that's probably where this idea fits into um that I just told you about, like using stacking to, you know, change the structure and then change the way electrons flow through that material.
SPEAKER_03Yeah.
SPEAKER_00Um, but something else we're interested in is like going back to this um kind of prototypical material I told you about molybdenum disulfide. Um this is like a really cool, amazing, uh super rich semiconducting 2D material. So semiconductors lie between metals and insulators, I would say, in terms of their electronic properties. So metals can conduct current like freely, essentially. And then insulators, um, there's a super large gap between the filled states and the empty states. So electrons cannot move through insulators.
SPEAKER_06Yeah, and it's the noble gases or the like purest insulators, right?
SPEAKER_00Yeah. Or like a vacuum is Oh, yeah, right.
SPEAKER_06Okay. Yeah, but a vacuum is not fair because there's nothing there.
SPEAKER_00Yeah. Like uh gases generally are vacuum is not an insulating material.
SPEAKER_06A vacuum is an insulating emptiness.
SPEAKER_00Right, right, right. So in terms of materials, like a lot of things that are insulators are things like polymers or like wood or like super pure water is pretty insulating. Yeah. Um, but you know, if you start adding some like ions in there, then they can start being current. Um but semiconductors are kind of in between. So um they don't have this like continuous uh these continuous states um that metals have. There's a gap, like an energy gap between But it's more continuous than the insulators. So I would say it's not continuous, but the gap is much smaller than an insulator. So that is what distinguishes. Like there isn't really a well-defined strict cutoff, but basically, insulators, there's a much larger gap between filled states and empty states, and it's hard for the electron to hop between to hop over that gap. But for a semiconductor, there's a smaller gap. Um, and so just for example, if some, you know, a semiconductor is at room temperature, that gives the electrons enough energy so that some of them can hop over that gap.
SPEAKER_06Yeah. Um what's a specific material that you're in your lab working on?
SPEAKER_00Yeah. So we're really interested in making um materials that can be.
SPEAKER_06Wait, wait, no, but no, before before it's like before it's like what we're gonna explore about the material. Don't we know that yeah, like what's what's it what's a material that you're one of you like your students have actually made that we're gonna test, but we haven't tested.
SPEAKER_00So so okay, this is where I maybe I don't know. I was listening to this. I don't want to give it away because like we're actively working on this.
SPEAKER_06Oh, fair enough. Okay, fair enough. No, no, no, that's fair. Okay, yeah, that's fair. Okay.
SPEAKER_00So sorry. Um no, that's okay.
SPEAKER_06That's totally fine. I didn't realize.
SPEAKER_00I would say like the Don't answer that question.
SPEAKER_06I take it back. Don't answer that question. No, no, I'm not trying to do that. Right. So that's why we're being sort of generalist, because we're like, we're like, we're not because it's like there's sort of like um either a proprietary or like a some kind of like, right, like it's important to like not. Yeah, yeah. That makes sense to me. Yeah, don't do that. Don't do that. Uh yeah.
SPEAKER_00Well, but how do you write a grant then? So yeah, it's a little bit um tricky. Like I would say in a grant, um you generally have to be a little bit more specific. Um and in a paper, right? Yeah, obviously.
SPEAKER_06Um, but then you've got the results. Then you can write the paper. Exactly. Then you want to tell people.
SPEAKER_05Yeah.
SPEAKER_06Yeah, yeah.
SPEAKER_05Oh, that's really interesting. Okay.
SPEAKER_06So, okay, so if you were to if we were like, we're not doing like we're not doing this yet, but if like this is a really interesting sort of like separate question for this podcast, which is if at some point we could like use this platform to offer like funding, to like crowdsource funding, right? Um you'd have to be able to tell people something that makes them want to fund you.
SPEAKER_00Yeah, and I think that's gets to something that's like a bit I mean, uh if you're talking to assistant professors, um maybe a lot of us are uh worried about getting the first few grants because a lot of times, and rightfully so, um, I think funding agencies, and I'm sure anyone else who's in a position to fund science like want to know that there is like a reasonable chance of success, right? And that depends on the track record. So it's very helpful to have some results that you can show that say, okay, we've done this before. So if we want to do what we're proposing, we have a pretty reasonable chance of accomplishing that.
SPEAKER_06But you also have to propose something specific.
SPEAKER_00Yeah, but then usually you have to include preliminary results as well. Yeah. Um, and so that's something that like, and you know, there's a lot of really great um funding programs, like mechanisms for early career researchers that, you know, I think that maybe you don't need sorry.
SPEAKER_06K grants and J Grants and all that. And like, and I'm sure there's plenty of other things. Like I know a lot of people.
SPEAKER_00Yeah, yeah, yeah. Like I think across different agencies um and different fields, different foundations.
SPEAKER_06Um, internal, internal ones at at institutions, right? There's all kinds of stuff. Yeah, yeah. But the point is to be like, we think you're worth it. And you show you're worth it based on your postdoc work. But but that's not totally different from what you're doing.
SPEAKER_00Yeah. I mean, and different fields have different conventions about, you know, like how much deviation there is between someone's postdoc work and their independent work. Um, there's like different expectations, different conventions. Um probably the funding expectations are also different, right? Like as a function of what's normal in different fields. Yeah. Um but yeah, I think that's a totally fair question. Like, you know, if people were interested in funding science, of course, they should want to see what that person has done before and what makes them confident that their ideas can succeed.
SPEAKER_06But if we were gonna if there were a hundred thousand people listening to this who wanted to give you 10 bucks each and you could get a million dollars, right? What would you tell them that you're gonna do with the money?
SPEAKER_00Um, that's a good question.
SPEAKER_06And and within the constraints of like that's part of it is like within the constraints of like you don't want to give away stuff that like you're still working on and isn't yet published, right? Like d like that's that's part of this, like for this to work, right? Like we it can't, you can't have to do that, right?
SPEAKER_01Right, right, right.
SPEAKER_06Right. That's that's just all this like thought experiment of like what how can we do it to like be like this is worth it? You should contribute to this. Like, this is gonna be super cool, but without giving the stuff you shouldn't give.
SPEAKER_00I would leave. I mean, I would be very curious to talk to you know, these hypothetical people who are interested in funding science out of their own pocket. That's what you're doing. Talk about a podcast. Why, yeah, like why why might they be interested, you know, in funding science?
SPEAKER_06Because they're the kind of person who would listen to a podcast that is about science that's more high-level than pop culture. That's like that's like not just like a property. That's what they're like. They like science brain somehow.
SPEAKER_00Yeah, like are they interested in the brain?
SPEAKER_06They like Legos too.
SPEAKER_00Right, right, right. Are they interested because you know, they think it's just fundamentally interesting to be uh learning about new things, or are they interested for like some you know technological application or some trans translational application? Um Yeah, I mean, if it's just about, you know, like pure fundamental interest in science and learning new things, um, I feel like materials are just an amazing playground, right? It's yeah, if you like playing with Legos, there's just a lot of things to explore, different combinations that you can put together. Um, it's almost like you're, you know, every day you go to the lab and you're like cooking something new and you don't know what's gonna come. Out and you don't know what it's gonna do. I think it's such an exciting like platform for discovery. Um, and I think the really cool thing for me, like I think different scientists like to have different degrees of control over what might happen in in their experiment or in their project or whatever. And I feel like um the type of materials chemistry I do, like sometimes you can get something that's like totally unexpected because nature is just very complicated. Atoms can interact with each other in very complicated ways. Like sometimes it's beyond your wildest expectations, right? So you have to have you know good hypotheses, you want to be looking at interesting systems and answering important questions, but sometimes there's just like something kind of like, whoa, like it's so much more interesting than I could have ever predicted.
SPEAKER_06Um is there anything that you've got that woe that you can talk about?
SPEAKER_00Yeah, I feel like at so many points in the world.
SPEAKER_06But anyway, so like Rev, any one thing, right? Like I know it's a lot, right? But is there any way?
SPEAKER_00I think that's the reason why I'm still in science is because there's all these like surprising little things that can happen along the way. So for example, um, in my um, well, I guess actually, maybe a really easy example is like from from my PhD, one of the first projects I worked on in my PhD. Um I was trying to grow this material and um based on a previous paper. Um, and then that paper had reported, so there's like there were different polymorphs of this material, which is kind of like for carbon, right? You have graphite and you have diamond. Um, they're both carbon, but there's like different arrangements of the carbon atoms, and that gives you very different properties. Um, so for lots of other like more chemically complex materials, you can have this happen as well. You can have different polymorphs, like different arrangements of the same building blocks.
SPEAKER_06What's the one you were working on in this project?
SPEAKER_00Yeah, so so in this case, we were interested. We I was trying to make this iron um tetrazylate material. So a tetrazole is um it's a five-membered ring with nitrogen.
SPEAKER_02Okay. Yeah.
SPEAKER_00Um and we were interested in studying this material for electrical carbon.
SPEAKER_02Tetrazole.
SPEAKER_00Yeah, and this was like the class of materials that this falls under is called metal organic frameworks.
SPEAKER_06Why does it always come back to porphyrin? Sorry, keep going.
SPEAKER_00So it's a little bit like porphyrin, like you have these bonds between iron and nitrogen and nitrogen. Yeah. Um, but in this case, like in this particular material, um actually, like all of the materials, all of the different polymorphs of this material, there were these continuous chains um of iron and nitrogens. And we thought that these chains could be good at conducting electricity.
SPEAKER_06Um help me understand the conformation, help me understand the shape of it. Is it like, is it like there's an iron inside each tetraz tetrazole?
SPEAKER_00Yeah, so it's not, it's not like a porphyrin where there's like a kind of a um like a pocket that the iron goes into. Um the tetrazole is a five-membered ring. Yeah. And then in this case, it's attached to a benzene, like it's at the one and four positions of the benzene. So it's like tetrazole, benzene, tetrazole.
SPEAKER_03Okay.
SPEAKER_00Um, and that's what we call the the ligand or the linker in this metal organic framework material.
SPEAKER_06So the tetrazoles don't all bond don't all bond to each other, they bond to the benzene rings.
SPEAKER_00Yeah, they're bonded to the benzene rings, and then like the two nitrogens at the edge are bonded to the irons. And then in the material, there's like iron and then the tetrazole and then another iron. And then there's kind of like um six sets of these tetrazoles uh bonded to each iron, if that makes sense. It's another case where like if you had a picture, it's really easy to show. Yeah. But it essentially boils down to there's like an iron, nitrogen, nitrogen, iron, like continuous chains.
SPEAKER_06Is it is it still a flat plane? Is it still, do we still end up with kind of like the benzenes are perpendicular, the the the tetrazoles are horizontal and the irons are also horizontal?
SPEAKER_00Uh so the tetrazole and the benzene, if it's if if that is oriented like this, then the chain is like um running like this. Does that make sense?
SPEAKER_06The chain of irons.
SPEAKER_00Yeah, that well, it's an iron tetrazole chain.
SPEAKER_06I see, I see, I see. So you have this like so you have this um say like a flat sheet of paper that is that is the benzene, tetrazole, benzene, tetrazole, benzene, tetrazole, but then where the two nitrogens land are like along the top ed that are gonna bind to the high the irons, like fall on the top edge of the paper. And so then the iron can hang out along the top edge of the paper, bound specifically to the nitrogens that are like at the at the top edge of that.
SPEAKER_00Right. It's kind of see, we got it. Yeah, we got it, we got it. Okay. So I think the really important part about this structure and the reason why we thought it was interesting, um, it could be interesting for studying the electrical conductivity was the fact that there are these like 1D chains and nitrogen. Yeah. Um, but uh I so basically, you know, I kind of took over this project a summer, like a super talented undergraduate student had been working on this project over the summer. Yeah. And then she had some like preliminary results that seemed really promising. So initially we were trying to figure out like which of these polymorphs had the highest conductivity.
SPEAKER_04Sure.
SPEAKER_00So I tried to reproduce, you know, what was in the paper. Um, and then like for one of the polymorphs, the paper reported the crystals are black. Um and that was also what the summer undergrad made. But then when I tried to produce, you know, reproduce the synthesis, my crystals were red. And they're like orange-ish red. And I was like very confused. I was like, oh, maybe this is this other polymorph, because the paper reported there's another polymorph that is red. Um so like didn't think too much about it. I was like, oh, maybe I did it wrong. Like, I'll try it again. And then basically I noticed that like, you know, a few days later I came back and the crystals are black.
SPEAKER_05Stop.
SPEAKER_00Um, and I was like, what's happening? Like, did I hallucinate something? You know, like first you like question yourself, right? You're like, oh, am I just like doing too many things and I'm just confused and you know, didn't like maybe I misremembered. Um but long story short, it turned out that Don't make it sure, wait, don't make sure, don't make sure.
SPEAKER_06So like then you did it again and it happened again.
SPEAKER_00Yeah, yeah, yeah. Like eventually, right. I did it again, and the same thing happened, and then I tried, you know, different experiments to see, like, I basically did other experiments over the course of like, you know, a few days, right? To see what is actually changing about the material.
SPEAKER_06What'd you do? Um, okay, so this is so this is really cool to me, is like, okay, so now you've got like here we are, real science, right? You've now got an unexpected result, right? But at the level of like macro visual, right? Like all you got is like I had this black crystal, I had this red crystal and now it's a black crystal. And I like I mixed some like liquids and maybe some powder, like in a thing, and it would like it all went and made a red crystal. That was cool. And now it's a black crystal, but I didn't change anything, right? So how do you actually investigate this?
SPEAKER_00Yeah, exactly. So, like, okay, so what you see with your eyes is actually super powerful. Um, especially if you're working with transition metals, because a lot of I think the reason why a lot of people get into inorganic chemistry is that a lot of the compounds have really nice colors.
SPEAKER_02Yeah.
SPEAKER_00Um so actually what you see with your eyes like can be really informative. So the fact that it changes from red to black, but then we first confirm by structural characterization. Like we just checked, you know, what is the crystal.
SPEAKER_06Using an MR N MMR or a mass spec or something?
SPEAKER_00Uh we usually use single um powder x-ray diffraction or single crystal x-ray diffraction.
SPEAKER_06Yeah, so like x-ray crystallography or whatever.
SPEAKER_00Yeah, yeah, yeah. Yeah.
SPEAKER_06You're like Rosalind Franciscan.
SPEAKER_00So that's like a super sorry?
SPEAKER_06Rosalind Franklin style. Like let's just figure it out.
SPEAKER_00Yeah.
SPEAKER_06Yeah, yeah. Yeah, yeah. Yeah. Okay. So now you've got your red free, you've got your black crystal now, which was red but is now black, and you're like, okay. And you put it in the x-ray crystallography to like figure out what's the actual arrangement of the of the nuclei here.
SPEAKER_00So we confirmed that the black crystal and the red crystal look the same um in terms of the structure according to X-ray diffraction.
SPEAKER_06Aaron Powell, Jr. Which doesn't make any sense because like how are there opposites shifting?
SPEAKER_00Yeah, something's clearly happening. So like the more you know scientific uh quantitative way to investigate the optical properties is we can do like UV visible spectroscopy. Okay.
SPEAKER_06Um that's which means just like shine UV light at it and see what spectra comes out.
SPEAKER_00Um essentially, yeah. So like U Well, it's called UV visible because we're interested generally, uh or in this case, I guess you could technically call it UV visible near IR, near infrared. So we're interested in like basically we've probably looked at like 300 nanometers to like 1200. Yeah, something like that.
SPEAKER_06Yeah, yeah.
SPEAKER_00Um but that basically just uh can tell us like what wavelengths our um material absorbs at. Right. And then that can tell us about like the electronic transitions, right? So we have some filled orbitals, we have some empty orbitals, or you know, steep. I mean it's great.
SPEAKER_06Back to like this is how we measure quanta is like let's say electronic see what is to see, yeah. Like it it if it can absorb at these wavelengths, that means it can absorb that energy quanta.
SPEAKER_00Yeah. And then if you see the color is changing, then that tells you like something about the electronic configuration is changing.
SPEAKER_06Wait, so did something shift between like the blush so like the the X-ray crystal, the like the shape, the like the the the atom arranged the like nuclei arrangement of the black and the red, right? Iron tetrazole is the same, but the spectra, the like UV absorption, but like from 300 to 1200 absorption of the black and the red are different.
SPEAKER_00Yeah, they're different. So like some of the some of the peaks remain the same, but we saw new features appearing over time um as the crystal turned from red to black.
SPEAKER_06Oh, at different times. So you have it like two hours and six hours and twelve hours?
SPEAKER_00Yeah, I think we ended up doing over maybe it was like three or five days or something.
SPEAKER_06Okay. And like over that period of time, like it it shifts. Does it shift in a quantized way? Did new features appear, like a bunch of new features at four hours? And then a bunch of new features. Is it like a quantized?
SPEAKER_00No, it wasn't quite like that. So, like for this measurement, um, like generally electronic spectroscopy, the transitions you see are like really broad. Um, so we can see there's just like a broad peak, you know, that comes in and it like grows in intensity over time. That's basically what what what we saw. And then the energy of like the new stuff that we saw basically was like totally consistent with the crystal changing color from red to black.
SPEAKER_06Sorry, my dog is whining. Um uh, but I really want to like, but I really okay. So what was happening? Was it like, was it like the iron is just oxidizing or something? Like what was that?
SPEAKER_00Uh exactly, exactly.
SPEAKER_06Is that what it was?
SPEAKER_00Yeah, that's what it was.
SPEAKER_06So if you put it in a vacuum and there's no oxygen, it doesn't turn black.
SPEAKER_00So it's a little bit tricky. If you put it under vacuum.
SPEAKER_06Wait, wait, give me just one second. I'm gonna, I'm gonna I'm gonna take my dog out because I feel like it's gonna wreck the audio, which we should not do. He's very sweet. He's very sweet.
SPEAKER_01Oh my god. He was so cute.
SPEAKER_04Yeah, dad's a puppy dog. Okay, but you gotta go. You gotta go, puppy dog. Sorry, man. You gotta know.
SPEAKER_06Alright. So why did this like why did this blow your mind when you were uh postdoc, an early postdoc?
SPEAKER_00Yeah, so it shouldn't have blown my mind, right? Because the answer is like super simple. Like it was iron two to begin with, and some of it oxidized to iron three.
SPEAKER_06Right. It's it's literally porphyry. Like that's what happens. Yeah, yeah, yeah. When it goes to iron three, that's when it's met hemoglobin, and you gotta get in and it's gotta get dis disposed of.
SPEAKER_00Yeah. But it was just like, um, I don't know. I didn't think it would happen. Um and it had been reported the crystal is black, right? But it was reported this is an iron two compound, right? But actually it's a mixed iron two, iron three compound, and the crystal is red and then it turns black. I mean, it's like a small, this is like a small thing, right? But uh I think just it's really uh fun. It was super fun to like try to figure out what was happening, even though in retrospect, right, the answer is like very obvious what's happening. Um, but I guess the cool thing was that that kind of buried the lead. Like as the crystal turned from red to black, the electrical conductivity also increased a lot. And that's what we were interested in. Um, so it turns out that like, you know, this oxidation is super important for electrical conductivity.
SPEAKER_06So you want it to oxidize to improve the conductivity.
SPEAKER_00Right. You do. I mean, we didn't know that like going into it, but it turns out yes, like you want it to be oxidized.
SPEAKER_06Could you then force more oxidation? Could you then like put it in an oxygen-rich rich environment? And like, was there like was there a was there a cap in like too much oxidation? Like there's an there's an amount of iron three that makes a really good conductor, but once you get too much, like was there a balance between iron two and iron three that made it a really good conductor?
SPEAKER_00Yeah, so we kind of we there was definitely a ceiling, I think, on the conductivity values that we were able to achieve. Um and we never quite figured out like a definitive answer as to why there is a ceiling. Like it could be a number of reasons. Um so yeah, I mean, I I think that's you know, with every single project, like at the end, there's more questions. I think that there's always more questions that you could answer.
SPEAKER_06I oh maybe. I I really want to know about the you said like tetra bio tetra something like this new it sounded like tetrafolate or something like that. This this new layer you're gonna put that's got like cool d orbitals that you're gonna put in between the molybdenum and disulfide layers.
SPEAKER_00Oh yeah. That's just it's just one example of like, I think, you know, a possibly cool molecule. But there's a lot of other um components that yeah, could have strong like pi stacking, uh just a lot of organic molecules that have some like aromaticity essentially. Yeah. Um, that can have different uh like oxidation states. Um I think that's a pretty general ingredient for like that might be interesting to put in materials.
SPEAKER_06What's like if if the to if like what's if it if like you're able to make a material that does like your wildest dreams, right? Like that does the things that you're like, this is the craziest thing it could possibly do. What would that be?
SPEAKER_00Yeah. I mean, I think a like a crazy one that has gotten a lot of attention recently, unfortunately, is like something like room temperature, superconductivity, right? I think superconductivity is super cool. So a superconductor is a material that can carry current with no resistance. Yeah, yeah.
SPEAKER_06Um room temperature, superconductivity, but then we actually a lot of times we don't want superconductivity. We want semiconductors because that's how because it makes better circuits. And we didn't really get into like we didn't get too much into quantized states and stuff.
SPEAKER_00Like Yeah, so like so superconductors, like superconducting circuits are one foundation that people are currently exploring pretty widely for quantum computers. Um it could be like the foundation for a different kind of computing technology. So our current computers run on semiconductors, they run on right now silicon um transistors. Um, but there's like other kinds of materials um with you know other properties that could be useful for kind of the future of computing technologies, right?
SPEAKER_06I get the sense that's a lot of what Fon News doing is like trying to get.
SPEAKER_00Yeah, I think a lot of people in this kind of like uh 2D materials or materials chemistry space are motivated um by some kind of connection to um computing technologies, maybe, or just like kind of materials for devices of the future.
SPEAKER_06And that's kind of what you're doing too.
SPEAKER_00Yeah, because I think there's just a lot of, you know, like we rely so much on computers, data storage for so much of our daily lives. And I think as you know, AI is becoming more and more embedded in our daily lives, um, that reliance is only going to increase. And then associated with that are all the energy demands for all these data centers. And all, I mean, this is not my area of expertise, but like for sure, this is a huge, like this is gonna be a global problem.
SPEAKER_06But it's what you're making materials for fundamentally.
SPEAKER_00Yeah, exactly. So that's like I think a super big picture motivation is like, can we make materials that have these properties that can enable these new technologies that can be better than what we're relying on today?
SPEAKER_06Yeah. This is awesome. I hope this was fun for you.
SPEAKER_00It was fun. It's I think it's like really hard to yeah, try to explain things without without my slides and without my script and all this stuff. But yeah. Thank you so much for going.