To start Season 3, Paolo talks with Dr. Emilie Ringe. The Canadian-born materials chemist has travelled the world and invested the better part of her still early in studying plasmonics, the synthesis and characterization of plasmonic materials, and their applications. We learn how magnesium is unique in this space and how it is being applied to fuel chemistry and fight cancer.
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One of the most difficult scientific concepts to grasp is how things behave differently in the macro- vs. the nano-scale. For example, everyone knows that gold is shiny and yellow, but gold nanoparticles suspended in a liquid (colloidal gold) are red. Dr. Emilie Ringe, a Canadian-born Assistant Professor at the University of Cambridge, travelled the world investing the best part of her still young career in studying one of these intriguing phenomena. She is an expert of the so-called plasmonic nano-materials, focusing specifically on magnesium. These materials can collect specific wavelengths of light and emit energy, behaving like nano antennas.
The potential applications are incredible, from an efficient way to apply localized energy to chemical reactions, to an innovative and benign cancer treatment. And in perfect Bringing Chemistry to Life style, the discovery of the science and the person go hand in hand, making for a great start of Season 3!
Dr. Emilie Ringe 00:06
Gold has no ways to get excreted from the body. But what you really want is something that completely dissolves and goes away after you're done with the treatment and that's magnesium.
Paolo 00:20
Plasmonic particles are tiny pieces of matter that can harness the power of light. Not many chemical elements lend themselves to this ability. But Dr. Emily Ringe is proving that there are some exciting plasmonic opportunities in the periodic table with magnesium bearing the greatest promises. Welcome to Season 3 of Bringing Chemistry to Life, in which we speak to members of the Chemical and Engineering News's 2021 Talented 12 about their work and trends in their field. I'm your host Paolo Braiuca from Thermo Fisher Scientific. We began by asking Dr. Ringe about the origins of her passion for chemical science.
Dr. Emilie Ringe 01:03
Now I come from a really small town, in workers family, no one of my you know, many, many, many cousins have ever been to university and, and I started, you know, in sort of high school and the equivalent of A levels or, you know, the lycees that we have in the in Quebec started being interested in science and interested in in first of all, how, you know, how molecules affect bodies, like from a really pharmaceutical sort of way, I actually spent a year interning at, at Merck working on in the pharma industry. And and that really sparked my curiosity for for the power of chemical sciences, right. But I really didn't quite know what kind of chemical sciences I wanted to do. And, and I eventually found my way into sort of the materials sort of realm a bit by, by chance, really a bit by who are the great mentors, and who do you do you see being your great teachers and what research you start doing as an undergrad and, and so on? But during my bachelor in late in my bachelor when I realized, Okay, well, there are things to research, there are careers and in unraveling new new science in the chemical sciences. And, and, and then, you know, again, leaps and bounds into into the avenue of sort of materials chemistry.
Paolo 02:37
So if I want to generalize broadly, you your research focuses on the study of optical properties of nanomaterials, and and particularly, you look at the plasmonics properties of, you know, certain specific, specific materials. Can you, first of all, am I right, or am I completely off? And can you describe that better?
Dr. Emilie Ringe 03:03
All the words are right, mostly in the correct order. So, good job. Yeah, so, so I'm really interested, kind of after basics, I'm interested in understanding the the effect of this structure of a material on this properties, right, because in the center of the bulk world, it doesn't matter if you make a cube or a sphere or whatnot, it has the same materials property, but in the nano world, this starts to matter if you make it, a cube of gold is not the same color as a sphere of gold and so on. And so that whole field is sort of new and exciting. And, you know, there's a million people working on this general idea, but specifically actually, we as a group look at magnesium nanoparticle as a way to interact with light and and magnesium behaves a little bit like silver and gold. So these particles have what we call plasmon resonance, or localized surface plasmon resonance gets to be a bit of a mouthful, but LSPR. And, and these interact with light in a way that makes these particles readily able to absorb light to scatter light, and to change the electric field of light around the particle. They like antennas for light essentially. And the gold and silver bit, the science behind the gold and silver has been known for a very, very long time. When I was a PhD student we worked on gold and silver, so that's, you know, quite a while ago. And now we're we're looking at other metals because first of all, gold and silver are rather expensive. Silver is not biocompatible, gold is bio inert, right? And they can't absorb light of all frequency. And so we we've been looking at magnesium for the past about four years, and we found that it has different behavior, it's not just sort of incrementally better than gold or incrementally better than silver, it's actually just different. And, and we're pretty excited about this, we found that there, they're stable enough to to use in a variety of solvents, we found ways to coat them, such that they have a lifetime of a few hours in water. And and they are actually plasmonic. They do this antenna for light behavior, really. So this is the kind of stuff we've been working on. I'm sure your next question is going to be like, well, what are these particles going to do?
Paolo 05:46
Well, yeah, of course, one of one of my questions, for sure. Please, yes, ask your question. And then give your answers. I'm completely unnecessary here, which makes it fun!
Dr. Emilie Ringe 06:01
No, you’re completely necessary! Plasmonics, you know, as I said, have been known for a while. And there's a few key application, but it's always about basically turning the light into something else. Because again, if you have an antenna for light, the deal is that you're going to turn light into another form of energy, then you're going to use that other form of the energy to do to do something. And so there's two things that we do quite a lot of in my group is first we turn that energy into a chemical energy. So we try to run a chemical reaction with this light, but now at the surface of this plasmonic particle, so we're concentrating that light energy. And then we can power a chemical reaction to actually limit our reliance on on heating up chemical reactions. And this heating up is typically done with with fossil fuels. So the idea is you'd be able to run a greener reaction, if you actually take your energy, at least in part, by sunlight. The other thing that I'm really excited about is this idea of photothermal cancer therapy. And so that's been shown by some of my colleagues at Rice, a long time ago, that if you can put gold on a on a tumor, and you can eliminate, well, actually, you, you can heat up locally, the tumor by a few degrees, but just enough to kill it. And there you go, you've you know, you've decreased the size of that tumor and and hopefully killed killed all of it. That's great. But gold has no ways to get excreted from the body. But what you really want is something that completely dissolves, and goes away after you're done with the treatment. And that's magnesium if you, if you put magnesium in an aqueous solution, with the special coatings that we have, you have a few hours. So that idea that you could treat someone send them home, and by the time they get home that magnesium is in their body, you need to eat magnesium every day to be healthy anyway. So this is this is really, I think, a big advantage of this reactivity.
Paolo 08:08
What you really seem to be speaking about is the way we deliver energy for making reactions happen. This is fascinating, because if we think about heating, our reaction, most of the energy we apply is completely wasted. Because what we really need is the energy in the point where the at the atomic level where the reaction is occurring, right? In a way, I thought, you know, you could use your plasmonic magnesium as a sort of catalyst. You're but you're not reducing the barrier, you're actually applying energy, right?
Dr. Emilie Ringe 08:41
Yeah, that's correct. Okay. So that antenna effect gives us basically a local delivery system for that energy. With only the magnesium particles we are indeed not changing the activation energy. But what we do for that is that then we go and decorate the surface of that particle with with clusters of atoms or various small few nanometer particle of materials that are known to then decrease that activation energy and are countless things like palladium, platinum, etc. And the beauty here is that we actually really don't need much of these materials because they're really only on the on the surface of that much larger antenna.
Paolo 09:29
What you're speaking about is kind of doping…
Dr. Emilie Ringe 09:34
Decorating:
Paolo 09:35
Ffair enough they decorating the metal catalyst with your nanoparticles in some way, so that the the energy can be delivered, where the catalysis happens.
Dr. Emilie Ringe 09:45
Exactly. So we're, we're capturing our energy from that central large plasmonic particle. And then that energy gets transferred to a variety of mechanisms, one of them being heat and other ones being electronic mechanism. To the small particles that are just at the at the surface of this large catalytic particle where, where the catalytically active sites are. So it's really helping us choreograph chemical reactions by, as you say, sending the energy, right at the right place without wasting sort of the the heating of the entire environment, the entire bath around.
Paolo 10:25
It is fascinating, because it's a completely new paradigm, right? And I can see how this works on heterogeneous catalysis. Can you do that in homogeneous catalysis as well?
Dr. Emilie Ringe 10:37
It would be difficult in homogeneous catalysis. And you'd have to have a bit of a hybrid construct if you wanted to use a molecular base catalyst, but you could always graft that that molecular catalyst on the surface of your of your magnesium nanoparticle. And then have it sort of dangle in the solvent where it would then interact with the molecules in solution. So it's not quite homogeneous catalyst but but a supported molecule.
Paolo 11:07
When do these nanoparticles stop being plasmonic? So how big are they?
Dr. Emilie Ringe 11:13
Yeah, so we can make them between about 50 nanometer and then several microns in size. The true localized surface plasmon happen roughly for particles that are smaller than the wavelength of light. So so it's truly nanoscale. But but it spans a really quite wide range, right, the 10 nanometer particle would be plasmonic. And so is a 500 nanometer particle. And everything in between changes properties.
Paolo 11:44
And I'm assuming that their shape is is massively influenced by the nature of magnesium or whatever other metal would be plasmonic properties, you know, they tend to do all the liquid structures.
Dr. Emilie Ringe 11:56
They basically form crystals, right? Just like if you formed a macro scale, magnesium crystal, it would have a specific shape, just like mineral shapes, right? And, and yes, magnesium actually forms really cool shapes. Whereas, you know, if you look at, say gold and silver and whatnot, they tend to form sort of cuboids and sort of spheric truncated octahedron, that almost look like spheres, because the underlying crystal structure is cubic. So you expect that they're quite, quite isotropic, whereas magnesium is a hexagonal lattice. So there's one unique direction in its crystallography, which means that it forms crystals with one unique direction. And a simple example of that is if you make a magnesium single crystal, it will be a hexagonal plate. So it's a sort of a pancake with a hexagonal pattern like a cookie. And as you say, right, the shape effect the properties and in this case, the shape effects, that electric field that concentrates around these particles. And and that's yet again, another example of magnesium being different because it intrinsically forms different shapes than gold, silver, copper, aluminum, all the other plasmonic metals. It intrinsically forms particles with different properties that are just not achievable in the other metals.
Paolo 13:31
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Paolo 14:08
So how do you make these nanoparticles? Do you start with a metal in solution as a salt? Or do you start with a sort of macroscopic metal?
Dr. Emilie Ringe 14:18
No. So we basically do bottom up, right. So we start with a magnesium organometallic precursor. So say a dibutyl magnesium, for instance, we've done it with other ways. And then we reduce that with a with an electron on an electron carrier. So one of the things we use is a napthalene, which we reduce with an electron from a lithium metal and that that gives you an electron carrier and then that reduces your magnesium organometallic precursor to go from a magnesium that's sort of nominally 2 plus to a magnesium that's basically zero and then that that aggregates into into these particles and grow and crystals in solution.
Paolo 15:02
How do you deal with these particles? You know, in vitro? are you handling them in solid form? Or do you always have like some sort of colloidal formulations?
Dr. Emilie Ringe 15:12
They're mostly suspended in ethanol or isopropanol, we can dry them. But we found that if we then try to resuspend them, it's just a little bit, a little bit more complicated. They are stable in air, you can actually dry them as a powder, and they remain magnesium metal in air. So that's kind of kind of good to know. But but on a day to day basis, we have them as vials, basically.
Paolo 15:44
You were mentioning, a coating technology to kind of control stability. Yet another, you know, technological aspect to control and look at them, right? Can you can you tell us a bit more about that? How do you coat them?
Dr. Emilie Ringe 15:57
The reason why we need to coat them is that you know, the form of magnesium oxide that's normally protective, but in water, this turns into a hydroxide, it dissolves and game over.The first type of technology we looked at was a silica coating. And we never really managed to get an enhancement of the stability of these particles, because that silica is often quite porous, and water molecules can go in and actually attack the magnesium. The way we found that that works is using what's called polydopamine. So basically is a is a is a polymer that is also biocompatible. So we're, you know, we're trying to use biocompatible materials here. And and it does form a conformal shell on these particles. And if this shell is 20 nanometers or more, it gives us a few hours of stability before the the particles actually dissolve and disappear. We've gotten to sort of where we want to be, because we don't want them to be stable forever, at least for the biological application, we just want them to be stable for the time you need to do this warming cancer cells operation and then we want them to disolve, so a few hours, really what we aim for, and we got it with polydopamine.
Paolo 17:19
Do you have already any proof of concept of the approach working in vitro or in vivo, on cancer cells?
Dr. Emilie Ringe 17:24
Not with the cancer cells. This has been done with gold. There's actually the gold for the thermal therapies in phase two clinical trials. So this is this is known technology. We believe that it is going to work with magnesium, we have numerical data on this showing us that we are expecting a temperature change very comparable to that of gold. And we really believe this is going to work this is on the on the very short-term horizon of our next few experiments.
Paolo 18:00
It is it is really interesting. And the way I see forward is like a sort of completely novel radiotherapy, right, with the radiation just being light in this case.
Dr. Emilie Ringe 18:13
Yes, it is infrared light. Which, which your body is mostly transparent to. And so you know, of course, you couldn't do a tumor that's really deep within you, but things like breast and cancer and skin and so on. That are, you know, moderately surface. It is it is a really, a really gentle way to really locally and incision free, basically kill tumor cells.
Paolo 18:46
Yeah, so the way the way this would work is you would inject the nanoparticles in the region of the cancer and then you would irradiate it with the infrared light and,
Dr. Emilie Ringe 18:54
Exactly.
Paolo 18:56
Right well, that's, that sounds very promising and super fascinating. How far do you think we are from something real in terms of application?
Dr. Emilie Ringe 19:06
I mean, not that far. There is a precedent for this kind of therapy. Of course, any any kind of medicine is takes a long time before reaching the customer if you want. But, but I think that you know, the proof concepts in a few years, and then we'll see where where that go, but 10 years.
Paolo 19:26
10 years in this in this field is nothing, it is practically tomorrow. What's the future for you, Emily, and your research or even even even the field? Because this this is what plasmonic properties have been known for a while. Right. But the metals that have been explored, are that are relatively limited. Is there any other element that could potentially become of interest for these properties?
Dr. Emilie Ringe 19:52
No, actually in terms of elements, I think I think you've named them all right, of course there. There are the group one metals, sodium and potassium are supposed to be fantastic plasmonic. But now as you say, this might become a little bit more challenging, you're not going to form a self-limiting surface oxide. But if you if you managed to coat them deliberately, right, during during a top down kind of evaporation synthesis, you might, you might have a shot, okay, they hold really good promise. But that's kind of it in the periodic table, because even if you mix two elements together, you've roughly get a mixture of their dielectric function. Okay, there's a few, there's a few exceptions, but they're very small exceptions to that rule. One of the exciting bit in the field is actually doped semiconductors. So in a semiconductor if you put enough electrons in, you can actually have one of these plasmon resonances, they often occur in the IR, but as great we need plasmonic in the IR too, and what's exciting about these is that they can be tuned, right, you can actually tune the electron density is not like in a metal where you're kind of stuck with the electron density in the metal. In semiconductors, you can tune that so that that's one of the area where the field is is going. It's not obvious that they are going to be better than the metallic structures and probably not in in sort of higher energy, but that they have proven to be very good IR plasmonic. So, this is something that I would I would look out for.
Paolo 21:47
Are you speaking about controlling electronic properties via light? Is this what this is about?
Dr. Emilie Ringe 21:53
No. So you can control their basically by the doping, you can control the electronic density.
Paolo 22:00
Okay. Now I see.
Dr. Emilie Ringe 22:01
And then that controls the localized surface plasmon resonance energy.
Paolo 22:06
I understand.
Dr. Emilie Ringe 22:06
Yeah
Paolo 22:07
I understand.
Dr. Emilie Ringe 22:07
Yeah.
Paolo 22:08
Interesting. So, so there are people in in the community doing research in this field?
Dr. Emilie Ringe 22:13
Yeah, yeah, there are several people. Delia Milliron, at UT Austin, is doing fantastic work. She's definitely one of the leaders in this field. There's a number of other people too. But I think that, you know, this, this is another example where this adds to the field, right, that the metallic people have one angle, and then the semiconductor people have have other knobs that can turn and end together we learn something about the fundamentals together.
Paolo 22:45
Yeah, of course, that makes sense. And, and, and probably you can't foresee all the potential interactions and overlaps that will happen, you know, a few years down the line, that there could be some exciting new angle and paths that would form. It is interesting. Well, you have a lot of exciting things in your hands. There's a couple of things I just wanted to explore, which I typically do at the end of every interview. You know, you are you're progressing your scientific career, you know, moving moving from being an individual researcher to leading to leading a team, you us spoken a lot about the importance of the community and you have also mentioned members of your team. I just like to, to get a feel for how is Emilie as a team leader, and what what is your role? with a, you know, for the people working in your in your group?
Dr. Emilie Ringe 23:39
Yeah, I try, I try to be very available to them. So I try to meet my students once a week. And, and just have really informal chats about, you know, where what they're doing in terms of science. And, and as I explained to them, when they join my group, it's not that I want to check on them is that I'm actually really interested in what they do. And as you become a team leader, you do you do less and less science, so I, you know, I might do electron microscopy myself, you know, once or twice a month, but but I'm not at the bench like they are. And actually, I'm just just really interested and curious about the ideas they've had. And one of the wonderful things about about Cambridge is that I can recruit some of the best students in on the planet. And they, you know, they really come up with amazing ideas. And we can have a discussion about how, how to implement these ideas. So, so I tried to be really available to them, and I really believe in fostering a positive group dynamic. And so we have lots of group interactions. We used to have a lot of in person social and during COVID we would play, you know, electronic board games every Tuesday night together. Just because I feel like getting getting them an idea of this sense of supportive community now, even in their own backyard, right is, is really, really important. And that the students can feel like if, if they don't quite know how to do something, well, there'll be someone in the lab that they can ask, and that they will be supported no matter, you know, who they are and what they do.
Paolo 25:28
It's beautiful to hear how you're trying to transfer the positives of your own experience, right. It's what a good leader should always do, so congratulations for that. And yeah, we can to do my typical final question. Now that you are, you know, still still very young but of course already already quite established in the community, you know, you're winning awards, your research is is very important, and you're doing exciting things. If you can stop and step back and and look at look at your own experience, what is the piece of advice you would give to someone younger, just starting in their career?
Dr. Emilie Ringe 26:07
I think it would be to, to really not hesitate to reach out to people and go talk to people. One of the things that helped me massively when I was applying for faculty positions, is that I didn't fear going knocking. Well, not quite knocking on doors, but but emailing anyways, faculty members, where I was a PhD and saying, "Hey, can I have a chat with you? I'm wondering about XYZ problem." And I think that a lot of people would be a bit a bit afraid of doing that. But but the reality is that, you know, in science, most people are really interested in science. And if you call them up and tell them you want to talk about their research, they're gonna be more than happy to do that. And so to really the advice is to develop into into a great researcher, really, don't hesitate to ask around, ask other great researchers, what they think of your ideas, what do you think of your approaches, and also what what they do and how how they got there.
Paolo 27:24
That was Dr. Emilie Ringe, Assistant Professor at the University of Cambridge, and one of the Chemical Engineering News' Talented 12. Thanks for joining us for this season three episode of Bringing Chemistry to Life, and keep an ear out for more. If you enjoyed this conversation you're sure to enjoy Dr. Ringe's book, video, podcast, and other content recommendations. Look in the episode notes in the app that you're using for listening to this podcast for a URL where you can access these recommendations and also register for a free Bringing Chemistry to Life t-shirt and consider sharing the episode with friends or colleagues if you like it. We are so excited to reach new chemistry lovers this season. This episode was produced by Sarah Briganti, Matt Ferris and Matthew Stock