The tiniest changes can have an enormous impact. Manipulating the way light and matter interact at atomic level has the potential to drive breakthroughs in solar energy – and thus help accelerate the transition to sustainable energy. “It will be of interest to any companies that work with light and metal interactions,” says Wiebke Albrecht, who leads the Hybrid Nanosystems group at AMOLF. Their dream, she says, is “to see how far we can get just using light, to see how these systems can be used to replace fossil fuels.”
You lead the Hybrid Nanosystems research group at AMOLF. Can you briefly explain what that work involves?
We are part of a research team dealing with sustainable energy materials: materials that are or will be important in sustainability applications such as photovoltaics or photocatalysis. We are interested in the interaction between light and matter of different nanoscale systems. We work a lot with plasmonic nanoparticles, which are very small metallic nanoparticles. Because they’re so small, they interact very efficiently with light. You can use them as a sort of nanoantenna, but also to create heat locally. We look at how these particles might interact with other materials on the nanoscale, such as a semiconductor. We focus on the single nanoparticle level and correlate the properties of these systems – mainly optical properties, but also electronic properties – with detailed structural and morphological information, down to the atomic scale.
Wiebke Albrecht , Tenure Track Group Leader at AMOLF “Big chemical companies like BASF and Toyota Europe and other analytical companies are part of the project ”
What are recent developments in your work?
What is interesting for the research we do now is that you can use laser excitation to engineer the atomic structure of these metallic nanoparticles. By carefully controlling how much heat we deposit by laser excitation and at what timescales, we can change the atomic surface facets or the internal structure of these metallic nanoparticles and create defects, for example, which is particularly important for catalytic research.
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Why is changing the shape of these atomic structures so significant?
Shape determines everything at the nanoscale, literally everything. If you change a nanoparticle by just one atomic layer, the optical properties will change. The structure and morphological features of the particle are that sensitive. We need to understand how that is related. We would also like to see if we can manipulate particles to make them the way we want them. That’s not so easy. Chemists have developed a lot of protocols to make all sorts of different shapes and morphologies, but they’re limited. If we use nonlinear processes like laser excitation to reshape and modify, we get quite different physics and chemistry, simply because we are highly out of equilibrium. For photocatalysis or catalysis in general, it is important what atoms sit at the surface. If there’s a way to control shape, that is a catalysis researcher’s dream. But it’s also important to understand the cases in which particles do not change under excitation, because these nanoparticles are used as local heat sources for biomedical applications, and then you want them to stay in the same shape.
How can this technology be used in the medical sector?
Plasmonic nanoparticles are used as local heat sources, because they very efficiently absorb light, and then they heat up. So you can bring them close to tumour cells, for example, heat them up locally and destroy the tumour without destroying healthy tissue. They’ve also been used as drug delivery systems: you can bring them close to a tumour and then excite them with light so they start releasing the drug.
And what other kind of applications are there?
In my specific field of hybrid nanoparticles, we are mainly interested in photovoltaic and photocatalytic applications. We want to learn more about how the light-and-matter interaction can create so-called hot charge carriers, also known as hot electrons or hot holes. These can be created by light excitation in metal nanoparticles, but they don’t live very long inside the particle because they bump into a lot of other things that are around. So the aim is to bring the charge carriers into a system that can accept them and where they will live longer, such as a semiconductor, and then see if we can harvest those hot carriers that hold a lot of energy.
How can this process be applied outside the lab?
We’re looking at how these systems can be used to replace fossil fuels and in the chemical industry. The dream would be to not have to burn fossil fuels to heat up a chemical reactor, but to use light, to guide it smartly towards nanoparticles that then generate heat. And maybe also create hot carriers, a combined effect that can be used to drive the chemical reaction. One of the projects we are working on is putting these particles into an optical fibre. You excite the fibre and then do chemistry inside the fibre. We want to see how far we can get by just purely using light. We do it on a single particle level first, because we need to understand how it works. But you could scale up using optical fibres or waveguides to distribute the light over larger volumes and surfaces.
Your group began work two years ago, so it’s still relatively early days in research terms. But are you already working with companies to apply this technology?
Yes, we have one project using these novel reactor concepts where we work together with a lot of industry partners. Big chemical companies like BASF and Toyota Europe are part of the project. It’s a collaboration involving several of the AMOLF groups and researchers from Utrecht University.
Are there other sectors where this technology could be of use?
Well, we’ve already got our hands quite full trying to solve the energy crisis, but it definitely has a larger range of applications. A lot of research still needs to be done in the field, and we have received a grant from NWO that will enable us to set up new infrastructure here at Amsterdam Science Park.
The project is called SHINE, because we will be shining light on atomic scale processes. We are acquiring an atomic resolution transmission electron microscope, which will enable us to combine light excitation with electron microscopy in situ. It’s a unique instrument and the infrastructure will be open to other researchers and for companies to come and do specific experiments. It will be of interest to any companies that work with light and matter interactions – for example, companies working with nanomaterials for LEDs or photovoltaic companies that want to look at their material under light excitation and see what’s happening to the atomic structure or just the structure in general. And possibly also biomedical companies that use nanoparticles.
How significant do you think the work that you’re doing is for sustainability?
Very important. We need materials that can harvest light very efficiently, generate chemical reactions more efficiently, and this is at the core of what we’re doing. So it’s definitely significant.
What are the advantages of the Amsterdam Science Park ecosystem for your work?
It’s a terrific location. AMOLF is known for being very collaborative and it’s great to have all the other institutes here. We have a lot of projects with our neighbour, ARCNL, the Advanced Research Center for Nanolithography. My group also works a lot with the CWI, the Institute for Mathematics and Computer Science. We do a lot of image analysis with them using artificial intelligence and our data processing. We have a good collaboration with Amsterdam Scientific Instruments – one of their detectors will be installed in our new SHINE infrastructure. And then there’s the University of Amsterdam, of course. We have a group of principal investigators in photochemistry and photophysics that comes together to discuss joint funding applications or grant proposals. Collaboration is also very much part of SHINE.
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