̽��ֱ�� of Cambridge - nanophotonics

Colour-changing magnifying glass gives clear view of infrared light

sc604 — Thu, 02 Dec 2021 19:00:00 +0000

Detecting light beyond the visible red range of our eyes is hard to do, because infrared light carries so little energy compared to ambient heat at room temperature. This obscures infrared light unless specialised detectors are chilled to very low temperatures, which is both expensive and energy-intensive.

Now researchers led by the ̽��ֱ�� of Cambridge have demonstrated a new concept in detecting infrared light, showing how to convert it into visible light, which is easily detected.

In collaboration with colleagues from the UK, Spain and Belgium, the team used a single layer of molecules to absorb the mid-infrared light inside their vibrating chemical bonds. These shaking molecules can donate their energy to visible light that they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum, which can then be detected by modern visible-light cameras.

̽��ֱ��results, reported in the journal Science, open up new low-cost ways to sense contaminants, track cancers, check gas mixtures, and remotely sense the outer universe.

̽��ֱ��challenge faced by the researchers was to make sure the quaking molecules met the visible light quickly enough. “This meant we had to trap light really tightly around the molecules, by squeezing it into crevices surrounded by gold,” said first author Angelos Xomalis from Cambridge’s Cavendish Laboratory.

̽��ֱ��researchers devised a way to sandwich single molecular layers between a mirror and tiny chunks of gold, only possible with ‘meta-materials’ that can twist and squeeze light into volumes a billion times smaller than a human hair.

“Trapping these different colours of light at the same time was hard, but we wanted to find a way that wouldn’t be expensive and could easily produce practical devices,” said co-author Dr Rohit Chikkaraddy from the Cavendish Laboratory, who devised the experiments based on his simulations of light in these building blocks.

“It’s like listening to slow-rippling earthquake waves by colliding them with a violin string to get a high whistle that’s easy to hear, and without breaking the violin,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

̽��ֱ��researchers emphasise that while it is early days, there are many ways to optimise the performance of these inexpensive molecular detectors, which then can access rich information in this window of the spectrum.

From astronomical observations of galactic structures to sensing human hormones or early signs of invasive cancers, many technologies can benefit from this new detector advance.

̽��ֱ��research was conducted by a team from the ̽��ֱ�� of Cambridge, KU Leuven, ̽��ֱ�� College London (UCL), the Faraday Institution, and Universitat Politècnica de València.

̽��ֱ��research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC), Trinity College Cambridge and KU Leuven.

Jeremy Baumberg is a Fellow of Jesus College, Cambridge.

Reference:
Angelos Xomalis et al. ‘Detecting mid-infrared light by molecular frequency upconversion with dual-wavelength hybrid nanoantennas’, Science (2021). DOI: 10.1126/science.abk2593

By trapping light into tiny crevices of gold, researchers have coaxed molecules to convert invisible infrared into visible light, creating new low-cost detectors for sensing.

It’s like listening to slow-rippling earthquake waves by colliding them with a violin string to get a high whistle that’s easy to hear, and without breaking the violin

Jeremy Baumberg

NanoPhotonics Cambridge /Ermanno Miele, Jeremy Baumberg

Nano-antennas convert invisible infrared into visible light

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Nano ‘camera’ made using molecular glue allows real-time monitoring of chemical reactions

sc604 — Thu, 02 Sep 2021 14:59:34 +0000

̽��ֱ��device, made by a team from the ̽��ֱ�� of Cambridge, combines tiny semiconductor nanocrystals called quantum dots and gold nanoparticles using molecular glue called cucurbituril (CB). When added to water with the molecule to be studied, the components self-assemble in seconds into a stable, powerful tool that allows the real-time monitoring of chemical reactions.

̽��ֱ��camera harvests light within the semiconductors, inducing electron transfer processes like those that occur in photosynthesis, which can be monitored using incorporated gold nanoparticle sensors and spectroscopic techniques. They were able to use the camera to observe chemical species which had been previously theorised but not directly observed.

̽��ֱ��platform could be used to study a wide range of molecules for a variety of potential applications, such as the improvement of photocatalysis and photovoltaics for renewable energy. ̽��ֱ��results are reported in the journal Nature Nanotechnology.

Nature controls the assemblies of complex structures at the molecular scale through self-limiting processes. However, mimicking these processes in the lab is usually time-consuming, expensive and reliant on complex procedures.

“In order to develop new materials with superior properties, we often combine different chemical species together to come up with a hybrid material that has the properties we want,” said Professor Oren Scherman from Cambridge’s Yusuf Hamied Department of Chemistry, who led the research. “But making these hybrid nanostructures is difficult, and you often end up with uncontrolled growth or materials that are unstable.”

̽��ֱ��new method that Scherman and his colleagues from Cambridge’s Cavendish Laboratory and ̽��ֱ�� College London developed uses cucurbituril – a molecular glue which interacts strongly with both semiconductor quantum dots and gold nanoparticles. ̽��ֱ��researchers used small semiconductor nanocrystals to control the assembly of larger nanoparticles through a process they coined interfacial self-limiting aggregation. ̽��ֱ��process leads to permeable and stable hybrid materials that interact with light. ̽��ֱ��camera was used to observe photocatalysis and track light-induced electron transfer.

“We were surprised how powerful this new tool is, considering how straightforward it is to assemble,” said first author Dr Kamil Sokołowski, also from the Department of Chemistry.

To make their nano camera, the team added the individual components, along with the molecule they wanted to observe, to water at room temperature. Previously, when gold nanoparticles were mixed with the molecular glue in the absence of quantum dots, the components underwent unlimited aggregation and fell out of solution. However, with the strategy developed by the researchers, quantum dots mediate the assembly of these nanostructures so that the semiconductor-metal hybrids control and limit their own size and shape. In addition, these structures stay stable for weeks.

“This self-limiting property was surprising, it wasn’t anything we expected to see,” said co-author Dr Jade McCune, also from the Department of Chemistry. “We found that the aggregation of one nanoparticulate component could be controlled through the addition of another nanoparticle component.”

When the researchers mixed the components together, the team used spectroscopy to observe chemical reactions in real time. Using the camera, they were able to observe the formation of radical species – a molecule with an unpaired electron – and products of their assembly such as sigma dimeric viologen species, where two radicals form a reversible carbon-carbon bond. ̽��ֱ��latter species had been theorised but never observed.

“People have spent their whole careers getting pieces of matter to come together in a controlled way,” said Scherman, who is also Director of the Melville Laboratory. “This platform will unlock a wide range of processes, including many materials and chemistries that are important for sustainable technologies. ̽��ֱ��full potential of semiconductor and plasmonic nanocrystals can now be explored, providing an opportunity to simultaneously induce and observe photochemical reactions.”

“This platform is a really big toolbox considering the number of metal and semiconductor building blocks that can be now coupled together using this chemistry– it opens up lots of new possibilities for imaging chemical reactions and sensing through taking snapshots of monitored chemical systems,” said Sokołowski. “ ̽��ֱ��simplicity of the setup means that researchers no longer need complex, expensive methods to get the same results.”

Researchers from the Scherman lab are currently working to further develop these hybrids towards artificial photosynthetic systems and (photo)catalysis where electron-transfer processes can be observed directly in real time. ̽��ֱ��team is also looking at mechanisms of carbon-carbon bond formation as well as electrode interfaces for battery applications.

̽��ֱ��research was carried out in collaboration with Professor Jeremy Baumberg at Cambridge’s Cavendish Laboratory and Dr Edina Rosta at ̽��ֱ�� College London. It was funded in part by the Engineering and Physical Sciences Research Council (EPSRC).

Reference:
Kamil Sokołowski et al. ‘Nanoparticle surfactants for kinetically arrested photoactive assemblies to track light-induced electron transfer.’ Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00949-6

Researchers have made a tiny camera, held together with ‘molecular glue’ that allows them to observe chemical reactions in real time.

This platform is a really big toolbox – it opens up lots of new possibilities for imaging chemical reactions

Kamil Sokołowski

Scherman Group

Nano camera

Yes

Giant 'quantum twisters' may form in liquid light

sc604 — Fri, 05 Mar 2021 16:55:21 +0000

Anyone who has drained a bathtub or stirred cream into coffee has seen a vortex, a ubiquitous formation that appears when fluid circulates. But unlike water, fluids governed by the strange rules of quantum mechanics have a special restriction: as was first predicted in 1945 by future Nobel winner Lars Onsager, a vortex in a quantum fluid can only twist by whole-number units.

These rotating structures are predicted to be widely useful for studying everything from quantum systems to black holes. But while the smallest possible quantum vortex, with a single unit of rotation, has been seen in many systems, larger vortices are not stable. While scientists have attempted to force larger vortices to hold themselves together, the results have been mixed: when the vortices have been formed, the severity of the methods used have generally destroyed their usefulness.

Now, Samuel Alperin and Professor Natalia Berloff from the ̽��ֱ�� of Cambridge have discovered a theoretical mechanism through which giant quantum vortices are not only stable but form by themselves in otherwise near-uniform fluids. ̽��ֱ��findings, published in the journal Optica, could pave the way for experiments that might provide insight into the nature of rotating black holes that have similarities with giant quantum vortices.

To do this, the researchers used a quantum hybrid of light and matter, called a polariton. These particles are formed by shining laser light onto specially layered materials. “When the light gets trapped in the layers, the light and the matter become inseparable, and it becomes more practical to look at the resulting substance as something that is distinct from either light or matter, while inheriting properties of both,” said Alperin, a PhD student at Cambridge’s Department of Applied Mathematics and Theoretical Physics.

One of the most significant properties of polaritons comes from the simple fact that light can’t be trapped forever. A fluid of polaritons, which requires a high density of the exotic particles, is constantly expelling light, and needs to be fed with fresh light from the laser to survive. “ ̽��ֱ��result,” said Alperin, “is a fluid which is never allowed to settle, and which doesn’t need to obey what are usually basic restrictions in physics, like the conservation of energy. Here the energy can change as a part of the dynamics of the fluid.”

It was exactly these constant flows of liquid light that the researchers exploited to allow the elusive giant vortex to form. Instead of shining the laser on the polariton fluid itself, the new proposal has the light shaped like a ring, causing a constant inward flow similarly to how water flows to a bathtub drain. According to the theory, this flow is enough to concentrate any rotation into a single giant vortex.

“That the giant vortex really can exist under conditions that are amenable to their study and technical use was quite surprising,” Alperin said, “but really it just goes to show how utterly distinct the hydrodynamics of polaritons are from more well-studied quantum fluids. It’s exciting territory.”

̽��ֱ��researchers say that they are just at the beginning of their work on giant quantum vortices. They were able to simulate the collision of several quantum vortices as they dance around each other with ever increasing speed until they collide to form a single giant vortex analogous to the collision of black holes. They also explained the instabilities that limit the maximum vortex size while exploring intricate physics of the vortex behaviour.

“These structures have some interesting acoustic properties: they have acoustic resonances that depend on their rotation, so they sort of sing information about themselves,” said Alperin. “Mathematically, it’s quite analogous to the way that rotating black holes radiate information about their own properties.”

̽��ֱ��researchers hope that the similarity could lead to new insights into the theory of quantum fluid dynamics, but they also say that polaritons might be a useful tool to study the behaviour of black holes.

Professor Berloff is jointly affiliated with Cambridge and the Skolkovo Institute of Science and Technology in Russia.

Reference:
Samuel N. Alperin and Natalia G. Berloff. ‘Multiply charged vortex states of polariton condensates.’ Optica (2021). DOI: 10.1364/OPTICA.418377

New mechanism found for generating giant vortices in quantum fluids of light.

Stable giant quantum vortices

Yes

Scientists write ‘traps’ for light with tiny ink droplets

sc604 — Mon, 23 Oct 2017 23:13:56 +0000

̽��ֱ��printing-based approach, jointly developed by researchers at the ̽��ֱ�� of Cambridge and the Hitachi Cambridge Laboratory, combines high-resolution inkjet printing with nanophotonics – the study and harnessing of light on the scale of a billionth of a metre – the first time that this combination has been successfully demonstrated. ̽��ֱ��results are reported in the journal Advanced Materials.

Over the last decade, inkjet printing – the same basic technology that many of us have in our homes – has advanced to the point where it can be used to print very small devices, using a range of printable materials, including living cells, as ‘ink’. This approach is both simple and low-cost, and it is widely used in electronics and biotechnology.

“Most inkjet printers push the ink through the nozzle by heating or applying pressure, producing ink droplets about the size of the diameter of a human hair,” said the paper’s co-first author Dr Vincenzo Pecunia, a former PhD student and postdoctoral researcher, and now visiting researcher, at the ̽��ֱ��’s Cavendish Laboratory.

Pecunia’s research focuses on printable optoelectronic materials for a range of applications, and his group recently obtained a printer based on electrohydrodynamic jets: a long word that essentially means a printer capable of ultra-high resolution printing. Instead of relying on pressure or heat, this type of printer applies a voltage to the ink, providing enough force to push it through a much smaller nozzle, producing ultra-small ink droplets – ten to a hundred times smaller than those produced by conventional printers.

Thanks to a chance meeting between Pecunia and co-first author Dr Frederic Brossard from the Hitachi Cambridge Laboratory, the researchers found that the new printer could print structures small enough to be used in nanophotonics, which is Brossard’s area of research.

“Previous efforts to combine these two areas had bumped into the limitations of conventional inkjet printing technology, which cannot directly deposit anything small enough to be comparable to the wavelength of light,” said Pecunia. “But through electrodynamic inkjet printing we’ve been able to move beyond these limitations.”

̽��ֱ��researchers were able to deposit ultra-small ink droplets onto photonic crystals. ̽��ֱ��ink droplets are small enough that they can be ‘drawn’ on the crystals on demand as if from a very fine pen, and locally change the properties of the crystals so that light could be trapped. This technique enables the creation of many types of patterns onto the photonic crystals, at high speed and over a large area. Additionally, the patterns can be made of all sorts of printable materials, and the method is scalable, low-cost, and the photonic crystal is reusable since the ink can be simply washed away.

“This fabrication technique opens the door for diverse opportunities in fundamental and applied sciences,” said Brossard. “A potential direction is the creation of a high density of highly sensitive sensors to detect minute amounts of biomolecules such as viruses or cancer cells. This could also be a very useful tool to study some fundamental phenomena requiring very strong interaction between light and matter in new materials and create lasers on demand. Finally, this technology could also enable the creation of highly compact optical circuits which would guide the light and which could be modified by inkjet printing using the photonic crystal template.”

̽��ֱ��research was funded in part by the Engineering and Physical Sciences Research Council (EPSRC) and the Science and Technology Facilities Council (STFC).

Reference
Frederic S.F. Brossard et al. ‘Inkjet printed nanocavities on a photonic crystal template.’ Advanced Materials (2017). DOI: 10.1002/adma.201704425

A microscopic ‘pen’ that is able to write structures small enough to trap and harness light using a commercially available printing technique could be used for sensing, biotechnology, lasers, and studying the interaction between light and matter.

Previous efforts to combine these two areas had bumped into the limitations of conventional inkjet printing technology.

Vincenzo Pecunia

Light trapped by a tiny droplet on a photonic crystal surface.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

How to train your drugs: from nanotherapeutics to nanobots

sc604 — Fri, 23 Jun 2017 15:00:56 +0000

Chemotherapy benefits a great many patients but the side effects can be brutal.

When a patient is injected with an anti-cancer drug, the idea is that the molecules will seek out and destroy rogue tumour cells. However, relatively large amounts need to be administered to reach the target in high enough concentrations to be effective. As a result of this high drug concentration, healthy cells may be killed as well as cancer cells, leaving many patients weak, nauseated and vulnerable to infection.

One way that researchers are attempting to improve the safety and efficacy of drugs is to use a relatively new area of research known as nanothrapeutics to target drug delivery just to the cells that need it.

Professor Sir Mark Welland is Head of the Electrical Engineering Division at Cambridge. In recent years, his research has focused on nanotherapeutics, working in collaboration with clinicians and industry to develop better, safer drugs. He and his colleagues don’t design new drugs; instead, they design and build smart packaging for existing drugs.

Nanotherapeutics come in many different configurations, but the easiest way to think about them is as small, benign particles filled with a drug. They can be injected in the same way as a normal drug, and are carried through the bloodstream to the target organ, tissue or cell. At this point, a change in the local environment, such as pH, or the use of light or ultrasound, causes the nanoparticles to release their cargo.

Nano-sized tools are increasingly being looked at for diagnosis, drug delivery and therapy. “There are a huge number of possibilities right now, and probably more to come, which is why there’s been so much interest,” says Welland. Using clever chemistry and engineering at the nanoscale, drugs can be ‘taught’ to behave like a Trojan horse, or to hold their fire until just the right moment, or to recognise the target they’re looking for.

“We always try to use techniques that can be scaled up – we avoid using expensive chemistries or expensive equipment, and we’ve been reasonably successful in that,” he adds. “By keeping costs down and using scalable techniques, we’ve got a far better chance of making a successful treatment for patients.”

In 2014, he and collaborators demonstrated that gold nanoparticles could be used to ‘smuggle’ chemotherapy drugs into cancer cells in glioblastoma multiforme, the most common and aggressive type of brain cancer in adults, which is notoriously difficult to treat. ̽��ֱ��team engineered nanostructures containing gold and cisplatin, a conventional chemotherapy drug. A coating on the particles made them attracted to tumour cells from glioblastoma patients, so that the nanostructures bound and were absorbed into the cancer cells.

Once inside, these nanostructures were exposed to radiotherapy. This caused the gold to release electrons that damaged the cancer cell’s DNA and its overall structure, enhancing the impact of the chemotherapy drug. ̽��ֱ��process was so effective that 20 days later, the cell culture showed no evidence of any revival, suggesting that the tumour cells had been destroyed.

While the technique is still several years away from use in humans, tests have begun in mice. Welland’s group is working with MedImmune, the biologics R&D arm of pharmaceutical company AstraZeneca, to study the stability of drugs and to design ways to deliver them more effectively using nanotechnology.

“One of the great advantages of working with MedImmune is they understand precisely what the requirements are for a drug to be approved. We would shut down lines of research where we thought it was never going to get to the point of approval by the regulators,” says Welland. “It’s important to be pragmatic about it so that only the approaches with the best chance of working in patients are taken forward.”

̽��ֱ��researchers are also targeting diseases like tuberculosis (TB). With funding from the Rosetrees Trust, Welland and postdoctoral researcher Dr Íris da luz Batalha are working with Professor Andres Floto in the Department of Medicine to improve the efficacy of TB drugs.

Their solution has been to design and develop nontoxic, biodegradable polymers that can be ‘fused’ with TB drug molecules. As polymer molecules have a long, chain-like shape, drugs can be attached along the length of the polymer backbone, meaning that very large amounts of the drug can be loaded onto each polymer molecule. ̽��ֱ��polymers are stable in the bloodstream and release the drugs they carry when they reach the target cell. Inside the cell, the pH drops, which causes the polymer to release the drug.

In fact, the polymers worked so well for TB drugs that another of Welland’s postdoctoral researchers, Dr Myriam Ouberaï, has formed a start-up company, Spirea, which is raising funding to develop the polymers for use with oncology drugs. Ouberaï is hoping to establish a collaboration with a pharma company in the next two years.

“Designing these particles, loading them with drugs and making them clever so that they release their cargo in a controlled and precise way: it’s quite a technical challenge,” adds Welland. “ ̽��ֱ��main reason I’m interested in the challenge is I want to see something working in the clinic – I want to see something working in patients.”

Could nanotechnology move beyond therapeutics to a time when nanomachines keep us healthy by patrolling, monitoring and repairing the body?

Nanomachines have long been a dream of scientists and public alike. But working out how to make them move has meant they’ve remained in the realm of science fiction.

But last year, Professor Jeremy Baumberg and colleagues in Cambridge and the ̽��ֱ�� of Bath developed the world’s tiniest engine – just a few billionths of a metre in size. It’s biocompatible, cost-effective to manufacture, fast to respond and energy efficient.

̽��ֱ��forces exerted by these ‘ANTs’ (for ‘actuating nano-transducers’) are nearly a hundred times larger than those for any known device, motor or muscle. To make them, tiny charged particles of gold, bound together with a temperature-responsive polymer gel, are heated with a laser. As the polymer coatings expel water from the gel and collapse, a large amount of elastic energy is stored in a fraction of a second. On cooling, the particles spring apart and release energy.

̽��ֱ��researchers hope to use this ability of ANTs to produce very large forces relative to their weight to develop three-dimensional machines that swim, have pumps that take on fluid to sense the environment and are small enough to move around our bloodstream.

Working with Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm, the team in Cambridge's Nanophotonics Centre hopes to commercialise the technology for microfluidics bio-applications. The work is funded by the Engineering and Physical Sciences Research Council and the European Research Council.

“There’s a revolution happening in personalised healthcare, and for that we need sensors not just on the outside but on the inside,” explains Baumberg, who leads an interdisciplinary Strategic Research Network and Doctoral Training Centre focused on nanoscience and nanotechnology.

“Nanoscience is driving this. We are now building technology that allows us to even imagine these futures.”

Read more about research on future therapeutics in Research Horizons magazine.

Nanotechnology is creating new opportunities for fighting disease – from delivering drugs in smart packaging to nanobots powered by the world’s tiniest engines.

Designing these particles, loading them with drugs and making them clever so that they release their cargo in a controlled and precise way: it’s quite a technical challenge.

Mark Welland

Yu Ji

Artist's impression of a nanobot

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Nano ‘hall of mirrors’ causes molecules to mix with light

sc604 — Mon, 13 Jun 2016 15:00:00 +0000

When a molecule emits a blink of light, it doesn’t expect it to ever come back. However researchers have now managed to place single molecules in such a tiny optical cavity that emitted photons, or particles of light, return to the molecule before they have properly left. ̽��ֱ��energy oscillates back and forth between light and molecule, resulting in a complete mixing of the two.

Previous attempts to mix molecules with light have been complex to produce and only achievable at very low temperatures, but the researchers, led by the ̽��ֱ�� of Cambridge, have developed a method to produce these ‘half-light’ molecules at room temperature.

These unusual interactions of molecules with light provide new ways to manipulate the physical and chemical properties of matter, and could be used to process quantum information, aid in the understanding of complex processes at work in photosynthesis, or even manipulate the chemical bonds between atoms. ̽��ֱ��results are reported in the journal Nature.

To use single molecules in this way, the researchers had to reliably construct cavities only a billionth of a metre (one nanometre) across in order to trap light. They used the tiny gap between a gold nanoparticle and a mirror, and placed a coloured dye molecule inside.

“It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

In order to achieve the molecule-light mixing, the dye molecules needed to be correctly positioned in the tiny gap. “Our molecules like to lie down flat on the gold, and it was really hard to persuade them to stand up straight,” said Rohit Chikkaraddy, lead author of the study.

To solve this, the team joined with a team of chemists at Cambridge led by Professor Oren Scherman to encapsulate the dyes in hollow barrel-shaped molecular cages called cucurbiturils, which are able to hold the dye molecules in the desired upright position.

When assembled together correctly, the molecule scattering spectrum splits into two separated quantum states which is the signature of this ‘mixing’. This spacing in colour corresponds to photons taking less than a trillionth of a second to come back to the molecule.

A key advance was to show strong mixing of light and matter was possible for single molecules even with large absorption of light in the metal and at room temperature. “Finding single-molecule signatures took months of data collection,” said Chikkaraddy.

̽��ֱ��researchers were also able to observe steps in the colour spacing of the states corresponding to whether one, two, or three molecules were in the gap.

̽��ֱ��Cambridge team collaborated with theorists Professor Ortwin Hess at the Blackett Laboratory, Imperial College London and Dr Edina Rosta at Kings College London to understand the confinement and interaction of light in such tiny gaps, matching experiments amazingly well.

Reference:
Rohit Chikkaraddy et al. ‘Single-molecule strong coupling at room temperature in plasmonic nanocavities.’ Nature (2016). DOI: 10.1038/nature17974

Researchers have successfully used quantum states to mix a molecule with light at room temperature, which will aid in the exploration of quantum technologies and provide new ways to manipulate the physical and chemical properties of matter.

It’s like a hall of mirrors for a molecule, only spaced a hundred thousand times thinner than a human hair.

Jeremy Baumberg

Yu Ji/ ̽��ֱ�� of Cambridge NanoPhotonics

Mixing light with dye molecules, trapped in golden gaps

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Little ANTs: researchers build the world’s tiniest engine

sc604 — Mon, 02 May 2016 19:01:00 +0000

Researchers have developed the world’s tiniest engine – just a few billionths of a metre in size – which uses light to power itself. ̽��ֱ��nanoscale engine, developed by researchers at the ̽��ֱ�� of Cambridge, could form the basis of future nano-machines that can navigate in water, sense the environment around them, or even enter living cells to fight disease.

̽��ֱ��prototype device is made of tiny charged particles of gold, bound together with temperature-responsive polymers in the form of a gel. When the ‘nano-engine’ is heated to a certain temperature with a laser, it stores large amounts of elastic energy in a fraction of a second, as the polymer coatings expel all the water from the gel and collapse. This has the effect of forcing the gold nanoparticles to bind together into tight clusters. But when the device is cooled, the polymers take on water and expand, and the gold nanoparticles are strongly and quickly pushed apart, like a spring. ̽��ֱ��results are reported in the journal PNAS.

“It’s like an explosion,” said Dr Tao Ding from Cambridge’s Cavendish Laboratory, and the paper’s first author. “We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them.”

“We know that light can heat up water to power steam engines,” said study co-author Dr Ventsislav Valev, now based at the ̽��ֱ�� of Bath. “But now we can use light to power a piston engine at the nanoscale.”

Nano-machines have long been a dream of scientists and public alike, but since ways to actually make them move have yet to be developed, they have remained in the realm of science fiction. ̽��ֱ��new method developed by the Cambridge researchers is incredibly simple, but can be extremely fast and exert large forces.

̽��ֱ��forces exerted by these tiny devices are several orders of magnitude larger than those for any other previously produced device, with a force per unit weight nearly a hundred times better than any motor or muscle. According to the researchers, the devices are also bio-compatible, cost-effective to manufacture, fast to respond, and energy efficient.

Professor Jeremy Baumberg from the Cavendish Laboratory, who led the research, has named the devices ‘ANTs’, or actuating nano-transducers. “Like real ants, they produce large forces for their weight. ̽��ֱ��challenge we now face is how to control that force for nano-machinery applications.”

̽��ֱ��research suggests how to turn Van de Waals energy – the attraction between atoms and molecules – into elastic energy of polymers and release it very quickly. “ ̽��ֱ��whole process is like a nano-spring,” said Baumberg. “ ̽��ֱ��smart part here is we make use of Van de Waals attraction of heavy metal particles to set the springs (polymers) and water molecules to release them, which is very reversible and reproducible.”

̽��ֱ��team is currently working with Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm, and several other companies with the aim of commercialising this technology for microfluidics bio-applications.

Reference:
Tao Ding et al. ‘Light-induced actuating nanotransducers.’ PNAS (2016). DOI: 10.1073/pnas.1524209113

Researchers have built a nano-engine that could form the basis for future applications in nano-robotics, including robots small enough to enter living cells.

Like real ants, they produce large forces for their weight.

Jeremy Baumberg

Yu Ji/ ̽��ֱ�� of Cambridge NanoPhotonics

Expanding polymer-coated gold nanoparticles

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Trapping the light fantastic

lw355 — Mon, 16 Jun 2014 08:13:42 +0000

Jeremy Baumberg and his 30-strong team of researchers are master manipulators of light. They are specialists in nanophotonics – the control of how light interacts with tiny chunks of matter, at scales as small as a billionth of a metre. It’s a field of physics that 20 years ago was unknown.

At the heart of nanophotonics is the idea that changing the structure of materials at the scale of a few atoms can be used to alter not only the way light interacts with the material, but also its functional properties.

“ ̽��ֱ��goal is to design materials with really intricate architecture on a really small scale, so small it’s smaller than the wavelength of light,” said Baumberg, Professor of Nanophotonics in the Department of Physics. “Whether the starting material is polystyrene or gold, changing the shape of its nanostructure can give us extraordinary control over how light energy is absorbed by the electrons locked inside. We’re learning how to use this to develop new functionality.”

One of their recent achievements is to develop synthetic materials that mimic some of nature’s most striking colours, among them the iridescent hue of opals. Naturally occurring opals are formed

‘Polymer opals’, however, are plastic – like the polystyrene in drinking cups – and formed within a matter of minutes. With some clever chemistry, the researchers have found a way of making polysterene spheres coated in a soft chewing-gum-like outer shell.

As these polymer opals are twisted and stretched, ‘metallic’ blue–green colours ripple across their surface. Their flexibility and the permanence of their intense colour make them ideal materials for security cards and banknotes or to replace toxic dyes in the textile industry.

“ ̽��ֱ��crucial thing is that by assembling things in the right way you get the function you want,” said Baumberg, who developed the polymer opals with collaborators in Germany (at the DKI, now the Fraunhofer Institute for Structural Durability and System Reliability). “If the spheres are random, the material looks white or colourless, but if stacked perfectly regularly you get colour. We’ve found that smearing the spheres against each other magically makes them fall into regular lines and, because of the chewing gum layer, when you stretch it the colour changes too.

“It’s such a good example of nanotechnology – we take a transparent material, we cut it up in the right form, we stack it in the right way and we get completely new function.”

Although nanophotonics is a comparatively new area of materials research, Baumberg believes that within two decades we will start to see nanophotonic materials in anything from smart textiles to buildings and food colouring to solar cells.

Now, one of the team’s latest discoveries looks set to open up applications in medical diagnostics.

“We’re starting to learn how we can make materials that respond optically to the presence of individual molecules in biological fluids,” he explained. “There’s a large demand for this. GPs would like to be able to test the patient while they wait, rather than sending samples away for clinical testing. And cheap and reliable tests would benefit developing countries that lack expensive diagnostic equipment.”

A commonly used technique in medical diagnostics is Raman spectroscopy, which detects the presence of a molecule by its ‘optical signature’. It measures how light is changed when it bounces off a molecule, which in turn depends on the bonds within the molecule. However, the machines need to be very powerful to detect what can be quite weak effects.

Baumberg has been working with Dr Oren Scherman, Director of the Melville Laboratory for Polymer Synthesis in the Department of Chemistry, on a completely new way to sense molecules they have developed using a barrel-shaped molecular container called cucurbituril (CB). Acting like a tiny test tube, CB enables single molecules to enter its barrel shape, effectively isolating them from a mixture of molecules.

In collaboration with researchers in Spain and France, and with funding from the European Union, Baumberg and Scherman have found a way to detect what’s in each barrel using light, by combining the barrels with particles of gold only a few thousand atoms across.

“Shining light onto this gold–barrel mixture focuses and enhances the light waves into tiny volumes of space exactly where the molecules are located,” Baumberg explained. “By looking at the colours of the scattered light, we can work out which molecules are present and what they are doing, and with very high sensitivity.”

Whereas most sensing equipment requires precise conditions that can only really be achieved in the laboratory, this new technology has the potential to be a low-cost, reliable and rapid sensor for mass markets. ̽��ֱ��amount of gold required for the test is extremely small, and the gold particles self-assemble with CB at room temperature.

Now, with funding from the Engineering and Physical Sciences Research Council, and working with companies and potential end users (including the NHS), Baumberg and Scherman have begun the process of developing their ‘plasmonic sensors’ to test biological fluids such as urine and tears, for uses such as detecting neurotransmitters in the brain and protein incompatibilities between mother and fetus.

“At the same time, we want to understand how we can go further with the technology, from controlling chemical reactions happening inside the barrel, to making captured molecules inside ‘flex’ themselves, and detecting each of these modifications through colour change,” added Baumberg.

“ ̽��ֱ��ability to look at small numbers of molecules in a sea of others has appealed to scientists for years. Soon we will be able to do this on an unprecedented scale: watching in real time how molecules come together and undergo chemical reactions, and even how they form a bond. This has huge implications for optimising catalysis in industrially relevant processes and is therefore at the heart of almost every product in our lives.”

Baumberg views nanophotonics technology as a whole new toolbox. “ ̽��ֱ��excitement for me is the challenge of how difficult the task is combined with the fact that you can see that, if only you could do it, you can get things out that are incredible.

“At the moment we are capable of assembling new structures with different optical properties in a highly controlled way. Eventually, though, we will be able to build things with light itself.”

̽��ֱ��development of a ‘nanobarrel’ that traps and concentrates light onto single molecules could be used as a low-cost and reliable diagnostic test.

Eventually... we will be able to build things with light itself

Jeremy Baumberg

Gen Kamita and Jeremy Baumberg

Light can be manipulated at the nanoscale, as in this elastic material which has been folded like nano-origami

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