Tag Archives: Okinawa Institute of Science and Technology Graduate University (OIST)

Nanoparticle detection with whispers and bubbles

Caption: A magnified photograph of a glass Whispering Gallery Resonator. The bubble is extremely small, less than the width of a human hair. Credit: OIST (Okinawa Institute of Science and Technology Graduate University)

It was the reference to a whispering gallery which attracted my attention; a July 11, 2018 news item on Nanowerk is where I found it,

Technology created by researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) [Japan] is literally shedding light on some of the smallest particles to detect their presence – and it’s made from tiny glass bubbles.

The technology has its roots in a peculiar physical phenomenon known as the “whispering gallery,” described by physicist Lord Rayleigh (John William Strutt) in 1878 and named after an acoustic effect inside the dome of St Paul’s Cathedral in London. Whispers made at one side of the circular gallery could be heard clearly at the opposite side. It happens because sound waves travel along the walls of the dome to the other side, and this effect can be replicated by light in a tiny glass sphere just a hair’s breadth wide called a Whispering Gallery Resonator (WGR).

A July 11, 2018 OIST press release by Andrew Scott (also on EurekAlert), provides more details,

When light is shined into the sphere, it bounces around and around the inner surface, creating an optical carousel. Photons bouncing along the interior of the tiny sphere can end up travelling for long distances, sometimes as far as 100 meters. But each time a photon bounces off the sphere’s surface, a small amount of light escapes. This leaking light creates a sort of aura around the sphere, known as an evanescent light field. When nanoparticles come within range of this field, they distort its wavelength, effectively changing its color. Monitoring these color changes allows scientists to use the WGRs as a sensor; previous research groups have used them to detect individual virus particles in solution, for example. But at OIST’s Light-Matter Interactions Unit, scientists saw they could improve on previous work and create even more sensitive designs. The study is published in Optica.

Today, Dr. Jonathan Ward is using WGRs to detect minute particles more efficiently than ever before. The WGRs they have made are hollow glass bubbles rather than balls, explains Dr. Ward. “We heated a small glass tube with a laser and had air blown down it – it’s a lot like traditional glass blowing”. Blowing the air down the heated glass tube creates a spherical chamber that can support the sensitive light field. The most noticeable difference between a blown glass ornament and these precision instruments is the scale: the glass bubbles can be as small as 100 microns- a fraction of a millimeter in width. Their size makes them fragile to handle, but also malleable.

Working from theoretical models, Dr. Ward showed that they could increase the size of the light field by using a thin spherical shell (a bubble, in other words) instead of a solid sphere. A bigger field would increase the range in which particles can be detected, increasing the efficacy of the sensor. “We knew we had the techniques and the materials to fabricate the resonator”, said Dr. Ward. “Next we had to demonstrate that it could outperform the current types used for particle detection”.

To prove their concept, the team came up with a relatively simple test. The new bubble design was filled with a liquid solution containing tiny particles of polystyrene, and light was shined along a glass filament to generate a light field in its liquid interior. As particles passed within range of the light field, they produced noticeable shifts in the wavelength that were much more pronounced than those seen with a standard spherical WGR.

With a more effective tool now at their disposal, the next challenge for the team is to find applications for it. Learning what changes different materials make to the light field would allow Dr Ward to identify and target them, and even control their activity.

Despite their fragility, these new versions of WGRs are easy to manufacture and can be safely transported in custom made cases. That means these sensors could be used in a wide verity of fields, such as testing for toxic molecules in water to detect pollution, or detecting blood borne viruses in extremely rural areas where healthcare may be limited.

For Dr. Ward however, there’s always room from improvement: “We’re always pushing to get even more sensitivity and find the smallest particle this sensor can detect. We want to push our detection to the physical limits.”

Here’s a link to and a citation for the paper,

Nanoparticle sensing beyond evanescent field interaction with a quasi-droplet microcavity by Jonathan M. Ward, Yong Yang, Fuchuan Lei, Xiao-Chong Yu, Yun-Feng Xiao, and Síle Nic Chormaic. Optica Vol. 5, Issue 6, pp. 674-677 (2018) https://doi.org/10.1364/OPTICA.5.000674

This paper is open access.

Molecular electronics: one atom at a time

This research on developing molecular electronics comes from Okinawa (Japan) according to a January 17, 2018 news item on Nanowerk,

Electronic devices are getting smaller and smaller. Early computers filled entire rooms. Today you can hold one in the palm of your hand. Now the field of molecular electronics is taking miniaturization to the next level. Researchers are creating electronic components so tiny they can’t be seen with the naked eye.

Molecular electronics is a branch of nanotechnology that uses single molecules, or nanoscale collections of molecules, as electronic components. The purpose is to create miniature computing devices, replacing bulk materials with molecular blocks.

For instance, metal atoms can be made into nanoscale ‘molecular wires.’ Also known as Extended Metal Atom Chains (EMACs), molecular wires are one-dimensional chains of single metal atoms connected to an organic molecule, called a ligand, that acts as a support. Molecular wire-type compounds have a diverse array of potential uses, from LED lights to catalysts.

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have found a simple way to create copper molecular wires of different lengths by adding or removing copper atoms one by one. “This is the first example of a molecular copper wire being formed in a stepwise, atom-by-atom process,” says Julia Khusnutdinova, head of the OIST Coordination Chemistry and Catalysis Unit. “Our method can be compared to Lego construction in which you add one brick at a time,” she says.

A January 16, 2018 OIST press release (also on EurekAlert but with a January 17, 2018 date) by Sophie Protheroe, which originated the news item, adds detail,

Molecular wires can vary in length, with different lengths having different molecular properties and practical applications.  At present, the longest EMAC reported in the literature is based on nickel and it contains 11 metal atoms in a single linear chain.

The structure of the longest EMAC reported in the literature, confirmed by X-ray crystallography. It contains 11 nickel atoms arranged in a linear chain.

Creating molecular wires of different lengths is difficult because it requires a specific ligand to be synthesized each time. The ligand, which can be seen as an ‘insulator’ by analogy to the macro world, helps the wires to form by bringing the metal atoms together and aligning them into a linear string. However, creating ligands of different lengths can be an elaborate and complicated process.

The OIST researchers have found a new way to overcome this problem.  “We have created a single dynamic ligand that can be used to synthesize multiple chain lengths,” says Dr. Orestes Rivada-Wheelaghan, first author of the paper.  “This is much more efficient than making a new ligand each time,” he says.

In their paper, published in Angewandte Chemie International Edition, the researchers describe their new stepwise method of creating copper molecular wires.  “The ligand opens up from one end to let a metal atom enter and, when the chain extends, the ligand undergoes a sliding movement along the chain to accommodate more metal atoms,” says Prof. Khusnutdinova.  “This can be likened to a molecular accordion that can be extended and shortened,” says Rivada-Wheelaghan. By adding or removing copper atoms one at a time in this way, the researchers can construct molecular wires of different lengths, varying from 1 to 4 copper atoms.

A cartoon by Dr. Rivada-Wheelaghan shows the simple stepwise process of copper atom chain synthesis using a dynamic ligand. Copper atoms can be added or removed one by one to make chains of different lengths.

This dynamic ligand offers a new way for chemists to synthesize molecules with specific shapes and properties, creating potential for many practical applications in microelectronics and beyond.

“The next step is to develop dynamic ligands that could be used to create molecular wires made from other metals, or a combination of different metals,” says Dr. Rivada-Wheelaghan. “For example, by selectively inserting copper atoms at the termini of the chain, and using a different type of metal at the center of the chain, we could create new compounds with interesting electronic properties,” says Prof. Khusnutdinova.

I particularly enjoy the cartoon. Getting back to business, here’s a link to and a citation for the paper,

Controlled and Reversible Stepwise Growth of Linear Copper(I) Chains Enabled by Dynamic Ligand Scaffolds by Dr. Orestes Rivada-Wheelaghan, Sandra L. Aristizábal, Dr. Joaquín López-Serrano, Dr. Robert R. Fayzullin, and Prof. Julia R. Khusnutdinova. Angewandte Chemie International Edition Version of Record online: 23 NOV 2017 Volume 56, Issue 51, pages 16267–16271, December 18, 2017 DOI: 10.1002/anie.201709167

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Ukidama-structured nanoparticles discovered

The researchers discovered a new nanoparticle structure that resemble the ukidama, glass fishing floats, used regularly by Japanese fishermen. The nanoparticle has a core of one element (copper) and is surrounded by a “cage” of another element (silver). The silver does not cover certain areas of the copper core, which is very similar to the rope that surrounds the glass float. Courtesy: Okinawa Institute of Science and Technology (OIST)

The researchers discovered a new nanoparticle structure that resemble the ukidama, glass fishing floats, used regularly by Japanese fishermen. The nanoparticle has a core of one element (copper) and is surrounded by a “cage” of another element (silver). The silver does not cover certain areas of the copper core, which is very similar to the rope that surrounds the glass float. Courtesy: Okinawa Institute of Science and Technology (OIST)

What a beautiful image to illustrate the new ukidama nanoparticle structure! Here’s the announcement in a June 13, 2016 news item on ScienceDaily,

Sometimes it is the tiny things in the world that can make an incredible difference. One of these things is the nanoparticle. Nanoparticles may be small, but they have a variety of important applications in areas such as, medicine, manufacturing, and energy. A team of researchers from Okinawa Institute of Science and Technology Graduate University (OIST) recently discovered a unique copper-silver nanoparticle structure that has a core of one element surrounded by a “cage” of the other element. However, the cage does not cover certain areas of the core, which very much resembles the Japanese glass fishing floats traditionally covered with rope called ukidama.

This previously undiscovered ukidama structure may have properties that can help the team on their mission for optimal nanotechnology. …

A June 13, 2016 OIST press release by Rebecca Holland (also on EurekAlert; the June 12, 2016 publication date discrepancy is likely due to timezone issues), which originated the news item, provides more insight into the research team’s workings,

“The ukidama is a unique structure, which means that it can likely give us unique properties,” said Panagiotis Grammatikopoulos, first author and group leader of the OIST Nanoparticles by Design Unit. “The idea is that now that we know about this structure we may be able to fine tune it to our applications.”

The OIST researchers are continually working to create and design nanoparticles that can be used in biomedical technology. Specifically, the team works to design the optimal nanoparticles for technologies like smart gas sensors that can send information about what is going on inside your body to your smart phone for better diagnoses. Another application is the label free biosensor, a device that can detect chemical substances without the hindrance of fluorescent or radioactive labels. The identification of the ukidama structure is important in this endeavour because having a new structure increases the possibilities for technological advancements.

“The more parameters that we can control the more flexibility we have in our applications and devices,” Prof. Mukhles Sowwan, author and head of OIST’s Nanoparticles by Design Unit said. “Therefore, we need to optimize many properties of these nanoparticles: the size, chemical composition, crystallinity, shape, and structure.”

The discovery of the ukidama structure was found through sputtering copper and silver atoms simultaneously, but independently, through a magnetron-sputtering system at high temperatures. When the atoms began to cool they combined into bi-metallic nanoparticles. During the sputtering process, researchers could control the ratio of silver to copper, with the rate of power with which the atoms were sputtered. They found that the ukidama structure was possible, especially when the copper was the dominant element, since silver atoms have a higher tendency to diffuse on the nanoparticle surface. From their experimental findings, the team was able to create simulations that can clearly show how the ukidama nanoparticles form.

The team is now looking to see if this structure can be recreated in other types of nanoparticles, which could be an even bigger step in the optimization of nanoparticles for biomedical application and nanotechnology.

“We design and optimize nanoparticles for biomedical devices and nanotechnology,” Sowwan said. “Because the ukidama is a new structure, it may have properties that could be utilized in our applications.”

Co-author, Antony Galea, formerly of the Nanoparticles by Design Unit, was responsible for the experimental portion of this study and has since moved to OIST’s Technology and Licensing Section to help research – like this work being done with nanoparticles that can be utilized in applications – move into the market.

“Our aim is to take research created by OIST from the lab to the real world,” Galea said. “This is a way that work done at OIST, such as by the Nanoparticles by Design Unit, can benefit society.”

Here’s a link to and a citation for the paper,

Kinetic trapping through coalescence and the formation of patterned Ag–Cu nanoparticles by Panagiotis Grammatikopoulos, Joseph Kioseoglou, Antony Galea, Jerome Vernieres, Maria Benelmekki, Rosa E. Diaz, Mukhles Sowwan. Nanoscale, 2016; 8 (18): 9780 DOI: 10.1039/C5NR08256K

I believe this paper is behind a paywall.