Tag Archives: Japan

Scaling graphene production up to industrial strength

If graphene is going to be a ubiquitous material in the future, production methods need to change. An Aug. 7, 2015 news item on Nanowerk announces a new technique to achieve that goal,

Producing graphene in bulk is critical when it comes to the industrial exploitation of this exceptional two-dimensional material. To that end, [European Commission] Graphene Flagship researchers have developed a novel variant on the chemical vapour deposition process which yields high quality material in a scalable manner. This advance should significantly narrow the performance gap between synthetic and natural graphene.

An Aug. 7, 2015 European Commission Graphene Flagship press release by Francis Sedgemore, which originated the news item, describes the problem,

Media-friendly Nobel laureates peeling layers of graphene from bulk graphite with sticky tape may capture the public imagination, but as a manufacturing process the technique is somewhat lacking. Mechanical exfoliation may give us pristine graphene, but industry requires scalable and cost-effective production processes with much higher yields.

On to the new method (from the press release),

Flagship-affiliated physicists from RWTH Aachen University and Forschungszentrum Jülich have together with colleagues in Japan devised a method for peeling graphene flakes from a CVD substrate with the help of intermolecular forces. …

Key to the process is the strong van der Waals interaction that exists between graphene and hexagonal boron nitride, another 2d material within which it is encapsulated. The van der Waals force is the attractive sum of short-range electric dipole interactions between uncharged molecules.

Thanks to strong van der Waals interactions between graphene and boron nitride, CVD graphene can be separated from the copper and transferred to an arbitrary substrate. The process allows for re-use of the catalyst copper foil in further growth cycles, and minimises contamination of the graphene due to processing.

Raman spectroscopy and transport measurements on the graphene/boron nitride heterostructures reveals high electron mobilities comparable with those observed in similar assemblies based on exfoliated graphene. Furthermore – and this comes as something of a surprise to the researchers – no noticeable performance changes are detected between devices developed in the first and subsequent growth cycles. This confirms the copper as a recyclable resource in the graphene fabrication process.

“Chemical vapour deposition is a highly scalable and cost-efficient technology,” says Christoph Stampfer, head of the 2nd Institute of Physics A in Aachen, and co-author of the technical article. “Until now, graphene synthesised this way has been significantly lower in quality than that obtained with the scotch-tape method, especially when it comes to the material’s electronic properties. But no longer. We demonstrate a novel fabrication process based on CVD that yields ultra-high quality synthetic graphene samples. The process is in principle suitable for industrial-scale production, and narrows the gap between graphene research and its technological applications.”

With their dry-transfer process, Banszerus and his colleagues have shown that the electronic properties of CVD-grown graphene can in principle match those of ultrahigh-mobility exfoliated graphene. The key is to transfer CVD graphene from its growth substrate in such a way that chemical contamination is avoided. The high mobility of pristine graphene is thus preserved, and the approach allows for the substrate material to be recycled without degradation.

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

Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper by Luca Banszerus, Michael Schmitz, Stephan Engels, Jan Dauber, Martin Oellers, Federica Haupt, Kenji Watanabe, Takashi Taniguchi, Bernd Beschoten, and Christoph Stampfer. Science Advances  31 Jul 2015: Vol. 1, no. 6, e1500222 DOI: 10.1126/sciadv.1500222

This article appears to be open access.

For those interested in finding out more about chemical vapour deposition (CVD), David Chandler has written a June 19, 2015 article for the Massachusetts Institute of Technology (MIT) titled:  Explained: chemical vapor deposition (Technique enables production of pure, uniform coatings of metals or polymers, even on contoured surfaces.)

Spins in artificial atoms same as spin in natural atoms

I wonder what impact this research on the spin in artificial and natural atoms will have on how we view the word ‘artificial’. (If artificial molecules/atoms are indistinguishable from natural ones, what does it mean to be artificial?)

An Aug. 7, 2015 news item on Nanowerk describes the finding about spin,

By extending the study of coupled quantum dots to five-electron systems, RIKEN [Japan] researchers have confirmed that the spin-based electron-filling rules for natural atoms apply to artificial molecules …

Systems consisting of electrons and semiconductor quantum dots—nanostructures that exhibit quantum properties—are highly intriguing artificial structures that in many ways mimic naturally occurring atoms. For example, electrons occupy the energy levels of quantum dots according to the same rules that determine how electrons fill atomic shells. Such systems are of both fundamental interest, for investigating phenomena related to nuclear spin, and applied interest, for manipulating spin in future quantum computers.

The Pauli exclusion principle, which prohibits any two electrons in an atom from having identical sets of quantum numbers, gives rise to a phenomenon known as the Pauli spin blockade in quantum-dot systems. This effect prevents electrons from following certain energetically favorable paths through a quantum-dot system since two electrons with the same spin cannot occupy the same energy level.
The Pauli spin blockade has been well studied in artificial molecules consisting of two quantum dots and two electrons. Shinichi Amaha and Seigo Tarucha from RIKEN’s Center for Emergent Matter Science, in collaboration with researchers in Japan and Canada, have extended the study of spin blockade to multilevel quantum-dot systems that have more than two electrons. This requires accessing high-spin states, which is difficult to achieve in practice.

TG Techno’s Aug. 7, 2015 posting of the identical news item fills in more details,

Using a two-quantum-dot system with three effective levels, the researchers have achieved spin blockade by exploiting Hund’s first rule, which dictates that electrons in an atom will first fill unoccupied orbitals of a subshell with greater total spin state. They used this principle to prepare the high-spin states needed for spin blockade …

The team discovered that the current of the device varied unexpectedly with the applied magnetic field. In most devices with spin effects, the current lags behind changes to the magnetic field, a phenomenon known as hysteresis. The researchers found that the hysteresis of their system follows the expected spin states based on a consideration of Hund’s rule and that in certain magnetic field regions two hysteresis effects cancelled each other out—clear evidence that competing ‘up’ and ‘down’ nuclear spin pumping processes influence the current.

These findings are expected to open the way to use arrays of such quantum dots as simulators for spin filling in real molecules. “Using an array of quantum dots as artificial atoms could assist investigations of novel spin-related phenomena in real molecules,” says Amaha.

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

Vanishing current hysteresis under competing nuclear spin pumping processes in a quadruplet spin-blockaded double quantum dot by  S. Amaha, T. Hatano, S. Tarucha, J. A. Gupta, and D. G. Austing. Appl. Phys. Lett. 106, 172401 (2015); http://dx.doi.org/10.1063/1.4919101

This paper is behind a paywall.

Canada and some graphene scene tidbits

For a long time It seemed as if every country in the world, except Canada, had some some sort of graphene event. According to a July 16, 2015 news item on Nanotechnology Now, Canada has now stepped up, albeit, in a peculiarly Canadian fashion. First the news,

Mid October [Oct. 14 -16, 2015], the Graphene & 2D Materials Canada 2015 International Conference & Exhibition (www.graphenecanada2015.com) will take place in Montreal (Canada).

I found a July 16, 2015 news release (PDF) announcing the Canadian event on the lead organizer’s (Phantoms Foundation located in Spain) website,

On the second day of the event (15th October, 2015), an Industrial Forum will bring together top industry leaders to discuss recent advances in technology developments and business opportunities in graphene commercialization.
At this stage, the event unveils 38 keynote & invited speakers. On the Industrial Forum 19 of them will present the latest in terms of Energy, Applications, Production and Worldwide Initiatives & Priorities.

Plenary:
Gary Economo (Grafoid Inc., Canada)
Khasha Ghaffarzadeh (IDTechEx, UK)
Shu-Jen Han (IBM T.J. Watson Research Center, USA)
Bor Z. Jang (Angstron Materials, USA)
Seongjun Park (Samsung Advanced Institute of Technology (SAIT), Korea)
Chun-Yun Sung (Lockheed Martin, USA)

Parallel Sessions:
Gordon Chiu (Grafoid Inc., Canada)
Jesus de la Fuente (Graphenea, Spain)
Mark Gallerneault (ALCERECO Inc., Canada)
Ray Gibbs (Haydale Graphene Industries, UK)
Masataka Hasegawa (AIST, Japan)
Byung Hee Hong (SNU & Graphene Square, Korea)
Tony Ling (Jestico + Whiles, UK)
Carla Miner (SDTC, Canada)
Gregory Pognon (THALES Research & Technology, France)
Elena Polyakova (Graphene Laboratories Inc, USA)
Federico Rosei (INRS–EMT, Université du Québec, Canada)
Aiping Yu (University of Waterloo, Canada)
Hua Zhang (MSE-NTU, Singapore)

Apart from the industrial forum, several industry-related activities will be organized:
– Extensive thematic workshops in parallel (Standardization, Materials & Devices Characterization, Bio & Health and Electronic Devices)
– An exhibition carried out with the latest graphene trends (Grafoid, RAYMOR NanoIntegris, Nanomagnetics Instruments, ICEX and Xerox Research Centre of Canada (XRCC) already confirmed)
– B2B meetings to foster technical cooperation in the field of Graphene

It’s still possible to contribute to the event with an oral presentation. The call for abstracts is open until July, 20 [2015]. [emphasis mine]

Graphene Canada 2015 is already supported by Canada’s leading graphene applications developer, Grafoid Inc., Tourisme Montréal and Université de Montréal.

This is what makes the event peculiarly Canadian: multiculturalism, anyone? From the news release,

Organisers: Phantoms Foundation www.phantomsnet.net & Grafoid Foundation (lead organizers)

CEMES/CNRS (France) | Grafoid (Canada) | Catalan Institute of Nanoscience and Nanotechnology – ICN2 (Spain) | IIT (Italy) | McGill University, Canada | Texas Instruments (USA) | Université Catholique de Louvain (Belgium) | Université de Montreal, Canada

It’s billed as a ‘Canada Graphene 2015’ and, as I recall, these types of events don’t usually have so many other countries listed as organizers. For example, UK Graphene 2015 would have mostly or all of its organizers (especially the leads) located in the UK.

Getting to the Canadian content, I wrote about Grafoid at length tracking some of its relationships to companies it owns, a business deal with Hydro Québec, and a partnership with the University of Waterloo, and a nonrepayable grant from the Canadian federal government (Sustainable Development Technology Canada [SDTC]) in a Feb. 23, 2015 posting. Do take a look at the post if you’re curious about the heavily interlinked nature of the Canadian graphene scene and take another look at the list of speakers and their agencies (Mark Gallerneault of ALCERECO [partially owned by Grafoid], Carla Miner of SDTC [Grafoid received monies from the Canadian federal department],  Federico Rosei of INRS–EMT, Université du Québec [another Quebec link], Aiping Yu, University of Waterloo [an academic partner to Grafoid]). The Canadian graphene community is a small one so it’s not surprising there are links between the Canadian speakers but it does seem odd that Lomiko Metals is not represented here. Still, new speakers have been announced since the news release (e.g., Frank Koppens of ICFO, Spain, and Vladimir Falko of Lancaster University, UK) so  time remains.

Meanwhile, Lomiko Metals has announced in a July 17, 2015 news item on Azonano that Graphene 3D labs has changed the percentage of its outstanding shares affecting the percentage that Lomiko owns, amid some production and distribution announcements. The bit about launching commercial sales of its graphene filament seems more interesting to me,

On March 16, 2015 Graphene 3D Lab (TSXV:GGG) (OTCQB:GPHBF) announced that it launched commercial sales of its Conductive Graphene Filament for 3D printing. The filament incorporates highly conductive proprietary nano-carbon materials to enhance the properties of PLA, a widely used thermoplastic material for 3D printing; therefore, the filament is compatible with most commercially available 3D printers. The conductive filament can be used to print conductive traces (similar to as used in circuit boards) within 3D printed parts for electronics.

So, that’s all I’ve got for Canada’s graphene scene.

Do artists see colour at the nanoscale? It would seem so

I’ve wondered how Japanese artists of the 16th to 18th centuries were able to beat gold down to the nanoscale for application to screens. How could they see what they were doing? I may have an answer at last. According to some new research, it seems that the human eye can detect colour at the nanoscale.

Before getting to the research, here’s the Namban screen story.

Japanese Namban Screen. ca. 1550. In Portugal-Japão: 450 anos de memórias. Embaixada de Portugal no Japão, 1993. [downloaded from http://www.indiana.edu/~liblilly/digital/exhibitions/exhibits/show/portuguese-speaking-diaspora/china-and-japan]

Japanese Namban Screen. ca. 1550. In Portugal-Japão: 450 anos de memórias. Embaixada de Portugal no Japão, 1993. [downloaded from http://www.indiana.edu/~liblilly/digital/exhibitions/exhibits/show/portuguese-speaking-diaspora/china-and-japan]

This image is from an Indiana University at Bloomington website featuring a page titled, Portuguese-Speaking Diaspora,

A detail from one of four large folding screens on display in the Museu de Arte Antiga in Lisbon. Namban was the word used to refer to Portuguese traders who, in this scene, are dressed in colorful pantaloons and accompanied by African slaves. Jesuits appear in black robes, while the Japanese observe the newcomers from inside their home. The screen materials included gold-covered copper and paper, tempera paint, silk, and lacquer.

Copyright © 2015 The Trustees of Indiana University

Getting back to the Japanese artists, here’s how their work was described in a July 2, 2014 Springer press release on EurekAlert,

Ancient Japanese gold leaf artists were truly masters of their craft. An analysis of six ancient Namban paper screens show that these artifacts are gilded with gold leaf that was hand-beaten to the nanometer scale. [emphasis mine] Study leader Sofia Pessanha of the Atomic Physics Center of the University of Lisbon in Portugal believes that the X-ray fluorescence technique her team used in the analysis could also be used to date other artworks without causing any damage to them. The results are published in Springer’s journal Applied Physics A: Materials Science & Processing.

Gold leaf refers to a very thin sheet made from a combination of gold and other metals. It has almost no weight and can only be handled by specially designed tools. Even though the ancient Egyptians were probably the first to gild artwork with it, the Japanese have long been credited as being able to produce the thinnest gold leaf in the world. In Japanese traditional painting, decorating with gold leaf is named Kin-haku, and the finest examples of this craft are the Namban folding screens, or byobu. These were made during the late Momoyama (around 1573 to 1603) and early Edo (around 1603 to 1868) periods.

Pessanha’s team examined six screens that are currently either part of a museum collection or in a private collection in Portugal. Four screens belong to the Momoyama period, and two others were decorated during the early Edo period. The researchers used various X-ray fluorescence spectroscopy techniques to test the thickness and characteristics of the gold layers. The method is completely non-invasive, no samples needed to be taken, and therefore the artwork was not damaged in any way. Also, the apparatus needed to perform these tests is portable and can be done outside of a laboratory.

The gilding was evaluated by taking the attenuation or weakening of the different characteristic lines of gold leaf layers into account. The methodology was tested to be suitable for high grade gold alloys with a maximum of 5 percent influence of silver, which is considered negligible.

The two screens from the early Edo period were initially thought to be of the same age. However, Pessanha’s team found that gold leaf on a screen kept at Museu Oriente in Lisbon was thinner, hence was made more recently. This is in line with the continued development of the gold beating techniques carried out in an effort to obtain ever thinner gold leaf.

So, how did these artists beat gold leaf down to the nanoscale and then use the sheets in their art work? This July 10, 2015 news item on Azonano may help to answer that question,

The human eye is an amazing instrument and can accurately distinguish between the tiniest, most subtle differences in color. Where human vision excels in one area, it seems to fall short in others, such as perceiving minuscule details because of the natural limitations of human optics.

In a paper published today in The Optical Society’s new, high-impact journal Optica, a research team from the University of Stuttgart, Germany and the University of Eastern Finland, Joensuu, Finland, has harnessed the human eye’s color-sensing strengths to give the eye the ability to distinguish between objects that differ in thickness by no more than a few nanometers — about the thickness of a cell membrane or an individual virus.

A July 9, 2015 Optical Society news release (also on EurkeAlert), which originated the news item, provides more details,

This ability to go beyond the diffraction limit of the human eye was demonstrated by teaching a small group of volunteers to identify the remarkably subtle color differences in light that has passed through thin films of titanium dioxide under highly controlled and precise lighting conditions. The result was a remarkably consistent series of tests that revealed a hitherto untapped potential, one that rivals sophisticated optics tools that can measure such minute thicknesses, such as ellipsometry.

“We were able to demonstrate that the unaided human eye is able to determine the thickness of a thin film — materials only a few nanometers thick — by simply observing the color it presents under specific lighting conditions,” said Sandy Peterhänsel, University of Stuttgart, Germany and principal author on the paper. The actual testing was conducted at the University of Eastern Finland.

The Color and Thickness of Thin Films

Thin films are essential for a variety of commercial and manufacturing applications, including anti-reflective coatings on solar panels. These films can be as small as a few to tens of nanometers thick. The thin films used in this experiment were created by applying layer after layer of single atoms on a surface. Though highly accurate, this is a time-consuming procedure and other techniques like vapor deposition are used in industry.

The optical properties of thin films mean that when light interacts with their surfaces it produces a wide range of colors. This is the same phenomenon that produces scintillating colors in soap bubble and oil films on water.

The specific colors produced by this process depend strongly on the composition of the material, its thickness, and the properties of the incoming light. This high sensitivity to both the material and thickness has sometimes been used by skilled engineers to quickly estimate the thickness of films down to a level of approximately 10-20 nanometers.

This observation inspired the research team to test the limits of human vision to see how small of a variation could be detected under ideal conditions.

“Although the spatial resolving power of the human eye is orders of magnitude too weak to directly characterize film thicknesses, the interference colors are well known to be very sensitive to variations in the film,” said Peterhänsel.

Experimental Setup

The setup for this experiment was remarkably simple. A series of thin films of titanium dioxide were manufactured one layer at a time by atomic deposition. While time consuming, this method enabled the researchers to carefully control the thickness of the samples to test the limitations of how small a variation the research subjects could identify.

The samples were then placed on a LCD monitor that was set to display a pure white color, with the exception of a colored reference area that could be calibrated to match the apparent surface colors of the thin films with various thicknesses.

The color of the reference field was then changed by the test subject until it perfectly matched the reference sample: correctly identifying the color meant they also correctly determined its thickness. This could be done in as little as two minutes, and for some samples and test subjects their estimated thickness differed only by one-to-three nanometers from the actual value measured by conventional means. This level of precision is far beyond normal human vision.

Compared to traditional automated methods of determining the thickness of a thin film, which can take five to ten minutes per sample using some techniques, the human eye performance compared very favorably.

Since human eyes tire very easily, this process is unlikely to replace automated methods. It can, however, serve as a quick check by an experienced technician. “The intention of our study never was solely to compare the human color vision to much more sophisticated methods,” noted Peterhänsel. “Finding out how precise this approach can be was the main motivation for our work.”

The researchers speculate that it may be possible to detect even finer variations if other control factors are put in place. “People often underestimate human senses and their value in engineering and science. This experiment demonstrates that our natural born vision can achieve exceptional tasks that we normally would only assign to expensive and sophisticated machinery,” concludes Peterhänsel.

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

Human color vision provides nanoscale accuracy in thin-film thickness characterization by Sandy Peterhänsel, Hannu Laamanen, Joonas Lehtolahti, Markku Kuittinen, Wolfgang Osten, and Jani Tervo. Optica Vol. 2, Issue 7, pp. 627-630 (2015) •doi: 10.1364/OPTICA.2.000627

This article appears to be open access.

It would seem that the artists creating the Namban screens exploited the ability to see at the nanoscale, which leads me to  wonder how many people who work with color/colour all the time such as visual artists, interior designers, graphic designers, printers, and more can perceive at the nanoscale. These German and Finnish researchers may want to work with some of these professionals in their next study.

Repeating patterns: earth’s daily rotation cycle seen in protein

This story made me think of fractals where a pattern at one scale is repeated at a smaller scale. Here’s more about the earth’s rotation and the protein from a June 25, 2015 news item on ScienceDaily,

A collaborative group of Japanese researchers has demonstrated that the Earth’s daily rotation period (24 hours) is encoded in the KaiC protein at the atomic level, a small, 10 nm-diameter biomolecule expressed in cyanobacterial cells.

For anyone who’s unfamiliar (me) with cyanobacteria, here’s a definition from its Wikipedia entry (Note: Links have been removed),

Cyanobacteria /saɪˌænoʊbækˈtɪəriə/, also known as Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis.[3] The name “cyanobacteria” comes from the color of the bacteria (Greek: κυανός (kyanós) = blue). They are often called blue-green algae (but some consider that name a misnomer, as cyanobacteria are prokaryotic and algae should be eukaryotic,[4] although other definitions of algae encompass prokaryotic organisms).[5]

By producing gaseous oxygen as a byproduct of photosynthesis, cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one, causing the “rusting of the Earth”[6] and dramatically changing the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of oxygen-intolerant organisms. According to endosymbiotic theory, the chloroplasts found in plants and eukaryotic algae evolved from cyanobacterial ancestors via endosymbiosis.

The idea that cyanobacteria may have changed the earth’s atmosphere into an oxidizing one and stimulating biodiversity is fascinating to me. Plus, cyanobacteria are pretty,

    CC BY-SA 3.0     File:Tolypothrix (Cyanobacteria).JPG     Uploaded by Matthewjparker     Created: January 22, 2013     Location: 29° 38′ 58.2″ N, 82° 20′ 40.8″ W [downloaded from https://en.wikipedia.org/wiki/Cyanobacteria]

CC BY-SA 3.0
File:Tolypothrix (Cyanobacteria).JPG
Uploaded by Matthewjparker
Created: January 22, 2013
Location: 29° 38′ 58.2″ N, 82° 20′ 40.8″ W [downloaded from https://en.wikipedia.org/wiki/Cyanobacteria]

A June 26, 2015 Japan National Institute of Natural Sciences, which originated the news item, provides more information,

The results of this joint research will help elucidate a longstanding question in chronobiology: How is the circadian period of biological clocks determined? The results will also help understand the basic molecular mechanism of the biological clock. This knowledge might contribute to the development of therapies for disorders associated with abnormal circadian rhythms.

The results will be disclosed online on June 25, 2015 (North American Eastern Standard Time) in ScienceExpress, the electronic version of Science, published by the American Association for the Advancement of Science (AAAS).
1. Research Background

In accordance with diurnal changes in the environment (notably light intensity and temperature) resulting from the Earth’s daily rotation around its axis, many organisms regulate their biological activities to ensure optimal fitness and efficiency. The biological clock refers to the mechanism whereby organisms adjust the timing of their biological activities. The period of this clock is set to approximately 24 hours. A wide range of studies have investigated the biological clock in organisms ranging from bacteria to mammals. Consequently, the relationship between the biological clock and multiple diseases has been clarified. However, it remains unclear how 24-hour circadian rhythms are implemented.

The research group mentioned above addressed this question using cyanobacteria. The cyanobacterial circadian clock can be reconstructed by mixing three clock proteins (KaiA, KaiB, and KaiC) and ATP. A study published in 2007 showed that KaiC ATPase activity, which mediates the ATP hydrolysis reaction, is strongly associated with circadian periodicity. The results of that study indicated that the functional structure of KaiC could be responsible for determining the circadian rhythm.

150626_en1.jpg

Figure 1  Earth and the circadian clock protein KaiC
2. Research Results

KaiC ATPase activity exhibits a robust circadian oscillation in the presence of KaiA and KaiB proteins (Figure 2). In the study reported here, the temporal profile of KaiC ATPase activity exhibited an attenuating and oscillating component even in the absence of KaiA and KaiB. A close analysis revealed that this signal had a frequency of 0.91 day-1, which approximately coincided with the 24-hour period. Thus, KaiC is the source of a steady cycle that is in tune with the Earth’s daily rotation.
150626_en2.jpg

Figure 2  KaiC ATPase activity-time profile
To identify causal structural factors, the N-terminal domain of KaiC was analyzed using high-resolution crystallography. The resultant atomic structures revealed the underlying cause of KaiC’s slowness relative to other ATPases (Figure 3). “A water molecule is prevented from attacking into the ideal position (a black dot in Figure 3) for the ATP hydrolysis by a steric hindrance near ATP phosphoryl groups. In addition, this hindrance is surely anchored to a spring-like structure derived from polypeptide isomerization,” elaborates Dr. Jun Abe. “The ATP hydrolysis, which involves access of a water molecule to the bound ATP and reverse isomerization of the polypeptide, is expected to require a significantly larger amount of free energy than for typical ATP hydrolysis. Thus, the three-dimensional atomic structure discovered in this study explains why the ATPase activity of KaiC is so much lower (by 100- to 1,000,000-fold) than that of typical ATPase molecules.”

150626_en3.jpgFigure 3  Structural basis for steady slowness. The steric barrier prevents access of a water molecule to the catalytic site (indicated by a black dot).

The circadian clock’s period is independent of ambient temperature, a phenomenon known as temperature compensation. One KaiC molecule is composed of six identical subunits, each containing duplicated domains with a series of ATPase motifs. The asymmetric atomic-scale regulation by the aforementioned mechanism dictates a feedback mechanism that maintains the ATPase activity at a constant low level. The authors of this study discovered that the Earth’s daily rotation period (24 hours) is implemented as the time constant of the feedback mechanism mediated in this protein structure.

3. Technological Implications

KaiC and other protein molecules are capable of moving on short time scales, on the order of 10-12 to 10-1 seconds. This study provides the first atomic-level demonstration that small protein molecules can generate 24-hour rhythms by regulating molecular structure and reactivity. Lab head and CIMoS Director Prof. Shuji Akiyama sees, “The fact that a water molecule, ATP, the polypeptide chain, and other universal biological components are involved in this regulation suggests that humans and other complex organisms may also share a similar molecular machinery. In the crowded intracellular environment that contains a myriad of molecular signals, KaiC demonstrates long-paced oscillations using a small amount of energy generated through ATP consumption. This clever mechanism for timekeeping in a noisy environment may inspire development of highly efficient and sustainable chemical reaction processes and molecular-system-based information processing.”
4. Glossary

1) Clock protein
A clock protein plays an essential role in the circadian pacemaker. Mutations and deficiencies in clock proteins can alter the intrinsic characteristics of circadian rhythm.

2) ATP
Adenosine triphosphate is a source of energy required for muscle contraction and many other biological activities. ATP, a nucleotide that mediates the storage and consumption of energy, is sometimes referred to as the “currency of biological energy” due to its universality and importance in metabolism. ATP consists of an adenosine molecule bound to three phosphate groups. Upon hydrolysis, the ATPase releases one phosphate molecule plus approximately 8 kcal/mol of energy.

3) Polypeptide isomerization
Protein polypeptide main chains undergo isomerization on a time scale of seconds or longer; therefore, protein isomerization is one of the slowest biological reactions. Most functional protein main chains have a trans conformation, and a few proteins have a functional cis conformation.

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

Atomic-scale origins of slowness in the cyanobacterial circadian clock by Jun Abe, Takuya B. Hiyama, Atsushi Mukaiyama, Seyoung Son, Toshifumi Mori, Shinji Saito, Masato Osako, Julie Wolanin, Eiki Yamashita, Takao Kondo, & Shuji Akiyama. Science DOI: 10.1126/science.1261040 Published Online June 25 2015 (on Science Express)

This paper is behind a paywall.

Kudos to the person(s) who wrote the news release.

Japanese researchers note the emergence of the ‘Devil’s staircase’

I wanted to know why it’s called the ‘Devil’s staircase’ and this is what I found. According to Wikipedia there are several of them,

I gather the scientists are referring to the Cantor function (mathematics), Note: Links have been removed,

In mathematics, the Cantor function is an example of a function that is continuous, but not absolutely continuous. It is also referred to as the Cantor ternary function, the Lebesgue function, Lebesgue’s singular function, the Cantor-Vitali function, the Devil’s staircase,[1] the Cantor staircase function,[2] and the Cantor-Lebesgue function.[3]

Here’s a diagram illustrating the Cantor function (from the Wikipedia entry),

CC BY-SA 3.0 File:CantorEscalier.svg Uploaded by Theon Created: January 24, 2009

CC BY-SA 3.0
File:CantorEscalier.svg
Uploaded by Theon
Created: January 24, 2009

As for this latest ‘Devil’s staircase’, a June 17, 2015 news item on Nanowerk announces the research (Note: A link has been removed),

Researchers at the University of Tokyo have revealed a novel magnetic structure named the “Devil’s staircase” in cobalt oxides using soft X-rays (“Observation of a Devil’s Staircase in the Novel Spin-Valve System SrCo6O11“). This is an important result since the researchers succeeded in determining the detailed magnetic structure of a very small single crystal invisible to the human eye.

A June 17, 2015 University of Tokyo press release, which originated the news item on Nanowerk, describes why this research is now possible and the impact it could have,

Recent remarkable progress in resonant soft x-ray diffraction performed in synchrotron facilities has made it possible to determine spin ordering (magnetic structure) in small-volume samples including thin films and nanostructures, and thus is expected to lead not only to advances in materials science but also application to spintronics, a technology which is expected to form the basis of future electronic devices. Cobalt oxide is known as one material that is suitable for spintronics applications, but its magnetic structure was not fully understood.

The research group of Associate Professor Hiroki Wada at the University of Tokyo Institute for Solid State Physics, together with the researchers at Kyoto University and in Germany, performed a resonant soft X-ray diffraction study of cobalt (Co) oxides in the synchrotron facility BESSY II in Germany. They observed all the spin orderings which are theoretically possible and determined how these orderings change with the application of magnetic fields. The plateau-like behavior of magnetic structure as a function of magnetic field is called the “Devil’s staircase,” and is the first such discovery in spin systems in 3D transition metal oxides including cobalt, iron, manganese.

By further resonant soft X-ray diffraction studies, one can expect to find similar “Devil’s staircase” behavior in other materials. By increasing the spatial resolution of microscopic observation of the “Devil’s staircase” may lead to the development of novel types of spintronics materials.

Here’s an example of the ‘cobalt’ Devil’s staircase,

The magnetic structure that gives rise to the Devil's Staircase Magnetization (vertical axis) of cobalt oxide shows plateau like behaviors as a function of the externally-applied magnetic field (horizontal axis). The researchers succeeded in determining the magnetic structures which create such plateaus. Red and blue arrows indicate spin direction. © 2015 Hiroki Wadati.

The magnetic structure that gives rise to the Devil’s Staircase
Magnetization (vertical axis) of cobalt oxide shows plateau like behaviors as a function of the externally-applied magnetic field (horizontal axis). The researchers succeeded in determining the magnetic structures which create such plateaus. Red and blue arrows indicate spin direction.
© 2015 Hiroki Wadati.

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

Observation of a Devil’s Staircase in the Novel Spin-Valve System SrCo6O11 by T. Matsuda, S. Partzsch, T. Tsuyama, E. Schierle, E. Weschke, J. Geck, T. Saito, S. Ishiwata, Y. Tokura, and H. Wadati. Phys. Rev. Lett. 114, 236403 – Published 11 June 2015 (paper: Vol. 114, Iss. 23 — 12 June 2015)  DOI: 10.1103/PhysRevLett.114.236403

This paper is behind a paywall.

Metallic nanoparticles: measuring their discrete quantum states

I tend to forget how new nanotechnology is and unconsciously take for granted stunning feats such as measuring a metallic nanoparticle’s electronic properties. A June 15, 2015 news item on Nanowerk provides a reminder with its description of the difficulties and a new technique to make it easier (Note:  A link has been removed),

How do you measure the electronic properties of individual nanoparticles or molecules that are only a few nanometers in size? Conventional methods using electron transport spectroscopy rely on contacting a material with two contacts, a source and a drain electrode. By applying a small potential difference over the electrodes and monitoring the resulting current, valuable information about the electronic properties are extracted. For example if a material is metallic or semiconducting.
But this becomes quite a challenge if the material is only a few nm in size. Even the most sophisticated fabrication tools such as electron-beam lithography have a resolution of about 10 nm at best, which is not precise enough. Scientists have developed workarounds such as creating small gaps in narrow metallic wires in which a nanoparticle can be trapped if it matches the gap size. However, even though there have been some notable successes using this approach, this method has a low yield and is not very reproducible.

Now an international collaboration including researchers in Japan, the university [sic] of Cambridge and the LCN [London Centre for Nanotechnology] in the UK have approached this in a different way as described in a paper in Nature’s Scientific Reports (“Radio-frequency capacitance spectroscopy of metallic nanoparticles”). Their method only requires a single electrode to be in direct contact with a nanoparticle or molecule, thus significantly simplifying fabrication.

A June 15, 2015 (?) LCN press release, which originated the news item, describes the achievement,

The researchers demonstrated the potential of the radio-frequency reflectometry technique by measurements on Au nanoparticles of only 2.7 nm in diameter. For such small particles, the electronic spectrum is discrete which was indeed observed in the measurements and in very good agreement with theoretical models. The researchers now plan to extend these measurements to other nanoparticles and molecules with applications in a range of areas such as biomedicine, spintronics and quantum information processing.

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

Radio-frequency capacitance spectroscopy of metallic nanoparticles by James C. Frake, Shinya Kano, Chiara Ciccarelli, Jonathan Griffiths, Masanori Sakamoto,  Toshiharu Teranishi, Yutaka Majima, Charles G. Smith & Mark R. Buitelaar. Scientific RepoRts 5:10858 DOi: 10.1038/srep10858 Published June 4, 2015

This is an open access paper.

Magnetic sensitivity under the microscope

Humans do not have the sense of magnetoreception (the ability to detect magnetic fields) unless they’ve been enhanced. On the other hand, species of fish, insects, birds, and some mammals (other than human) possess the sense naturally. Scientists at the University of Tokyo (Japan) have developed a microscope capable of observing magnetoreception according to a June 4, 2015 news item on Nanowerk (Note: A link has been removed),

Researchers at the University of Tokyo have succeeded in developing a new microscope capable of observing the magnetic sensitivity of photochemical reactions believed to be responsible for the ability of some animals to navigate in the Earth’s magnetic field, on a scale small enough to follow these reactions taking place inside sub-cellular structures (Angewandte Chemie International Edition, “Optical Absorption and Magnetic Field Effect Based Imaging of Transient Radicals”).

A June 4, 2015 University of Tokyo news release on EurekAlert, which originated the news item, describes the research in more detail,

Several species of insects, fish, birds and mammals are believed to be able to detect magnetic fields – an ability known as magnetoreception. For example, birds are able to sense the Earth’s magnetic field and use it to help navigate when migrating. Recent research suggests that a group of proteins called cryptochromes and particularly the molecule flavin adenine dinucleotide (FAD) that forms part of the cryptochrome, are implicated in magnetoreception. When cryptochromes absorb blue light, they can form what are known as radical pairs. The magnetic field around the cryptochromes determines the spins of these radical pairs, altering their reactivity. However, to date there has been no way to measure the effect of magnetic fields on radical pairs in living cells.

The research group of Associate Professor Jonathan Woodward at the Graduate School of Arts and Sciences are specialists in radical pair chemistry and investigating the magnetic sensitivity of biological systems. In this latest research, PhD student Lewis Antill made measurements using a special microscope to detect radical pairs formed from FAD, and the influence of very weak magnetic fields on their reactivity, in volumes less than 4 millionths of a billionth of a liter (4 femtoliters). This was possible using a technique the group developed called TOAD (transient optical absorption detection) imaging, employing a microscope built by postdoctoral research associate Dr. Joshua Beardmore based on a design by Beardmore and Woodward.

“In the future, using another mode of the new microscope called MIM (magnetic intensity modulation), also introduced in this work, it may be possible to directly image only the magnetically sensitive regions of living cells,” says Woodward. “The new imaging microscope developed in this research will enable the study of the magnetic sensitivity of photochemical reactions in a variety of important biological and other contexts, and hopefully help to unlock the secrets of animals’ miraculous magnetic sense.”

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

Optical Absorption and Magnetic Field Effect Based Imaging of Transient Radicals by Dr. Joshua P. Beardmore, Lewis M. Antill, and Prof. Jonathan R. Woodward. Angewandte Chemie International Edition DOI: 10.1002/anie.201502591 Article first published online: 3 JUN 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

I mentioned human enhancement earlier with regard to magnetoreception. There are people (body hackers) who’ve had implants that give them this extra sense. Dann Berg in a March 21, 2012 post on his website blog (iamdann.com) describes why he implanted a magnet into his finger and his experience with it (at that time, three years and counting),

I quickly learned that magnetic surfaces provided almost no sensation at all. Rather, it was movement that caused my finger to perk up. Things like power cord transformers, microwaves, and laptop fans became interactive in a whole new way. Each object has its own unique field, with different strength and “texture.” I started holding my finger over almost everything that I could, getting a feeling for each object’s invisible reach.

Portable electronics proved to be an experience as well. There were two fairly large electronic items that hit the shelves around the same time as I got my implant: the first iPad and the Kindle 2.

Something to consider,

Courtesy: iamdann.com (Dann Berg)

Courtesy: iamdann.com (Dann Berg)

Policing, detecting, and arresting pollution

The title for a May 13, 2015 news item on ScienceDaily was certainly eye-catching,

Nano-policing pollution

Pollutants emitted by factories and car exhausts affect humans who breathe in these harmful gases and also aggravate climate change up in the atmosphere. Being able to detect such emissions is a critically needed measure.

New research by the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), in collaboration with the Materials Center Leoben Austria and the Austrian Centre for Electron Microscopy and Nanoanalysis has developed an efficient way to improve methods for detecting polluting emissions using a sensor at the nanoscale. …

A May 13, 2015 OIST press release (also on EurekAlert) by Joykrit Mitra, which originated the news item, details the research (Note: A link has been removed),

The researchers used a copper oxide nanowire decorated with palladium nanoparticles to detect carbon monoxide, a common industrial pollutant.  The sensor was tested in conditions similar to ambient air since future devices developed from this method will need to operate in these conditions.

Copper oxide is a semiconductor and scientists use nanowires fabricated from it to search for potential application in the microelectronics industry. But in gas sensing applications, copper oxide was much less widely investigated compared to other metal oxide materials.

A semiconductor can be made to experience dramatic changes in its electrical properties when a small amount of foreign atoms are made to attach to its surface at high temperatures.  In this case, the copper oxide nanowire was made part of an electric circuit. The researchers detected carbon monoxide indirectly, by measuring the change in the resulting circuit’s electrical resistance in presence of the gas. They found that copper oxide nanowires decorated with palladium nanoparticles show a significantly greater increase in electrical resistance in the presence of carbon monoxide than the same type of nanowires without the nanoparticles.

The OIST Nanoparticles by Design Unit used a sophisticated technique that allowed them to first sift nanoparticles according to size, then deliver and deposit the palladium nanoparticles onto the surface of the nanowires in an evenly distributed manner. This even dispersion of size selected nanoparticles and the resulting nanoparticles-nanowire interactions are crucial to get an enhanced electrical response.  The OIST nanoparticle deposition system can be tailored to deposit multiple types of nanoparticles at the same time, segregated on distinct areas of the wafer where the nanowire sits. In other words, this system can be engineered to be able to detect multiple kinds of gases.  The next step is to detect different gases at the same time by using multiple sensor devices, with each device utilizing a different type of nanoparticle.

Compared to other options being explored in gas sensing which are bulky and difficult to miniaturize, nanowire gas sensors will be cheaper and potentially easier to mass produce.

The main energy cost in operating this kind of a sensor will be the high temperatures necessary to facilitate the chemical reactions for ensuring certain electrical response. In this study 350 degree centigrade was used.  However, different nanowire-nanoparticle material configurations are currently being investigated in order to lower the operating temperature of this system.

“I think nanoparticle-decorated nanowires have a huge potential for practical applications as it is possible to incorporate this type of technology into industrial devices,” said Stephan Steinhauer, a Japan Society for the Promotion of Science (JSPS) postdoctoral research fellow working under the supervision of Prof. Mukhles Sowwan at the OIST Nanoparticles by Design Unit.

The researchers have provided this image showing their work,

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background.  They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground.   On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other.  Courtesy OIST

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background. They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground.
On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other. Courtesy OIST

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

Single CuO nanowires decorated with size-selected Pd nanoparticles for CO sensing in humid atmosphere by Stephan Steinhauer, Vidyadhar Singh, Cathal Cassidy, Christian Gspan, Werner Grogger, Mukhles Sowwan, and Anton Köck. Nanotechnology 2015 Volume 26 Number 17 doi:10.1088/0957-4484/26/17/175502

This paper is behind a paywall.

US National Institute of Standards and Technology (NIST) and its whispering gallery for graphene electrons

I like this old introduction about research that invoked whispering galleries well enough to reuse it here. From a Feb. 8, 2012 post about whispering galleries for light,

Whispering galleries are always popular with all ages. I know that because I can never get enough time in them as I jostle with seniors, children, young adults, etc. For most humans, the magic of having someone across from you on the other side of the room sound as if they’re beside you whispering in your ear is ever fresh.

According to a May 12, 2015 news item on Nanowerk, the US Institute of National Standards and Technology’s (NIST) whispering gallery is not likely to cause any jostling for space as it exists at the nanoscale,

An international research group led by scientists at the U.S. Commerce Department’s National Institute of Standards and Technology (NIST) has developed a technique for creating nanoscale whispering galleries for electrons in graphene. The development opens the way to building devices that focus and amplify electrons just as lenses focus light and resonators (like the body of a guitar) amplify sound.

The NIST has provided a rather intriguing illustration of this work,

Caption: An international research group led by scientists at NIST has developed a technique for creating nanoscale whispering galleries for electrons in graphene. The researchers used the voltage from a scanning tunneling microscope (right) to push graphene electrons out of a nanoscale area to create the whispering gallery (represented by the protuberances on the left), which is like a circular wall of mirrors to the electron. credit: Jon Wyrick, CNST/NIST

Caption: An international research group led by scientists at NIST has developed a technique for creating nanoscale whispering galleries for electrons in graphene. The researchers used the voltage from a scanning tunneling microscope (right) to push graphene electrons out of a nanoscale area to create the whispering gallery (represented by the protuberances on the left), which is like a circular wall of mirrors to the electron.
credit: Jon Wyrick, CNST/NIST

A May 8, 2015 NIST news release, which originated the news item, gives a delightful introduction to whispering galleries and more details about this research (Note: Links have been removed),

In some structures, such as the dome in St. Paul’s Cathedral in London, a person standing near a curved wall can hear the faintest sound made along any other part of that wall. This phenomenon, called a whispering gallery, occurs because sound waves will travel along a curved surface much farther than they will along a flat one. Using this same principle, scientists have built whispering galleries for light waves as well, and whispering galleries are found in applications ranging from sensing, spectroscopy and communications to the generation of laser frequency combs.

“The cool thing is that we made a nanometer scale electronic analogue of a classical wave effect,” said NIST researcher Joe Stroscio. “These whispering galleries are unlike anything you see in any other electron based system, and that’s really exciting.”

Ever since graphene, a single layer of carbon atoms arranged in a honeycomb lattice, was first created in 2004, the material has impressed researchers with its strength, ability to conduct electricity and heat and many interesting optical, magnetic and chemical properties.

However, early studies of the behavior of electrons in graphene were hampered by defects in the material. As the manufacture of clean and near-perfect graphene becomes more routine, scientists are beginning to uncover its full potential.

When moving electrons encounter a potential barrier in conventional semiconductors, it takes an increase in energy for the electron to continue flowing. As a result, they are often reflected, just as one would expect from a ball-like particle.

However, because electrons can sometimes behave like a wave, there is a calculable chance that they will ignore the barrier altogether, a phenomenon called tunneling. Due to the light-like properties of graphene electrons, they can pass through unimpeded—no matter how high the barrier—if they hit the barrier head on. This tendency to tunnel makes it hard to steer electrons in graphene.

Enter the graphene electron whispering gallery.

To create a whispering gallery in graphene, the team first enriched the graphene with electrons from a conductive plate mounted below it. With the graphene now crackling with electrons, the research team used the voltage from a scanning tunneling microscope (STM) to push some of them out of a nanoscale-sized area. This created the whispering gallery, which is like a circular wall of mirrors to the electron.

“An electron that hits the step head-on can tunnel straight through it,” said NIST researcher Nikolai Zhitenev. “But if electrons hit it at an angle, their waves can be reflected and travel along the sides of the curved walls of the barrier until they began to interfere with one another, creating a nanoscale electronic whispering gallery mode.”

The team can control the size and strength, i.e., the leakiness, of the electronic whispering gallery by varying the STM tip’s voltage. The probe not only creates whispering gallery modes, but can detect them as well.

NIST researcher Yue Zhao fabricated the high mobility device and performed the measurements with her colleagues Fabian Natterer and Jon Wyrick. A team of theoretical physicists from the Massachusetts Institute of Technology developed the theory describing whispering gallery modes in graphene.

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

Creating and probing electron whispering-gallery modes in graphene by Yue Zhao, Jonathan Wyrick, Fabian D. Natterer1, Joaquin F. Rodriguez-Nieva, Cyprian Lewandowski, Kenji Watanabe, Takashi Taniguchi, Leonid S. Levitov, Nikolai B. Zhitenev, & Joseph A. Stroscio. Science 8 May 2015:
Vol. 348 no. 6235 pp. 672-675 DOI: 10.1126/science.aaa7469

This paper is behind a paywall.