Tag Archives: Japan

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.

3D imaging biological cells with picosecond ultrasonics (acoustic imaging)

An April 22, 2015 news item on Nanowerk describes an acoustic imaging technique that’s been newly applied to biological cells,

Much like magnetic resonance imaging (MRI) is able to scan the interior of the human body, the emerging technique of “picosecond ultrasonics,” a type of acoustic imaging, can be used to make virtual slices of biological tissues without destroying them.

Now a team of researchers in Japan and Thailand has shown that picosecond ultrasonics can achieve micron resolution of single cells, imaging their interiors in slices separated by 150 nanometers — in stark contrast to the typical 0.5-millimeter spatial resolution of a standard medical MRI scan. This work is a proof-of-principle that may open the door to new ways of studying the physical properties of living cells by imaging them in vivo.

An April 20, 2015 American Institute of Physics news release, which originated the news item, provides a description of picosecond ultrasonics and more details about the research,

Picosecond ultrasonics has been used for decades as a method to explore the mechanical and thermal properties of materials like metals and semiconductors at submicron scales, and in recent years it has been applied to biological systems as well. The technique is suited for biology because it’s sensitive to sound velocity, density, acoustic impedance and the bulk modulus of cells.

This week, in a story appearing on the cover of the journal Applied Physics Letters, from AIP Publishing, researchers from Walailak University in Thailand and Hokkaido University in Japan describe the first known demonstration of 3-D cell imaging using picosecond ultrasonics.

Their work centers on imaging two types of mammalian biological tissue — a bovine aortic endothelial cell, a type of cell that lines a cow’s main artery blood vessel, and a mouse “adipose” fat cell. Endothelial cells were chosen because they play a key role in the physiology of blood cells and are useful in the study of biomechanics. Fat cells, on the other hand, were studied to provide an interesting comparison with varying cell geometries and contents.

How the Work was Done

The team accomplished the imaging by first placing a cell in solution on a titanium-coated sapphire substrate and then scanning a point source of high-frequency sound generated by using a beam of focused ultrashort laser pulses over the titanium film. This was followed by focusing another beam of laser pulses on the same point to pick up tiny changes in optical reflectance caused by the sound traveling through the cell tissue.

“By scanning both beams together, we’re able to build up an acoustic image of the cell that represents one slice of it,” explained co-author Professor Oliver B. Wright, who teaches in the Division of Applied Physics, Faculty of Engineering at Hokkaido University. “We can view a selected slice of the cell at a given depth by changing the timing between the two beams of laser pulses.”

The team’s work is particularly noteworthy because “in spite of much work imaging cells with more conventional acoustic microscopes, the time required for 3-D imaging probably remains too long to be practical,” Wright said. “Building up a 3-D acoustic image, in principle, allows you to see the 3-D relative positions of cell organelles without killing the cell. In our experiments in vitro, while we haven’t yet resolved the cell contents — possibly because cell nuclei weren’t contained within the slices we viewed — it should be possible in the future with various improvements to the technique.”

: Fluorescence micrographs of fat and endothelial cells superimposed on differential-interference and phase-contrast images, respectively.

Fluorescence micrographs of fat and endothelial cells superimposed on differential-interference and phase-contrast images, respectively. The nuclei are stained blue in the micrographs. The image on the right is a picosecond-ultrasonic image of a single endothelial cell with approximately 1-micron lateral and 150-nanometer depth resolutions. Deep blue corresponds to the lowest ultrasonic amplitude.
CREDIT: O. Wright/Hokkaido University

So far, the team has used infrared light to generate sound waves within the cell, “limiting the lateral spatial resolution to about one micron,” Wright explains. “By using an ultraviolet-pulsed laser, we could improve the lateral resolution by about a factor of three — and greatly improve the image quality. And, switching to a diamond substrate instead of sapphire would allow better heat conduction away from the probed area, which, in turn, would enable us to increase the laser power and image quality.”

So lowering the laser power or using substrates with higher thermal conductivity may soon open the door to in vivo imaging, which would be invaluable for investigating the mechanical properties of cell organelles within both vegetal and animal cells.

What’s next for the team? “The method we use to image the cells now actually involves a combination of optical and elastic parameters of the cell, which can’t be easily distinguished,” Wright said. “But we’ve thought of a way to separate them, which will allow us to measure the cell mechanical properties more accurately. So we’ll try this method in the near future, and we’d also like to try our method on single-celled organisms or even bacteria.”

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

Three-dimensional imaging of biological cells with picosecond ultrasonics by Sorasak Danworaphong, Motonobu Tomoda, Yuki Matsumoto, Osamu Matsuda, Toshiro Ohashi, Hiromu Watanabe, Masafumi Nagayama, Kazutoshi Gohara, Paul H. Otsuka, and Oliver B. Wright. Appl. Phys. Lett. 106, 163701 (2015); http://dx.doi.org/10.1063/1.4918275

This paper is open access.

This research reminded me of a data sonification project that I featured in a Feb. 7, 2014 post which includes an embedded sound file of symphonic music based on data from NASA’s (US National Aeronautics and Space Administration) Voyager spacecraft.

Smectic liquid crystals

From an April 10, 2015 news release from the Tokyo Institute of Technology,

Researchers at Tokyo Institute of Technology have designed a smectic liquid crystal that overcomes many of the challenges posed by organic field effect transistor materials.

Crystalline organic semiconductors have attracted a lot of interest for convenient low-cost fabrication by printed electronics. However progress has been stymied by the low thermal durability and reproducibility of these materials. Now researchers at Tokyo Institute of Technology and the Japan Science and Technology Agency have designed a liquid crystal molecule that produces high-performance organic field effect transistors (FETs) with good temperature resilience and relatively low device variability in addition to high mobility.

Hiroaki Iino, Takayuki Usui and Jun-ichi Hanna designed a molecule that would incorporate a number of desirable liquid crystal qualities, in particular the smectic E phase. Low ordered liquid crystal phases form droplets at their melting temperature, but the smectic E phase has the advantage of retaining the thin-film shape.

They then fabricated organic FETs by spin coating a solution of their material at 110 °C before allowing it to cool. Comparison of the FET characteristics before and after mild annealing revealed a phase transition. Using atomic force microscopy the researchers identified that at around 120°C in the crystal formed a bilayer crystal phase.

The mobility of a bottom gated FET made from the material was around 12 cm2V-1s-1 comparable to single-crystal devices. “Considering that it could potentially be necessary to fabricate millions of FETs for display applications, polycrystalline OFETs may have an advantage over single-crystal OFETs,” point out the researchers in a report of the work. The devices also exhibited a minimal variability of just 1.2 cm2V-1s-1, which is likely an advantage from the smoothness of the obtained film.

The researchers conclude, “The discovery of a dramatic enhancement of FET mobility up to 13.9cm2V-1s-1, resulting from the phase transition from a monolayer to a bilayer crystal structure in mono-alkylated liquid crystalline molecules may lead to the possibility of designing new materials for the burgeoning field of printed electronics.”

Background

Small-molecule versus polymer FETs

The main issues around organic semiconductor FETs with small molecules are the low thermal durability. The same bonding that makes the molecules soluble for printing fabrication processes also leaves them prone to low melting points, which greatly inhibits the methods available for processing the materials. They also tend to form rough surfaces, which makes it difficult to reproducibly fabricate the devices that have the desired characteristics.

Attempts to use polymers with benzene-like delocalised electron bonding alleviated issues around the thermal durability to a certain extent. However, it exacerbated others, such as reproducible synthesis and purification of the polymers, as well as control of crystallinity and the molecular orientations towards both the substrate surface and the electrodes.

The design of the molecule

The researchers identified specific characteristics to enrol in the design of their molecule. They used a fused ring system of molecules with benzene-like delocalised electron bonding so that the material would readily crystallise. They then added a phenyl group to introduce the kind of disorder required for smectic E phase liquid crystals. A long flexible carbon chain was also added to encourage formation of a liquid crystal.

The molecule was also designed to have a single side chain so that crystallisation on cooling would be lower than that on heating. This is more convenient for fabrication processes with the material.

The phase transition

Studies of the field effect transistors before and after mild annealing revealed an improvement in carrier mobility by over an order of magnitude. The researchers concluded that the material underwent a phase transition between 70 °C and 120 °C. Improvements in device performance plateaued above 120 °C.

Atomic force microscope studies of the materials identified a step structure that changed from monolayer 2.8 nm steps to bilayer 5.7 nm steps following the phase transition. In the absence of a change in grain size or contact resistance, the researchers concluded that  crystal-to-crystal phase change from a monolayer to a bilayer structure was responsible for the improved transistor performance in annealed devices.

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

Liquid crystals for organic thin-film transistors by Hiroaki Iino, Takayuki Usui & Jun-ichi Hanna. Nature Communications 6, Article number: 6828 doi:10.1038/ncomms7828 Published 10 April 2015

This is an open access paper.