2018 6

International Center for Materials Nanoarchitectonics (WPI-MANA) Controlling nanoscale order Architectonics connecting nanomaterials with macro materials International Center for Materials Nanoarchitectonics (WPI-MANA) Controlling nanoscale order Architectonics connecting nanomaterials with macro materials NIMS NOW NIMS NOW

02 One-billionth-of-a-millimeter nanomaterials—atomic-scale in diameter and thickness 03 2018 No.6 2018 No.6 —come in a variety of forms, including nanoparticles, nanosheets and nanotubes. Only close examination can reveal the unique, nanoscale-specific behavior of these materials.

The properties of nanomaterials have fascinated and inspired many scientists, leading to rapid advances in nanotechnology. The International Center for Materials Nanoarchitectonics (WPI-MANA) was established in 2007 to accelerate nanotechnological research and development. MANA has attained world-class status in the application of nanotechnology NANO to as a result of implementing its 10-year plan. Having made many significant research achievements, MANA is now ready for even more advanced challenges.

MANA operates under solid guiding principles. Its twofold mission is to create highly functional nanoarchitectures by actively assembling and cross-linking nanomaterial components and to build novel physics knowledge through basic research. ARCHITE

Nanoscale order can be achieved in countless ways, e.g., by varying the combinations of or stacking methods for nanomaterial components and by identifying unique and stable properties using mathematical concepts. The unknown nano-functions that await discovery are potentially as abundant as unknown nano-forms. CTONICS NIMS NOW NIMS NOW

04 05 2018 No.6 2018 No.6 Takuzo Aida Takayoshi Sasaki Professor Director Department of and Biotechnology International Center for Materials Nanoarchitectonics (MANA) School of Engineering National Institute for Materials Science (NIMS)

The NIMS International Center Techniques to connect sic research performed at MANA can great- metals and organics. In addition, active re- noarchitectonic products. nanosheets. This idea inspired me to en- for Materials Nanoarchitectonics nanomaterials and macro materials ly contribute to this endeavor. search efforts have been made on one-di- Aida: I believe you are referring to a hydro- gage in a joint research with Dr. Sasaki. (MANA) was launched in 2007 with Aida: Advances in nanoscience have mensional materials, such as carbon nano- , which was developed in 2015. This is a At that time, my lab had just acquired a the support of the World Premier Sasaki: MANA is alone among NIMS’ made the fabrication of organic nanomate- tubes, three-dimensional materials, such as very unique material: this soft material is superconducting magnet. A postdoctoral International Research Center seven research centers and divisions spe- rials relatively easy. However, little at- nanoparticles, and then two-dimensional tolerant against a vertical compression researcher in my lab used the magnet to ap- Initiative (WPI Program) run by cialized for basic research. “Nanoarchitec- tempt has been made to develop funda- materials, such as . force, but it deforms easily and drastically ply a magnetic field to water containing ti- the Ministry of Education, Culture, tonics” is a concept proposed by MANA: mental science to elaborate mesoscale As you mentioned earlier, the most im- in response to a horizontal shear force. tanium oxide nanosheets. As a result, all of Sports, Science and Technology. creation of materials with novel functions structures: intermediate structures in scale portant and difficult challenges in nanoar- This anisotropic hydrogel was derived the nanosheets neatly lined up in parallel in Takayoshi Sasaki became MANA’s by assembling or specifically organizing between nano and macroscopic size re- chitectonics are the development of meth- from an “aqua material” developed in a direction perpendicular to the magnetic new Director in 2017 to continue to nano-sized materials (or nanomaterials). gimes. A current challenge in ods of synthesizing nanomaterials uniform 2010. Although the water content of the flux lines. Adjacent nanosheets were always fulfill its mission. University of Tokyo Rapid progress of electronics and informa- chemistry—my area of expertise—is the in shape and size and of precisely organiz- aqua material is greater than 98%, it is separated by a gap due to mutual electro- Professor Takuzo Aida is a leader tion/communication technology as well as development of fundamental science to fill ing them. These challenges represent the very strong mechanically. The material static repulsion. The researcher then al- in in Japan. the deteriorating environmental and energy this missing link. essence of nanoarchitectonics. Addressing can be readily prepared by mixing togeth- lowed the nanosheet suspension to gelati- Sasaki and Aida discussed the situations have led to the growing demand Sasaki: Nanomaterial research has them could allow us to discover novel er natural clay mineral sheets and two nize in a manner similar to konjac jelly, re- current status and future prospects for miniaturization, weight reduction and evolved from the initial discovery of functions. types of in water. Although the sulting in the creation of a new anisotropic of “nanoarchitectonics,” a concept increased efficiency of various devices. fullerenes and carbon nanotubes in the You developed a novel material containing aqua material has many useful properties, material (anisotropic hydrogel) in which the proposed by MANA. Materials used in these technologies there- 1980s and 1990s to the development of titanium oxide nanosheets (see p. 12), a ma- I thought that an even more innovative ma- nanosheets are only allowed to slide hori- fore need to be more compact, highly func- nanomaterials in a wider range of com- terial I studied for many years. I think this terial could be created by replacing the zontally. I think that this new material pro- tional or multifunctional. I believe that ba- pound classes, such as oxides, nitrides, exemplifies the practical application of na- clay mineral sheets with titanium oxide vides an excellent example to show what exciting things happen if the missing link vates us to create innovative materials. Field and the Nano-System Field. A third ities. Computer Go programs are certainly Aida. MANA currently has approximately during basic research conducted at between the nano and mesoscopic size re- When we encounter unexpected or acciden- field—the Nano-Theory Field—was newly capable of advanced learning based on the 200 researchers, which represent about a MANA, the subject matter is transferred gimes is filled. tal events during our research, we should added to MANA three years ago. It was ar- rules of Go, but humans, as the inventers quarter of the total number of NIMS re- from MANA to a NIMS mission-oriented Sasaki: After the development of anisotro- find them interesting and actively pursue ranged that a majority of the computational of Go, have immense creative abilities. searchers. MANA researchers engage in a research center to advance it to the applied pic hydrogel, your lab’s extremely talented their causes. An interdisciplinary approach scientists at NIMS would join the Nano-The- For this reason, it is very important for us wide variety of research. They fabricate research stage. Many of the researchers at researchers have produced a variety of new to research is also important and our joint ory Field in an effort to integrate the theoret- to train young researchers. We particular- various types of materials, such as nanow- the Center for Functional Sensors and Ac- materials. All are very creative, including research really confirmed this point. ical and experimental approaches. Our ly need researchers capable of coming up ires, nanosheets, nanoporous materials and tuators, which was established in July “photonic water” capable of changing color Aida: Basic research should always be a method is to first make predictions regard- with their own ideas and acting inde- supramolecular materials, which may be 2018, were trained at MANA. This is a when the orientation of and intervals be- vigorous scientific activity, like producing ing new materials and new physical proper- pendently in order for Japan’s materials applicable to next-generation electronics good example of MANA’s contribution to tween nanosheets in water are altered by the something from scratch. ties using theoretical and computational ap- science to remain strong in the future. and energy technologies. In addition, they NIMS as a whole. application of an external force, such as heat. proaches and then to verify these predictions Sasaki: That issue needs to be addressed fabricate a large variety of different devic- Aida: Practical application of new materi- Aida: Because researchers sometimes Power of computational science experimentally. We hope this combined cooperatively between educational insti- es, from atomic switches to odor sensors. als takes 20 to 30 years after their discov- make discoveries by accident, I do not mind and human capabilities method produces many successes. tutions—namely, universities—and na- MANA has also produced positive results ery. It is important for future basic materi- mistakes by researchers in my lab. When My hobby is to play the game of Go. I was tional research institutions, such as NIMS in the development of nano-level analyti- als research to identify practical application students conduct experiments and encoun- Aida: I heard that NIMS actively integrates overwhelmed by the news that a computer and RIKEN. We are at a crossroads: we cal technologies. For example, MANA re- potential. I look forward to continued out- ter unexpected results, I always encourage computational science into its efforts to find program, AlphaGo, had defeated a profes- have to take appropriate action for Japan searchers combined a transmission elec- standing work at MANA. them to explore the possible causes of these new materials. Has this approach been ef- sional Go player. Relating this story to ma- to maintain its scientific strength and re- tron microscope and a scanning probe mi- (by Kumi Yamada) results with curiosity. fective? terials science, I hope that the use of compu- main attractive to scientists from all over croscope to enable simultaneous observa- Sasaki: I am deeply impressed with your Sasaki: We consider computational sci- tational science and machine learning will the world. tion of a single nanomaterial at atomic work ethic. I believe that a sense of surprise ence to be a very valuable means of obtain- eventually lead us to make discoveries that resolution and measurement of its mechan- serves as an important inspiration for scien- ing certain types of information and insight are beyond our imagination. The future of nanoarchitectonics ical and electrical properties. The use of tists at research organizations, such as that cannot be obtained solely experimental- Aida: My lab has integrated computation- this technology has led to many unexpect- NIMS NOW NIMS NOW MANA, seeking to discover new materials, ly. MANA was initially organized into two al science into our research to a limited Aida: MANA’s WPI Program has pro- ed discoveries. functions and phenomena. Surprise moti- major research fields: the Nano-Materials extent. For now, we use it only for the pur- duced internationally recognized achieve- When practical applicability is identified pose of verifying the consistency of our ments in material-related nanotechnologi- 06 experimental results theoretically. Al- cal research. I have had the opportunity to 07 2018 No.6 2018 No.6 Basic research should be a vigorous though I ultimately want to increase the review many significant MANA accom- A sense of surprise motivates us to create use of computational science in our pursuit plishments as a member of the MANA scientific activity. of the discovery of new materials, I also evaluation committee. innovative materials. Takuzo Aida want to continue to rely on human capabil- Sasaki: Thank you very much, Professor Takayoshi Sasaki Architectonics: Drawing blueprints

ally irrespective of their external environ- cannot disintegrate easily. charge carriers. In other words, this work Topology: ment,” Tanaka said. “Similar to the pole To investigate the relation between the oc- was the first to show explicitly that for a and rubber band example above, in which currence of the mutiferroic feature and the certain range of magnetic field strength, designing materials the number of wrappings is not easily formation of the skyrmion structure, Post- skyrmions are the source of the multiferro- changed, the conductivity at the surface of doctoral Researcher Sergey Nikolaev and ic function of GaV4S8. Tanaka surmises that a topological insulator remains largely un- Principal Researcher Igor Solovyev—both the mechanism found may lead to a novel with changed, being resilient to a considerable members of Tanaka’s research group— charge transport application, where the lat- degree of perturbation.” performed first principle calculations from tice of skyrmions migrates in response to a new language Tanaka continued, “One of our group’s which they extracted the magnetization an electric or magnetic field. goals is to follow in the footsteps of the dis- distribution within GaV4S8 under the influ- In many of the topological materials known coverers of the topological insulator, and ence of an external magnetic field. They to date, it is the correlation among electrons identify topological states of matter exhibit- found that many skyrmions form into a lat- from which exotic properties very different

ing new functions. For this purpose, let us tice when GaV4S8 is exposed to a magnetic from those of the individual electrons recall that each electron is endowed with a field whose intensity falls within a certain emerge. Tanaka, using an analogy to this as- spin ―a tiny source of magnetism, in addi- range (Figure 2). pect, remarks: “We are a group of research- Akihiro Tanaka tion to its charge. If one finds a state where Following this, the group evaluated the ers with a considerably diverse background. Group Leader, these tiny magnets are assembled into some charge distribution pattern and established As such, I am hoping that the correlation Emergent Materials Property Theory Group, Nano-Theory Field, nontrivial spatial pattern that is topological- that these skyrmions are electrically polar- among members will result in the discovery International Center for Materials Nanoarchitectonics (WPI-MANA) ly stable, there is hope that a unique and ex- ized－negative charges were present at of materials with exciting new functions.”

NIMS NOW tremely robust function is lurking within higher density in the inner region of the (by Shino Suzuki, PhotonCreate) NIMS NOW that material. Armed with this insight, skyrmions than in the outer regions (Figure Material properties are ultimately governed by the rules of quantum mechanics, which dictates the members of our group undertook a theoreti- 3). This implies that a flow of mobile skyr- microscopic world consisting of arrays of atoms and a huge number of electrons swirling around them. cal investigation into the properties of mions will generate an electric current. 08 A team of researchers led by Akihiro Tanaka is attempting to draw blueprints for materials exhibiting new 09 GaV S , a magnetic insulator composed of Tanaka explains: “In the absence of an ex- 2018 No.6 2018 No.6 functions, by looking into this quantum realm through the eyes of a new language – topology – and 4 8

predicting their properties with the help of high precision numerical techniques. gallium, vanadium and sulfur. This material ternal magnetic field, GaV4S8 is a feature- had been reported to exhibit peculiar multi- less insulator. When subjected to a magnet- ferroic properties and a topologically stable ic field of the right strength, some of the topologically stable means it can persist again need to cut the band before you can do spin structure known as the skyrmion, but spins flip their orientations, leading to sky- Figure 1. Skyrmion spin structure Understanding materials A skyrmion is composed of radially aligned spins. The even when perturbed by a fair dose of dis- so. Thus, once the rubber band is tied around the precise relation between these two fea- rmion formation. What people in our group outer spins point upward while the inner spins point through mathematics downward. As a whole, the spins point in all possible order such as crystalline defects, impuri- the pole, winding and unwinding require a tures was unknown.” demonstrated through their numerical directions exactly once. In precise analogy to the pole and rubber band example discussed in the text, this “In 2016, a trio of scientists were awarded ties, or thermal noise. In time, people real- major external change (i.e., cutting). This study was that these skyrmions exhibit number cannot change continuously; changing it will be energetically costly. Once formed, skyrmions are there- a Nobel Prize in physics for their ‘theoreti- ized that this unusual robustness could be state －the number of wraps－is therefore The search for electric polarization and can serve as fore stable and will not readily decay. cal discoveries of topological phase transi- turned into a huge advantage for designing said to be topologically stable. new topological materials tions and topological phases of matter’,” material functions. Hence the enormous Tanaka said. “After the award announce- current focus on the subject.” Materials that are neither metals The term multiferroics refers to materials ment, I did an interview on this subject with Here is a simple example ― taken from nor insulators that are simultaneously a magnet and a fer- a reporter from a TV station. The opening everyday life as opposed to the quantum roelectric －the latter are materials which question was: what is ‘topology’ ?” mechanical world of materials ― of a topo- Incorporating topological ideas into con- exhibit electric polarization in response to Topology is a branch of mathematics logically stable state. Imagine that you have densed matter physics has led to the discov- an applied electric field. This dichotomy al- which concerns itself with geometric prop- a pole and a strip of rubber band. You wrap ery of a number of topologically stable elec- lows magnetic (electric) properties to be erties that do not change when an object is the rubber band around the pole once and tronic states, which in turn give rise to ex- controlled by an electric (magnetic) field in a gradually deformed; by the latter we mean then tie together the two ends. Notice that traordinarily stable materials properties. multiferroic material, a feature which has a that where topology is concerned, objects stretching or twisting the band does not The prototype example is the topological great potential for use in next-generation de- can be pulled or twisted, but cannot be change the number of times it has been insulator，whose interior behaves as a metal, vices with a high energy efficiency. ripped, cut, or glued together. wrapped around the pole. If you now want to while its surface behaves as an insulator. Meanwhile, as depicted in Fig.1, the “Ideas having roots in topology began to wind the rubber band around the pole one Predicted theoretically in 2005, it was real- spins forming a skyrmion pattern point enter into condensed matter physics in the more time, you first need to cut the band. If, ized experimentally two years later. outward in a radial fashion. For this rea-

1980s,” Tanaka explains. “It started to alternatively you have wrapped the band “Topological insulators are unique in that son, it is sometimes also called a “hedge- Figure 2. Formation of magnetic skyrmions in Figure 3. Magnetization distribution (top) and elec- GaV S under an applied magnetic field tric polarization (bottom) in a GaV S layer dawn on physicists of that time that creat- around the pole twice and have tied the two they allow electric current to flow across hog.” Skyrmions are known to be topolog- 4 8 4 8 In GaV4S8, a layered material, skyrmions form a lattice Electric polarization in a skyrmion causes negative ing a state of matter which is in some sense ends, but now want to unwind it once, you their surfaces at a constant intensity virtu- ically stable; once formed, the pattern pattern on each layer. charges to be present at higher densities in the inner region than in the outer region.

Sergey Nikolaev and I. Solovyev, arXiv: 1808.08008 Longitudinal縦伝導度 conductivity (e2/h) (e2/h) 0.01 100 Architectonics: Extracting hidden functions 6 5 4 3

Searching for 磁場 (T) 2

Magnetic field (T) 1 0 functions woven -30 -20 -10 0 10 20 30 Gate voltage (V) ゲート電圧 (V) into sheet material

Two-dimensional sheet materials are only one to several Graphene/hBN atoms in thickness. When different types of sheet materials moiréグラフェン superlattice / hBN structure are stacked, the combination may exhibit properties differ- Figure 3. “Butterfly” thatモアレ超格子構造 describes both the quantum Hall effect and moiré superlattice structures ent from those of the individual monolayers. Multiple layers (Top) A color scale plot descibing electrical conductivity (longitudinal of the same sheet material may also show different proper- conductivity in e2/h, where e and h denote elementary charge and the Planck constant, respectively) as a function of the gate voltage and ties depending on the number of layers stacked and the Shu Nakaharai Satoshi Moriyama the magentic field applied perpendicular to the graphene sheet. The angular differences between the layers. Shu Nakaharai and Principal Researcher, Quantum Device Engineering Group Senior Researcher, Quantum Device Engineering Group pattern shown, called a “Hofstadter's butterfly,” indicates that electri- Nano-System Field Nano-System Field cal conductivity is high and the angular difference between the two Satoshi Moriyama have been searching for new functions stacked honeycomb structuers is 1° degree or less. (Bottom) A sche- International Center for Materials Nanoarchitectonics (WPI-MANA) International Center for Materials Nanoarchitectonics (WPI-MANA) matic diagram of a moiré superlattice structure. For better visibility, an and physics hidden in these layered structures. angular difference of 10° between the two sheets is shown. NIMS NOW NIMS NOW Dawn of the exploration of thin material with high charge mobility (i.e., behaves as a semiconductor,” Nakaharai said. potentially allows controlling the transistor world and that a unique phenomenon called verified,” Moriyama said. “I expect that our two-dimensional materials high electrical conductivity), can replace sili- “I later transferred to NIMS and began study- type of p- and n-types. After examining com- the quantum Hall effect occurred in the de- first-in-the-world observation of quantum val- con, highly integrated and power-efficient ing the use of TMDCs in transistors.” binations of MoTe with various metals, Naka- vice. In addition, analysis of measurement ley current will allow quantum computing de- 10 2 11 Imagine that you have a block. You transistors may be developed.” However, Nakaharai had to deal with yet harai discovered in 2015 that MoTe displays data revealed that a moiré superlattice struc- vices to be more widely applied.” 2018 No.6 2018 No.6 2 attach adhesive tape to the block and peel it to another issue. Transistors have two types of p-type behavior in combination with platinum ture was formed when the angular difference An American research group recently report- remove the surface layers. You then attach an- Advent of a predecessor to p- and n-types, and both need to be incorpo- and n-type behavior in combination with tita- between the two stacked honeycomb struc- ed that stacking two graphene layers with an other piece of tape to the removed surface layers graphene rated into an integrated circuit. However, it nium (Figure 1). Thus, he has come one step tures was 1° or less (Figure 3). angular difference of 1.1° between them induc- for further peeling. If you repeat this process was difficult to control the transistor type be- closer to achieving the use of two-dimensional “‘Valley current’ had been predicted to occur es superconductivity in the stacked material. over and over, you eventually obtain a single-at- When graphene first became available, it at- tween p- and n-types in TMDCs. materials in transistors. In addition to these ef- in materials with moiré superlattice struc- “Two-dimensional materials can be com- om-thick graphite or graphene sheet. Graphene tracted Nakaharai’s attention; he was then TMDC properties vary greatly depending forts, Nakaharai has also been attempting to tures,” Moriyama said. Electrons in solid crys- bined in myriad ways by changing the num- has driven two-dimensional material research. developing transistors at an electronics man- on the combinations of transition metals and use graphene and TMDCs in sensors. tals have hidden degrees of freedom, called ber of stacked layers and the angular differ- Graphene is composed of carbon atoms ar- ufacturer. However, he found that its useful- chalcogens. While studying these combina- valley degrees of freedom, in addition to ence between the layers,” Moriyama said. ranged in a honeycomb pattern. Due to its ness in transistors was limited because highly tions, Nakaharai found molybdenum ditel- Stacking two types of charge and spin degrees of freedom. “Valley- “These experiments stimulate my imagina-

unique properties—it is strong yet flexible and conductive graphene was to be used as a luride (MoTe2) to be promising. “MoTe2 had honeycomb structures tronics”—the use of valley current to transmit tion because manipulation of these combina- highly conductive electrically and thermal- semiconductor. “I discovered that graphene been researched only to a limited extent be- information without the involvement of charge tions may lead to the discovery of novel func- ly—graphene is potentially useful for a variety can be used as a semiconductor by irradiating cause it is difficult to deal with,” Nakaharai “Another fascinating aspect of two-dimen- current—has the potential to lead to the devel- tions.” Nakaharai also shared his goals going of purposes. “Graphene may be applicable to it with helium ions, thereby creating defects said. “However, when high-quality sin- sional materials is that they exhibit new proper- opment of highly energy efficient electronics. forward. “I hope to continue investigating the

transistors—semiconductor devices that con- in its crystalline structure,” Nakaharai said. gle-crystalline MoTe2 became available, I ties when stacked,” said Moriyama, who fabri- However, previous valleytronics research had functions and physics of two-dimensional trol the flow of electric current in electronic “However, this treatment also caused selected it as my research focus in the hope cated a device composed of stacked sheets of detected only very weak signals inappropriate materials in the hope of contributing to the circuits,” Nakaharai said. “Most transistors graphene’s charge mobility to decrease, un- of discovering interesting physics.” graphene and hexagonal boron nitride (hBN) for practical application. development of next-generation electronics.” today are made from silicon. If graphene, a dermining its advantages.” Nakaharai focused on a Schottky barrier to which electrodes were attached at opposite Moriyama converted electrical signals in the (by Shino Suzuki, PhotonCreate) While struggling with this issue, Nakaharai formed at the junction between a metallic elec- ends (Figure 2). hBN is a material composed of device he fabricated into valley currents. He Electrode (platinum) Metallic MoTe 2 Electrode (titanium) saw an intriguing report about a group of ma- trode and a semiconductor. This barrier blocks boron and nitrogen atoms arranged in a honey- then converted the valley currents back into electrode terials called transition metal dichalcogenides the flow of electrons and holes. Nakaharai comb pattern. Very high quality crystalline electrical signals, which enabled him to suc- (TMDCs) which are composed of multiple found that the Schottky barriers formed in hBN was fabricated and provided to Moriyama cessfully detect the substantial electrical sig- Monolayer graphene Insulator substrate Back gate electrode Silicon (Si) dioxide layer stacked sheets made of transition metals and MoTe2 were more easily removable than those by Research Fellow Takashi Taniguchi and nals indicative of valley current. Fabrication of Positive charge Negative charge hBN layers (p-type) (n-type) chalcogens. He learned that individual TMDC formed in other TMDCs, such as molybde- Chief Researcher Kenji Watanabe at NIMS. the high-quality device made this accomplish- Si substrate Figure 1. MoTe transistor structure Figure 2. Graphene superlattice device 2 layers can be isolated using adhesive tape in a num disulfide. If the Schottky barriers are re- Electrical conductivity measurement results ment possible. “I believe that the valley current MoTe2 exhibits both p- and n-type behaviors by accepting Graphene was placed on top of an hBN layer. Another both positively charged holes from the platinum electrode manner similar to graphite layers. “Each moved, electrons and holes can be injected confirmed that the charge mobility of Mori- we detected recently was actually quantum hBN layer was then placed on top of the graphene to pre- and negatively charged electrons from the titanium elec- vent contamination. Finally, electrodes to measure electri- trode, respectively. TMDC sheet is several atoms in thickness and from the metal electrodes into MoTe2, which yama’s device was among the highest in the valley current, although this still needs to be cal conductivity were attached to the stacked layers.

S. Nakaharai, et al., ACS Applied Materials & Interfaces 8, 14732-14739 (2016). DOI: 10.1021/acsami.6b02036 K. Komatsu et al., Science Advances 4, eaaq0194 (2018). DOI: 10.1126/sciadv.aaq0194 NIMS NOW 13 2018 No.6 ------複合材料 複合材料 nanosheet 2 Graphene MnO Composite material Composite 溶液法 自己組織化 溶液法 nanosheets and graphene nanosheets graphene and nanosheets 2 自己組織化 method Self-assembly Solution-based electrons into and the out of electrodes. I as sumed that graphene could perform the same function as these conductive fine carbon par ticles if used in a battery system and I was very happy to graphene perform find outstandingly—the per that batteriesformance values obtained we were superior with to those reported previously using other met al oxide anode materials. also have been We developing supercapacitors and electrode cat alysts. If all these of technologies are put into practical use, should to be we able dramati cally increase energy storage efficiency.” Other nanosheet assembling techniques are also available that allow gradual, sheet-by- sheet stacking. “The use these of techniques enablesprecise control nanosheet of assem bling in terms layering of order and the num ber layers, of like stacking Ma Lego blocks,” said. “There are countless combinations in nanosheet assembling. In future research, we will these apply techniques only not to the electrode of development materials but also to the other of development functional mate rials.” (by Kaori Oishi) PDDA PDDA nanosheets and graphene nanosheets graphene and nanosheets 2 - - - - ~ 正に帯電した rGOナノシート ~ DOI:Xiong 10.1021/acsnano.7b08522 et al,. ACS Nano 1768-1777(2018). 12, Positively charged Positively 正に帯電した rGOナノシート graphene nanosheets and graphene 2 Ma & Sasaki, Accounts of Chemical Research DOI: (2015). 48, 136-143 10.1021/ar500311w nanosheets can be assembled alternately by simply mixing and lightly stirring the solutions. the stirring lightly and mixing simply by alternately assembled be can nanosheets 2 and graphene nanosheets. 2 electrodes are supplemented supplemented are electrodes 2 nanosheets 2 ナノシート nanosheetsthickness in nm 0.8 arewhile PDDA-modified reduced graphene oxide (rGO) nanosheets nm 1.4 are 2 2 MnO nO ositively charged graphene nanosheets are prepared by allowing PDDA (poly [diallyldimethylammonium chloride]) chloride]) [diallyldimethylammonium (poly PDDA allowing by prepared are nanosheets graphene charged ositively Negatively chargedNegatively M in thickness. A transmission electron micrograph of the layered structure is showncapacity on the right. of Ma this said, material “The anode at its current density A/g mAh/g. is 1,325 Its of 0.1 cycle life has been greatly increased.” Figure 2. Anode material composed of assembled alternating MnO alternating assembled of composed material Anode 2. Figure P polymers attach to reduced to graphene oxide (rGO) nanosheets. Positively charged graphene nanosheets and neg atively charged MnO charged atively Figure 1. Mechanism of alternately assembling MnO assembling alternately of Mechanism 1. Figure 負に帯電した ナノシート MnO nanosheets ratio are area. by present in 1:1 a Its anode capacity was at least twice that of commercial lithium batteries, ion while its capacity decay was per only cycle 0.004% after 5,000 charge/discharge cycles. blings MnO of “This proceduredoes to have not be carried out at high temperature or high pressure,” Ma thissaid. “Although manufacturing tech niquedoes allow not precise control the of number layers assembled, of enabled it us to produce composite materials consisting of approximately to 20 layers five 2).” (Figure group evaluated the Ma’s composite mate rial its for usefulness in electrodes and found that can it serve as a high-capacity, long-life anode material when MnO Expanding the applications of applications the Expanding nanosheets had another “We reason using for graphene,” Ma said. “In conventional rechargeable bat teries, MnO with electrically conductive fine carbon incles order to facilitate the of movement parti 2 負に帯電した

2 ------MnO is at 2 nanosheets monolayers 2 nanosheets, 2 2 and graphene nanosheets— 2 nanosheets (Figure 1). 2 to Mn releasing by ions. oxygen How crystalline structure. Only two or three 2 2 charge/dischargemay severely damage cycles the crystalline structure and significantly re duce its Separate capacity. MnO tributed to its tendency to be reduced from MnO are facing the issue a short life. of cycle group attempted Ma’s to this resolve issue using graphene sheet material (a composed of carbon atoms arranged in a honeycomb pat tern). The group initially proposed that a crystalline structure assembled composed of alternating MnO are even more fragile and tend to clump to gether. Thus, high-capacity MnO makingalternating assembling impossible. addressTo this issue, the group developed a processto polymers attach to rGO PDDA nanosheets, resulting in the production of positively charged, PDDA-modified rGO nanosheets whichare attracted to negatively charged MnO which resembles mille-feuille in appear ance—would collapse not might (though it anddeform) clump not would together when ions areoxygen released. However, the group encountered difficul ties when implementing the planned alter nating assembling.The groupwas to able synthesize large quantities graphene of at cost subjecting by low graphite to a chemi cal oxidation treatment and separating into it nanosheets. this treatment However, gener ateddefects in the synthesized graphene nanosheets, altering their properties. The group thus treated the graphene nanosheets with electron donors to induce reduction re actions, repairing the defects and restoring theproperties theof nanosheets tosatisfaca tory The level. resulting reduced graphene nanosheets,oxide (rGO) had nega however, chargedtively surfaces which repelled simi larly negatively charged MnO Drop-by-drop addition graphene of to MnO nanosheets in an Erlenmeyer flaskwhile it is being stirred yields self-assembly compos of itematerials consisting alternating of assem area exposed to an electrolyte was increased. The high theoreticalcapacity MnOof ever, the ions releaseever, damage oxygen of the MnO

2 ------surface surface 2 is at least three times 2 - as an alternative to the carbon 2 The capacity the of rechargeable batteries cur rently used in electric vehicles is insufficient in terms mileage of per charge. The development higher-capacityof batteries is therefore indis pensable. In addition, new batteries will be re quired in to extended have i.e., lives; cycle creased enduranceto the deterioration caused repeatedby charge and discharge. Lithium batteries—the ion most widespread rechargeable batteries in current use—are composed an of electrolyte, cathode and an ode. The capacity rechargeable of batteries is influenced by the properties and combina tions battery of materials group used. Ma’s recently to worked increase anode capacity usingMnO higher than that carbon of materials. If MnO were separated into individual one-mole cule-thick monolayers, the reactionwas expected to increase efficiency when used asan anode material, because the MnO anode materials in current use. The theoreti cal capacity MnO of ------]) 2 Architectonics: Assembling Nanosheets Assembling Architectonics: Constructinghighly functional materials by assembling nanosheets like “mille-feuille” layers roup Leader, roup Renzhi Ma G Group Nanomaterials Functional Field Nano-Materials (WPI-MANA) Nanoarchitectonics Materials for Center International ] and manganese dioxide [MnO 2 and hydroxides containing transition metals or rare earth elements. MANA has also developed its original tech niques for use in fabricating artificial lattice materials composed different of types as of sembled nanosheets.These techniques may enable breakthroughs to be made in the devel opment various of devices, such as the world’s smallest, high-performance capacitors, elec quick trochemical of supercapacitors capable storingly and releasing large amounts elec of trical energy within tens seconds of and ex tremely high efficiency electrode catalysts free platinum of and other precious metals. Development of energy materials energy of Development as of composed control and design skillful through materials lattice Artificial sembled nanosheets many have potential ap group has beenplications. focusing Ma’s on their use as rechargeable battery materials. ide [TiO ------rials in the liquid reflected light in random directions. These are nanosheets—ultimate thinly two-dimensional materials one to sev eral atoms in thickness and more than several thousand atoms in width with unique na properties.noscale In nature, single-sheet materials rarely exist; theynormally exist as multilayered solids (lay ered materials). If the individual layers in lay ered materials first are together held weak by bonds, they can be separated using adhesive world’s the if theytape. are together However, held by developed strong bonds, this method may be not feasible. has MANA technique that can effectively separate lay ered materialsinto individualnanosheet components. Optimum nanosheet separa tion techniques are various available for ma terials,titanium including oxides (e.g., diox As Ma swirled a liquid in a flask, tiny mate Exceptional layer separation layer Exceptional techniques assembling and prints may exhibit unique functions different from those of homogeneous materials. Somelayered materials are difficult them. Renzhi Maand colleagues at MANA have developed to chemical techniquesseparate easily to separate into individualthese layers. layers In addition,due to they the are strong able to bonds sheet materials assemble in a designated Artificialorder. between many composite materialssynthesized according to differentblue types of single-molecule-thick

2018 No.6

NIMS NOW 12 NIMS NOW 15 2018 No.6 ------27 ). These). bacteria may 4 O 3 be used to efficiently produce great quanti ties nanomagnets of without large equip ment—an appealing ideain various indus tries seeking to introduce microbial tech learned I have nologies. that international scientific meetings are now being held spe cifically to discuss magnetic bacteria and that magnetic bacteria are the subject of active research, from basic science to indus trial applications. Proteins in (enzymes) theinvolved synthe sis of fine magnetic particleswere recently discovered, and mechanisms that control thecrystalline structures these of particles have been identified. In addition, TokyoUniversity Agriculture of and Technology has reportedly succeeded in sequencing magnetic bacterial genomes for the time and firsthas identified agene set common to all magnet-producing microorganisms. If theengineering magnetic of bacterial genes enables controlled synthesis nano of magnets in various forms, expect I would wide-ranging demand them. for I also thatbelieve magnetic bacteria great have potential use for in drug delivery systems in whichthe bacteria could be manipulated to ingest drugs to be delivered and guided to a target site through the application an of external magnetic force. no doubt that I have humans will continue to heavily on microorganisms. rely purposes. The earth acts as a giant magnet, with its magnetic north pointing to geo graphic south and its magnetic south point ing to geographic north. The rota earth’s tional axis is tilted from the ecliptic plane. Magnetic bacteria are thought to use their internal magnets like compasses to navigate northward they (if are in the Northern Hemi or southwardsphere) they (if are in the Southern Hemisphere) in search more of suitable water bottom habitats. Magnetic bacteria ingest iron ions and use them to synthesize fine magnetic particles magnetiteof (Fe - - - organisms throughout our lives, humans have so far identified only a fractionof the microbial species in existence. example, For ivermectin, an important life-saving medi cation developed by 2015 Nobel PrizeNobel cation developed 2015 by winner Satoshi Ōmura, was derived from a new microbial species isolated from soil samples collected from various locations. This indicates that unknown microbial spe cies living in our habitats the have potential to bring great benefits ourto lives. So-called “magnetic bacteria” inhabit var ious aquatic environments around the such world, as ponds, marshes and lakes. They are currently attracting a great deal of attention their for ability to produce tiny magnets within themselves. The most widely accepted theory that holds these bacteria produce magnets migration for ------Akio Etori: Born in Science 1934. journalist. After graduating from College of Arts and Sciences,producer the and University director at Nihon of Tokyo, he Educational produced mainly Television science (current programs TV Asahi) as a television and TV Tokyo, after he held which posts he became including the editor director in chief of Nikkei of the science Science magazine Inc., executive director Nikkei Science. ofMita Press Successively Inc., visitingUniversity professor of Tokyo, andof the director Research of the Japan Center Science for Advanced Foundation. Science and Technology, the and many saved have lives. Although interact closely we with micro ing penicillin, been have used medically to suppress disease-causing microorganisms fungusto make miso andcertain bacteria to make yogurt. The inventionmicroscopes of enabled scientists to begin to understand microbial activity, which led to a wider range of includ Antibiotics, applications. microbial mated to exist in a single human Our body. intestines are known to contain particularly large amounts microorganisms, of including intestinal kg of about 1.5 bacteria. Humankind has been taking advantage of some microorganisms since ancient times, such as yeasts to make bread, the koji eral billion tons, while total plant biomass amounts to from one to two trillion tons. The total biomass microorganisms, of by comparison, is estimated to amount to 200 to 300 billion tons. has It been theorized that underground-dwelling microorgan isms will add greatly to this figure. trillion About 100 microorganisms are esti Microorganisms that that Microorganisms nanomagnets produce by Akio Etori Text Illustration by Joe Okada (vision track) Countless microorganisms are living and movingaround us They every are day. sev eral microns in size and are, course,of invisible to thenaked human are all (as eye objects smaller than approximately mm 0.1 microns). or 100 According to some estimates, the total animal biomass the of earth amounts to sev - - o-director of the L'Oréal- Jun Sasai C Innovation Materials NIMS Center for Science and Beauty, K.K. L'Oréal Nihon mercialize cosmetic products, includingcos metic scientists and product testing facilities. Ebara previously devoted his efforts to applied research on medical products. “I beenhave researching smart polymer sheets that can be attached directly to cancer cells as a cancer treatment with the saving goal of as many lives aspossible. Although beauty care research lives as does affect not people’s directly, can it improve quality life. Thisof collaboration opportunity has broadened my perspective. In the future I will strive to productsdevelop thatwill bring smiles to faces.” people’s (by Kaori Oishi) the assembly original of analytical devices,” Ebara has Nihon all said L'Oréal proudly. of the infrastructure necessary to speedily com ------may enable put us to innovative cosmetics concepts into practice. the At Materials Innovation Center for Science and Beauty, intend we combine to materials science and cosmetic science formulate to unique ideas and develop new materials capable meeting of consumers’ beauty care needs. hope We bring to innovation the to world cosmetics of introducing by with collaboration our through developed materials products. NIMS L'Oréal to lency of theselencyof polymers exposing by them to certain types stimuli. of Smartpolymers greathave potential as functional materials. In addition, the shapes smart of polymers that have been processed into films, or liq uids, etc. can be designed as needed. Because they are inexpensive, they can be used even as advanced medical materials people for in developing countries and disaster-affected areas.” These useful smart polymers are also to cosmetics. potentially applicable and Nihon NIMS L'Oréal jointly founded the Materials Innovation Center Science for Theyand Beauty plan to in July 2018. versatile develop products that will satisfy various needs, such as shape-memory hair styling products and anti-wrinkle, anti-sag skincare products, in relation to country-spe cific consumer needs and socialsituations. resources are ideal the “MANA’s for pro duction new nanomaterials,” of said Ebara. “I beenhave striving to establish polymersyn thesis techniques that will enable precise molecular design faithful to the original blue prints based on the nanoarchitectonics con cept.MANA has many experts in various fields who share this concept. opportunityI enjoy to consult with analytical the spe cialists about methods evaluating of synthe sized polymers, which sometimes leads to - - - - Launch of L'Oréal-NIMS Materials Innovation Center for Science and Beauty

TOPIC L'Oréal’s mission “provide is to the bestL'Oréal’s in cosmetics innovation women to and men around the world while respecting their world-class NIMS—a diversity.” materials research institute that has put a number of with collaboration in use practical into technologies various an industries—is indispensable partner that can help fulfill us to this mission. Our initial goal in products commercial develop to partnership is this that materials promising smartusing polymers—very o-Director of the L'Oréal-NIMS Materials Mitsuhiro Ebara C Innovation Center for Science and Beauty; Investigator, Principal Associate MANA for Center International Group, Mechanobiology NIMS (WPI-MANA), Nanoarchitectonics Materials ical structure mixing by with chemicals in a reaction tank. The properties smart of poly mers, contrast, by can be readily changed by certain ultraviolet,humidity, temperature or conditions.pH “Polymers synthesized by precisely combining and sequencing mole cules can exhibit various functions,” Mit suhiro Ebara said. example, can you “For change the transparency and water repel- Smart polymers are easily controllable materialswhose properties can be changed or restored external by stimuli. example, For some smart polymers that been have stretched are to able instantly return to their original shapes when placed in is It water. hot difficult to change the propertiespolymers; most need of to be changed its chem most

NIMS establishedjoint a research center K.K., with in JulyNihon 2018 the L'Oréal Japanese subsidiary of the world’s largest cosmetics company, L’Oréal S.A. Nihon L'Oréal has identified “smart polymers” properties The cosmetics. smartto ultraviolet as of such external stimuli, polymers response to in changing are capable of be potentially applicableto light, temperature and humidity. Use of these materials may allow development of next-generation “smart” cosmetics. Smart Smart beauty polymers

2018 No.6

NIMS NOW 14 MANA INTERNATIONAL SYMPOSIUM 2019 Jointly with ICYS No. mon wed 6 3/ ~ 2018 Time and date: 4 6 March 4-6, 2019 Banquet: March 5, 18:30-20:30 Venue: Tsukuba International Congress Center EPOCHAL TSUKUBA Symposium Registration Fee: free / Banquet Participation Fee: 3,000yen, 1,500yen (student) Sponsored by National Institute for Material Science (NIMS) International Center for Materials Nanoarchitectonics (WPI-MANA)

Requires Online-Registration prior to February 25, 2019. Please access the following web site. http://www.nims.go.jp/mana/2019/index.html

The International Center for Materials Nanoarchitectonics the symposium to initiate discussion about “Nano Percep- (WPI-MANA) is attempting to create a new paradigm for tive Materials, Devices, and Systems”. In addition to guest materials science, called “nanoarchitectonics”, based on lectures renowned nanotechnology and material science an innovative nanotechnology. WPI-MANA has held the achievements in relevant research fields, the researchers MANA International Symposium every year to discuss the from MANA and ICYS will present their latest findings for current status and the future perspective of materials extensive discussion for future. science based on the state-of-the-art nanotechnology We hope many scientists, researchers and students who together with many distinguished scientists and young are interested in materials science and technology will join scientists from around the world. this symposium and obtain fresh inspiration from the talks In the 12th MANA International Symposium (jointly with and discussions towards the future. ICYS: International Center for Young Scientists), we design

Prof. DECHER, Gero (University of Strasbourg, France) Keynote “Bioinspired nano-composite materials with complex anisotropies” Speakers Prof. IWASA, Yoshihiro (The University of Tokyo, Japan) “Emergent Iontronics”

Prof. MALLOUK, Thomas E. (The Pennsylvania State University, USA) “How Do You Make a Micro-Robot?” ※All lectures will be conducted in English. ※Programs are subject to change without notice.

NIMS NOW International 2018. Vol.16 No.6 National Institute for Materials Science To subscribe, contact: Dr. Yasufumi Nakamichi, Publisher Percentage of Waste http://www.nims.go.jp/eng/publicity/nimsnow/ Public Relations Office, NIMS Paper pulp 70% © 2019 All rights reserved by the National Institute for Materials Science 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047 JAPAN photo by Michito Ishikawa Phone: +81-29-859-2026, Fax: +81-29-859-2017 editorial design by Barbazio Inc. Email: [email protected] on the cover: Principal Researcher Shu Nakaharai and vacuum prober system