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Home > Press > A clue to generate electric current without energy consumption at room temperature Abstract: A group of researchers in Japan and China identified the requirements for the development of new types of extremely low power consumption electric devices by studying Cr-doped (Sb, Bi)2Te3 thin films. This study has been reported in Nature Communications. At extremely low temperatures, an electric current flows around the edge of the film without energy loss, and under no external magnetic field. This attractive phenomenon is due to the material's ferromagnetic properties; however, so far, it has been unclear how the material gains this property. For the first time, researchers have revealed the mechanism by which this occurs. "Hopefully, this achievement will lead to the creation of novel materials that operate at room temperature in the future," said Akio Kimura, a professor at Hiroshima University and a member of the research group. Their achievement can be traced back to the discovery of the quantum Hall effect in the 1980's, where an electric current flows along an edge (or interface) without energy loss. However, this requires both a large external magnetic field and an extremely low temperature. This is why practical applications have not been possible. Researchers believed that this problem could be overcome with new materials called topological insulators that have ferromagnetic properties such as those found in Cr-doped (Sb, Bi)2Te3. A topological insulator, predicted in 2005 and first observed in 2007, is neither a metal nor an insulator, and has exotic properties. For example, an electric current is generated only at the surface or the edge of the material, while no electric current is generated inside it. It looks as if only the surface or the edge of the material has metallic properties, while on the inside it is an insulator. At extremely low temperatures, a thin film made of Cr-doped (Sb, Bi)2Te3 shows a peculiar phenomenon. As the film itself is ferromagnetic, an electric current is spontaneously generated without an external magnetic field and electric current flows only around the edge of the film without energy loss. However, it was previously unknown as to why Cr-doped (Sb, Bi)2Te3 had such ferromagnetic properties that allowed it to generate electric current. "That's why we selected the material as the object of our study," said Professor Kimura. Because Cr is a magnetic element, a Cr atom is equivalent to an atomic-sized magnet. The N-S orientations of such atomic-sized magnets tend to be aligned in parallel by the interactions between the Cr atoms. When the N-S orientations of Cr atoms in Cr-doped (Sb, Bi)2Te3 are aligned in parallel, the material exhibits ferromagnetism. However, the interatomic distances between the Cr atoms in the material are, in fact, too long to interact sufficiently to make the material ferromagnetic. The group found that the non-magnetic element atoms, such as the Sb and Te atoms, mediate the magnetic interactions between Cr atoms and serve as the glue to fix the N-S orientations of Cr atoms that face one direction. In addition, the group expects that its finding will provide a way to increase the critical temperature for relevant device applications. The experiments for this research were mainly conducted at SPring-8. "We would not have achieved perfect results without the facilities and the staff there. They devoted themselves to detecting the extremely subtle magnetism that the atoms of non-magnetic elements exhibit with extremely high precision. I greatly appreciate their efforts," Kimura said. Authors and their affiliations: Mao Ye1,2, Wei Li1,2, Siyuan Zhu3, Yukiharu Takeda4, Yuji Saitoh4, Jiajia Wang5, Hong Pan6, Munisa Nurmamat3, Kazuki Sumida3, Fuhao Ji6, Zhen Liu6, Haifeng Yang1, Zhengtai Liu1, Dawei Shen1,2, Akio Kimura3, Shan Qiao1,2,5, and Xiaoming Xie1,2,5 1 State Key Laboratoryof Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 2 CAS-Shanghai Science Research Center 3 Graduate School of Science, Hiroshima University 4 Condensed Matter Science Division, Quantum Beam Science Center, Japan Atomic Energy Agency 5 School of physical science and technology, ShanghaiTech University 6 Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article
Site: http://phys.org/chemistry-news/

Fighting large-scale fires usually involves firefighting foams based on synthetic substances, such as prefluorinated surfactants, that, despite their effectiveness, are extremely toxic for living organisms. Complete biodegradation of such foams can last for more than 200 years, with residues quickly penetrating deep into soil and surface water. This leads to the accumulation of toxic elements in living organisms, such as plants, animals and men. Many countries have declined the use of such fire extinguishing agents or opted for reducing the production of such substances despite the absence of any decent alternatives. A group of scientists from the International Laboratory of Advanced Materials and Technologies (SCAMT) at ITMO University in Saint Petersburg and research company SOPOT devised a foam with full biodegradability and whose fire extinguishing capacity is higher than that of any existing analogue currently in use by fire fighters. After the fire is extinguished, the substance actively absorbs water, softens and falls apart into bioinert silica particles. And even when the foam accidentally enters living organisms, it does not not pose any danger to them. "Our foam is based on silica nanoparticles, which create a polymer network when exposed to air," says Alexander Vinogradov, deputy head of the SCAMT laboratory. "Such a network embraces and adheres to the burning object and momentarily cools it down. At the same time, the foam itself hardens. The inorganic origin of this polymer network allows it to resist temperatures above 1000 degrees Celsius, which ensures gigantic stability from the aggressive environment in the midst of a raging fire." "Most existing foams are made of organic materials and quickly deteriorate when temperature approaches 300 degrees Celsius. In our case, the foam creates a hard frame that not only puts out the fire, but also protects the object from re-ignition. With ordinary foams, re-ignition occurs within seconds after flame is applied to the object again." The scientists conducted a series of large-scale experiments of the hardening foam, including the imitation of an actual forest fire. The foam was used to create a flame retardant belt that was supposed stop the spread of the fire. The tests demonstrated that the foam easily localizes the forest fire seat and can stay active during the whole fire season. "The flame retardant belt made of our foam will prevent the spread of any forest fire, regardless of its strength and level of complexity," says Gennady Kuprin, head of SOPOT. "We can localize the fire and be sure that the adjacent territories will be safe. This is crucial to organize evacuation works during forest fires, where 9 of 10 people die in our and other countries." Explore further: Novel coatings show great promise as flame retardants in polyurethane foam More information: Alexander V. Vinogradov et al. Silica foams for fire prevention and firefighting, ACS Applied Materials & Interfaces (2015). DOI: 10.1021/acsami.5b08653


Chen Z.-X.,Fudan University | Ma H.,Laboratory of Advanced Materials | Chen M.-H.,Fudan University | Zhou X.-F.,Fudan University | And 5 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We present design techniques for special optical lattices that allow quantum simulation of spin frustration in two-dimensional systems. By carefully overlaying optical lattices with different periods and orientations we are able to adjust the ratio between the nearest-neighbor and next-nearest-neighbor interaction strengths in a square spin lattice and realize frustration effects. We show that only laser beams of a single frequency are required and the parameter space reachable in our design is broad enough to study the important phases in the J 1-J 2 frustrated Heisenberg model and checkerboard antiferromagnet model. By using the polarization spectroscopy for detection, distinct quantum phases and quantum phase transition points can be characterized straightforwardly. Our design thus offers a suitable setup for simulation of frustrated spin systems. © 2012 American Physical Society. Source


Sun X.,Sun Yat Sen University | Sun X.,Fudan University | Kong B.,Laboratory of Advanced Materials | Kong B.,Monash University | And 11 more authors.
Journal of Materials Chemistry B | Year: 2015

Mesoporous silica nanoparticles (MSNs) that can stably load therapeutic drugs and release them in response to a specific trigger are of great interest in disease diagnosis and treatment. However, the controlled-release of gaseous drug molecules such as hydrogen sulfide (H2S) from a long-range and stable MSN-based system still presents a great challenge. Herein, a MSN-based glutathione (GSH)-triggered controlled-release H2S system has been fabricated with high entrapment efficiency (99.0 ± 0.3%) and loading content (44.2 ± 0.1%) of diallyl trisulfide (DATS). After the addition of GSH (2 mM), DATS-MSN (100 μg mL-1) steadily releases moderate amounts of H2S (peaking at the 4th hour, ∼60 μM) in phosphate buffer solution (PBS). The release of H2S in plasma is similar to a physiological process (peaking at the 4th hour) and the DATS-MSN remains in the plasma of a rat's system over 9 hours without significantly affecting the blood pressure, heart rate and cardiac function. Moderate quantities of nanoparticles can be taken up by cardiomyocytes in vitro, while in vivo study shows that nanoparticles mainly accumulate in the liver and spleen, affecting the H2S level in these organs. Furthermore, DATS-MSN shows excellent biocompatibility, as well as superior cytoprotection and an isolated heart protection effect of H2S under ischemic/reperfusion injury. This study provides a new insight into controlled-release applications of MSN-based H2S releasing systems both in vitro and in vivo. © 2015 The Royal Society of Chemistry. Source


News Article
Site: http://www.nanotech-now.com/

Home > Press > New ceramic firefighting foam becomes stronger when temperature increases Abstract: A team of chemists from ITMO University, in collaboration with research company SOPOT, has developed a novel type of firefighting foam based on inorganic silica nanoparticles. The new foam beats existing analogues in fire extinguishing capacity, thermal and mechanical stability and biocompatibility. The results of the study were published in ACS Advanced Materials & Interfaces. Fighting large-scale fires usually involves firefighting foams based on synthetic substances, such as prefluorinated surfactants, that, despite their effectiveness, are extremely toxic for living organisms. Complete biodegradation of such foams can last for more than 200 years, with residues quickly penetrating deep into soil and surface water. This leads to the the accumulation of toxic elements in living organisms, such as plants, animals and men. Many countries have declined the use of such fire extinguishing agents or opted for reducing the production of such substances despite the absence of any decent alternatives. A group of scientists from the International Laboratory of Advanced Materials and Technologies (SCAMT) at ITMO University in Saint Petersburg and research company SOPOT devised a foam, which was awarded full biodegradability and whose fire extinguishing capacity is higher than that of any existing analogue currently in use by fire fighters. After the fire is extinguished, the substance actively absorbs water, softens and falls apart into bioinert silica particles. And even when the foam accidentally enters living organisms, it does not not pose any danger to them. "Our foam is based on silica nanoparticles, which create a polymer network when exposed to air," says Alexander Vinogradov, deputy head of the SCAMT laboratory. "Such a network embraces and adheres to the burning object and momentarily cools it down. At the same time, the foam itself hardens. The inorganic origin of this polymer network allows it to resist temperatures above 1000 degrees Celsius, which ensures gigantic stability from the aggressive environment in the midst of a raging fire." "Most existing foams are made of organic materials and quickly deteriorate when temperature approaches 300 degrees Celsius. In our case, the foam creates a hard frame that not only puts out the fire, but also protects the object from re-ignition. With ordinary foams, re-ignition occurs within seconds after flame is applied to the object again." The scientists conducted a series of large-scale experiments of the hardening foam, including the imitation of an actual forest fire. The foam was used to create a flame retardant belt that was supposed stop the spread of the fire. The tests demonstrated that the foam easily localizes the forest fire seat and can stay active during the whole fire season. "The flame retardant belt made of our foam will prevent the spread of any forest fire, regardless of its strength and level of complexity," says Gennady Kuprin, head of SOPOT. "We can localize the fire and be sure that the adjacent territories will be safe. This is crucial to organize evacuation works during forest fires, where 9 of 10 people die in our and other countries." For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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