Tag Archives: material

In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles.

Credit: CCNY

Study Unveils New Half-Light Half-Matter Quantum Particles

Prospects of developing computing and communication technologies based on quantum properties of light and matter may have taken a major step forward thanks to research by City College of New York physicists led by Dr. Vinod Menon.

In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles.

“Besides being a fundamental breakthrough, this opens up the possibility of making devices which take the benefits of both light and matter,” said Professor Menon.  

In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles. Credit: CCNY
In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles.
Credit: CCNY

For example one can start envisioning logic gates and signal processors that take on best of light and matter. The discovery is also expected to contribute to developing practical platforms for quantum computing. 

Dr. Dirk Englund, a professor at MIT whose research focuses on quantum technologies based on semiconductor and optical systems, hailed the City College study.

“What is so remarkable and exciting in the work by Vinod and his team is how readily this strong coupling regime could actually be achieved. They have shown convincingly that by coupling a rather standard dielectric cavity to exciton–polaritons in a monolayer of molybdenum disulphide, they could actually reach this strong coupling regime with a very large binding strength,” he said. 

Professor Menon’s research team included City College PhD students, Xiaoze Liu, Tal Galfsky and Zheng Sun, and scientists from Yale University, National Tsing Hua University (Taiwan) and Ecole Polytechnic -Montreal (Canada).

The study appears in the January issue of the journal “Nature Photonics.” It was funded by the U.S. Army Research Laboratory’s Army Research Office and the National Science Foundation through the Materials Research Science and Engineering Center – Center for Photonic and Multiscale Nanomaterials. 

Source: The City College New of York

KAUST team synthesizes novel metal-organic framework for efficient CO2 removal

By Caitlin Clark

“In Professor Mohamed Eddaoudi’s research group, we are always on the quest to find novel nanostructured functionalized materialsfor specific applications,” explained KAUST Research Scientist Dr. Youssef Belmabkhout, a member of Prof. Eddaoudi’s Functional Materials Design, Discovery, and Development (FMD3) group, part of KAUST’s Advanced Membranes and Porous Materials (AMPM) research center.

Dr. Osama Shekhah, Senior Research Scientist in the FMD3 group added that the group searches “for materials that will be highly suitable for trace and low CO2 concentration removal using purely physical adsorption. These will help in energy saving and in the reduction of the cost of the production, purification, and enrichment of highly valuable commodities such as CH4, H2, O2, N2, and others.”

Drs. Shekhah and Belmabkhout and a team of researchers from Prof. Eddaoudi’s group recently discovered and synthesized a new porous, moisture-resistant, inexpensive and reusable copper-based metal-organic framework (MOF) called SIFSIX-3-Cu that can selectively adsorb and remove trace CO2 from mixtures of various gases. Their findings were published in the June 25 edition of Nature Communications (DOI: 10.1038/ncomms5228).

MOFs are a promising new class of hybrid solid-state materials for CO2 removal. “Their uniqueness,” explained Prof. Eddaoudi, “resides in the ability to control their assembly and introduce functionality on demand. This feature is not readily available in other solid-state materials.”

The researchers showed for the first time that MOF crystal chemistry permits the assembly of a new isostructural hexafluorosilicate MOF (SIFSIX-3-Cu) based on copper instead of zinc.

“This technology is anticipated to outperform the existing mature technologies for CO2 physical adsorption in terms of energy efficiency,” says Dr. Shekhah. “The key factors for this finding are the combination of suitable pore size and high, uniform charge density in the pores of the MOF.”

Using their newly synthesized MOF, the researchers examined the conditions relevant to direct air capture (DAC), a mechanism to remove CO2 from air and reduce greenhouse gas emissions uniformly around the world.

DAC is more challenging than post-combustion capture, but it may be practical if alternative “suitable adsorbent combining optimum uptake, kinetics, energetics and CO2 selectivity is available at trace CO2 concentration,” the researchers stated.

The team discovered that contracting SIFSIX-3-Cu’s pore system to 3.5 Å enhanced the material’s efficiency, making it able to adsorb relatively large CO2 amounts 10-15 times higher than zinc-based metal-organic adsorbents, such as SIFSIX-3-Zn. In SIFSIX-3-Zn, the pore size is 3.84 Å.

“We attribute this property to enhanced physical sorption through the favorable electrostatic interactions between CO2 molecules and fluorine atoms present on the surface of the adsorbent,” explained Zhijie Chen, a Ph.D. student in the FMD3 group and a co-author of the paper.

Dr. Vincent Guillerm, a post-doctoral fellow in the FMD3 group and a co-author of the paper also noted that, “the pore contraction gives CO2 uptake and selectivity at very low partial pressures. This is relevant to DAC and trace carbon dioxide removal.”

“SIFSIX-3-Cu gives enhanced CO2 physical adsorption properties, uptake, and selectivity in highly diluted gas streams, and this performance is unachievable with other classes of porous materials,” added Dr. Karim Adil, a co-author of the paper and Research Scientist in the FMD3 group.

The researchers are excited about their finding as it offers the potential to be used not only for DAC but also for other applications related to energy, the environment, and the healthcare field. For example, SIFSIX-3-Cu could be used to remove and recycle CO2 in confined spaces, such as in submarines or space shuttles, and could also be used in anesthesia machines, which require efficient CO2 sorbents.

“Our work paves the way for scientists to develop new separation agents suitable for challenging endeavor pertaining to CO2 ultra-purification processing,” said Dr. Shekhah. “Our study is also part of a greater critical effort to develop economical and practical pathways to reduce cumulative CO2 emissions provoking the undesirable greenhouse gas effect.”

Prof. Eddaoudi reiterated that “MOFs offer remarkable CO2 physical adsorption attributes in highly diluted gas streams thanks to their ability for rational pore size modification and inorganic-organics moieties substitution. Other classes of plain materials are unable to attain this.”

In the future, Prof. Eddaoudi’s FMD3 group will continue to develop topologically and chemically different MOFs. “We aim to target novel MOFs with suitable pore size and high charge density,” explained Prof. Eddaoudi. “We will then use these for the important task of removing trace and low and high concentration CO2.”

Source: KAUST


 

Magnetic states at oxide interfaces controlled by electricity. Top image show magnetic state with -3 volts applied, and bottom image shows nonmagnetic state with 0 volts applied. Credit: University of Pittsburgh

New Discovery Could Pave the Way for Spin-based Computing

Novel oxide-based magnetism follows electrical commands

PITTSBURGH—Electricity and magnetism rule our digital world. Semiconductors process electrical information, while magnetic materials enable long-term data storage. A University of Pittsburgh research team has discovered a way to fuse these two distinct properties in a single material, paving the way for new ultrahigh density storage and computing architectures.

Whilephones and laptops rely on electricity to process and temporarily store information, long-term data storage is still largely achieved via magnetism. Discs coated with magnetic material are locally oriented (e.g. North or South to represent “1” and “0”), and each independent magnet can be used to store a single bit of information. However, this information is not directly coupled to the semiconductors used to process information. Having a magnetic material that can store and process information would enable new forms of hybrid storage and processing capabilities.Such a material has been created by the Pitt research team led by Jeremy Levy, a Distinguished Professor of Condensed Matter Physics in Pitt’s Kenneth P. Dietrich School of Arts and Sciences and director of the Pittsburgh Quantum Institute.

Magnetic states at oxide interfaces controlled by electricity. Top image show magnetic state with -3 volts applied, and bottom image shows nonmagnetic state with 0 volts applied. Credit: University of Pittsburgh
Magnetic states at oxide interfaces controlled by electricity. Top image show magnetic state with -3 volts applied, and bottom image shows nonmagnetic state with 0 volts applied. Credit: University of Pittsburgh

Levy, other researchers at Pitt, and colleagues at the University of Wisconsin-Madison today published their work in Nature Communications, elucidating their discovery of a form of magnetism that can be stabilized with electric fields rather than magnetic fields. The University of Wisconsin-Madision researchers were led by Chang-Beom Eom, the Theodore H. Geballe Professor and Harvey D. Spangler Distinguished Professor in the Department of Materials Science and Engineering. Working with a material formed from a thick layer of one oxide—strontium titanate—and a thin layer of a second material—lanthanum aluminate—these researchers have found that the interface between these materials can exhibit magnetic behavior that is stable at room temperature. The interface is normally conducting, but by “chasing” away the electrons with an applied voltage (equivalent to that of two AA batteries), the material becomes insulating and magnetic. The magnetic properties are detected using “magnetic force microscopy,” an imaging technique that scans a tiny magnet over the material to gauge the relative attraction or repulsion from the magnetic layer.

The newly discovered magnetic properties come on the heels of a previous invention by Levy, so-called “Etch-a-Sketch Nanoelectronics” involving the same material. The discovery of magnetic properties can now be combined with ultra-small transistors, terahertz detectors, and single-electron devices previously demonstrated.

“This work is indeed very promising and may lead to a new type of magnetic storage,” says Stuart Wolf, head of the nanoSTAR Institute at the University of Virginia. Though not an author on this paper, Wolf is widely regarded as a pioneer in the area of spintronics.

“Magnetic materials tend to respond to magnetic fields and are not so sensitive to electrical influences,” Levy says. “What we have discovered is that a new family of oxide-based materials can completely change its behavior based on electrical input.”

This discovery was supported by grants from the National Science Foundation, the Air Force Office of Scientific Research, and the Army Research Office.

Source: University of Pittsburgh News