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Nano News & Events
Researchers have demonstrated ultrafast and highly sensitive gas sensors using platinum selenide. This material - a transition metal dichalcogenide (TMD) - has promising potential in different areas of nanoelectronics, including optoelectonics as well as sensing.
For the first time, EPA is using TSCA to collect existing exposure and health and safety information on chemicals currently in the marketplace when manufactured or processed as nanoscale materials.
Paper, probably the cheapest and most widely used flexible and eco-friendly material in daily life, is a promising substrate for making flexible devices ranging from electronics to microfluidics, energy storage and sensors. In new work, researchers have developed a new and reliable method to achieve conformal coating of individual cellulose fibers in the paper and the fabrication of a metal electrode via patterning of gold and silver layers on the coated paper.
<?xml version="1.0" encoding="UTF-8"?> 2D nanomaterial pulls ahead with working registers and latch circuits and devices that let electrons zip through unimpeded Image: Stanford University Molybdenum disulfide, a two dimensional semiconductor that’s just 3 atoms thick, has had a big year. In October, a group of researchers made a 1-nanometer transistor from the material, showing that even if silicon transistors stop shrinking, the new material might provide a path forward. In December, at the IEEE International Electron Devices Meeting in San Francisco, researchers presented work they say shows that molybdenum disulfide not only makes for superlative single transistors, but can be made into complex circuits using realistic manufacturing methods. At the meeting, a group from Stanford showed that molybdenum disulfide transistors made from large sheets of MoS2 can be used to make transistors with 10-nanometer-long, gate shaving electronic properties that approach the material’s theoretical limits. The devices displayed traits close to ballistic conduction, a state of very low electrical resistance that allows the unimpeded flow of charge over relatively long distances—a phenomenon that should lead to speedy circuits. Separately, a team from MIT demonstrated complex circuit elements made from MoS2 transistors. Most of the work on molybdenum disulfide so far has been what Stanford electrical engineer Eric Pop calls “Powerpoint devices.” These one-off devices, made by hand in the lab, have terrific performance that looks great in a slide. This step is an important one, says Pop, but the 2D material is now maturing. Image: Stanford University The Stanford lab’s transistors are not as small as the record-breaking ones demonstrated in October. What’s significant, says group leader Pop, is that these latest transistors maintained similar performance even though they were made using more industrial-type techniques. Instead of using Scotch tape to peel off a layer of molybdenum disulfide from a rock of the material, then carefully placing it down and crafting one transistor at a time, Pop’s grad student started by growing a large sheet of the material on a wafer of silicon. In a transistor, a gate electrode switches the semiconductor channel between conducting and insulating states. In the Stanford device, the tricky part was coming up with an easy way to make a small gate atop the molybdenum disulfide without harming it, says Pop. That is, until his student, Christopher English, realized they could harness the power of rust. English chose a somewhat unusual material, aluminum, to serve as the gate electrode. He deposited a 20-nanometer finger of aluminum on the molybdenum, then allowed it to oxidize and shrink down to a smaller size. The gate ends up being about 10 nanometers. At these relatively small dimensions, the molybdenum disulfide transistors approach their ultimate electrical limit, a state called ballistic conduction. When a device is small enough (or at low enough temperature), electrons will travel through the conducting medium without scattering because of collisions with the atoms that make up the material. Transistors operating ballistically should switch very fast and enable high-performance processors. Pop estimates that about 1 in 5 electrons moves though the rusty transistors ballistically. By further improving the quality of the material (or making the transistors smaller), he expects that ratio to improve. The important thing, he says, is the way they achieved this: using methods that could translate to larger scales. “We have all the ingredients we need to scale this up,” says Pop. Zippy nanoscale transistors are great on their own, but they’re useful only if you can build them into circuits. Researchers from MIT demonstrated just that by constructing working registers and latches. They managed the feat, says electrical engineer Dina El-Damak, by creating computer-aided design software tailored to MoS2. This sort of software is common in the silicon world and enables designers to come up with new circuits relatively easily. (El-Damak worked on the molybdenum disulfide project at MIT and is now a professor at the University of Southern California in Los Angeles.) Since molybdenum disulfide is so new, not many circuit designers have worked with the material. So far, most work has been done by trial and error, one device at a time. The MIT group can create an informed circuit design, using their computer models to simulate the best and worst cases, based on the material’s known properties and the performance of previous devices, says El-Damak. Then the group fabricates the design that seems most likely to work, tests its performance, and feeds the results back into the program. “By doing this, we have more confidence in scaling up this technology,” she says. Both Pop and El-Damak say molybdenum disulfide is unlikely to be a direct replacement for silicon. The material will either be used to build complementary systems on top of silicon chips, or it will be used on its own in flexible, transparent electronics. It’s also possible that some other 2D semiconductor will end up being a better option. Molybdenum disulfide is a few steps ahead because researchers have worked with it more than, say, tungsten selenide, and know how to grow the material over large areas. The Stanford and MIT research demonstrates important progress in this field, says Deji Akinwande, an electrical engineer at the University of Texas at Austin who co-chaired the IEDM session on 1D and 2D devices. People who work in industry are always asking when these materials will be made into useful circuits, and now it’s happening, he says. “Industry is starting to take this more seriously, now that it’s no longer just the grad student in the basement working on it,” he says.
Researchers designed an extremely efficient catalytic system to remove carbon monoxide.
Drunen (The Netherlands) and Leuven (Belgium)—January 3, 2017—Today, the world-leading research and innovation hub in nano-electronics, energy and digital technology imec (partner in...
A new review article discusses recent developments in stimuli-responsive membranes with an emphasis on membranes manufactured by polymer self-assembly.
By harnessing the intrinsic organizational properties of polymeric tethers, nanoparticles can be programmed to self-assemble into a variety of micron-sized domain structures in a reversible way.
Nanoparticles containing three different layers of material can help to boost the performance of a zinc-air battery, researchers have found.
By suspending tiny metal nanoparticles in liquids, scientists are brewing up conductive ink-jet printer 'inks' to print inexpensive, customizable circuit patterns on just about any surface.
Duane Boning has been named the Clarence J. LeBel Professor of Electrical Engineering. The chair is named for Clarence Joseph LeBel '26, SM '27, who co-founded Audio Devices in 1937, and was a pioneer in recording discs, magnetic media for tapes, and in hearing aids and stethoscopes. “Boning’s teaching is recognized as outstanding at both the undergraduate and graduate levels, and he is a leader in the field of manufacturing and design,” said Anantha Chandrakasan, the Vannevar Bush Professor of Electrical Engineering and head of the Department of Electrical Engineering and Computer Science (EECS). “This is fitting recognition of his outstanding contributions to research, teaching, mentoring, and service.” Boning’s research focuses on manufacturing and design, with emphasis on statistical modeling, control, and variation reduction in semiconductor, MEMS, photonic, and nanomanufacturing processes. His early work developed computer integrated manufacturing approaches for flexible design of IC fabrication processes. He also drove the development and adoption of run-by-run, sensor-based, and real-time model-based control methods in the semiconductor industry. He is a leader in the characterization and modeling of spatial variation in IC and nanofabrication processes, including plasma etch and chemical-mechanical polishing (CMP), where test mask design and modeling tools developed in his group have been commercialized and adopted in industry. Boning served as editor in chief for the IEEE Transactions on Semiconductor Manufacturing from 2001 to 2011, and was named a fellow of the IEEE for contributions to modeling and control in semiconductor manufacturing in 2005. In addition to creating the graduate-level course 6.780J/2.830J (Control of Manufacturing Process), he has lectured in several core EECS subjects, including 6.003 (Signals and Systems) and 6.001 (Structure and Interpretation of Computer Programs), and is also an outstanding recitation and laboratory instructor. His teaching has been recognized with the MIT Ruth and Joel Spira Teaching Award. Boning won the Best Advisor Award from the MIT ACM/IEEE student organization in 2012 and the 2016 Capers and Marion McDonald Award for Excellence in Mentoring and Advising in the School of Engineering. Boning served as associate head from Electrical Engineering in EECS from 2004 to 2011. He has previously and presently serves as associate director in the Microsystems Technology Laboratories, where he oversees the information technology and computer-aided design services organization in the laboratories. He is a long-standing and active participant in the MIT Leaders for Global Operations program. Since 2011, he has served as the director for the MIT/Masdar Institute Cooperative Program, fostering many joint activities between MIT and Masdar Institute. From 2011 through 2013, he served as founding faculty lead in the MIT Skoltech Initiative, working to launch the Skolkovo Institute of Science and Technology (Skoltech). Within MIT, Boning has served on several Institute committees, including as chair of the Committee on Undergraduate Admissions and Financial Aid (CUAFA) in 2007, and he will serve as chair of the Committee on the Undergraduate Program (CUP) in 2016-2017.
MIT researchers have developed low-cost chemical sensors, made from chemically altered carbon nanotubes, that enable smartphones or other wireless devices to detect trace amounts of toxic gases. Using the sensors, the researchers hope to design lightweight, inexpensive radio-frequency identification (RFID) badges to be used for personal safety and security. Such badges could be worn by soldiers on the battlefield to rapidly detect the presence of chemical weapons — such as nerve gas or choking agents — and by people who work around hazardous chemicals prone to leakage. “Soldiers have all this extra equipment that ends up weighing way too much and they can’t sustain it,” says Timothy Swager, the John D. MacArthur Professor of Chemistry and lead author on a paper describing the sensors that was published in the Journal of the American Chemical Society. “We have something that would weigh less than a credit card. And [soldiers] already have wireless technologies with them, so it’s something that can be readily integrated into a soldier’s uniform that can give them a protective capacity.” The sensor is a circuit loaded with carbon nanotubes, which are normally highly conductive but have been wrapped in an insulating material that keeps them in a highly resistive state. When exposed to certain toxic gases, the insulating material breaks apart, and the nanotubes become significantly more conductive. This sends a signal that’s readable by a smartphone with near-field communication (NFC) technology, which allows devices to transmit data over short distances. The sensors are sensitive enough to detect less than 10 parts per million of target toxic gases in about five seconds. “We are matching what you could do with benchtop laboratory equipment, such as gas chromatographs and spectrometers, that is far more expensive and requires skilled operators to use,” Swager says. Moreover, the sensors each cost about a nickel to make; roughly 4 million can be made from about 1 gram of the carbon nanotube materials. “You really can’t make anything cheaper,” Swager says. “That’s a way of getting distributed sensing into many people’s hands.” The paper’s other co-authors are from Swager’s lab: Shinsuke Ishihara, a postdoc who is also a member of the International Center for Materials Nanoarchitectonics at the National Institute for Materials Science, in Japan; and PhD students Joseph Azzarelli and Markrete Krikorian. Wrapping nanotubes In recent years, Swager’s lab has developed other inexpensive, wireless sensors, called chemiresistors, that have detected spoiled meat and the ripeness of fruit, among other things. All are designed similarly, with carbon nanotubes that are chemically modified, so their ability to carry an electric current changes when exposed to a target chemical. This time, the researchers designed sensors highly sensitive to “electrophilic,” or electron-loving, chemical substances, which are often toxic and used for chemical weapons. To do so, they created a new type of metallo-supramolecular polymer, a material made of metals binding to polymer chains. The polymer acts as an insulation, wrapping around each of the sensor’s tens of thousands of single-walled carbon nanotubes, separating them and keeping them highly resistant to electricity. But electrophilic substances trigger the polymer to disassemble, allowing the carbon nanotubes to once again come together, which leads to an increase in conductivity. In their study, the researchers drop-cast the nanotube/polymer material onto gold electrodes, and exposed the electrodes to diethyl chlorophosphate, a skin irritant and reactive simulant of nerve gas. Using a device that measures electric current, they observed a 2,000 percent increase in electrical conductivity after five seconds of exposure. Similar conductivity increases were observed for trace amounts of numerous other electrophilic substances, such as thionyl chloride (SOCl2), a reactive simulant in choking agents. Conductivity was significantly lower in response to common volatile organic compounds, and exposure to most nontarget chemicals actually increased resistivity. Creating the polymer was a delicate balancing act but critical to the design, Swager says. As a polymer, the material needs to hold the carbon nanotubes apart. But as it disassembles, its individual monomers need to interact more weakly, letting the nanotubes regroup. “We hit this sweet spot where it only works when it’s all hooked together,” Swager says. Resistance is readable To build their wireless system, the researchers created an NFC tag that turns on when its electrical resistance dips below a certain threshold. Smartphones send out short pulses of electromagnetic fields that resonate with an NFC tag at radio frequency, inducing an electric current, which relays information to the phone. But smartphones can’t resonate with tags that have a resistance higher than 1 ohm. The researchers applied their nanotube/polymer material to the NFC tag’s antenna. When exposed to 10 parts per million of SOCl2 for five seconds, the material’s resistance dropped to the point that the smartphone could ping the tag. Basically, it’s an “on/off indicator” to determine if toxic gas is present, Swager says. According to the researchers, such a wireless system could be used to detect leaks in Li-SOCl2 (lithium thionyl chloride) batteries, which are used in medical instruments, fire alarms, and military systems. Alexander Star, a professor of chemistry and bioengineering and clinical and translational science at the University of Pittsburgh, says the researchers’ design for a wireless sensor (or dosimeter) for electrophilic substances could improve soldier safety. “The authors were able to synthesize a [carbon nanotube] composite sensitive to … a class of chemicals of high interest for sensing,” Star says. “This type of device architecture is important for real-life application, due to the fact that a chemical weapon dosimeter worn by military and security personnel requires rapid reading.” The next step, Swager says, is to test the sensors on live chemical agents, outside of the lab, which are more dispersed and harder to detect, especially at trace levels. In the future, there’s also hope for developing a mobile app that could make more sophisticated measurements of the signal strength of an NFC tag: Differences in the signal will mean higher or lower concentrations of a toxic gas. “But creating new cell phone apps is a little beyond us right now,” Swager says. “We’re chemists.” The work was supported by the National Science Foundation and the Japan Society for the Promotion of Science.
<?xml version="1.0" encoding="UTF-8"?> Could safe, durable and high-temperature Li-S batteries lead to EV applications? Image: iStockphoto Lithium-sulfur (Li-S) batteries have been pursued as an alternative to lithium-ion (Li-ion) batteries for powering electric vehicles due to their ability to hold up to four times as much energy per unit mass as Li-ion. However, Li-S batteries don’t come without some problems. For instance, the sulfur in the electrode can become depleted after just a few charge-discharge cycles, or polysulfides can pass through the cathode and foul the electrolyte. Another issue Li-S batteries face is the difficulty of ensuring that they operate safely at high temperatures due to their low boiling and flash temperatures. Now, researchers at the University of Western Ontario, in collaboration with a team from the Canadian Light Source, have leveraged a relatively new coating technique dubbed molecular layer deposition (MLD) that promises to lead to safe and durable high-temperature Li-S batteries. This MLD technique is essentially an adaptation of the conventional atomic layer deposition (ALD) techniques that have been used to deposit thin inorganic oxide films. Where MLD departs from its predecessor is that it can incorporate organic components into the films, making it possible to create hybrid organic-inorganic thin films. MLD is a technique that has proven itself applicable for use in energy storage systems; it provides a high level of control over film thickness and the chemical composition of the target material at a molecular scale. In research described in the journal Nano Letters , the Canadian researchers were able to fabricate safe, high-temperature Li–S batteries on universal carbon–sulfur electrodes using an MLD alucone coating “We demonstrated that MLD alucone coating offers a safe and versatile approach toward lithium-sulfur batteries at elevated temperature,” said Andy Xueliang Sun, who led the research at the University of Western Ontario, in a press release. In the experiments, the researchers demonstrated that the MLD alucone coated carbon-sulfur electrodes remained stable and even showed improved performance at temperatures as high as 55 degrees Celsius. The researchers expect that these performance figures should significantly prolong battery life for high-temperature Li-S batteries.
A new graphene and nanomaterials research centre, known as MackGraphe, has officially opened in São Paulo
University of Sydney has unveiled the country’s first purpose-built nanoscience institute
In the nanoworld, tiny particles of gold can operate like snow blowers, churning through surface layers of an important class of semiconductors to dig unerringly straight paths. The surprising trenching capability, reported by scientists ...
Heat may be the key to killing certain types of cancer, and new research from a team including National Institute of Standards and Technology (NIST) scientists has yielded unexpected results that should help optimize the design of ...
The characterization technology needed for nanoelectronic materials and device research, development, and manufacturing was discussed by experts from industry, government, and academia at the 2015 International Conference on Frontiers of ...
Truth shines a light into dark places. But sometimes to find that truth in the first place, its better to stay in the dark. Thats what recent findings* at the National Institute of Standards and Technology (NIST) show about methods for ...
Rechargeable battery manufacturers may get a jolt from research performed at the National Institute of Standards and Technology (NIST) and several other institutions, where a team of scientists has discovered* a safe, inexpensive, ...