News from the NNI Community - Research Advances Funded by Agencies Participating in the NNI

Researchers from the U.S. Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL), Purdue University, and the University of Illinois Urbana−Champaign have used a nanoscale quantum sensor to measure spin fluctuations near a phase transition in a magnetic thin film. Thin films with magnetic properties at room temperature are essential for data storage, sensors and electronic devices because their magnetic properties can be precisely controlled and manipulated. The researchers used a specialized instrument called a scanning nitrogen-vacancy center microscope at the Center for Nanophase Materials Sciences, a DOE Office of Science user facility at ORNL. A nitrogen-vacancy center is an atomic-scale defect in diamond in which a nitrogen atom takes the place of a carbon atom, and a neighboring carbon atom is missing, creating a special configuration of quantum spin states.

Scientists have blended electron microscopy with artificial intelligence (AI) so they can observe the movements of atoms in nanoparticles at an unprecedented time resolution. Because the atoms are usually barely visible in electron microscope images, scientists cannot be sure how they are behaving. So, the scientists in this study trained a deep neural network, AI’s computational engine, that can “light up” the electron-microscope images, revealing the underlying atoms and their dynamic behaviors. “We have developed an artificial-intelligence method that opens a new window for the exploration of atomic-level structural dynamics in materials,” says Carlos Fernandez-Granda, one of the scientists involved in this study.

Researchers at Northwestern University have created a new platform for monitoring chemical contaminants in the environment. The platform can detect the metals lead and cadmium at concentrations down to two and one parts per billion, respectively, in a matter of minutes. It was created by interfacing nanomechanical microcantilevers with synthetic biology biosensors. When the tiny cantilevers are coated with DNA molecules, biosensing molecules bind to the DNA, causing the cantilevers to bend. When exposed to toxic metals, the biosensors unbind, causing the cantilever to “de-bend,” which can be measured precisely to detect the toxic metals.

Researchers from the University of Illinois Urbana-Champaign have developed organic-material-based nanozymes – synthetic nanomaterials that have enzyme-like catalytic properties – that are non-toxic, environmentally friendly, and cost effective. To create these nanozymes, the researchers used a novel particle synthesis technique that brought each nanozyme’s size down to less than 100 nanometers. In one study, the researchers showed that these nanozymes, combined with a colorimetric sensing platform, could detect the presence of histamine in spinach and eggplant. In another study, the nanozymes were used to detect the presence of glyphosate, a common agricultural herbicide, in plants. “We were able to show that our system doesn’t just work in the lab, it has the potential to be utilized for real-world applications as a cost-effective molecule sensing system for food and agriculture,” said Dong Hoon Lee, lead author of the study.

Researchers at the Massachusetts Institute of Technology (MIT), Brown University, and the Rhode Island School of Design in Providence, RI, have developed an autonomous programmable computer in the form of an elastic fiber, which could monitor health conditions and physical activity, alerting the wearer to potential health risks in real time. Clothing containing the fiber computer was comfortable and machine washable, and the fibers were nearly imperceptible to the wearer, the researchers report. “Our bodies broadcast gigabytes of data through the skin every second in the form of heat, sound, biochemicals, electrical potentials, and light, all of which carry information about our activities, emotions, and health. Wouldn’t it be great if we could teach clothes to capture, analyze, store, and communicate this important information in the form of valuable health and activity insights?” says Yoel Fink, senior author of a paper on the research and principal investigator in MIT’s Research Laboratory of Electronics and the Institute for Soldier Nanotechnologies at MIT.

Scientists from the Massachusetts Institute of Technology and the National Institute for Materials Science in Tsukuba, Japan, have discovered that electrons can form crystalline structures in materials composed of either four or five layers of graphene. (Graphene is a one-atom-thick layer of carbon atoms arranged in hexagons, which looks like a honeycomb structure.) Last year, the scientists reported that electrons became fractions of themselves upon applying a current to a material composed of rhombohedral pentalayer graphene and hexagonal boron nitride. This time, the scientists have shown that electrons can become fractions of themselves without a magnetic field. They also found that what they saw last time can be understood to emerge in an electron “liquid” phase, analogous to water, and what they have now observed can be interpreted as an electron “solid” phase that looks like the formation of electronic “ice.”

Researchers from the Molecular Foundry, a user facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, Columbia University, and Universidad Autónoma de Madrid in Spain have developed a new optical computing material from photon-avalanching nanoparticles. This approach offers a path toward realizing smaller, faster components for next-generation computers by taking advantage of intrinsic optical bistability – a property that allows a material to use light to switch between two different states, such as glowing brightly or not at all. For decades, researchers have sought ways to make a computer that uses light instead of electricity. But in previous studies, optical bistability had almost exclusively been observed in bulk materials that were too big for a microchip and challenging to mass produce. Now, the researchers suggest that the new photon-avalanching nanoparticles could overcome these challenges in realizing optical bistability at the nanoscale.

Using an approach called DNA origami, scientists at Caltech have developed a technique that could lead to cheaper, reusable biomarker sensors for quickly detecting proteins in bodily fluids, eliminating the need to send samples out to lab centers for testing. DNA origami enables long strands of DNA to fold, through self-assembly, into molecular structures at the nanoscale. In this study, DNA origami was used to create a lilypad-like structure – a flat, circular surface about 100 nanometers in diameter, tethered by a DNA linker to a gold electrode. Both the lilypad and the electrode have short DNA strands available to bind with an analyte, a molecule of interest in solution – whether that be a molecule of DNA, a protein, or an antibody. 

Scientists from the University of Oklahoma and Northwestern University have shown that adding a crystalized molecular layer to quantum dots made of perovskite prevents them from darkening or blinking. Quantum dots, which are nanoparticles that have unique optical and electronic properties, usually fade out after 10–20 minutes of use. The crystal coverings developed in this study extend the continuous light emission of quantum dots to more than 12 hours with virtually no blinking. According to Yitong Dong, the scientist who led this study, these findings pave the way for the future design of quantum emitters – devices that emit single photons on demand, with applications in quantum computing. 

Researchers from the University of Connecticut; Harvard University; the Massachusetts Institute of Technology; RTX BBN Technologies in Arlington, VA; and the National Institute for Materials Science in Tsukuba, Japan, have discovered that electrons in twisted trilayer graphene behave unlike those described by Bardeen-Cooper-Schrieffer theory of paired electrons. However,  twisted trilayer graphene shares properties with high-temperature cuprates, in which electrons also pair up, but differently from traditional superconductors. Many previous studies in graphene are limited in describing superconductivity, because those experiments focus on the properties of single electrons rather than electron pairs, says Pavel Volkov, one of the researchers involved in this study. "What matters is that electrons form pairs, and somehow you want to probe the properties of those pairs to be able to study superconductivity,” he says.