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

Researchers from the University of Nebraska Lincoln and the University at Buffalo have crafted a new type of transistor, called a magneto-electric transistor, that generates less heat than a typical silicon-based transistor. Rather than depend on electric charge – as silicon-based transistors do – a magneto-electric transistor depends on spin, a magnetism-related property of electrons that points up or down and can be read, like an electric charge can, as a 1 or 0. The team underlaid graphene – an ultra-robust material just one atom thick – with chromium oxide. When applying voltage, the spins of the underlying chromium oxide pointed up or down, ultimately forcing the spin orientation of the graphene's electric current to veer left or right, respectively.

From new biomaterials to novel photonic devices, materials built through a process called bottom-up self-assembly are opening up pathways to new technologies, with properties tuned at the nanoscale. But to unlock the potential of these materials, researchers need to "see" into them so they can control their design and fabrication and enable the materials’ desired properties. Now, researchers from Columbia University and the U.S. Department of Energy's Brookhaven National Laboratory have imaged the inside of a novel material self-assembled from nanoparticles, with seven-nanometer resolution. 

A research team from Northwestern University and South China University of Technology in Guangzhou has demonstrated, for the first time, that a nano-sized material called a metal-organic framework is a stable and selective catalyst for breaking down polyester-based plastic into its component parts. Only three things were needed: plastic, hydrogen, and the metal-organic framework. An important bonus is that one of the component parts into which the plastic was broken down was terephthalic acid, a chemical used to produce plastic.

A major research challenge in the field of nanotechnology is finding efficient ways to control light, which is essential for high-resolution imaging, biosensors, and cell phones. Because light is an electromagnetic wave that carries no charge, it is difficult to manipulate it with voltage or an external magnetic field. To solve this challenge, engineers have already found indirect ways to manipulate light using properties of the materials from which light reflects. But the challenge is difficult on the nanoscale, because materials behave differently in atomically thin states. Now, researchers from the University of Pennsylvania, Kenyon College, and the Air Force Research Laboratory have discovered a magnetic property in antiferromagnetic materials that allows for the manipulation of light on the nanoscale and simultaneously links the semiconductor material to magnetism, a gap that scientists have been trying to bridge for decades. 

Using a protein nanoparticle they designed, scientists at the University of Illinois Chicago have identified two distinct subtypes of neutrophils and found that one of the subtypes can be used as a drug target for inflammatory diseases. Neutrophils are a type of white blood cell that help fight infection, clear dead cell debris, and heal tissue injury. Further investigation with the nanoparticle showed that the subtypes have different cell surface receptors and that they are functionally distinct in their helpful capacities to kill bacteria and their harmful potential to promote inflammation. 

Scientists at the University of Illinois Chicago have developed a treatment for pulmonary fibrosis by using nanoparticles coated in mannose – a type of sugar – to stop a population of lung cells called macrophages that contribute to lung tissue scarring. The cell-targeting method holds promise for preventing this severe lung scarring disease, which can result in life-threatening complications, such as shortness of breath.

Curcumin, a compound found in turmeric, has anti-inflammatory and antioxidant properties and is known to suppress the production of blood vessels in malignant tumors. Bioengineers at the University of California Riverside have now discovered that when delivered through magnetic hydrogels into stem cell cultures, curcumin paradoxically also promotes the secretion of vascular endothelial growth factor, which helps vascular tissues grow. (The hydrogel contained magnetic iron oxide nanoparticles that were coated with curcumin.)

Researchers from the University of California, Berkeley, the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, and the National Institute for Materials Science in Tsukuba, Japan, have determined that interactions between electrons are what give rise to the divergent effects observed when graphene is doped with electrons versus holes. Electron–hole asymmetry in graphene has mainly been attributed to extrinsic sources such as impurities and strain, as opposed to intrinsic effects such as particle interactions. In this work, the researchers determined that, contrary to earlier thinking, intrinsic electronic correlations are, in fact, the primary driver of graphene’s electron–hole asymmetry.

An international team of scientists has shown that extremely small arrays of magnets can order themselves by increasing entropy, or the tendency of physical systems to disorder, a behavior that appears to contradict standard thermodynamics. The system examined in this work, called tetris spin ice, is composed of two-dimensional arrays of very small magnets that are “frustrated,” that is, they remain disordered, even though the system retains some order. 

Researchers from Texas A&M University have developed water-stable, 2D covalent organic framework (COF) nanoparticles that can direct the differentiation of human mesenchymal stem cells into bone cells. Until now, the difficulty of processing COFs into nanosized materials – along with their poor stability – has limited their application in regenerative medicine. The researchers state that to the best of their knowledge, this is the first report demonstrating the ability of COFs to direct stem cells toward bone tissue.