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

Researchers from the University of Nebraska-Lincoln and South Dakota School of Mines and Technology are exploring the physical properties of two-dimensional materials called MXenes. Previous research by the Nebraska team on other MXene materials revealed their n-type (electron-rich) character and decreased conductivity in response to light. In contrast, the new material is the first MXene with demonstrated p-type (electron-deficient) property and increasing conductivity under illumination. "Previously studied MXenes were all n-type, but now we demonstrate the first p-type MXene,” said Alexander Sinitskii, the scientist who led this study. “This should enable complex structures where complementary MXenes are used together to achieve new electronic functionalities."The researchers performed experiments at the Nebraska Center for Materials and Nanoscience, a user facility that is part of the National Science Foundation-funded National Nanotechnology Coordinated Infrastructure.

Researchers from the University of Chicago; the University of California, Berkeley; Northwestern University; the University of Colorado Boulder; and  the U.S. Department of Energy’s Argonne National Laboratory have developed a new technique for growing quantum dots – nanocrystals used in lasers, quantum light-emitting diode (QLED) televisions, and solar cells. The researchers replaced organic solvents typically used to create quantum dots with molten salt – literally superheated sodium chloride of the type sprinkled on baked potatoes. "Sodium chloride is not a liquid in your mind, but assume you heat it to such a crazy temperature that it becomes a liquid … [N]obody ever considered these liquids as media” for the synthesis of quantum dots, said Dmitri Talapin, one of the scientists involved in this study.

Researchers from Carnegie Mellon University and the Indian Institute of Technology Bombay in Mumbai, India, have linked the immune response caused by lipid nanoparticles to their lipid chemistry. They found that some lipid structures bind strongly to receptors and others bind weakly. The strong interactions trigger the receptor and ultimately the immune response. The findings will help engineers tailor immune responses when designing lipid nanoparticles for drug delivery. "For vaccines, we might want something that's more immunogenic, so that the vaccine responds better,” said Namit Chaudhary, one of the scientists involved in this study. “But if we are delivering something to the brain or the liver, for example, we might not want to evoke substantial immune responses that might cause toxicity." 

Researchers from Penn State, the Massachusetts Institute of Technology (MIT) (including @MIT_ISN), and North Carolina Agricultural and Technical State University have discovered a different version of the Hall effect, called the nonreciprocal Hall effect, which, unlike the conventional Hall effect, does not require a magnetic field. In particular, in this case, the Hall voltage is proportional to the square of the current instead of being proportional to the current. Also, unlike the conventional Hall effect, which is driven by a force induced by the magnetic field, the nonreciprocal Hall effect arises from flowing electrons interacting with platinum nanoparticles. This discovery could lead to applications in the development of quantum communication and harvesting of energy via radio frequencies.

Researchers from the University of Virginia, the University of California-Berkeley, the University of Florida, the University of Tennessee-Knoxville, the University of Michigan, and the U.S. Department of Energy’s Sandia National Laboratories and Center for Integrated Nanotechnologies have developed an innovative technique to better determine the nanoscale effects of radiation on materials. Using advanced time-series imaging techniques with a transmission electron microscope, the team compiled more than 1,000 images capturing more than 250,000 defects formed during ion irradiation. The study revealed that defects in copper and gold exhibit different behaviors compared to those in palladium. This distinction underscores the need for specialized analytical models to accurately study these materials under radiation.

A difficult-to-describe nanoscale object called a magnetic skyrmion – which can be thought of as spinning circles of magnetism – might one day yield new microelectronic devices that can do more while consuming less power. Researchers from the Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab), Paul Scherrer Institute in Villigen, Switzerland, and Western Digital Corporation (San Jose, CA) have now made three-dimensional (3D) X-ray images of magnetic skyrmions. "Our results provide a foundation for nanoscale metrology for spintronics devices," said Peter Fischer, the scientist who led this study. The research was conducted in part at the Molecular Foundry, a DOE Office of Science user facility at Berkeley Lab.

Researchers from New York University, the U.S. Department of Energy’s Brookhaven National Laboratory, the Korea Advanced Institute of Science and Technology, and the National Institute for Materials Science in Tsukuba, Japan, have pioneered a new technique to identify and characterize atomic-scale defects in a two-dimensional (2D) material called hexagonal boron nitride. The team was able to detect the presence of individual carbon atoms replacing boron atoms in this material. "In this project, we essentially created a stethoscope for 2D materials," said Davood Shahrjerdi, one of the researchers involved in this study. "By analyzing the tiny and rhythmic fluctuations in electrical current, we can 'perceive' the behavior of single atomic defects."

Researchers from the U.S. Department of Energy’s Argonne National Laboratory and Lawrence Berkeley National Laboratory; Rice University; and Penn State University have revealed an adaptive response with a ferroelectric device, which responds to light pulses in a way that resembles the plasticity of neural networks. This behavior could find application in energy-efficient microelectronics. The material is laden with networked islands or domains that are nanometers in size and can rearrange themselves in response to light pulses. 

Researchers from Johns Hopkins University and the National Institute of Standards and Technology have developed a new blood test that diagnoses heart attacks in minutes rather than hours. The heart of the invention is a tiny chip with a groundbreaking nanostructured surface on which blood is tested. The chip's "metasurface" enhances electric and magnetic signals during Raman spectroscopy analysis, making heart attack biomarkers visible in seconds. The tool is sensitive enough to flag heart attack biomarkers that might not be detected with current tests. "We're talking about speed, we're talking about accuracy, and we're talking of the ability to perform measurements outside of a hospital," said Ishan Barman, one of the scientists involved in this study.

A nanocrystalline material is made up of many tiny crystals, but as they grow, the nanocrystalline material can weaken. Researchers from Lehigh University, Johns Hopkins University, George Mason University, the University of Tennessee, Knoxville, and the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and Sandia National Laboratories have discovered that the key to maintaining the stability of nanocrystalline materials at high temperatures lies in triple junctions – corners where three of these nanocrystals meet. What the scientists found is that when certain atoms are added to form an alloy, they prefer to occupy sites at these triple junctions, which prevents the nanocrystalline material from losing its strength over time.