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

Tiny fluorescent semiconductor dots, called quantum dots, are useful in a variety of health and electronic technologies but are made of toxic, expensive metals. Nontoxic and economic carbon-based dots are easy to produce, but they emit less light. Now, researchers from the University of Illinois Urbana-Champaign and the University of Maryland, Baltimore County have found good and bad emitters among populations of carbon-based dots, also called carbon nanodots. This observation suggests that by selecting only super-emitters, carbon nanodots can be purified to replace toxic metal quantum dots in many applications.

Researchers from Vanderbilt University and the U.S. Department of Energy’s Oak Ridge National Laboratory have used a drop of rubbing alcohol, an office laminator, and creativity to develop scalable processes for manufacturing single-atom-thin graphene membranes. The membranes outperformed state-of-the-art commercial dialysis membranes, and the approach is fully compatible with roll-to-roll manufacturing.

Scientists trying to create a new photocathode need to develop a material that meets three different parameters: It has to have high "quantum efficiency"—the ratio of electrons produced per incoming photon; it needs to have low intrinsic emittance, which measures how much the beam may diverge after it is produced; and the photocathode must tolerate conditions less than a perfect vacuum. Researchers from the U.S. Department of Energy's Argonne National Laboratory have demonstrated a new material, called ultrananocrystalline diamond, that has an excellent balance of these parameters.

Researchers from the University of Michigan, Jilin University in China, and the Federal University of São Carlos in Brazil have developed a new drug screening technique that relies on gold nanorods to twist light, so that a red glow can signal whether a medication designed to treat type II diabetes and pancreatic cancer is working. The researchers were able to take advantage of the chirality of a protein marker for these diseases, called islet amyloid polypeptides.  

Researchers at Columbia University have developed a technique that exploits the tunable symmetry of 2D materials for nonlinear optical applications and next-generation optical quantum information processing and computing. With the ability to control symmetry at the atomic-layer limit, the researchers demonstrated precise tuning and giant enhancement of optical second harmonic generation with micro-rotator devices and superlattice structures, respectively. Tunable second harmonic generation from micro-rotators could lead to novel on-chip transducers that couple micromechanical motion to sensitive optical signals by turning mechanical motion into light, which is critical for many sensors and atomic force microscopes.

An international team of researchers led by the University of Michigan has discovered a new path toward sending and receiving information with single photons (elementary particles that make up light). The physicists and engineers used a new kind of semiconductor to create quantum dots arranged like an egg carton, the quantum dots being the pockets in the egg carton. These new semiconductors have the potential to bring quantum devices up to room temperature, rather than the extreme cold of liquid nitrogen or liquid helium.

COSMIC, a multipurpose X-ray instrument at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, has made headway in the scientific community since its launch less than two years ago, with groundbreaking contributions in fields ranging from batteries to biominerals. Its capabilities include world-leading soft X-ray microscopy resolution below 10 nanometers, extreme chemical sensitivity, and the ability to measure nanoscale chemical changes in samples in real time. In two journal articles, scientists highlight some of COSMIC’s existing capabilities, including examples of 8-nanometer resolution achieved in imaging magnetic nanoparticles, as well as the first-ever use of X-ray linear dichroic ptychography, a specialized high-resolution imaging technique that maps the orientations of a crystal present in coral skeletons at 35-nanometer resolution.

The properties of two- dimensional (2D) materials, which are just one or a few atoms thick, can be modified by stacking two layers together and rotating one slightly in relation to the other. This creates what are known as Moire patterns, in which tiny shifts in the alignment of atoms between the two sheets create larger-scale patterns. Now, an international team led by MIT researchers has come up with a way of imaging what goes on at the interfaces between these 2D materials, down to the level of individual atoms, and of correlating the Moire patterns at the 2D-3D boundary.

At the nanoscale, water freezes in various ways, and not all of them are completely understood. A researcher at Yale University has focused on a particularly fast process known as contact freezing, in which a supercooled (below freezing, but unfrozen) liquid droplet in the atmosphere collides with a nucleating particle—that is, a particle that facilitates the freezing of a liquid that comes into contact with it. His team of researchers has demonstrated that the proximity of surfaces is enough to induce freezing, but it happens only when there is a liquid prone to surface freezing.

Physicists from the U.S. Department of Energy’s Princeton Plasma Physics Laboratory have made a discovery that could facilitate production of carbon nanotubes. The physicists produced a model showing that nanoparticle formation depends on several factors and that as the electric current transitions from low-to-high strength, the evaporation rate of the carbon atoms also transitions from low-to-high strength. This finding is important because researchers want to control the evaporation of carbon atoms at a moderate rather than rapid rate when performing experiments and creating nanoparticles for industry.