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

To create hybrid nanomaterials, chemists marry nanocrystals of light-capturing semiconductors with "charge acceptor" molecules that act as ligands, attaching to the semiconductor's surface and transporting electrons away from the nanocrystals. A few published experiments have shown that electron transfer rates initially increase with ligand surface concentration and then fall if surface concentrations continue to rise. Now, chemists from Rice University and the University of Texas at Austin have confirmed that this is the case when the ligand molecule is an often-studied dye called perylene diimide.

Many thin films are made by using a technique called epitaxy, which consists of placing atoms of a material on a substrate, or a template of sorts, to create a thin sheet of material, one atomic layer at a time. However, most thin films created via epitaxy are "stuck" on their host substrate, limiting their uses. Now, a University of Minnesota Twin Cities-led team of scientists and engineers has found a new way to successfully create a membrane of a particular metal oxide (strontium titanate), and their method circumvents several issues that have plagued the synthesis of freestanding metal oxide films in the past.

A team of engineers and neuroscientists from the University of California San Diego, the Salk Institute for Biological Studies, Boston University, and Oslo University Hospital in Norway has demonstrated, for the first time, that human brain organoids implanted in mice have established functional connectivity to the animals’ cortex and responded to external sensory stimuli. The implanted organoids reacted to visual stimuli in the same way as surrounding tissues, an observation that researchers were able to make in real time over several months thanks to an innovative experimental setup that combines transparent graphene microelectrode arrays and two-photon imaging.

Researchers at Georgia Tech have developed a new nanoelectronics platform based on graphene – a single sheet of carbon atoms – that is compatible with conventional microelectronics manufacturing. To create the new nanoelectronics platform, the researchers created a modified form of epigraphene – a layer of graphene that can spontaneously form on top of silicon carbide crystal, a semiconductor used in high-power electronics. In collaboration with researchers at Tianjin University in China, they produced unique silicon carbide chips from electronics-grade silicon carbide crystals. Then, the researchers used electron beam lithography to carve the graphene nanostructures and weld their edges to the silicon carbide chips. 

Scientists at the U.S. Department of Energy’s Lawrence Livermore National Laboratory have created vertically aligned single-walled carbon nanotubes on metal foils. Vertically aligned carbon nanotubes have exceptional mechanical, electrical, and transport properties in addition to an aligned architecture, which is key for applications such as membrane separation, thermal management, fiber spinning, electronic interconnects, and energy storage.

Researchers at Penn State have discovered that a new type of active pixel sensors that use a novel two-dimensional (2D) material may both enable ultra-sharp cell phone photos and create a new class of extremely energy-efficient Internet of Things (IoT) sensors. The 2D material is molybdenum disulfide, a semiconductor that is sensitive to light.

Researchers at Princeton University have discovered the first known protein that catalyzes the synthesis of quantum dots. Quantum dots are fluorescent nanocrystals used in electronic applications from light-emitting diode (LED) screens to solar panels. Quantum dots are normally made in industrial settings with high temperatures and toxic, expensive solvents. But the researchers pulled off the process in a lab by using water as a solvent, making a stable end product at room temperature.

Triboelectric nanogenerators are energy-harvesting devices that convert mechanical energy into electricity. To enhance the design and performance of these devices, researchers at Penn State and Hebei University of Technology have combined a porous 2D material, known as MXene, and a laser-induced graphene foam nanocomposite to form a system that enables a triboelectric nanogenerator to be stretchy and perform on the human skin or the leaf of a plant.

Engineers at the Massachusetts Institute of Technology have developed ultralight fabric solar cells that can quickly and easily turn any surface into a power source. These durable, flexible solar cells can provide energy on the go as a wearable power fabric or be transported and rapidly deployed in remote locations for assistance in emergencies. To produce the solar cells, the engineers used nanomaterials that are in the form of printable electronic inks. 

For decades, astronomers and physicists have been trying to solve one of the deepest mysteries about the cosmos: An estimated 85% of its mass is missing. Some kind of invisible matter, dubbed dark matter, could provide the extra gravitational glue. Scientists from the National Institute of Standards and Technology and elsewhere have used tungsten silicide superconducting nanowires as dark-matter detectors. Systems of such nanowires are exquisitely sensitive to extremely small amounts of energy imparted by particles of light, and perhaps dark matter particles, when they collide with these systems of nanowires.