However, in order to create future generations of electronics—such as more powerful phones, more efficient solar cells, and even quantum computers—scientists will need to come up with entirely new technologies at the smallest scale.
One area of interest is nanocrystals. These tiny crystals can assemble themselves into many configurations, but scientists have long struggled to figure out how to make them “talk” to each other.
A new study introduces a breakthrough in enabling nanocrystals to work together electronically. Published in the journal *Science* on March 24, this research could open the door to devices with novel capabilities in the future.
“We call these superatomic building blocks because they can give them new capabilities—for example, allowing cameras to see in the infrared range,” said Dmitri Talapin, a professor at the University of Chicago and the paper’s corresponding author. “But until now, it has been very difficult to assemble them into structures and get them to ‘talk’ to each other. Now, for the first time, we don’t have to make choices anymore. This is a revolutionary improvement.”
Josh Portner, a chemistry PhD student and one of the study's first authors, said that in their paper, the scientists proposed design rules that should allow for the creation of many different types of materials.
Scientists can grow nanocrystals from many different materials: metals, semiconductors, and magnets will each produce different properties. But the problem is that whenever they try to assemble these nanocrystals into an array, long "hairs" grow around the new supercrystals.
These "hairs" make it very difficult for electrons to jump from one nanocrystal to another. Electrons are the messengers of electronic communication; their ability to move easily is a key part of any electronic device.
Researchers need a way to reduce the “hair” around each nanocrystal so they can pack them tighter and reduce the gaps in between. “When these gaps are only a third of what they used to be, the probability of electrons skipping over is about a billion times higher,” said Talapin, Ernest DeWitt Burton Distinguished Service Professor of Chemical and Molecular Engineering at the University of Chicago and a senior scientist at Argonne National Laboratory. “It varies very strongly with distance.”
To shave off these "hairs," they tried to understand what was happening at the atomic level. For this, they needed the powerful X-rays from Argonne's Center for Nanomaterials and the Stanford Synchrotron Radiation Facility at SLAC National Accelerator Laboratory, as well as robust simulations and chemical and physical models. All of this enabled them to understand what was happening on the surface and find the key to utilizing it for production.
Part of the process of growing supercrystals takes place in solution, that is, in a liquid. As the crystals grow, they undergo an unusual transformation in which gaseous, liquid, and solid phases all coexist. By precisely controlling the chemical reactions at this stage, they can create crystals with harder, finer surfaces that can be packed more tightly together. “Understanding their phase behavior is a giant leap for us,” Portner says.
The full range of applications remains unclear, but scientists can envision several potential areas for this technology. Talapin says, "For example, perhaps each crystal could become a qubit in a quantum computer; coupling qubits into arrays is one of the fundamental challenges of quantum technology today."
Portner is also interested in exploring the unusual intermediate states observed during the growth of supercrystals. "The coexistence of three phases like this is so rare that it's very interesting to think about how to utilize this chemical property and build new materials."
This study included scientists from the University of Chicago, Dresden University of Technology, Northwestern University, Arizona State University, SLAC, Lawrence Berkeley National Laboratory, and the University of California, Berkeley.
This research was conducted at the U.S. Department of Energy’s Advanced Materials Center for Energy-Water Systems, the Midwest Computational Materials Center, Argonne’s Center for Nanomaterials, and the Stanford Synchrotron Radiation Facility at SLAC National Accelerator Laboratory.
