Nanoparticles fused with DNA act like electrons — challenging our understanding of matter

Discovery of nanoparticle/DNA fusion and its extraordinary electron-like behaviour opens possibilities for revolutionary new materials

It’s not an electron. But it sure does act like one.

A strange and startling discovery has been made by scientists at Northwestern University— extremely small nanoparticles engineered with DNA, behave just like electrons. Not only has this finding — detailed in the journal Science — upended the current, accepted notion of matter, it also opens the door for new possibilities in materials design.

Northwestern’s Monica Olvera de la Cruz, who made the initial observation through computational work, says: “We have never seen anything like this before. In our simulations, the particles look just like orbiting electrons.”

The researchers have coined a new term, ‘metallicity’ — the mobility of electrons in a metal — to describe the phenomenon observed. In colloidal crystals, tiny nanoparticles roam similarly to electrons and act as a glue binding the material together.

The divide between the behaviours of nanoparticles fused with DNA. The smaller particles displayed ‘metallicity’ — behaviour like electrons (Morris, Northwestern)

Northwestern’s Chad Mirkin, who led the experimental work, adds: “This is going to get people to think about matter in a new way.

“It’s going to lead to all sorts of materials that have potentially spectacular properties that have never been observed before. Properties that could lead to a variety of new technologies in the fields of optics, electronics and even catalysis.”

Olvera de la Cruz is the Lawyer Taylor Professor of Materials Science and Engineering in Northwestern’s McCormick School of Engineering. Mirkin is the George B. Rathmann Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences.

Mirkin’s group previously invented the chemistry for engineering colloidal crystals with DNA, which has forged new possibilities for materials design. In these structures, DNA strands act as a sort of smart glue to link together nanoparticles in a lattice pattern.

“Over the past two decades, we have figured out how to make all sorts of crystalline structures where the DNA effectively takes the particles and places them exactly where they are supposed to go in a lattice,” said Mirkin, founding director of the International Institute of Nanotechnology.

In these previous studies, the particles’ diameters are on the tens of nanometers length scale. Particles in these structures are static, fixed in place by DNA. In the current study, however, Mirkin and Olvera de la Cruz shrunk the particles down to 1.4 nanometers in diameter in computational simulations. This is where the magic happened.

Simulations courtesy of Northwestern

Olvera de la Cruz continues: “The bigger particles have hundreds of DNA strands linking them together.

“The small ones only have four to eight linkers. When those links break, the particles roll and migrate through the lattice holding together the crystal of bigger particles.”

When Mirkin’s team performed the experiments to image the small particles, they found that Olvera de la Cruz’s team’s computational observations proved true. Because this behaviour is reminiscent of how electrons behave in metals, the researchers termed in ‘metallicity.’

Mirkin elaborates: “A sea of electrons migrates throughout metals, acting as a glue, holding everything together.

“That’s what these nanoparticles become. The tiny particles become the mobile glue that holds everything together.”

Olvera de la Cruz and Mirkin next plan to explore how to exploit these electron-like particles in order to design new materials with useful properties. Although their research used gold nanoparticles, Olvera de la Cruz said ‘metallicity’ applies to other classes of particles in colloidal crystals.

Mirkin concludes: “In science, it’s really rare to discover a new property, but that’s what happened here.

“It challenges the whole way we think about building matter. It’s a foundational piece of work that will have a lasting impact.”

Original research: https://science.sciencemag.org/content/364/6446/1174