By Josh Perry, Editor
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Scientists at Michigan Technological University (Houghton, Mich.) developed a process for converting metallic gold into quantum dots and customizing their bandgap atom-by-atom by laying them out on boron nitride nanotubes, according to a report from the university.

Researchers made gold quantum dots on the surface of boron nitride nanotubes.
(Michigan Tech/YouTube)

Researchers used a scanning transmission electron microscope (STEM) to watch the atoms move in real-time and they were able to visualize the gold atoms gliding along the surface of the nanotubes and “stabilize in a hover just above the hexagon honeycomb of the boron nitride nanotubes.”

The principle behind this movement is energy selective deposition.

“In the lab, the team takes an array of boron nitride nanotubes and runs a gold-laden mist past it; the gold atoms in the mist either stick as multilayered nanoparticles or bounce off the nanotube, but some of the more energetic ones glide along the circumference of the nanotube and stabilize, then start to clump into monolayers of gold quantum dots,” the article explained. “The team shows that gold preferentially deposits behind other gold particles that have stabilized.”

Researchers will try to convert this breakthrough into all-metal electronics, and they hope that this work will show the promise of metal monolayers for future electronics.

The research was recently published in ACS Nano. The abstract read:

“Metallic gold nanoparticles (Au NPs) with multilayer Au atoms are useful for plasmonic, chemical, medical, and metamaterial application. In this article, we report the opening of the bandgap in substrate-supported two-dimensional (2D) gold quantum dots (Au QDs) with monolayer Au atoms.

“Calculations based on density functional theory suggest that 2D Au QDs are energetically favorable over 3D Au clusters when coated on hexagonal boron nitride (BN) surfaces. Experimentally, we find that BN nanotubes (BNNTs) can be used to stabilize 2D Au QDs on their cylindrical surfaces as well as Au atoms, dimers, and trimers.

“The electrically insulating and optically transparent BNNTs enable the detection of the optical bandgaps of the Au QDs in the visible spectrum.

“We further demonstrate that the size and shapes of 2D Au QDs could be atomically trimmed and restructured by electron beam irradiation. Our results may stimulate further exploration of energetically stable, metal-based 2D semiconductors, with properties tunable atom by atom.”

Learn more in the video below: