Tiny metallic snowflakes were produced by atom-scale research carried out by scientists in Australia and New Zealand.
Nanoscale structures can help with electronic manufacturing, make materials stronger yet lighter, or assist with environmental clean-ups by binding to toxins. A nanometer is one billionth of a meter.
Gallium is a soft, silvery metal used in semiconductors and, unusually, liquefies at just above room temperature. New Zealand and Australian scientists have been experimenting with gallium to make metallic nanocrystals. The findings were recently published in Science.
Dr. Krista Steenbergen of Te Herenga Waka, Victoria University of Wellington, Professor Nicola Gaston, and research fellow Dr Steph Lambie of Waipapa Taumata Rau, University of Auckland, worked with Australian colleagues under the direction of Professor Kourosh Kalantar-Zadeh at the University of New South Wales.
Platinum, bismuth, silver, aluminum, copper, zinc, tin, and nickel were among the materials used in the lab by the Australian team. Gallium dissolved metals when heated to a high temperature. The metallic crystals appeared after cooling, but the gallium remained liquid.
The New Zealand team used simulations of molecular dynamics to explain why differently shaped crystals emerge from different metals. The team is a part of the MacDiarmid Institute for Advanced Materials and Nanotechnology, a national Center of Research Excellence. The study was funded by the government based Marsden Fund.
What we are learning is that the structure of the liquid gallium is very important. That is novel because we usually think of liquids as lacking structure or being only randomly structured.
Nicola Gaston, Professor, Waipapa Taumata Rau, University of Auckland
According to the research, different-shaped crystals emerge due to interactions between the atomistic structures of the various metals and the liquid gallium.
The crystals had shapes like cubes, rods, hexagonal plates, and zinc snowflakes. The snowflake pattern is explained by zinc’s six-branched symmetry, which surrounds each atom with six neighbors who are spaced at equivalent intervals.
Gaston added, “In contrast to top-down approaches to forming nanostructure—by cutting away material—this bottom-up approaches relies on atoms self-assembling. This is how nature makes nanoparticles, and is both less wasteful and much more precise than top-down methods.”
According to her, the study has revealed a previously unexplored route for metallic nanostructures.
“There is also something very cool in creating a metallic snowflake!”, she stated.
Idrus-Saidi, S. A., et al. (2022) Liquid metal synthesis solvents for metallic crystals. Science. doi:10.1126/science.abm2731.