Technion researchers have presented an innovative method for the formation of nanowires. In it, the nanowires form within line defects that exist in metals. Such defects are known as dislocations. This is the first time that dislocation lines in a material of one kind serve as a template for the growth of a different inorganic material in the form of nanowires. The study, which was published in PNAS, was led by Professor Boaz Pokroy and Ph.D. student Lotan Portal of the Faculty of Materials Science and Engineering and the Russell Berrie Nanotechnology Institute (RBNI).

Dislocations are a significant phenomenon in materials science since they affect the material’s properties on both the macro- and microscales. For example, a high dislocation density increases a metal’s strength and hardness. The dislocation edges on metal surfaces and the atoms in their proximity tend to be more chemically activated compared to other atoms in the material and tend to facilitate various chemical reactions, such as corrosion and catalysis.

The researchers in Prof. Pokroy’s group created nanowires of gold-cyanide complex from classic Au-Ag alloy. In professional terminology, they synthesized inorganic gold(I)-cyanide (AuCN) systems in the shape of nanowires, using an autocatalytic reaction (i.e. through the acceleration of a reaction by one of its reactants). Gold-cyanide complex is used in numerous fields including ammonia gas detection (NH3 sensors), catalysis (acceleration) of water-splitting reactions, and others.

In the process developed by the researchers, nanowires crystallize at the dislocation ends on the surface of the original gold-silver (Au-Ag) alloy, and the final structure obtained is classic nanoporous (sponge-like) gold, with a layer of nanowires emerging from it. Formation of the nanowires occurs during the classic selective dealloying process that separates the silver from the system and forms the nanoporous gold and is achieved only when the dislocation density exceeds a critical value, as presented in the kinetic model developed and demonstrated in the article.

The model provides a possible route for growing one-dimensional inorganic complexes while controlling the growth direction, shape, and morphology of a crystal according to the original alloy’s slip system. As mentioned, this scientific and technological achievement has numerous potential applications.

The research was sponsored by a European Research Council (ERC) Proof of Concept Grant (“np-Gold” project) as part of the Horizon 2020 Program.

For more than a century, the Technion – Israel Institute of Technology has pioneered in science and technology education and delivered world-changing impact. Proudly a global university, the Technion has long leveraged boundary-crossing collaborations to advance breakthrough research and technologies. Now with a presence in three countries, the Technion will prepare the next generation of global innovators. Technion people, ideas and inventions make immeasurable contributions to the world, innovating in fields from cancer research and sustainable energy to quantum computing and computer science to do good around the world.

The American Technion Society supports visionary education and world-changing impact through the Technion – Israel Institute of Technology. Based in New York City, we represent thousands of US donors, alumni and stakeholders who invest in the Technion’s growth and innovation to advance critical research and technologies that serve the State of Israel and the global good. Since 1940, our nationwide supporter network has funded new Technion scholarships, research, labs, and facilities that have helped deliver world-changing contributions and extend Technion education to campuses in three countries.