2D Gold Sheet Draws Graphene Comparisons

The flatlands of two-dimensional materials just got a little more crowded and a bit more upscale. Researchers at Linköping University in Sweden have synthesized the first freestanding single layer of gold atoms, dubbed “goldene.”

According to the Linköping researchers, goldene could play a pivotal role in the development of next-generation electronic components, thanks to its remarkable thinness—one-500th the thickness of gold leaf.

Among the attractions of an effectively two-dimensional gold sheet include a high surface-area-to-volume ratio that enhances the sheet’s catalytic properties. This is critical for carbon dioxide conversion and hydrogen evolution, according to Shun Kashiwaya, an assistant professor in the department of physics, chemistry, and biology at Linköping.

Noble metals, such as gold, are used in a wide range of applications such as chemical, biological, pharmaceutical, and electrical applications because of a property known as “plasmonics.” Plasmonics exploit the waves of electrons (a.k.a. surface plasmons) that are triggered when photons strike a metal surface.

“By leveraging these plasmonic properties of gold, goldene would efficiently split water to produce hydrogen by harvesting solar power,” said Kashiwaya.

Moreover, these same plasmonic properties in graphene hold promise for applications in various fields, including water purification, advanced sensors, and electronics.

Goldene’s ultrathin profile not only offers substantial cost savings in manufacturing, particularly in printed circuit boards, but also opens up new avenues for miniaturization and efficiency in electronic devices.

Taking Metals Into 2D

While there have previously been other 2D metals produced (namely, 2D lead and tin), this latest development is distinct from those other instances: Both 2D lead and tin have to be adhered to other materials—they are not freestanding.

Also, Linköping researchers consider their work distinct from research that came out of New York University Abu Dhabi (NYUAD) in late 2022 that synthesized goldene because that work was limited to freestanding goldene that was several atoms thick. The Linköping team claims that their goldene is only a single layer of gold atoms.

Unlocking the full potential of gold in its thinnest form has remained a formidable task, according to the researchers. Previous attempts to create goldene were hindered by the inherent tendency of metals, including gold, to clump together, making it difficult to achieve atomic-level thinness.

By leveraging a three-dimensional base material comprised of layers of titanium and carbon, embedded with gold atoms, Kashiwaya and his colleagues successfully overcame the challenges of clumping and achieved the desired atomic-level thinness. This novel compound they developed served as the foundation for the subsequent extraction of goldene through meticulous etching processes.

Furthermore, the manufacturing method used to produce goldene holds promise for isolating other 2D materials. By using a process known as intercalation in which a molecule or ions are placed between two other molecules in multilayered structures or compounds, noble metals can be layered into ceramics and then produced leveraging a straightforward etching process. The method enables the extraction of various 2D metals with inert chemical properties.

Kashiwaya said he suspects the process is scalable, indicating its potential for industrial application beyond the confines of the laboratory. “This process is mainly composed of quite facile three steps: deposition, of the titanium and carbon, gold intercalation, and exfoliation by etching,” he added.

Looking ahead, the researchers expect to refine the synthesis processes next, exploring the fundamental properties of goldene, expanding its applications, and envisioning the production of other 2D metals, known as metallenes.

The researchers published their results earlier this month in the journal Nature Synthesis.