Gold monolayers could provide platform for studying properties of 2D metals

Large-scale, nearly freestanding two-dimensional (2D) gold monolayers, composed of nanostructured patches, have been synthesised using a novel bottom-up approach.

The researchers say that the monolayers, which were found to be able to withstand high temperatures, could provide a useful platform for studying the catalytic activity of 2D gold.

The synthesis of large, freestanding, single-atom-thick 2D metallic materials remains a challenge due to the isotropic nature of metallic bonding. To try and overcome this, the researchers developed an approach that involved forming a gold monolayer on an iridium substrate, and then embedding boron atoms at the interface between the gold and iridium. This resulted in suspended monoatomic sheets of gold with a hexagonal structure and nanoscale triangular patterns.

Using scanning tunnelling microscopy, x-ray spectroscopies and theoretical calculations they showed that the boron interlayer had a crucial role in formation of the nanostructured gold mono- and bilayers, helping to ensure their stability and structural integrity.

Angle-resolved photoelectron spectroscopy and density functional theory revealed that a decoupling of the gold monolayer from the metal substrate triggered a transition in its electronic properties, reflecting a shift from 3D to essentially 2D metal bonding.

As the samples were prepared at relatively high temperatures, they found they were thermally stable up to 500°C in vacuum and, with gold comprising the top layer, could withstand exposure to ambient conditions.

The researchers say their approach not only advances understanding of the fundamental properties of 2D metals but also provides a platform for more practical studies. ‘For example, the nanostructured Au films may facilitate the ordered arrangement of large molecules or various size-selected clusters at a macroscopic scale for further investigations of their catalytic, optical, or magnetic properties,’ they write.