Goldene

Goldene is a single-layer allotrope of gold. The thinnest commercial gold leaf is some 400 times thicker than goldene.^[1] It features 9% lattice contraction compared to bulk gold.^[1]

Goldene was first synthesized as a free-standing material in 2024 by a team at Linköping University in Sweden. A 2022 claim by a team at New York University Abu Dhabi has been disputed as actually containing multiple layers.^[2]

The team used a material containing silicene between layers of titanium carbide. Gold layered on top of this combination diffused into the structure and replaced the silicon. Etching away the titanium carbide released free-standing goldene sheets that were up to 100 nanometres wide. The etching was performed using Murakami's reagent, in a 100-year-old technique used to decorate ironwork by Japanese blacksmiths. Surfactant molecules formed a barrier between goldene and the surrounding liquid — to stop the sheets from adhering.^[2]

The team is exploring the potential for preparing goldene from other non-van der Waals Au-intercalated phases, including developing etching schemes.^[1]

Forming 2D allotropes of metals such as gold has been difficult because metal atoms tend to cluster together and form nanoparticles instead of nanosheets.^[2]

The material displayed Au 4f binding energy increase of 0.88 eV. The material is a semiconductor, with the valence band maximum 50 meV below the Fermi level.^[1]

Potential applications included sensing and catalysis.

• Single-layer materials