Goldene: Free-standing Single-atom-thick Sheets of Gold

Abstract The quest to make free-standing monolayer gold has hitherto been limited to free-standing several-atoms-thick layers, or monolayers but confined on or inside another template. Examples are monolayers diffused into double hydroxides 1 , membranes framed in alloys under electron irradiation 2 , nano-ribbons suspended in graphene 3 , quantum dots on hexagonal BN 4 , monolayers in between SiC wafers and monolayer graphene 5 , and fragments produced via thermal dewetting on sapphire 6 . Here, we report the synthesis of free-standing single-atom-thick 2D gold (named goldene ) by wet-chemically etching away Ti 3 C 2 from Ti 3 AuC 2 , a nano-laminated MAX-phase ceramic initially formed by substituting Si in Ti 3 SiC 2 with Au 7 . The free-standing goldene layers are revealed by scanning transmission electron microscopy. While ab initio molecular dynamics simulations show that 2D goldene is inherently stable, the experiments reveal a tendency for curling and agglomeration at edges. Prospects for preparing goldene from a series of non-van der Waals Au-intercalated MAX-phases, including developing etching schemes, are also presented.