A series of intrinsically chiral gold nanocage structures.

We present a series of intrinsically chiral gold nanocage structures, Au9n+6, which are stable for n ≥ 2. These structures consist of an Au9n tube which is capped with Au3 units at each end. Removing the Au3 caps, we obtain a series of intrinsically chiral gold nanotube structures, Au9n, which are stable for n ≥ 4. The intrinsic chirality of these structures results from the helicity of the gold strands which form the tube and not because an individual Au atom is a chiral center. The symmetry of these structures is C3 and substructures of gold hexagons with a gold atom in the middle are particularly prominent. We focus on the properties of Au42 (C3) and Au105 (C3) which are the two smallest gold nanocage structures to be completely tiled by these Au7 "golden-eye" substructures. Our main focus is on Au42 (C3) since gold clusters in the 40-50 atom regime are currently being investigated in gas phase experiments. We show that the intrinsically chiral Au42 cage structure is energetically comparable with previously reported achiral cage and compact Au42 structures. Cage structures are of particular interest because species can be encapsulated (and stabilized) inside the cage and we provide strong evidence that Au6@Au42 (C3) is the global minimum Au48 structure. The intrinsically chiral gold nanocage structures, which exhibit a range of size-related properties, have potential applications in chiral catalysis and as components in nanostructured devices.