A series of intrinsically chiral gold nanocage structures

We present a series of intrinsically chiral gold nanocage structures, Au_9n+6, which are stable for n ≥ 2. These structures consist of an Au_9n tube which is capped with Au₃ units at each end. Removing the Au₃ caps, we obtain a series of intrinsically chiral gold nanotube structures, Au_9n, 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.