High performance catalysts are central for the development of new generation energy conversion and storage technologies. 1,2 While industrial catalysts can be optimized empirically by tuning the elemental composition, changing the supports, or altering preparation conditions in order to achieve higher activity and selectivity, these conventional catalysts are typically not uniform in composition and/or surface structure at the nano-to micro-scale. In order to significantly improve our capability of designing better catalysts, new concepts for the rational design and assembly of metal-metal oxide interfaces are desired. Metal nanocrystals with well-controlled shape and size are interesting materials for catalyst design from both electronic structure and surface structure aspects. 3,4,5 From the electronic structure point of view, small metal nanoclusters have size-dependent electronic states, which make them fundamentally different from the bulk. From the surface structure point of view, the shaped nanocrystals have surfaces with well-defined atomic arrangements. It has been clearly demonstrated by surface science studies in recent decades that the atomic arrangement on the crystal surface can affect catalytic phenomena in terms of activity, selectivity, and durability.

A room-temperature nanocarving strategy is developed for the fabrication of complex gold nanoplates having corolla- and propeller-like architectures. It is based on the simultaneous growth and etching of gold nanoplates in aqueous solution, which occur in the course of photoreduction of Au(OH)(4)(-) ions. The presence of bromide ion, poly(vinylpyrrolidone) (PVP), and molecular oxygen is indispensable, where bromide ions play multiple roles. First, they promote formation of nanoplate structures by forming adlayers on the fcc(111) surface. Second, they facilitate oxidative dissolution of gold nanocrystals by converting the oxidized Au(I) species to soluble AuBr(2)(-) ions, which lead to the formation of ultrathin nanocrevasses. PVP also stabilizes the nucleation of gold nanoplates. Although the overall reactions proceed in one-pot, the crystal growth and etching show interplay and occur with different kinetics due to changes in the concentration of Au(OH)(4)(-) and other species with time. Corolla- or propeller-like gold nanoplates formed under these conditions are single-crystalline, as indicated by selected area electron diffraction patterns and the observation of moire fringes. The morphology of corolla- or propeller-like gold nanoplates is controllable depending on the concentration of bromide ion and PVP in the aqueous mixture. On the basis of these results, a preliminary mechanism is proposed which involves the concurrent crystal growth and oxidative etching on the surface of nanocrystals.

Gold nanowires are obtained by photoreduction of linear self‐assemblies formed from Au(OH)4− and tetra‐alkyl ammonium ions at the water–chloroform interface. They are dissipative nanostructures formed only under non‐equilibrium conditions, which require continuous vectorial transport of ammonium ions across the interface. Nanocavities are observed in nanowires at almost regular intervals, which is a salient feature of dissipative structures.

The aim of this study is to prepare Au clusters with a mean size (d) of less than 3.0 nm, at which nonmetallic properties can be expected to appear. Au clusters (d < 3.0 nm) have been formed rapidly (<2 min) on TiO2 surfaces by a two-step method consisting of Au(III)-complex chemisorption and subsequent photoreduction (λex > 300 nm) at temperatures below 25 °C. In the photoreduction of the Au(III) complex to Au0, chemisorbed and physisorbed H2O on the TiO2 surface acts as a reductant. This method also enables us to produce Au clusters selectively at the UV-irradiated TiO2 surfaces.