Selective Formation of Lotus Leaf- and Donut-Like Gold Nanoplates via Seeded Growth

Graphical Non-planar platelets of gold nanocrystals with the lotus leaf- and donut-like morphologies are selectively prepared via seeded growth. The preferable deposition of Au on the central region of plate-like Au seeds is realized by the underpotential-deposition (UPD) effect of Ag ions, while epitaxial growth on the edge part and cold-welding of the newly-formed branches lead to formation of an in-plane hole when Ag + is absent. We report a seeded growth of gold (Au) nanoplates with two distinct morphologies, which are similar to a lotus leaf and a donut, respectively. The success of this synthesis relies on the use of flat Au nanoplates in high purity as seeds, followed by a controlled deposition. In particular, the presence of Ag + led to the deposition of Au atoms preferentially occurred at the central part of one face of the nanoplate and thus the formation of lotus leaf-like shape. In contrast, when Ag + was absent, the growth mainly occurred to the edge region. Then, cold-welding of newly-formed branches and further diffusion of Au atoms created holes in the nanoplate, resulting in the formation of donut-like shape. The Au nano-lotus leaves with tunable sizes exhibited absorbance in near-infrared region and enhanced chemical activities in electrochemical measurements. The current strategy is extended to fabricate Au−Ag nanoplates with a similar lotus leaf-like morphology, which also exhibited strong absorbance in near-infrared region in UV-vis extinction spectra. The current work allows the fabrication of two-dimensional Au-based nanomaterials with concave shape and three-dimensional architecture and could be potentially extended to other noble metals and alloys.