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We report the preparation of gold (Au) nanosheets with a quasi‐square morphology and curved edges (Au QSNSs). The atomic packing on the edge, corner, and central part of an individual Au QSNS is carefully observed via spherical aberration corrected high‐resolution transmission electron microscopy, and the atomic‐resolution images confirm the dominant presence of {100} facets on all these regions. Such type of two‐dimensional nanostructure is of great interest, as conventional gold nanoplates/nanoprisms are mainly enclosed with {111} facets on upper/bottom faces. The use of glutathione and octadecyltrimethylammonium chloride as the shape‐directing agent and the capping agent, respectively, at appropriate amounts, together with a dropwise addition of Au precursor at controlled rate, have been validated to be crucial for the formation of such a unique two‐dimensional nanostructure. When acting as electrocatalysts for the methanol oxidation reaction in alkaline medium, the Au QSNSs/C exhibited noticeable enhancement, compared to spherical counterparts, in terms of mass activity, reaction kinetics, and long‐term durability, demonstrating their structural advantage. [ABSTRACT FROM AUTHOR]

We report a niche synthetic strategy to manipulate the shape of gold‐silver (AuAg) nanocrystals based on kinetics control. The success of current work relies on the use of two syringe pumps to add Au and Ag precursor solutions independently at distinct injection rates, which allows the separate control over the feeding rate of Au and Ag atoms, respectively. Such strategy is validated effective in both one‐pot reduction and seeded growth involving spherical and rod‐likes Au seeds. By conducting orthogonal experiments setting two injection rates at three levels, a set of morphologies are obtained. Interestingly, AuAg alloy nanocrystals in the form of multipod, hollow protruded particles, and branched hollow nanoplate, that are rare to obtain via conventional routes, are successfully screened out, exhibiting the unique advantage of this strategy. The current work provides a feasible approach to applying kinetics control over AuAg bimetallic nanocrystals, which could be extended to other noble metals or material combinations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We report the seeded growth of gold@silver (Au@Ag) core‐shell nanocrystals with the shape of truncated right bipyramids (TRB) and their hollow derivatives obtained via a galvanic replacement reaction. In particular, by depositing Ag on single‐crystal Au seeds under kinetic control, the resultant Au@Ag core‐shell products exhibit planar defects. Morphology and structure characterization is performed to confirm the crystallinity variation and the resultant TRB shape. Considering that elemental Au and Ag have similar lattice constants and negligible lattice mismatch, this phenomenon is quite unique, as the crystallinity of product is typically governed by the seed. The size of final product can be controlled in the range of 37–85 nm by varying the volume of the Au seed solution. In addition, by reacting with gold precursor, the as‐prepared Au@Ag TRBs can be converted into Au‐based nanostructures with hollow interiors, showing absorbance properties continuously tuned in the visible range, which could find important use in photocatalysis, sensing, and fluorescence enhancement, among others. [ABSTRACT FROM AUTHOR]

A synthetic case is reported that demonstrates the cationic additive, Ag+, can influence the crystallinity and thus shape of final product during seeded growth of Au nanocrystals. Using single‐crystal Au seeds as reference, the crystallinity difference between seed and final product could be directly compared. In particular, three different types of crystallinity/morphology can be obtained by varying the concentration of Ag+ in the particle growth solutions: single‐crystal quasi‐spheres, multiply twinned particles (MTPs), and protruded MTPs, with no Ag+ added and solution Ag+ /Au3+ ratios of 1 : 20 and 1 : 5, respectively. The reaction kinetics are investigated using extinction spectroscopy, indicating the presence of Ag+ leads to a dampened growth of Au nanocrystals. This principle is validated using single‐crystal Au seeds with different morphology and amounts. We also test the anti‐corrosion performance of as‐prepared Au nanocrystals with different crystallinity by treating them with sodium thiosulfate. Interestingly, in addition to reduction in size, the morphology of single‐crystal ones varies from quasi‐sphere to cube, indicating the anisotropy in oxidative etching of Au nanocrystals. [ABSTRACT FROM AUTHOR]

A synthetic case is reported that demonstrates the cationic additive, Ag+, can influence the crystallinity and thus shape of final product during seeded growth of Au nanocrystals. Using single‐crystal Au seeds as reference, the crystallinity difference between seed and final product could be directly compared. In particular, three different types of crystallinity/morphology can be obtained by varying the concentration of Ag+ in the particle growth solutions: single‐crystal quasi‐spheres, multiply twinned particles (MTPs), and protruded MTPs, with no Ag+ added and solution Ag+ /Au3+ ratios of 1 : 20 and 1 : 5, respectively. The reaction kinetics are investigated using extinction spectroscopy, indicating the presence of Ag+ leads to a dampened growth of Au nanocrystals. This principle is validated using single‐crystal Au seeds with different morphology and amounts. We also test the anti‐corrosion performance of as‐prepared Au nanocrystals with different crystallinity by treating them with sodium thiosulfate. Interestingly, in addition to reduction in size, the morphology of single‐crystal ones varies from quasi‐sphere to cube, indicating the anisotropy in oxidative etching of Au nanocrystals. [ABSTRACT FROM AUTHOR]