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Open-mouthed, yolk–shell Au@AgPd nanoparticles are successfully produced via galvanic replacement reaction in water at room temperature., We have successfully produced open-mouthed, yolk–shell (OM-YS) Au@AgPd nanoparticles (NPs) via galvanic replacement reaction at room temperature; each NP has a large opening on its AgPd shells. Owing to the openings on the AgPd shells, the inner surfaces of the AgPd shells of as-prepared OM-YS Au@AgPd NPs become accessible to the surrounding media. These new structural characters make the present OM-YS Au@AgPd NPs excellent catalysts for electrochemical oxidation of ethanol in alkaline media. Their electrochemical active surface area is 87.8 m2 g–1 and the mass activity is 1.25 A mgPd–1. Moreover, the openings on the AgPd shells also make the surfaces of the Au cores in OM-YS Au@AgPd NPs accessible to the reaction media, which significantly facilitates the removal of CO and other carbonaceous intermediate species, thus leading to substantially enhanced durability and stability. This superior electrocatalytic performance cannot be implemented by using conventional YS Au@AgPd NPs or commercially available Pd/C catalysts.

We have successfully produced open-mouthed, yolk–shell (OM-YS) Au@AgPd nanoparticles (NPs) via galvanic replacement reaction at room temperature; each NP has a large opening on its AgPd shells. Owing to the openings on the AgPd shells, the inner surfaces of the AgPd shells of as-prepared OM-YS Au@AgPd NPs become accessible to the surrounding media. These new structural characters make the present OM-YS Au@AgPd NPs excellent catalysts for electrochemical oxidation of ethanol in alkaline media. Their electrochemical active surface area is 87.8 m2 g−1 and the mass activity is 1.25 A mgPd−1. Moreover, the openings on the AgPd shells also make the surfaces of the Au cores in OM-YS Au@AgPd NPs accessible to the reaction media, which significantly facilitates the removal of CO and other carbonaceous intermediate species, thus leading to substantially enhanced durability and stability. This superior electrocatalytic performance cannot be implemented by using conventional YS Au@AgPd NPs or commercially available Pd/C catalysts. Refereed/Peer-reviewed

We investigate the effect of gold (Au) seeds prepared in cetyltrimethylammonium chloride solution (CTAC-Au seeds) on the index facets of trisoctahedral gold nanocrystals (TOH Au NCs). We demonstrate that monodisperse {331}-faceted TOH Au NCs with controllable sizes (from 60 to 255 nm) can be successfully prepared in high yield by using 3.0 nm CTAC-Au seeds or as-prepared 70 nm TOH Au NCs as seeds. We find that the electrocatalytic performance on methanol oxidation and surface enhancement Raman spectroscopy (SERS) activity of {331}-faceted TOH Au NCs is size-dependent. In comparison with well-known nanoporous gold (0.088 mA cm−2), {331}-faceted TOH Au NCs with sizes of 110 nm exhibit fairly high catalytic activity (0.178 mA cm−2) on methanol oxidation (1.0 M) in alkaline media due to the presence of increasing density of atomic steps, ledges, and kinks on the NC surfaces. Their current density is reduced by less than 7% after 500 cycling tests. {331}-Faceted TOH Au NCs with sizes of 175 nm exhibit the highest SERS activity for 4-aminothiophenol (4-ATP) molecules. The enhancement factors of a1 modes of 4-ATP molecules can reach the order of 109 when the 4-ATP concentration is 3 × 10−6 M. Moreover, Raman signals (ag modes) of 4,4′-dimercaptoazobenzene (DMAB) molecules on TOH Au NCs are stronger than those on spherical Au NCs of comparable size due to the enhanced laser-induced transformation of 4-ATP molecules by high-index {331}-facets during SERS measurement. Furthermore, the SERS intensities of 4-methylbenzenethiol (4-MTP) molecules on TOH Au NCs are also higher than those on spherical Au NCs of comparable size due to sharp extremities. Refereed/Peer-reviewed

Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/cphc.201402648. The Turkevich method, involving the reduction of HAuCl4 with citrate in boiling water, allows the facile production of monodisperse, quasispherical gold nanoparticles (AuNPs). Although, it is well-known that the size of the AuNPs obtained with the same recipe vary slightly (as little as approximately 4 nm), but noticeably, from one report to another, it has rarely been studied. The present work demonstrates that this size variation can be reconciled by the small, but noticeable, effect that the latent heat in boiling water has on the size of the AuNPs obtained by using the Turkevich method. The increase in latent heat during water boiling caused an approximately 3 nm reduction in the size of the as-prepared AuNPs; this reduction in size is mainly a result of accelerated nucleation driven by the extra heat. It was further demonstrated that, the heating temperature can be utilized as an additional measure to adjust the growth rate of AuNPs during the reduction of HAuCl4 with citrate in boiling water. Therefore, the latent heat of boiling solvents may provide one way to control nucleation and growth in the synthesis of monodisperse nanoparticles.

We demonstrate that monodisperse, quasi-spherical gold nanocrystals (Au NCs) can be produced via quick addition of an aqueous solution of sodium citrate containing Ag+ and Fe2+ or Cu+ ions into a boiling aqueous solution of HAuCl4. The size of the resulting Au NCs increases from 12 nm to 60 nm with the decrease of citrate concentration. Compared with those obtained via a conventional Frens method, the NCs obtained via our approach have a fairly narrow distributed size and spherical shape. The significant improvement in the size polydispersity and shape sphericity is a result of the synergic effect of Ag+ and Fe2+ (or Cu+) ions. During the formation of Au NCs, the Ag+ ions are utilized to accelerate the nucleation via catalysis of the oxidation of citrate and regulate the NC isotropic growth, while the Fe2+ (or Cu+) ions significantly accelerate the reduction of Au3+ ions to Au0 atoms to speed up the nucleation when the concentration of citrate and silver ions was reduced to below 6.0 × 10−3 wt% and 8.5 × 10−4 wt%, respectively. Refereed/Peer-reviewed