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 10(9) 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.

Open-mouthed, yolk–shell Au@AgPd nanoparticles are successfully produced via galvanic replacement reaction in water at room temperature.

In this work, we have successfully developed a new and consistent model to describe the growth of gold nanoparticles (Au NPs) via citrate reduction of auric acid (HAuCl4) by carefully assessing the temporal evolution of the NP sizes and surface charges by means of dynamic light scattering (DLS) and zeta-potential measurements. The new model demonstrates that the nucleation and growth of the Au NPs occur exclusively in the particles of the complexes of Au(+) ions and sodium acetone dicarboxylate (SAD) derived from the citrate/HAuCl4 redox reaction, which proceeds as described by the classic LaMer model. Concomitant with the Au NP growing therein, the Au(+)/SAD complex particles undergo reversible agglomeration with the reaction time, which may result in an abnormal color change of the reaction media but have little impact on the Au NP growth. Built on the new model, we have successfully produced monodisperse quasi-spherical Au NPs with sizes precisely regulated from 2 to 330 nm via simple citrate reduction in a one-pot manner. To date, highly uniform Au NPs with sizes spanning such a large size range could not be formed otherwise even via deliberately controlled seeded growth methods.

The present work introduces a new way to prepare Au-Pd alloy nanowire networks (NWNs) via deposition of Pd atoms onto Au nanowires in reaction media at room temperature without the aid of additional reducing agents. Thanks to their excellent colloidal stability in water as well as in ethanol, the resulting NWNs can be utilized to produce composite thin films with Nafion (perfluorinated sulfonic acid) with dimensions above dozens of square centimeters by means of solution casting on the glass substrate. Most importantly, these films can be easily transferred onto different solid substrates by lift-off technology. Moreover, the resulting Au-Pd alloy NWNs can also be easily and thoroughly loaded into macroscopic carbon fiber cloth (CFC). Both the Au-Pd alloy NWN/Nafion composite film and the Au-Pd alloy NWN-loaded CFC can be used as flexible electrodes for electrocatalysis of ethanol oxidation, with electrocatalytic performance at different distorted states superior by 2 orders of magnitude to those reported in the literature (e.g., commercial Pd/C catalysts and Pd-based nanostructured catalysts). This work opens new possibilities for the large-scale manufacturing of electrodes for fuel cells.

In this work, uniform, quasi‐spherical gold nanoparticles (Au NPs) with sizes of 31–577 nm are prepared via one‐pot seeded growth with the aid of tris‐base (TB). Distinct from the seeded growth methods available in literature, the present method can be simply implemented by subsequently adding the aqueous dispersion of the 17 nm Au‐NP seeds and the aqueous solution of HAuCl4 into the boiling aqueous TB solution. It is found that at the optimal pH range, the sizes of the final Au NPs and their concentrations are simply controlled by either the particle number of the Au seed dispersion or the concentration of the HAuCl4 solution, while the latter enables us to produce large Au NPs at very high concentration. Moreover, as‐prepared Au NPs of various sizes are coated on glass substrates to test their surface‐enhanced Raman scattering (SERS) activities by using 4‐aminothiophenol (4‐ATP) molecules as probes, which exhibit “volcano type” dependence on the Au NP sizes at fixed excitation wavelength. Furthermore, the Au NPs with sizes of ≈97 and 408 nm exhibit the largest SERS enhancement at the excitation wavelength of 633 and 785 nm, respectively.

In this work, we reported the synthesis of monodisperse, quasispherical Ag nanoparticles (NPs) with sizes of 40–300 nm by using ascorbic acid reduction of a silver–ammonia complex onto preformed, 23 nm Ag-NP seeds in the aqueous solution with an optimal pH of about 9.6 at room temperature. The as-prepared Ag NPs with such a large size span (from 40 to 300 nm) and high quality by one-pot seeded growth method are reported for the first time to the best of our knowledge. It is found that the key in the present seed-mediated growth method is to introduce a proper amount of ammonia water for the formation of a stable complex with a silver precursor (silver–ammonia complex) while maintaining the pH value of the growth solution simultaneously. By using rhodamine 6G molecules as probes, the surface-enhanced Raman scattering (SERS) activities of the as-prepared Ag NPs in ethanol solution are highly dependent on the sizes of Ag NPs at the fixed 633 nm laser and at the fixed particle number, which show a volcano-like curve. Moreover, 125 nm Ag NPs bear the largest SERS activity among them. Furthermore, Ag NPs with narrow distributions in shape and size (say, less than 10%) can achieve the uniformity and reproducibility of their SERS signals in solution; their relative standard deviations can be as low as 5% in space and temporal scale.

Dendritic nanostructures are capturing increasing attention in electrocatalysis owing to their unique structural features and low density. Herein, we report for the first time, bromide ion mediated synthesis of low Pt-content PdCuPt ternary nanodendrites via galvanic replacement reaction between a Pt precursor and a PdCu template in aqueous solution. The experimental results show that the ternary PdCuPt nanodendrites present enhanced electrocatalytic performance for oxygen reduction reaction in acid solution compared with commercial Pt/C as well as some state-of-the-art catalysts. In detail, the mass activity of the PdCuPt catalyst with optimized composition is 1.73 A mg at 0.85 V vs. RHE, which is 14 times higher than that of a commercial Pt/C catalyst. Moreover, the long-term stability test demonstrates its better durability in acid solution. After 5k cycles, there is still 70% electrochemical surface area maintained. This method provides an efficient method to synthesize trimetallic alloys with controllable composition and specific structure for oxygen reduction reaction.

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.