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Abstract Combining different precious metals to generate alloy nanocrystals with desirable shapes and compositions remains a challenge because of the low miscibility between these metals and/or the different reduction potentials of their salt precursors. Specifically, Rh and Pd are considered to be immiscible in the bulk solid over the entire composition range. Here we demonstrate that Rh−Pd alloy nanorods with well‐distributed and tunable compositions can be synthesized using a one‐pot polyol method. The success of our synthesis relies on the introduction of bromide as a coordination ligand to tune the redox potentials of Rh(III) and Pd(II) ions for the achievement of co‐reduction. The atomic ratio of the Rh−Pd alloy nanorods can be facilely tuned by changing the molar feeding ratio between the two precursors. We also systematically investigate the effects of water on the morphology of the Rh−Pd alloy nanocrystals. In an attempt to promote future use of these alloy nanorods, we successfully scale up their synthesis in a continuous‐flow reactor with no degradation to the product quality. 

Abstract Surface ligands play an important role in shape‐controlled growth and stabilization of colloidal nanocrystals. Their quick removal tends to cause structural deformation and/or aggregation to the nanocrystals. Herein, we demonstrate that the surface ligand based on poly(vinylpyrrolidone) (PVP) can be slowly removed from Pd nanosheets (NSs, 0.93±0.17 nm in thickness) by simply aging the colloidal suspension. The aged Pd NSs show well‐preserved morphology, together with significantly enhanced stability toward both e‐beam irradiation and electrocatalysis (e.g., ethanol oxidation). It is revealed that the slow desorption of PVP during aging forces the re‐exposed Pd atoms to reorganize, facilitating the surface to transform from being nearly perfect to defect‐rich. The resultant Pd NSs with abundant defects no longer rely on surface ligand to stabilize the atomic arrangement and thus show excellent structural and electrochemical stability. This work provides a facile and effective method to maintain the integrity of colloidal nanocrystals by slowly removing the surface ligand. 

Despite remarkable progress, colloidal synthesis of metal nanocrystal is still far away from reaching the goal for robust, reproducible, and scalable production. Even with the adoption of seed-mediated growth, the synthesis can still be complicated by issues such as self-nucleation, galvanic replacement, stochastic symmetry reduction, and unwanted compositional variation. All these issues can be addressed by switching to steady-state synthesis characterized by a slow, constant, and tightly controlled reduction rate. Steady-state synthesis can be achieved by adding one reactant dropwise while using the other reactant in large excess, but this method is not suitable for scale-up production in a continuous flow reactor. There is a pressing need to develop alternative methods capable of establishing the steady-state kinetics characteristic of dropwise addition while introducing both reactants by one-shot injection. In this Perspective, we discuss a number of methods that allow for both one-shot injection and steady-state synthesis.