Kinetically Controlled Overgrowth of Ag or Au on Pd Nanocrystal Seeds: From Hybrid Dimers to Nonconcentric and Concentric Bimetallic Nanocrystals

Abstract

This article describes a systematic study of the nucleation and growth of Ag (and Au) on Pd nanocrystal seeds. By carefully controlling the reaction kinetics, the newly formed Ag atoms could be directed to selectively nucleate and then epitaxially grow on a specific number (ranging from one to six) of the six faces on a cubic Pd seed, leading to the formation of bimetallic nanocrystals with a variety of different structures. In addition to changing the injection rate of precursor, we also systematically investigated other reaction parameters including the capping agent, reductant, and reaction temperature. Our results suggest that the site-selective growth of Ag on cubic Pd seeds could be readily realized by optimizing these reaction parameters. On the basis of the positions of Pd seeds inside the bimetallic nanocrystals as revealed by TEM imaging and elemental mapping, we could identify the exact growth pathways and achieve a clear and thorough understanding of the mechanisms. We have successfully applied the same strategy based on kinetic control to cubic Pd seeds with different sizes and octahedral Pd seeds of one size to generate an array of novel bimetallic nanocrystals with well-controlled structures. With cubic Pd seeds as an example, we have also extended this strategy to the Pd-Au system. We believe this work will provide a promising route to the fabrication of bimetallic nanocrystals with novel structures and properties for applications in plasmonics, catalysis, and other areas.

Seeded growth of ferrite nanoparticles from Mn oxides: observation of anomalies in magnetic transitions

“…4g and 4k) with the Moiré fringes residing on the diagonals of these cubes. Similar formation of Moiré fringes perpendicular to <110> direction in cubes was also identified in Pd@Ag, 26 Au@Pd, 22 and MnZn ferrite core-shell nanocubes. 27 It is also known that cubic shapes are easier to be made as coreshell structures by epitaxial growth.…”

Keimvermitteltes Wachstum kolloidaler Metallnanokristalle

“…Diese unterschiedlichen Wachstumsmuster führten, wie in Abbildung c–e gezeigt, zur Bildung von Pd‐Ag‐Hybridstangen, nicht‐konzentrischen Pd‐Ag‐Nanowürfeln bzw. Pd@Ag‐Kern‐Schale‐Nanowürfeln . War die Injektionsgeschwindigkeit von AgNO 3 ausreichend langsam (und folglich auch die Abscheidung), nahm nur eine der sechs Seitenflächen Ag‐Atome auf.…”

“…auf allen sechs Seitenflächen (für Pd‐Ag‐Kern‐Schale‐Nanowürfel) erfolgen. Dieselbe Strategie auf Basis einer eingeschränkten Versorgung mit Atomen und einer Inhibierung der Oberflächendiffusion kann auf andere Systeme mit unterschiedlichen Metallen und Keimen erweitert werden, einschließlich des Wachstums von Ag oder Au auf Pd‐Nanowürfeln, von Ag auf Ag‐Nanowürfeln, von Au auf kubischen und oktaedrischen Pd‐Keimen, von Ag auf Au‐Keimen, von Au auf Au‐Keimen und von Pd auf kubischen Pd‐Keimen …”

Novel Pd Nanocubes Supported on Activated Carbon as a Catalyst for the Suzuki-Miyaura Coupling Reaction

“…The capping agent bromide ions, has been widely employed in inducing new shapes. With bromide ions introduced into the reaction system, they may chemisorb onto the surface of Pd seed and alter the relative order of surface free energies [24]. Additionally PVP was employed as a stabilizing agent to prevent the aggregation of particles.…”