New Insights into the Growth Mechanism and Surface Structure of Palladium Nanocrystals

Lim, B., H. Kobayashi, P.H.C. Camargo, L.F. Allard, J. Liu and Y. Xia, 2010

Image courtesy of Nano Research

Abstract

This paper presents a systematic study of the growth mechanism for Pd nanobars synthesized by reducing Na2PdCl4 with L-ascorbic acid in an aqueous solution in the presence of bromide ions as a capping agent. Transmission electron microscopy (TEM) and high-resolution TEM analyses revealed that the growth at early stages of the synthesis was dominated by particle coalescence, followed by shape focusing via recrystallization and further growth via atomic addition. We also investigated the detailed surface structure of the nanobars using aberration-corrected scanning TEM and found that the exposed {100} surfaces contained several types of defects such as an adatom island, a vacancy pit, and atomic steps. Upon thermal annealing, the nanobars evolved into a more thermodynamically favored shape with enhanced truncation at the corners.

Impact Statement

The authors synthesize Pd nanobars and characterize them at high temperatures. They use Fusion to heat to 500° C and observe the nanobars transforming into rounder particles to reduce surface area. The TEM used was a JEOL 2200FS Cs corrected STEM.