Morphology and control of Pd nanoparticles

Polymer-stabilized Pd nanoparticles synthesized by reduction of Pd salt with methanol are of various geometric shapes besides spherical. The TEM micrographs show that most of the triangular particles are plate-like although some tetrahedral particles are also observed. The four-sided rhombohedral and square particles and some of the hexagonal particles are plate-like as well. The pentagonal particles are decahedra formed from multiple twinning with imperfection. Most of the hexagonal particles and the icosahedral particles are imperfectly twinned. Extensive multiple twinning are observed under other synthesis conditions. Growing crystals were captured at intermediate stage of the particle formation. The proportion of the different morphologies could be varied by changing the conditions of the synthesis including the molar ratio of precursor salt: polymer, reducing agent, stabilizing polymer, reducing temperature and time, pH of the solution as well as average molecular weight of the polymer. A mechanism is proposed for the particle growth. (c) 2005 Elsevier B.V. All rights reserved.