Hollow platinum-gold and palladium-gold nanoparticles: synthesis and characterization of composition-structure relationship

Abstract

Hollow palladium-gold (PdAu) and platinum-gold (PtAu) alloy nanoparticles (NPs) were synthesized through galvanic replacement reactions. PdAu NPs denoted PdAu-99.99 and PdAu-98 were produced using palladium precursors with different purity degree: Na2PdCl4 ≥ 99.99% and Na2PdCl4 98%, respectively. The effect of the addition time of the gold palladium precursor solution on the size of the generated NPs was evaluated. Two types of particles, with a rough and a smooth surface, were identified in the suspensions of PtAu and PdAu NPs by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM). The atomic percentage of gold, platinum, palladium, and cobalt (atomic %) in the nanoparticles was determined by energy dispersive X-ray spectroscopy (EDX). PtAu NPs (26–42 nm) contain Pt (41 at%), Au (36 at%), and Co (23 at%). Two groups of hollow palladium gold NPs (30–50 nm) with a different residual cobalt content were produced. PdAu-99.99 NPs consisted of Pd (68 at%), Au (26 at%), and Co (6 at%), whereas PdAu-98 NPs were composed of Pd (70 at%), Au (22 at%), and Co (8 at%). The hollow structure of the NPs was confirmed by EDX line scanning. Selected area electron diffraction analysis (SAED) revealed the formation of PtAu and PdAu alloys and it was used in estimating the lattice parameters, too.