Wet‐Chemical Synthesis of Pd‐Au Core‐Shell Nanoparticles (8 nm): From Nanostructure to Biological Properties

Abstract

Pd−Au core‐shell nanoparticles with a palladium core (diameter about 5.5 nm) and a gold shell (thickness about 1.7 nm) were wet‐chemically synthesized in an easy water‐based one‐pot synthesis by sequential reduction of Pd2+ and Au3+ with glucose in the presence of poly(N‐vinylpyrrolidone) (PVP). The metals are present in about equal amounts (molar ratio Pd:Au about 2:1) with a clear separation between core and shell. The reaction was monitored in‐situ by small‐angle X‐ray scattering (SAXS), showing the initial growth of the palladium seeds, followed by the epitactic formation of the gold shell. The core‐shell character of the particles was confirmed by high‐resolution scanning transmission electron microscopy (STEM) and energy‐dispersive X‐ray spectroscopy (EDX). However, X‐ray powder diffraction with Rietveld analysis indicated a partial alloying, i. e. a gradual border between the two metals. Cell culture experiments showed no adverse effects on human mesenchymal stem cells (hMSCs) with a Pd−Au nanoparticle concentration (computed as total metal) up to 50 μg mL−1 after 24 h incubation, i. e. the particles can be considered as biologically harmless, even after unintended human exposure.

Bimetallic Gold-Silver Nanoparticles Supported on Zeolitic Imidazolate Framework-8 as Highly Active Heterogenous Catalysts for Selective Oxidation of Benzyl Alcohol into Benzaldehyde

“…However, the selectivity of ester was only 10.8% over the catalyst of Au–Pd/Fe–Gr. Due to the high price and limited resources of Au metal, a variety of catalyst preparation strategies have been developed to maximize Au utilization [11,12]. For example, core-shell structured catalysts with Au shells are considered to be promising alternatives to improve Au metal dispersion.…”

X-ray powder diffraction to analyse bimetallic core–shell nanoparticles (gold and palladium; 7–8 nm)

“…39 The core-shell nanoparticles Pd-Au and Au-Pd were then prepared by reduction of the second metal, using a modied seeded growth approach. 10,39,41 The presence of the reducing agent glucose prevented the galvanic replacement of the palladium seeds by the gold ions that would have led to a hollow gold nanoshell. 42 The colloidal stabilization was accomplished by an external layer of PVP in all cases.…”

“…cores) for the following synthesis of bimetallic core–shell nanoparticles as described earlier. 39 The core–shell nanoparticles Pd–Au and Au–Pd were then prepared by reduction of the second metal, using a modified seeded growth approach. 10,39,41 The presence of the reducing agent glucose prevented the galvanic replacement of the palladium seeds by the gold ions that would have led to a hollow gold nanoshell.…”

“…Pd nanoparticles (seeds), Au nanoparticles (seeds), and Pd-Au core-shell nanoparticles were synthesized as described earlier. 39,40 Au-Pd core-shell nanoparticles were synthesized in analogy to Pd-Au core-shell nanoparticles as follows: In a twoneck round bottom ask, 600 mg (3 mmol) D-glucose and 50 mg (0.125 mmol) PVP were dissolved in 50 mL water. The mixture was vigorously stirred (700 rpm) and heated to 100 C under reux.…”

“…10 Only rarely, X-ray powder diffraction has been applied to such systems in closer detail. [37][38][39] Here, well-dened samples with high monodispersity were prepared to exclude the effects of impurities and larger crystals. We will show that X-ray powder diffraction is well suited to distinguish between different systems, making it suitable for a rapid analysis of many nanoparticles in the same experiment.…”