Synchrotron Radiation-Assisted Oxidation of Gold Nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Gold nanoparticles exhibit unique properties influenced by their size and surface chemistry.
• Understanding oxidation mechanisms is crucial for controlling nanoparticle stability and reactivity.
• Ambient oxidation of gold nanoparticles remains an area requiring detailed investigation.

Purpose of the Study:

• To investigate the oxidation of solid gold nanoparticles under ambient conditions.
• To elucidate the transformation process from disordered nanoparticles to nanocrystallites.
• To characterize the resulting gold oxide phases and their structural evolution.

Main Methods:

• Utilized X-ray nanodiffraction at a synchrotron radiation source for nanoscale analysis.
• Evaporated carbohydrate-ligand-functionalized gold nanoclusters on a superhydrophobic surface.
• Raster-scanned the nanoparticle layer through a nanoscale X-ray focal spot.

Main Results:

• Observed radiation-induced formation of disordered gold nanoparticles (∼1.3 nm) from nanoclusters.
• These nanoparticles transformed into face-centered cubic gold nanocrystallites (∼2.1 nm) via nucleation and growth.
• Identified a disordered gold oxide surface layer evolving into epitaxially stabilized Au2O nanocrystallites with a cuprite structure, exhibiting lattice expansion due to oxygen uptake.

Conclusions:

• Gold nanoparticles undergo significant structural transformation and oxidation under ambient conditions when exposed to X-rays.
• The study provides insights into the nucleation, growth, and structural stabilization of gold oxide phases.
• Lattice expansion beyond stoichiometry indicates continued oxygen uptake and a transition towards short-range order.