Anomalous Shape Evolution of Ag₂O₂ Nanocrystals Modulated by Surface Adsorbates during Electron Beam Etching

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Nanocrystal shape is crucial for applications like catalysis and plasmonics.
• Surface adsorbates can significantly influence nanocrystal shape development.
• Observing dynamic shape evolution in situ at high resolution is challenging.

Purpose of the Study:

• To investigate the anomalous shape evolution of silver oxide (Ag2O2) nanocrystals.
• To understand the role of silver (Ag) cluster adsorbates in modulating this evolution.
• To reveal the atomic mechanisms behind adsorbate-influenced nanocrystal shape changes.

Main Methods:

• In situ transmission electron microscopy (TEM) for dynamic observation.
• Electron beam etching to induce shape changes.
• Analysis of nanocrystal morphology and facet development.

Main Results:

• Ag2O2 nanocrystals with Ag adsorbates exhibited anomalous shape evolution during electron beam etching.
• Three distinct stages of shape transformation were observed: sphere-to-cube, side etching, and bottom etching.
• Ag adsorbates selectively capped facet junctions, preventing atom etching and blocking diffusion pathways.

Conclusions:

• Surface Ag adsorbates play a critical role in modulating the shape evolution of Ag2O2 nanocrystals.
• This modulation occurs by altering surface atomic configurations and diffusion processes.
• Findings offer insights into controlling nanocrystal shape through surface modification.