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Oxidation-Induced Internal Chemical Patterning in Copper-Gold Nanoalloys
Zhikang Zhou1, Hanlei Zhang1, Dongxiang Wu1
1Materials Science and Engineering Program & Department of Mechanical Engineering, State University of New York, Binghamton, New York, USA.
Small (Weinheim an Der Bergstrasse, Germany)
|August 4, 2026
Summary
Surface oxidation of copper-gold nanoalloys drives internal chemical separation via twin boundaries, creating unique lamellar structures. This contrasts with typical core-shell formation, revealing new pathways for nanoalloy design.
Area of Science:
- Materials Science
- Nanotechnology
- Surface Chemistry
Background:
- Chemical segregation in nanoalloys typically forms core-shell structures under vacuum.
- Surface free energy minimization drives conventional segregation behavior.
Purpose of the Study:
- To investigate the effect of surface oxidation on chemical segregation in copper-gold (Cu-Au) nanoalloys.
- To elucidate the mechanisms behind altered chemical separation under oxidizing conditions.
Main Methods:
- In situ electron microscopy
- Ambient-pressure X-ray photoelectron spectroscopy
- Density functional theory (DFT) calculations
Main Results:
- Surface oxidation suppresses conventional surface segregation in Cu-Au nanoalloys.
- Oxidation induces twin-boundary (TB)-mediated chemical separation within the nanoalloy interior.
- Gold (Au) atoms migrate to internal TBs via uphill diffusion, forming alternating Au-rich and Cu-rich lamellae.
- Local Au enrichment reached up to ~50 at.% due to CuOₓ overlayer inhibiting surface segregation.
Conclusions:
- Surface oxidation acts as a chemical pump, redirecting atomic flux internally.
- Defect-mediated segregation at internal TBs lowers free energy by maximizing Cu-Au bonding.
- Surface chemistry, alloy thermodynamics, and lattice defects collectively control nanoalloy internal structure and stability in reactive environments.
